fe-connect.c

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/*-------------------------------------------------------------------------
 *
 * fe-connect.c
 *    functions related to setting up a connection to the backend
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/interfaces/libpq/fe-connect.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres_fe.h"
 
#include <sys/stat.h>
#include <fcntl.h>
#include <ctype.h>
#include <limits.h>
#include <netdb.h>
#include <time.h>
#include <unistd.h>
 
#include "common/base64.h"
#include "common/ip.h"
#include "common/link-canary.h"
#include "common/scram-common.h"
#include "common/string.h"
#include "fe-auth.h"
#include "fe-auth-oauth.h"
#include "libpq-fe.h"
#include "libpq-int.h"
#include "mb/pg_wchar.h"
#include "pg_config_paths.h"
#include "port/pg_bswap.h"
 
#ifdef WIN32
#include "win32.h"
#ifdef _WIN32_IE
#undef _WIN32_IE
#endif
#define _WIN32_IE 0x0500
#ifdef near
#undef near
#endif
#define near
#include <shlobj.h>
#include <mstcpip.h>
#else
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <pwd.h>
#endif
 
#ifdef WIN32
#include "pthread-win32.h"
#else
#include <pthread.h>
#endif
 
#ifdef USE_LDAP
#ifdef WIN32
#include <winldap.h>
#else
/* OpenLDAP deprecates RFC 1823, but we want standard conformance */
#define LDAP_DEPRECATED 1
#include <ldap.h>
typedef struct timeval LDAP_TIMEVAL;
#endif
static int  ldapServiceLookup(const char *purl, PQconninfoOption *options,
                              PQExpBuffer errorMessage);
#endif
 
#ifndef WIN32
#define PGPASSFILE ".pgpass"
#else
#define PGPASSFILE "pgpass.conf"
#endif
 
/*
 * Pre-9.0 servers will return this SQLSTATE if asked to set
 * application_name in a startup packet.  We hard-wire the value rather
 * than looking into errcodes.h since it reflects historical behavior
 * rather than that of the current code.
 */
#define ERRCODE_APPNAME_UNKNOWN "42704"
 
/* This is part of the protocol so just define it */
#define ERRCODE_INVALID_PASSWORD "28P01"
/* These too */
#define ERRCODE_CANNOT_CONNECT_NOW "57P03"
#define ERRCODE_PROTOCOL_VIOLATION "08P01"
 
/*
 * Cope with the various platform-specific ways to spell TCP keepalive socket
 * options.  This doesn't cover Windows, which as usual does its own thing.
 */
#if defined(TCP_KEEPIDLE)
/* TCP_KEEPIDLE is the name of this option on Linux and *BSD */
#define PG_TCP_KEEPALIVE_IDLE TCP_KEEPIDLE
#define PG_TCP_KEEPALIVE_IDLE_STR "TCP_KEEPIDLE"
#elif defined(TCP_KEEPALIVE_THRESHOLD)
/* TCP_KEEPALIVE_THRESHOLD is the name of this option on Solaris >= 11 */
#define PG_TCP_KEEPALIVE_IDLE TCP_KEEPALIVE_THRESHOLD
#define PG_TCP_KEEPALIVE_IDLE_STR "TCP_KEEPALIVE_THRESHOLD"
#elif defined(TCP_KEEPALIVE) && defined(__darwin__)
/* TCP_KEEPALIVE is the name of this option on macOS */
/* Caution: Solaris has this symbol but it means something different */
#define PG_TCP_KEEPALIVE_IDLE TCP_KEEPALIVE
#define PG_TCP_KEEPALIVE_IDLE_STR "TCP_KEEPALIVE"
#endif
 
/*
 * fall back options if they are not specified by arguments or defined
 * by environment variables
 */
#define DefaultHost     "localhost"
#define DefaultOption   ""
#ifdef USE_SSL
#define DefaultChannelBinding   "prefer"
#else
#define DefaultChannelBinding   "disable"
#endif
#define DefaultTargetSessionAttrs   "any"
#define DefaultLoadBalanceHosts "disable"
#ifdef USE_SSL
#define DefaultSSLMode "prefer"
#define DefaultSSLCertMode "allow"
#else
#define DefaultSSLMode  "disable"
#define DefaultSSLCertMode "disable"
#endif
#define DefaultSSLNegotiation   "postgres"
#ifdef ENABLE_GSS
#include "fe-gssapi-common.h"
#define DefaultGSSMode "prefer"
#else
#define DefaultGSSMode "disable"
#endif
 
/* ----------
 * Definition of the conninfo parameters and their fallback resources.
 *
 * If Environment-Var and Compiled-in are specified as NULL, no
 * fallback is available. If after all no value can be determined
 * for an option, an error is returned.
 *
 * The value for the username is treated specially in conninfo_add_defaults.
 * If the value is not obtained any other way, the username is determined
 * by pg_fe_getauthname().
 *
 * The Label and Disp-Char entries are provided for applications that
 * want to use PQconndefaults() to create a generic database connection
 * dialog. Disp-Char is defined as follows:
 *      ""      Normal input field
 *      "*"     Password field - hide value
 *      "D"     Debug option - don't show by default
 *
 * NB: Server-side clients -- dblink, postgres_fdw, libpqrcv -- use dispchar to
 * determine which options to expose to end users, and how. Changing dispchar
 * has compatibility and security implications for those clients. For example,
 * postgres_fdw will attach a "*" option to USER MAPPING instead of the default
 * SERVER, and it disallows setting "D" options entirely.
 *
 * PQconninfoOptions[] is a constant static array that we use to initialize
 * a dynamically allocated working copy.  All the "val" fields in
 * PQconninfoOptions[] *must* be NULL.  In a working copy, non-null "val"
 * fields point to malloc'd strings that should be freed when the working
 * array is freed (see PQconninfoFree).
 *
 * The first part of each struct is identical to the one in libpq-fe.h,
 * which is required since we memcpy() data between the two!
 * ----------
 */
typedef struct _internalPQconninfoOption
{
    char       *keyword;        /* The keyword of the option            */
    char       *envvar;         /* Fallback environment variable name   */
    char       *compiled;       /* Fallback compiled in default value   */
    char       *val;            /* Option's current value, or NULL      */
    char       *label;          /* Label for field in connect dialog    */
    char       *dispchar;       /* Indicates how to display this field in a
                                 * connect dialog. Values are: "" Display
                                 * entered value as is "*" Password field -
                                 * hide value "D"  Debug option - don't show
                                 * by default */
    int         dispsize;       /* Field size in characters for dialog  */
    /* ---
     * Anything above this comment must be synchronized with
     * PQconninfoOption in libpq-fe.h, since we memcpy() data
     * between them!
     * ---
     */
    off_t       connofs;        /* Offset into PGconn struct, -1 if not there */
} internalPQconninfoOption;
 
static const internalPQconninfoOption PQconninfoOptions[] = {
    {"service", "PGSERVICE", NULL, NULL,
        "Database-Service", "", 20,
    offsetof(struct pg_conn, pgservice)},
 
    {"servicefile", "PGSERVICEFILE", NULL, NULL,
        "Database-Service-File", "", 64,
    offsetof(struct pg_conn, pgservicefile)},
 
    {"user", "PGUSER", NULL, NULL,
        "Database-User", "", 20,
    offsetof(struct pg_conn, pguser)},
 
    {"password", "PGPASSWORD", NULL, NULL,
        "Database-Password", "*", 20,
    offsetof(struct pg_conn, pgpass)},
 
    {"passfile", "PGPASSFILE", NULL, NULL,
        "Database-Password-File", "", 64,
    offsetof(struct pg_conn, pgpassfile)},
 
    {"channel_binding", "PGCHANNELBINDING", DefaultChannelBinding, NULL,
        "Channel-Binding", "", 8,   /* sizeof("require") == 8 */
    offsetof(struct pg_conn, channel_binding)},
 
    {"connect_timeout", "PGCONNECT_TIMEOUT", NULL, NULL,
        "Connect-timeout", "", 10,  /* strlen(INT32_MAX) == 10 */
    offsetof(struct pg_conn, connect_timeout)},
 
    {"dbname", "PGDATABASE", NULL, NULL,
        "Database-Name", "", 20,
    offsetof(struct pg_conn, dbName)},
 
    {"host", "PGHOST", NULL, NULL,
        "Database-Host", "", 40,
    offsetof(struct pg_conn, pghost)},
 
    {"hostaddr", "PGHOSTADDR", NULL, NULL,
        "Database-Host-IP-Address", "", 45,
    offsetof(struct pg_conn, pghostaddr)},
 
    {"port", "PGPORT", DEF_PGPORT_STR, NULL,
        "Database-Port", "", 6,
    offsetof(struct pg_conn, pgport)},
 
    {"client_encoding", "PGCLIENTENCODING", NULL, NULL,
        "Client-Encoding", "", 10,
    offsetof(struct pg_conn, client_encoding_initial)},
 
    {"options", "PGOPTIONS", DefaultOption, NULL,
        "Backend-Options", "", 40,
    offsetof(struct pg_conn, pgoptions)},
 
    {"application_name", "PGAPPNAME", NULL, NULL,
        "Application-Name", "", 64,
    offsetof(struct pg_conn, appname)},
 
    {"fallback_application_name", NULL, NULL, NULL,
        "Fallback-Application-Name", "", 64,
    offsetof(struct pg_conn, fbappname)},
 
    {"keepalives", NULL, NULL, NULL,
        "TCP-Keepalives", "", 1,    /* should be just '0' or '1' */
    offsetof(struct pg_conn, keepalives)},
 
    {"keepalives_idle", NULL, NULL, NULL,
        "TCP-Keepalives-Idle", "", 10,  /* strlen(INT32_MAX) == 10 */
    offsetof(struct pg_conn, keepalives_idle)},
 
    {"keepalives_interval", NULL, NULL, NULL,
        "TCP-Keepalives-Interval", "", 10,  /* strlen(INT32_MAX) == 10 */
    offsetof(struct pg_conn, keepalives_interval)},
 
    {"keepalives_count", NULL, NULL, NULL,
        "TCP-Keepalives-Count", "", 10, /* strlen(INT32_MAX) == 10 */
    offsetof(struct pg_conn, keepalives_count)},
 
    {"tcp_user_timeout", NULL, NULL, NULL,
        "TCP-User-Timeout", "", 10, /* strlen(INT32_MAX) == 10 */
    offsetof(struct pg_conn, pgtcp_user_timeout)},
 
    /*
     * ssl options are allowed even without client SSL support because the
     * client can still handle SSL modes "disable" and "allow". Other
     * parameters have no effect on non-SSL connections, so there is no reason
     * to exclude them since none of them are mandatory.
     */
    {"sslmode", "PGSSLMODE", DefaultSSLMode, NULL,
        "SSL-Mode", "", 12,     /* sizeof("verify-full") == 12 */
    offsetof(struct pg_conn, sslmode)},
 
    {"sslnegotiation", "PGSSLNEGOTIATION", DefaultSSLNegotiation, NULL,
        "SSL-Negotiation", "", 9,   /* sizeof("postgres") == 9  */
    offsetof(struct pg_conn, sslnegotiation)},
 
    {"sslcompression", "PGSSLCOMPRESSION", "0", NULL,
        "SSL-Compression", "", 1,
    offsetof(struct pg_conn, sslcompression)},
 
    {"sslcert", "PGSSLCERT", NULL, NULL,
        "SSL-Client-Cert", "", 64,
    offsetof(struct pg_conn, sslcert)},
 
    {"sslkey", "PGSSLKEY", NULL, NULL,
        "SSL-Client-Key", "", 64,
    offsetof(struct pg_conn, sslkey)},
 
    {"sslcertmode", "PGSSLCERTMODE", NULL, NULL,
        "SSL-Client-Cert-Mode", "", 8,  /* sizeof("disable") == 8 */
    offsetof(struct pg_conn, sslcertmode)},
 
    {"sslpassword", NULL, NULL, NULL,
        "SSL-Client-Key-Password", "*", 20,
    offsetof(struct pg_conn, sslpassword)},
 
    {"sslrootcert", "PGSSLROOTCERT", NULL, NULL,
        "SSL-Root-Certificate", "", 64,
    offsetof(struct pg_conn, sslrootcert)},
 
    {"sslcrl", "PGSSLCRL", NULL, NULL,
        "SSL-Revocation-List", "", 64,
    offsetof(struct pg_conn, sslcrl)},
 
    {"sslcrldir", "PGSSLCRLDIR", NULL, NULL,
        "SSL-Revocation-List-Dir", "", 64,
    offsetof(struct pg_conn, sslcrldir)},
 
    {"sslsni", "PGSSLSNI", "1", NULL,
        "SSL-SNI", "", 1,
    offsetof(struct pg_conn, sslsni)},
 
    {"requirepeer", "PGREQUIREPEER", NULL, NULL,
        "Require-Peer", "", 10,
    offsetof(struct pg_conn, requirepeer)},
 
    {"require_auth", "PGREQUIREAUTH", NULL, NULL,
        "Require-Auth", "", 14, /* sizeof("scram-sha-256") == 14 */
    offsetof(struct pg_conn, require_auth)},
 
    {"min_protocol_version", "PGMINPROTOCOLVERSION",
        NULL, NULL,
        "Min-Protocol-Version", "", 6,  /* sizeof("latest") = 6 */
    offsetof(struct pg_conn, min_protocol_version)},
 
    {"max_protocol_version", "PGMAXPROTOCOLVERSION",
        NULL, NULL,
        "Max-Protocol-Version", "", 6,  /* sizeof("latest") = 6 */
    offsetof(struct pg_conn, max_protocol_version)},
 
    {"ssl_min_protocol_version", "PGSSLMINPROTOCOLVERSION", "TLSv1.2", NULL,
        "SSL-Minimum-Protocol-Version", "", 8,  /* sizeof("TLSv1.x") == 8 */
    offsetof(struct pg_conn, ssl_min_protocol_version)},
 
    {"ssl_max_protocol_version", "PGSSLMAXPROTOCOLVERSION", NULL, NULL,
        "SSL-Maximum-Protocol-Version", "", 8,  /* sizeof("TLSv1.x") == 8 */
    offsetof(struct pg_conn, ssl_max_protocol_version)},
 
    /*
     * As with SSL, all GSS options are exposed even in builds that don't have
     * support.
     */
    {"gssencmode", "PGGSSENCMODE", DefaultGSSMode, NULL,
        "GSSENC-Mode", "", 8,   /* sizeof("disable") == 8 */
    offsetof(struct pg_conn, gssencmode)},
 
    /* Kerberos and GSSAPI authentication support specifying the service name */
    {"krbsrvname", "PGKRBSRVNAME", PG_KRB_SRVNAM, NULL,
        "Kerberos-service-name", "", 20,
    offsetof(struct pg_conn, krbsrvname)},
 
    {"gsslib", "PGGSSLIB", NULL, NULL,
        "GSS-library", "", 7,   /* sizeof("gssapi") == 7 */
    offsetof(struct pg_conn, gsslib)},
 
    {"gssdelegation", "PGGSSDELEGATION", "0", NULL,
        "GSS-delegation", "", 1,
    offsetof(struct pg_conn, gssdelegation)},
 
    {"replication", NULL, NULL, NULL,
        "Replication", "D", 5,
    offsetof(struct pg_conn, replication)},
 
    {"target_session_attrs", "PGTARGETSESSIONATTRS",
        DefaultTargetSessionAttrs, NULL,
        "Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
    offsetof(struct pg_conn, target_session_attrs)},
 
    {"load_balance_hosts", "PGLOADBALANCEHOSTS",
        DefaultLoadBalanceHosts, NULL,
        "Load-Balance-Hosts", "", 8,    /* sizeof("disable") = 8 */
    offsetof(struct pg_conn, load_balance_hosts)},
 
    {"scram_client_key", NULL, NULL, NULL, "SCRAM-Client-Key", "D", SCRAM_MAX_KEY_LEN * 2,
    offsetof(struct pg_conn, scram_client_key)},
 
    {"scram_server_key", NULL, NULL, NULL, "SCRAM-Server-Key", "D", SCRAM_MAX_KEY_LEN * 2,
    offsetof(struct pg_conn, scram_server_key)},
 
    /* OAuth v2 */
    {"oauth_issuer", NULL, NULL, NULL,
        "OAuth-Issuer", "", 40,
    offsetof(struct pg_conn, oauth_issuer)},
 
    {"oauth_client_id", NULL, NULL, NULL,
        "OAuth-Client-ID", "", 40,
    offsetof(struct pg_conn, oauth_client_id)},
 
    {"oauth_client_secret", NULL, NULL, NULL,
        "OAuth-Client-Secret", "*", 40,
    offsetof(struct pg_conn, oauth_client_secret)},
 
    {"oauth_scope", NULL, NULL, NULL,
        "OAuth-Scope", "", 15,
    offsetof(struct pg_conn, oauth_scope)},
 
    {"sslkeylogfile", NULL, NULL, NULL,
        "SSL-Key-Log-File", "D", 64,
    offsetof(struct pg_conn, sslkeylogfile)},
 
    /* Terminating entry --- MUST BE LAST */
    {NULL, NULL, NULL, NULL,
    NULL, NULL, 0}
};
 
static const PQEnvironmentOption EnvironmentOptions[] =
{
    /* common user-interface settings */
    {
        "PGDATESTYLE", "datestyle"
    },
    {
        "PGTZ", "timezone"
    },
    /* internal performance-related settings */
    {
        "PGGEQO", "geqo"
    },
    {
        NULL, NULL
    }
};
 
static const pg_fe_sasl_mech *supported_sasl_mechs[] =
{
    &pg_scram_mech,
    &pg_oauth_mech,
};
#define SASL_MECHANISM_COUNT lengthof(supported_sasl_mechs)
 
/* The connection URI must start with either of the following designators: */
static const char uri_designator[] = "postgresql://";
static const char short_uri_designator[] = "postgres://";
 
static bool connectOptions1(PGconn *conn, const char *conninfo);
static bool init_allowed_encryption_methods(PGconn *conn);
#if defined(USE_SSL) || defined(ENABLE_GSS)
static int  encryption_negotiation_failed(PGconn *conn);
#endif
static bool connection_failed(PGconn *conn);
static bool select_next_encryption_method(PGconn *conn, bool have_valid_connection);
static PGPing internal_ping(PGconn *conn);
static void pqFreeCommandQueue(PGcmdQueueEntry *queue);
static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
static void freePGconn(PGconn *conn);
static void release_conn_addrinfo(PGconn *conn);
static int  store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
static void sendTerminateConn(PGconn *conn);
static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
static PQconninfoOption *parse_connection_string(const char *connstr,
                                                 PQExpBuffer errorMessage, bool use_defaults);
static int  uri_prefix_length(const char *connstr);
static bool recognized_connection_string(const char *connstr);
static PQconninfoOption *conninfo_parse(const char *conninfo,
                                        PQExpBuffer errorMessage, bool use_defaults);
static PQconninfoOption *conninfo_array_parse(const char *const *keywords,
                                              const char *const *values, PQExpBuffer errorMessage,
                                              bool use_defaults, int expand_dbname);
static bool conninfo_add_defaults(PQconninfoOption *options,
                                  PQExpBuffer errorMessage);
static PQconninfoOption *conninfo_uri_parse(const char *uri,
                                            PQExpBuffer errorMessage, bool use_defaults);
static bool conninfo_uri_parse_options(PQconninfoOption *options,
                                       const char *uri, PQExpBuffer errorMessage);
static bool conninfo_uri_parse_params(char *params,
                                      PQconninfoOption *connOptions,
                                      PQExpBuffer errorMessage);
static char *conninfo_uri_decode(const char *str, PQExpBuffer errorMessage);
static bool get_hexdigit(char digit, int *value);
static const char *conninfo_getval(PQconninfoOption *connOptions,
                                   const char *keyword);
static PQconninfoOption *conninfo_storeval(PQconninfoOption *connOptions,
                                           const char *keyword, const char *value,
                                           PQExpBuffer errorMessage, bool ignoreMissing, bool uri_decode);
static PQconninfoOption *conninfo_find(PQconninfoOption *connOptions,
                                       const char *keyword);
static void defaultNoticeReceiver(void *arg, const PGresult *res);
static void defaultNoticeProcessor(void *arg, const char *message);
static int  parseServiceInfo(PQconninfoOption *options,
                             PQExpBuffer errorMessage);
static int  parseServiceFile(const char *serviceFile,
                             const char *service,
                             PQconninfoOption *options,
                             PQExpBuffer errorMessage,
                             bool *group_found);
static char *pwdfMatchesString(char *buf, const char *token);
static char *passwordFromFile(const char *hostname, const char *port,
                              const char *dbname, const char *username,
                              const char *pgpassfile, const char **errmsg);
static void pgpassfileWarning(PGconn *conn);
static void default_threadlock(int acquire);
static bool sslVerifyProtocolVersion(const char *version);
static bool sslVerifyProtocolRange(const char *min, const char *max);
static bool pqParseProtocolVersion(const char *value, ProtocolVersion *result, PGconn *conn, const char *context);
 
 
/* global variable because fe-auth.c needs to access it */
pgthreadlock_t pg_g_threadlock = default_threadlock;
 
 
/*
 *      pqDropConnection
 *
 * Close any physical connection to the server, and reset associated
 * state inside the connection object.  We don't release state that
 * would be needed to reconnect, though, nor local state that might still
 * be useful later.
 *
 * We can always flush the output buffer, since there's no longer any hope
 * of sending that data.  However, unprocessed input data might still be
 * valuable, so the caller must tell us whether to flush that or not.
 */
void
pqDropConnection(PGconn *conn, bool flushInput)
{
    /* Drop any SSL state */
    pqsecure_close(conn);
 
    /* Close the socket itself */
    if (conn->sock != PGINVALID_SOCKET)
        closesocket(conn->sock);
    conn->sock = PGINVALID_SOCKET;
 
    /* Optionally discard any unread data */
    if (flushInput)
        conn->inStart = conn->inCursor = conn->inEnd = 0;
 
    /* Always discard any unsent data */
    conn->outCount = 0;
 
    /* Likewise, discard any pending pipelined commands */
    pqFreeCommandQueue(conn->cmd_queue_head);
    conn->cmd_queue_head = conn->cmd_queue_tail = NULL;
    pqFreeCommandQueue(conn->cmd_queue_recycle);
    conn->cmd_queue_recycle = NULL;
 
    /* Free authentication/encryption state */
    if (conn->cleanup_async_auth)
    {
        /*
         * Any in-progress async authentication should be torn down first so
         * that cleanup_async_auth() can depend on the other authentication
         * state if necessary.
         */
        conn->cleanup_async_auth(conn);
        conn->cleanup_async_auth = NULL;
    }
    conn->async_auth = NULL;
    /* cleanup_async_auth() should have done this, but make sure */
    conn->altsock = PGINVALID_SOCKET;
#ifdef ENABLE_GSS
    {
        OM_uint32   min_s;
 
        if (conn->gcred != GSS_C_NO_CREDENTIAL)
        {
            gss_release_cred(&min_s, &conn->gcred);
            conn->gcred = GSS_C_NO_CREDENTIAL;
        }
        if (conn->gctx)
            gss_delete_sec_context(&min_s, &conn->gctx, GSS_C_NO_BUFFER);
        if (conn->gtarg_nam)
            gss_release_name(&min_s, &conn->gtarg_nam);
        if (conn->gss_SendBuffer)
        {
            free(conn->gss_SendBuffer);
            conn->gss_SendBuffer = NULL;
        }
        if (conn->gss_RecvBuffer)
        {
            free(conn->gss_RecvBuffer);
            conn->gss_RecvBuffer = NULL;
        }
        if (conn->gss_ResultBuffer)
        {
            free(conn->gss_ResultBuffer);
            conn->gss_ResultBuffer = NULL;
        }
        conn->gssenc = false;
    }
#endif
#ifdef ENABLE_SSPI
    if (conn->sspitarget)
    {
        free(conn->sspitarget);
        conn->sspitarget = NULL;
    }
    if (conn->sspicred)
    {
        FreeCredentialsHandle(conn->sspicred);
        free(conn->sspicred);
        conn->sspicred = NULL;
    }
    if (conn->sspictx)
    {
        DeleteSecurityContext(conn->sspictx);
        free(conn->sspictx);
        conn->sspictx = NULL;
    }
    conn->usesspi = 0;
#endif
    if (conn->sasl_state)
    {
        conn->sasl->free(conn->sasl_state);
        conn->sasl_state = NULL;
    }
}
 
/*
 * pqFreeCommandQueue
 * Free all the entries of PGcmdQueueEntry queue passed.
 */
static void
pqFreeCommandQueue(PGcmdQueueEntry *queue)
{
    while (queue != NULL)
    {
        PGcmdQueueEntry *cur = queue;
 
        queue = cur->next;
        free(cur->query);
        free(cur);
    }
}
 
/*
 *      pqDropServerData
 *
 * Clear all connection state data that was received from (or deduced about)
 * the server.  This is essential to do between connection attempts to
 * different servers, else we may incorrectly hold over some data from the
 * old server.
 *
 * It would be better to merge this into pqDropConnection, perhaps, but
 * right now we cannot because that function is called immediately on
 * detection of connection loss (cf. pqReadData, for instance).  This data
 * should be kept until we are actually starting a new connection.
 */
static void
pqDropServerData(PGconn *conn)
{
    PGnotify   *notify;
    pgParameterStatus *pstatus;
 
    /* Forget pending notifies */
    notify = conn->notifyHead;
    while (notify != NULL)
    {
        PGnotify   *prev = notify;
 
        notify = notify->next;
        free(prev);
    }
    conn->notifyHead = conn->notifyTail = NULL;
 
    /* Reset ParameterStatus data, as well as variables deduced from it */
    pstatus = conn->pstatus;
    while (pstatus != NULL)
    {
        pgParameterStatus *prev = pstatus;
 
        pstatus = pstatus->next;
        free(prev);
    }
    conn->pstatus = NULL;
    conn->client_encoding = PG_SQL_ASCII;
    conn->std_strings = false;
    conn->default_transaction_read_only = PG_BOOL_UNKNOWN;
    conn->in_hot_standby = PG_BOOL_UNKNOWN;
    conn->scram_sha_256_iterations = SCRAM_SHA_256_DEFAULT_ITERATIONS;
    conn->sversion = 0;
 
    /* Drop large-object lookup data */
    free(conn->lobjfuncs);
    conn->lobjfuncs = NULL;
 
    /* Reset assorted other per-connection state */
    conn->last_sqlstate[0] = '\0';
    conn->pversion_negotiated = false;
    conn->auth_req_received = false;
    conn->client_finished_auth = false;
    conn->password_needed = false;
    conn->gssapi_used = false;
    conn->write_failed = false;
    free(conn->write_err_msg);
    conn->write_err_msg = NULL;
    conn->oauth_want_retry = false;
 
    /*
     * Cancel connections need to retain their be_pid and be_cancel_key across
     * PQcancelReset invocations, otherwise they would not have access to the
     * secret token of the connection they are supposed to cancel.
     */
    if (!conn->cancelRequest)
    {
        conn->be_pid = 0;
        if (conn->be_cancel_key != NULL)
        {
            free(conn->be_cancel_key);
            conn->be_cancel_key = NULL;
        }
        conn->be_cancel_key_len = 0;
    }
}
 
 
/*
 *      Connecting to a Database
 *
 * There are now six different ways a user of this API can connect to the
 * database.  Two are not recommended for use in new code, because of their
 * lack of extensibility with respect to the passing of options to the
 * backend.  These are PQsetdb and PQsetdbLogin (the former now being a macro
 * to the latter).
 *
 * If it is desired to connect in a synchronous (blocking) manner, use the
 * function PQconnectdb or PQconnectdbParams. The former accepts a string of
 * option = value pairs (or a URI) which must be parsed; the latter takes two
 * NULL terminated arrays instead.
 *
 * To connect in an asynchronous (non-blocking) manner, use the functions
 * PQconnectStart or PQconnectStartParams (which differ in the same way as
 * PQconnectdb and PQconnectdbParams) and PQconnectPoll.
 *
 * The non-exported functions pqConnectDBStart, pqConnectDBComplete are
 * part of the connection procedure implementation.
 */
 
/*
 *      PQconnectdbParams
 *
 * establishes a connection to a postgres backend through the postmaster
 * using connection information in two arrays.
 *
 * The keywords array is defined as
 *
 *     const char *params[] = {"option1", "option2", NULL}
 *
 * The values array is defined as
 *
 *     const char *values[] = {"value1", "value2", NULL}
 *
 * Returns a PGconn* which is needed for all subsequent libpq calls, or NULL
 * if a memory allocation failed.
 * If the status field of the connection returned is CONNECTION_BAD,
 * then some fields may be null'ed out instead of having valid values.
 *
 * You should call PQfinish (if conn is not NULL) regardless of whether this
 * call succeeded.
 */
PGconn *
PQconnectdbParams(const char *const *keywords,
                  const char *const *values,
                  int expand_dbname)
{
    PGconn     *conn = PQconnectStartParams(keywords, values, expand_dbname);
 
    if (conn && conn->status != CONNECTION_BAD)
        (void) pqConnectDBComplete(conn);
 
    return conn;
}
 
/*
 *      PQpingParams
 *
 * check server status, accepting parameters identical to PQconnectdbParams
 */
PGPing
PQpingParams(const char *const *keywords,
             const char *const *values,
             int expand_dbname)
{
    PGconn     *conn = PQconnectStartParams(keywords, values, expand_dbname);
    PGPing      ret;
 
    ret = internal_ping(conn);
    PQfinish(conn);
 
    return ret;
}
 
/*
 *      PQconnectdb
 *
 * establishes a connection to a postgres backend through the postmaster
 * using connection information in a string.
 *
 * The conninfo string is either a whitespace-separated list of
 *
 *     option = value
 *
 * definitions or a URI (refer to the documentation for details.) Value
 * might be a single value containing no whitespaces or a single quoted
 * string. If a single quote should appear anywhere in the value, it must be
 * escaped with a backslash like \'
 *
 * Returns a PGconn* which is needed for all subsequent libpq calls, or NULL
 * if a memory allocation failed.
 * If the status field of the connection returned is CONNECTION_BAD,
 * then some fields may be null'ed out instead of having valid values.
 *
 * You should call PQfinish (if conn is not NULL) regardless of whether this
 * call succeeded.
 */
PGconn *
PQconnectdb(const char *conninfo)
{
    PGconn     *conn = PQconnectStart(conninfo);
 
    if (conn && conn->status != CONNECTION_BAD)
        (void) pqConnectDBComplete(conn);
 
    return conn;
}
 
/*
 *      PQping
 *
 * check server status, accepting parameters identical to PQconnectdb
 */
PGPing
PQping(const char *conninfo)
{
    PGconn     *conn = PQconnectStart(conninfo);
    PGPing      ret;
 
    ret = internal_ping(conn);
    PQfinish(conn);
 
    return ret;
}
 
/*
 *      PQconnectStartParams
 *
 * Begins the establishment of a connection to a postgres backend through the
 * postmaster using connection information in a struct.
 *
 * See comment for PQconnectdbParams for the definition of the string format.
 *
 * Returns a PGconn*.  If NULL is returned, a malloc error has occurred, and
 * you should not attempt to proceed with this connection.  If the status
 * field of the connection returned is CONNECTION_BAD, an error has
 * occurred. In this case you should call PQfinish on the result, (perhaps
 * inspecting the error message first).  Other fields of the structure may not
 * be valid if that occurs.  If the status field is not CONNECTION_BAD, then
 * this stage has succeeded - call PQconnectPoll, using select(2) to see when
 * this is necessary.
 *
 * See PQconnectPoll for more info.
 */
PGconn *
PQconnectStartParams(const char *const *keywords,
                     const char *const *values,
                     int expand_dbname)
{
    PGconn     *conn;
    PQconninfoOption *connOptions;
 
    /*
     * Allocate memory for the conn structure.  Note that we also expect this
     * to initialize conn->errorMessage to empty.  All subsequent steps during
     * connection initialization will only append to that buffer.
     */
    conn = pqMakeEmptyPGconn();
    if (conn == NULL)
        return NULL;
 
    /*
     * Parse the conninfo arrays
     */
    connOptions = conninfo_array_parse(keywords, values,
                                       &conn->errorMessage,
                                       true, expand_dbname);
    if (connOptions == NULL)
    {
        conn->status = CONNECTION_BAD;
        /* errorMessage is already set */
        return conn;
    }
 
    /*
     * Move option values into conn structure
     */
    if (!fillPGconn(conn, connOptions))
    {
        PQconninfoFree(connOptions);
        return conn;
    }
 
    /*
     * Free the option info - all is in conn now
     */
    PQconninfoFree(connOptions);
 
    /*
     * Compute derived options
     */
    if (!pqConnectOptions2(conn))
        return conn;
 
    /*
     * Connect to the database
     */
    if (!pqConnectDBStart(conn))
    {
        /* Just in case we failed to set it in pqConnectDBStart */
        conn->status = CONNECTION_BAD;
    }
 
    return conn;
}
 
/*
 *      PQconnectStart
 *
 * Begins the establishment of a connection to a postgres backend through the
 * postmaster using connection information in a string.
 *
 * See comment for PQconnectdb for the definition of the string format.
 *
 * Returns a PGconn*.  If NULL is returned, a malloc error has occurred, and
 * you should not attempt to proceed with this connection.  If the status
 * field of the connection returned is CONNECTION_BAD, an error has
 * occurred. In this case you should call PQfinish on the result, (perhaps
 * inspecting the error message first).  Other fields of the structure may not
 * be valid if that occurs.  If the status field is not CONNECTION_BAD, then
 * this stage has succeeded - call PQconnectPoll, using select(2) to see when
 * this is necessary.
 *
 * See PQconnectPoll for more info.
 */
PGconn *
PQconnectStart(const char *conninfo)
{
    PGconn     *conn;
 
    /*
     * Allocate memory for the conn structure.  Note that we also expect this
     * to initialize conn->errorMessage to empty.  All subsequent steps during
     * connection initialization will only append to that buffer.
     */
    conn = pqMakeEmptyPGconn();
    if (conn == NULL)
        return NULL;
 
    /*
     * Parse the conninfo string
     */
    if (!connectOptions1(conn, conninfo))
        return conn;
 
    /*
     * Compute derived options
     */
    if (!pqConnectOptions2(conn))
        return conn;
 
    /*
     * Connect to the database
     */
    if (!pqConnectDBStart(conn))
    {
        /* Just in case we failed to set it in pqConnectDBStart */
        conn->status = CONNECTION_BAD;
    }
 
    return conn;
}
 
/*
 * Move option values into conn structure
 *
 * Don't put anything cute here --- intelligence should be in
 * pqConnectOptions2 ...
 *
 * Returns true on success. On failure, returns false and sets error message.
 */
static bool
fillPGconn(PGconn *conn, PQconninfoOption *connOptions)
{
    const internalPQconninfoOption *option;
 
    for (option = PQconninfoOptions; option->keyword; option++)
    {
        if (option->connofs >= 0)
        {
            const char *tmp = conninfo_getval(connOptions, option->keyword);
 
            if (tmp)
            {
                char      **connmember = (char **) ((char *) conn + option->connofs);
 
                free(*connmember);
                *connmember = strdup(tmp);
                if (*connmember == NULL)
                {
                    libpq_append_conn_error(conn, "out of memory");
                    return false;
                }
            }
        }
    }
 
    return true;
}
 
/*
 * Copy over option values from srcConn to dstConn
 *
 * Don't put anything cute here --- intelligence should be in
 * pqConnectOptions2 ...
 *
 * Returns true on success. On failure, returns false and sets error message of
 * dstConn.
 */
bool
pqCopyPGconn(PGconn *srcConn, PGconn *dstConn)
{
    const internalPQconninfoOption *option;
 
    /* copy over connection options */
    for (option = PQconninfoOptions; option->keyword; option++)
    {
        if (option->connofs >= 0)
        {
            const char **tmp = (const char **) ((char *) srcConn + option->connofs);
 
            if (*tmp)
            {
                char      **dstConnmember = (char **) ((char *) dstConn + option->connofs);
 
                if (*dstConnmember)
                    free(*dstConnmember);
                *dstConnmember = strdup(*tmp);
                if (*dstConnmember == NULL)
                {
                    libpq_append_conn_error(dstConn, "out of memory");
                    return false;
                }
            }
        }
    }
    return true;
}
 
/*
 *      connectOptions1
 *
 * Internal subroutine to set up connection parameters given an already-
 * created PGconn and a conninfo string.  Derived settings should be
 * processed by calling pqConnectOptions2 next.  (We split them because
 * PQsetdbLogin overrides defaults in between.)
 *
 * Returns true if OK, false if trouble (in which case errorMessage is set
 * and so is conn->status).
 */
static bool
connectOptions1(PGconn *conn, const char *conninfo)
{
    PQconninfoOption *connOptions;
 
    /*
     * Parse the conninfo string
     */
    connOptions = parse_connection_string(conninfo, &conn->errorMessage, true);
    if (connOptions == NULL)
    {
        conn->status = CONNECTION_BAD;
        /* errorMessage is already set */
        return false;
    }
 
    /*
     * Move option values into conn structure
     */
    if (!fillPGconn(conn, connOptions))
    {
        conn->status = CONNECTION_BAD;
        PQconninfoFree(connOptions);
        return false;
    }
 
    /*
     * Free the option info - all is in conn now
     */
    PQconninfoFree(connOptions);
 
    return true;
}
 
/*
 * Count the number of elements in a simple comma-separated list.
 */
static int
count_comma_separated_elems(const char *input)
{
    int         n;
 
    n = 1;
    for (; *input != '\0'; input++)
    {
        if (*input == ',')
            n++;
    }
 
    return n;
}
 
/*
 * Parse a simple comma-separated list.
 *
 * On each call, returns a malloc'd copy of the next element, and sets *more
 * to indicate whether there are any more elements in the list after this,
 * and updates *startptr to point to the next element, if any.
 *
 * On out of memory, returns NULL.
 */
static char *
parse_comma_separated_list(char **startptr, bool *more)
{
    char       *p;
    char       *s = *startptr;
    char       *e;
    size_t      len;
 
    /*
     * Search for the end of the current element; a comma or end-of-string
     * acts as a terminator.
     */
    e = s;
    while (*e != '\0' && *e != ',')
        ++e;
    *more = (*e == ',');
 
    len = e - s;
    p = (char *) malloc(sizeof(char) * (len + 1));
    if (p)
    {
        memcpy(p, s, len);
        p[len] = '\0';
    }
    *startptr = e + 1;
 
    return p;
}
 
/*
 * Initializes the prng_state field of the connection. We want something
 * unpredictable, so if possible, use high-quality random bits for the
 * seed. Otherwise, fall back to a seed based on the connection address,
 * timestamp and PID.
 */
static void
libpq_prng_init(PGconn *conn)
{
    uint64      rseed;
    struct timeval tval = {0};
 
    if (pg_prng_strong_seed(&conn->prng_state))
        return;
 
    gettimeofday(&tval, NULL);
 
    rseed = ((uintptr_t) conn) ^
        ((uint64) getpid()) ^
        ((uint64) tval.tv_usec) ^
        ((uint64) tval.tv_sec);
 
    pg_prng_seed(&conn->prng_state, rseed);
}
 
/*
 * Fills the connection's allowed_sasl_mechs list with all supported SASL
 * mechanisms.
 */
static inline void
fill_allowed_sasl_mechs(PGconn *conn)
{
    /*---
     * We only support two mechanisms at the moment, so rather than deal with a
     * linked list, conn->allowed_sasl_mechs is an array of static length. We
     * rely on the compile-time assertion here to keep us honest.
     *
     * To add a new mechanism to require_auth,
     * - add it to supported_sasl_mechs,
     * - update the length of conn->allowed_sasl_mechs,
     * - handle the new mechanism name in the require_auth portion of
     *   pqConnectOptions2(), below.
     */
    StaticAssertDecl(lengthof(conn->allowed_sasl_mechs) == SASL_MECHANISM_COUNT,
                     "conn->allowed_sasl_mechs[] is not sufficiently large for holding all supported SASL mechanisms");
 
    for (int i = 0; i < SASL_MECHANISM_COUNT; i++)
        conn->allowed_sasl_mechs[i] = supported_sasl_mechs[i];
}
 
/*
 * Clears the connection's allowed_sasl_mechs list.
 */
static inline void
clear_allowed_sasl_mechs(PGconn *conn)
{
    for (int i = 0; i < lengthof(conn->allowed_sasl_mechs); i++)
        conn->allowed_sasl_mechs[i] = NULL;
}
 
/*
 * Helper routine that searches the static allowed_sasl_mechs list for a
 * specific mechanism.
 */
static inline int
index_of_allowed_sasl_mech(PGconn *conn, const pg_fe_sasl_mech *mech)
{
    for (int i = 0; i < lengthof(conn->allowed_sasl_mechs); i++)
    {
        if (conn->allowed_sasl_mechs[i] == mech)
            return i;
    }
 
    return -1;
}
 
/*
 *      pqConnectOptions2
 *
 * Compute derived connection options after absorbing all user-supplied info.
 *
 * Returns true if OK, false if trouble (in which case errorMessage is set
 * and so is conn->status).
 */
bool
pqConnectOptions2(PGconn *conn)
{
    int         i;
 
    /*
     * Allocate memory for details about each host to which we might possibly
     * try to connect.  For that, count the number of elements in the hostaddr
     * or host options.  If neither is given, assume one host.
     */
    conn->whichhost = 0;
    if (conn->pghostaddr && conn->pghostaddr[0] != '\0')
        conn->nconnhost = count_comma_separated_elems(conn->pghostaddr);
    else if (conn->pghost && conn->pghost[0] != '\0')
        conn->nconnhost = count_comma_separated_elems(conn->pghost);
    else
        conn->nconnhost = 1;
    conn->connhost = (pg_conn_host *)
        calloc(conn->nconnhost, sizeof(pg_conn_host));
    if (conn->connhost == NULL)
        goto oom_error;
 
    /*
     * We now have one pg_conn_host structure per possible host.  Fill in the
     * host and hostaddr fields for each, by splitting the parameter strings.
     */
    if (conn->pghostaddr != NULL && conn->pghostaddr[0] != '\0')
    {
        char       *s = conn->pghostaddr;
        bool        more = true;
 
        for (i = 0; i < conn->nconnhost && more; i++)
        {
            conn->connhost[i].hostaddr = parse_comma_separated_list(&s, &more);
            if (conn->connhost[i].hostaddr == NULL)
                goto oom_error;
        }
 
        /*
         * If hostaddr was given, the array was allocated according to the
         * number of elements in the hostaddr list, so it really should be the
         * right size.
         */
        Assert(!more);
        Assert(i == conn->nconnhost);
    }
 
    if (conn->pghost != NULL && conn->pghost[0] != '\0')
    {
        char       *s = conn->pghost;
        bool        more = true;
 
        for (i = 0; i < conn->nconnhost && more; i++)
        {
            conn->connhost[i].host = parse_comma_separated_list(&s, &more);
            if (conn->connhost[i].host == NULL)
                goto oom_error;
        }
 
        /* Check for wrong number of host items. */
        if (more || i != conn->nconnhost)
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "could not match %d host names to %d hostaddr values",
                                    count_comma_separated_elems(conn->pghost), conn->nconnhost);
            return false;
        }
    }
 
    /*
     * Now, for each host slot, identify the type of address spec, and fill in
     * the default address if nothing was given.
     */
    for (i = 0; i < conn->nconnhost; i++)
    {
        pg_conn_host *ch = &conn->connhost[i];
 
        if (ch->hostaddr != NULL && ch->hostaddr[0] != '\0')
            ch->type = CHT_HOST_ADDRESS;
        else if (ch->host != NULL && ch->host[0] != '\0')
        {
            ch->type = CHT_HOST_NAME;
            if (is_unixsock_path(ch->host))
                ch->type = CHT_UNIX_SOCKET;
        }
        else
        {
            free(ch->host);
 
            /*
             * This bit selects the default host location.  If you change
             * this, see also pg_regress.
             */
            if (DEFAULT_PGSOCKET_DIR[0])
            {
                ch->host = strdup(DEFAULT_PGSOCKET_DIR);
                ch->type = CHT_UNIX_SOCKET;
            }
            else
            {
                ch->host = strdup(DefaultHost);
                ch->type = CHT_HOST_NAME;
            }
            if (ch->host == NULL)
                goto oom_error;
        }
    }
 
    /*
     * Next, work out the port number corresponding to each host name.
     *
     * Note: unlike the above for host names, this could leave the port fields
     * as null or empty strings.  We will substitute DEF_PGPORT whenever we
     * read such a port field.
     */
    if (conn->pgport != NULL && conn->pgport[0] != '\0')
    {
        char       *s = conn->pgport;
        bool        more = true;
 
        for (i = 0; i < conn->nconnhost && more; i++)
        {
            conn->connhost[i].port = parse_comma_separated_list(&s, &more);
            if (conn->connhost[i].port == NULL)
                goto oom_error;
        }
 
        /*
         * If exactly one port was given, use it for every host.  Otherwise,
         * there must be exactly as many ports as there were hosts.
         */
        if (i == 1 && !more)
        {
            for (i = 1; i < conn->nconnhost; i++)
            {
                conn->connhost[i].port = strdup(conn->connhost[0].port);
                if (conn->connhost[i].port == NULL)
                    goto oom_error;
            }
        }
        else if (more || i != conn->nconnhost)
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "could not match %d port numbers to %d hosts",
                                    count_comma_separated_elems(conn->pgport), conn->nconnhost);
            return false;
        }
    }
 
    /*
     * If user name was not given, fetch it.  (Most likely, the fetch will
     * fail, since the only way we get here is if pg_fe_getauthname() failed
     * during conninfo_add_defaults().  But now we want an error message.)
     */
    if (conn->pguser == NULL || conn->pguser[0] == '\0')
    {
        free(conn->pguser);
        conn->pguser = pg_fe_getauthname(&conn->errorMessage);
        if (!conn->pguser)
        {
            conn->status = CONNECTION_BAD;
            return false;
        }
    }
 
    /*
     * If database name was not given, default it to equal user name
     */
    if (conn->dbName == NULL || conn->dbName[0] == '\0')
    {
        free(conn->dbName);
        conn->dbName = strdup(conn->pguser);
        if (!conn->dbName)
            goto oom_error;
    }
 
    /*
     * If password was not given, try to look it up in password file.  Note
     * that the result might be different for each host/port pair.
     */
    if (conn->pgpass == NULL || conn->pgpass[0] == '\0')
    {
        /* If password file wasn't specified, use ~/PGPASSFILE */
        if (conn->pgpassfile == NULL || conn->pgpassfile[0] == '\0')
        {
            char        homedir[MAXPGPATH];
 
            if (pqGetHomeDirectory(homedir, sizeof(homedir)))
            {
                free(conn->pgpassfile);
                conn->pgpassfile = malloc(MAXPGPATH);
                if (!conn->pgpassfile)
                    goto oom_error;
                snprintf(conn->pgpassfile, MAXPGPATH, "%s/%s",
                         homedir, PGPASSFILE);
            }
        }
 
        if (conn->pgpassfile != NULL && conn->pgpassfile[0] != '\0')
        {
            for (i = 0; i < conn->nconnhost; i++)
            {
                /*
                 * Try to get a password for this host from file.  We use host
                 * for the hostname search key if given, else hostaddr (at
                 * least one of them is guaranteed nonempty by now).
                 */
                const char *pwhost = conn->connhost[i].host;
                const char *password_errmsg = NULL;
 
                if (pwhost == NULL || pwhost[0] == '\0')
                    pwhost = conn->connhost[i].hostaddr;
 
                conn->connhost[i].password =
                    passwordFromFile(pwhost,
                                     conn->connhost[i].port,
                                     conn->dbName,
                                     conn->pguser,
                                     conn->pgpassfile,
                                     &password_errmsg);
 
                if (password_errmsg != NULL)
                {
                    conn->status = CONNECTION_BAD;
                    libpq_append_conn_error(conn, "%s", password_errmsg);
                    return false;
                }
            }
        }
    }
 
    /*
     * parse and validate require_auth option
     */
    if (conn->require_auth && conn->require_auth[0])
    {
        char       *s = conn->require_auth;
        bool        first,
                    more;
        bool        negated = false;
 
        /*
         * By default, start from an empty set of allowed methods and
         * mechanisms, and add to it.
         */
        conn->auth_required = true;
        conn->allowed_auth_methods = 0;
        clear_allowed_sasl_mechs(conn);
 
        for (first = true, more = true; more; first = false)
        {
            char       *method,
                       *part;
            uint32      bits = 0;
            const pg_fe_sasl_mech *mech = NULL;
 
            part = parse_comma_separated_list(&s, &more);
            if (part == NULL)
                goto oom_error;
 
            /*
             * Check for negation, e.g. '!password'. If one element is
             * negated, they all have to be.
             */
            method = part;
            if (*method == '!')
            {
                if (first)
                {
                    /*
                     * Switch to a permissive set of allowed methods and
                     * mechanisms, and subtract from it.
                     */
                    conn->auth_required = false;
                    conn->allowed_auth_methods = -1;
                    fill_allowed_sasl_mechs(conn);
                }
                else if (!negated)
                {
                    conn->status = CONNECTION_BAD;
                    libpq_append_conn_error(conn, "negative require_auth method \"%s\" cannot be mixed with non-negative methods",
                                            method);
 
                    free(part);
                    return false;
                }
 
                negated = true;
                method++;
            }
            else if (negated)
            {
                conn->status = CONNECTION_BAD;
                libpq_append_conn_error(conn, "require_auth method \"%s\" cannot be mixed with negative methods",
                                        method);
 
                free(part);
                return false;
            }
 
            /*
             * First group: methods that can be handled solely with the
             * authentication request codes.
             */
            if (strcmp(method, "password") == 0)
            {
                bits = (1 << AUTH_REQ_PASSWORD);
            }
            else if (strcmp(method, "md5") == 0)
            {
                bits = (1 << AUTH_REQ_MD5);
            }
            else if (strcmp(method, "gss") == 0)
            {
                bits = (1 << AUTH_REQ_GSS);
                bits |= (1 << AUTH_REQ_GSS_CONT);
            }
            else if (strcmp(method, "sspi") == 0)
            {
                bits = (1 << AUTH_REQ_SSPI);
                bits |= (1 << AUTH_REQ_GSS_CONT);
            }
 
            /*
             * Next group: SASL mechanisms. All of these use the same request
             * codes, so the list of allowed mechanisms is tracked separately.
             *
             * supported_sasl_mechs must contain all mechanisms handled here.
             */
            else if (strcmp(method, "scram-sha-256") == 0)
            {
                mech = &pg_scram_mech;
            }
            else if (strcmp(method, "oauth") == 0)
            {
                mech = &pg_oauth_mech;
            }
 
            /*
             * Final group: meta-options.
             */
            else if (strcmp(method, "none") == 0)
            {
                /*
                 * Special case: let the user explicitly allow (or disallow)
                 * connections where the server does not send an explicit
                 * authentication challenge, such as "trust" and "cert" auth.
                 */
                if (negated)    /* "!none" */
                {
                    if (conn->auth_required)
                        goto duplicate;
 
                    conn->auth_required = true;
                }
                else            /* "none" */
                {
                    if (!conn->auth_required)
                        goto duplicate;
 
                    conn->auth_required = false;
                }
 
                free(part);
                continue;       /* avoid the bitmask manipulation below */
            }
            else
            {
                conn->status = CONNECTION_BAD;
                libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
                                        "require_auth", method);
 
                free(part);
                return false;
            }
 
            if (mech)
            {
                /*
                 * Update the mechanism set only. The method bitmask will be
                 * updated for SASL further down.
                 */
                Assert(!bits);
 
                if (negated)
                {
                    /* Remove the existing mechanism from the list. */
                    i = index_of_allowed_sasl_mech(conn, mech);
                    if (i < 0)
                        goto duplicate;
 
                    conn->allowed_sasl_mechs[i] = NULL;
                }
                else
                {
                    /*
                     * Find a space to put the new mechanism (after making
                     * sure it's not already there).
                     */
                    i = index_of_allowed_sasl_mech(conn, mech);
                    if (i >= 0)
                        goto duplicate;
 
                    i = index_of_allowed_sasl_mech(conn, NULL);
                    if (i < 0)
                    {
                        /* Should not happen; the pointer list is corrupted. */
                        Assert(false);
 
                        conn->status = CONNECTION_BAD;
                        libpq_append_conn_error(conn,
                                                "internal error: no space in allowed_sasl_mechs");
                        free(part);
                        return false;
                    }
 
                    conn->allowed_sasl_mechs[i] = mech;
                }
            }
            else
            {
                /* Update the method bitmask. */
                Assert(bits);
 
                if (negated)
                {
                    if ((conn->allowed_auth_methods & bits) == 0)
                        goto duplicate;
 
                    conn->allowed_auth_methods &= ~bits;
                }
                else
                {
                    if ((conn->allowed_auth_methods & bits) == bits)
                        goto duplicate;
 
                    conn->allowed_auth_methods |= bits;
                }
            }
 
            free(part);
            continue;
 
    duplicate:
 
            /*
             * A duplicated method probably indicates a typo in a setting
             * where typos are extremely risky.
             */
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "require_auth method \"%s\" is specified more than once",
                                    part);
 
            free(part);
            return false;
        }
 
        /*
         * Finally, allow SASL authentication requests if (and only if) we've
         * allowed any mechanisms.
         */
        {
            bool        allowed = false;
            const uint32 sasl_bits =
                (1 << AUTH_REQ_SASL)
                | (1 << AUTH_REQ_SASL_CONT)
                | (1 << AUTH_REQ_SASL_FIN);
 
            for (i = 0; i < lengthof(conn->allowed_sasl_mechs); i++)
            {
                if (conn->allowed_sasl_mechs[i])
                {
                    allowed = true;
                    break;
                }
            }
 
            /*
             * For the standard case, add the SASL bits to the (default-empty)
             * set if needed. For the negated case, remove them.
             */
            if (!negated && allowed)
                conn->allowed_auth_methods |= sasl_bits;
            else if (negated && !allowed)
                conn->allowed_auth_methods &= ~sasl_bits;
        }
    }
 
    /*
     * validate channel_binding option
     */
    if (conn->channel_binding)
    {
        if (strcmp(conn->channel_binding, "disable") != 0
            && strcmp(conn->channel_binding, "prefer") != 0
            && strcmp(conn->channel_binding, "require") != 0)
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
                                    "channel_binding", conn->channel_binding);
            return false;
        }
    }
    else
    {
        conn->channel_binding = strdup(DefaultChannelBinding);
        if (!conn->channel_binding)
            goto oom_error;
    }
 
#ifndef USE_SSL
 
    /*
     * sslrootcert=system is not supported. Since setting this changes the
     * default sslmode, check this _before_ we validate sslmode, to avoid
     * confusing the user with errors for an option they may not have set.
     */
    if (conn->sslrootcert
        && strcmp(conn->sslrootcert, "system") == 0)
    {
        conn->status = CONNECTION_BAD;
        libpq_append_conn_error(conn, "%s value \"%s\" invalid when SSL support is not compiled in",
                                "sslrootcert", conn->sslrootcert);
        return false;
    }
#endif
 
    /*
     * validate sslmode option
     */
    if (conn->sslmode)
    {
        if (strcmp(conn->sslmode, "disable") != 0
            && strcmp(conn->sslmode, "allow") != 0
            && strcmp(conn->sslmode, "prefer") != 0
            && strcmp(conn->sslmode, "require") != 0
            && strcmp(conn->sslmode, "verify-ca") != 0
            && strcmp(conn->sslmode, "verify-full") != 0)
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
                                    "sslmode", conn->sslmode);
            return false;
        }
 
#ifndef USE_SSL
        switch (conn->sslmode[0])
        {
            case 'a':           /* "allow" */
            case 'p':           /* "prefer" */
 
                /*
                 * warn user that an SSL connection will never be negotiated
                 * since SSL was not compiled in?
                 */
                break;
 
            case 'r':           /* "require" */
            case 'v':           /* "verify-ca" or "verify-full" */
                conn->status = CONNECTION_BAD;
                libpq_append_conn_error(conn, "%s value \"%s\" invalid when SSL support is not compiled in",
                                        "sslmode", conn->sslmode);
                return false;
        }
#endif
    }
    else
    {
        conn->sslmode = strdup(DefaultSSLMode);
        if (!conn->sslmode)
            goto oom_error;
    }
 
    /*
     * validate sslnegotiation option, default is "postgres" for the postgres
     * style negotiated connection with an extra round trip but more options.
     */
    if (conn->sslnegotiation)
    {
        if (strcmp(conn->sslnegotiation, "postgres") != 0
            && strcmp(conn->sslnegotiation, "direct") != 0)
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
                                    "sslnegotiation", conn->sslnegotiation);
            return false;
        }
 
#ifndef USE_SSL
        if (conn->sslnegotiation[0] != 'p')
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "%s value \"%s\" invalid when SSL support is not compiled in",
                                    "sslnegotiation", conn->sslnegotiation);
            return false;
        }
#endif
 
        /*
         * Don't allow direct SSL negotiation with sslmode='prefer', because
         * that poses a risk of unintentional fallback to plaintext connection
         * when connecting to a pre-v17 server that does not support direct
         * SSL connections. To keep things simple, don't allow it with
         * sslmode='allow' or sslmode='disable' either. If a user goes through
         * the trouble of setting sslnegotiation='direct', they probably
         * intend to use SSL, and sslmode=disable or allow is probably a user
         * mistake anyway.
         */
        if (conn->sslnegotiation[0] == 'd' &&
            conn->sslmode[0] != 'r' && conn->sslmode[0] != 'v')
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "weak sslmode \"%s\" may not be used with sslnegotiation=direct (use \"require\", \"verify-ca\", or \"verify-full\")",
                                    conn->sslmode);
            return false;
        }
    }
    else
    {
        conn->sslnegotiation = strdup(DefaultSSLNegotiation);
        if (!conn->sslnegotiation)
            goto oom_error;
    }
 
#ifdef USE_SSL
 
    /*
     * If sslrootcert=system, make sure our chosen sslmode is compatible.
     */
    if (conn->sslrootcert
        && strcmp(conn->sslrootcert, "system") == 0
        && strcmp(conn->sslmode, "verify-full") != 0)
    {
        conn->status = CONNECTION_BAD;
        libpq_append_conn_error(conn, "weak sslmode \"%s\" may not be used with sslrootcert=system (use \"verify-full\")",
                                conn->sslmode);
        return false;
    }
#endif
 
    /*
     * Validate TLS protocol versions for ssl_min_protocol_version and
     * ssl_max_protocol_version.
     */
    if (!sslVerifyProtocolVersion(conn->ssl_min_protocol_version))
    {
        conn->status = CONNECTION_BAD;
        libpq_append_conn_error(conn, "invalid \"%s\" value: \"%s\"",
                                "ssl_min_protocol_version",
                                conn->ssl_min_protocol_version);
        return false;
    }
    if (!sslVerifyProtocolVersion(conn->ssl_max_protocol_version))
    {
        conn->status = CONNECTION_BAD;
        libpq_append_conn_error(conn, "invalid \"%s\" value: \"%s\"",
                                "ssl_max_protocol_version",
                                conn->ssl_max_protocol_version);
        return false;
    }
 
    /*
     * Check if the range of SSL protocols defined is correct.  This is done
     * at this early step because this is independent of the SSL
     * implementation used, and this avoids unnecessary cycles with an
     * already-built SSL context when the connection is being established, as
     * it would be doomed anyway.
     */
    if (!sslVerifyProtocolRange(conn->ssl_min_protocol_version,
                                conn->ssl_max_protocol_version))
    {
        conn->status = CONNECTION_BAD;
        libpq_append_conn_error(conn, "invalid SSL protocol version range");
        return false;
    }
 
    /*
     * validate sslcertmode option
     */
    if (conn->sslcertmode)
    {
        if (strcmp(conn->sslcertmode, "disable") != 0 &&
            strcmp(conn->sslcertmode, "allow") != 0 &&
            strcmp(conn->sslcertmode, "require") != 0)
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
                                    "sslcertmode", conn->sslcertmode);
            return false;
        }
#ifndef USE_SSL
        if (strcmp(conn->sslcertmode, "require") == 0)
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "%s value \"%s\" invalid when SSL support is not compiled in",
                                    "sslcertmode", conn->sslcertmode);
            return false;
        }
#endif
#ifndef HAVE_SSL_CTX_SET_CERT_CB
 
        /*
         * Without a certificate callback, the current implementation can't
         * figure out if a certificate was actually requested, so "require" is
         * useless.
         */
        if (strcmp(conn->sslcertmode, "require") == 0)
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "%s value \"%s\" is not supported (check OpenSSL version)",
                                    "sslcertmode", conn->sslcertmode);
            return false;
        }
#endif
    }
    else
    {
        conn->sslcertmode = strdup(DefaultSSLCertMode);
        if (!conn->sslcertmode)
            goto oom_error;
    }
 
    /*
     * validate gssencmode option
     */
    if (conn->gssencmode)
    {
        if (strcmp(conn->gssencmode, "disable") != 0 &&
            strcmp(conn->gssencmode, "prefer") != 0 &&
            strcmp(conn->gssencmode, "require") != 0)
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "invalid %s value: \"%s\"", "gssencmode", conn->gssencmode);
            return false;
        }
#ifndef ENABLE_GSS
        if (strcmp(conn->gssencmode, "require") == 0)
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "gssencmode value \"%s\" invalid when GSSAPI support is not compiled in",
                                    conn->gssencmode);
            return false;
        }
#endif
    }
    else
    {
        conn->gssencmode = strdup(DefaultGSSMode);
        if (!conn->gssencmode)
            goto oom_error;
    }
 
    /*
     * validate target_session_attrs option, and set target_server_type
     */
    if (conn->target_session_attrs)
    {
        if (strcmp(conn->target_session_attrs, "any") == 0)
            conn->target_server_type = SERVER_TYPE_ANY;
        else if (strcmp(conn->target_session_attrs, "read-write") == 0)
            conn->target_server_type = SERVER_TYPE_READ_WRITE;
        else if (strcmp(conn->target_session_attrs, "read-only") == 0)
            conn->target_server_type = SERVER_TYPE_READ_ONLY;
        else if (strcmp(conn->target_session_attrs, "primary") == 0)
            conn->target_server_type = SERVER_TYPE_PRIMARY;
        else if (strcmp(conn->target_session_attrs, "standby") == 0)
            conn->target_server_type = SERVER_TYPE_STANDBY;
        else if (strcmp(conn->target_session_attrs, "prefer-standby") == 0)
            conn->target_server_type = SERVER_TYPE_PREFER_STANDBY;
        else
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
                                    "target_session_attrs",
                                    conn->target_session_attrs);
            return false;
        }
    }
    else
        conn->target_server_type = SERVER_TYPE_ANY;
 
    if (conn->scram_client_key)
    {
        int         len;
 
        len = pg_b64_dec_len(strlen(conn->scram_client_key));
        conn->scram_client_key_binary = malloc(len);
        if (!conn->scram_client_key_binary)
            goto oom_error;
        len = pg_b64_decode(conn->scram_client_key, strlen(conn->scram_client_key),
                            conn->scram_client_key_binary, len);
        if (len < 0)
        {
            libpq_append_conn_error(conn, "invalid SCRAM client key");
            return false;
        }
        if (len != SCRAM_MAX_KEY_LEN)
        {
            libpq_append_conn_error(conn, "invalid SCRAM client key length: %d", len);
            return false;
        }
        conn->scram_client_key_len = len;
    }
 
    if (conn->scram_server_key)
    {
        int         len;
 
        len = pg_b64_dec_len(strlen(conn->scram_server_key));
        conn->scram_server_key_binary = malloc(len);
        if (!conn->scram_server_key_binary)
            goto oom_error;
        len = pg_b64_decode(conn->scram_server_key, strlen(conn->scram_server_key),
                            conn->scram_server_key_binary, len);
        if (len < 0)
        {
            libpq_append_conn_error(conn, "invalid SCRAM server key");
            return false;
        }
        if (len != SCRAM_MAX_KEY_LEN)
        {
            libpq_append_conn_error(conn, "invalid SCRAM server key length: %d", len);
            return false;
        }
        conn->scram_server_key_len = len;
    }
 
    /*
     * validate load_balance_hosts option, and set load_balance_type
     */
    if (conn->load_balance_hosts)
    {
        if (strcmp(conn->load_balance_hosts, "disable") == 0)
            conn->load_balance_type = LOAD_BALANCE_DISABLE;
        else if (strcmp(conn->load_balance_hosts, "random") == 0)
            conn->load_balance_type = LOAD_BALANCE_RANDOM;
        else
        {
            conn->status = CONNECTION_BAD;
            libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
                                    "load_balance_hosts",
                                    conn->load_balance_hosts);
            return false;
        }
    }
    else
        conn->load_balance_type = LOAD_BALANCE_DISABLE;
 
    if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
    {
        libpq_prng_init(conn);
 
        /*
         * This is the "inside-out" variant of the Fisher-Yates shuffle
         * algorithm. Notionally, we append each new value to the array and
         * then swap it with a randomly-chosen array element (possibly
         * including itself, else we fail to generate permutations with the
         * last integer last).  The swap step can be optimized by combining it
         * with the insertion.
         */
        for (i = 1; i < conn->nconnhost; i++)
        {
            int         j = pg_prng_uint64_range(&conn->prng_state, 0, i);
            pg_conn_host temp = conn->connhost[j];
 
            conn->connhost[j] = conn->connhost[i];
            conn->connhost[i] = temp;
        }
    }
 
    if (conn->min_protocol_version)
    {
        if (!pqParseProtocolVersion(conn->min_protocol_version, &conn->min_pversion, conn, "min_protocol_version"))
        {
            conn->status = CONNECTION_BAD;
            return false;
        }
    }
    else
    {
        conn->min_pversion = PG_PROTOCOL_EARLIEST;
    }
 
    if (conn->max_protocol_version)
    {
        if (!pqParseProtocolVersion(conn->max_protocol_version, &conn->max_pversion, conn, "max_protocol_version"))
        {
            conn->status = CONNECTION_BAD;
            return false;
        }
    }
    else
    {
        /*
         * Default to PG_PROTOCOL_GREASE, which is larger than all real
         * versions, to test negotiation. The server should automatically
         * downgrade to a supported version.
         *
         * This behavior is for 19beta only. It will be reverted before RC1.
         */
        conn->max_pversion = PG_PROTOCOL_GREASE;
    }
 
    if (conn->min_pversion > conn->max_pversion)
    {
        conn->status = CONNECTION_BAD;
        libpq_append_conn_error(conn, "\"%s\" is greater than \"%s\"", "min_protocol_version", "max_protocol_version");
        return false;
    }
 
    /*
     * Resolve special "auto" client_encoding from the locale
     */
    if (conn->client_encoding_initial &&
        strcmp(conn->client_encoding_initial, "auto") == 0)
    {
        free(conn->client_encoding_initial);
        conn->client_encoding_initial = strdup(pg_encoding_to_char(pg_get_encoding_from_locale(NULL, true)));
        if (!conn->client_encoding_initial)
            goto oom_error;
    }
 
    /*
     * Only if we get this far is it appropriate to try to connect. (We need a
     * state flag, rather than just the boolean result of this function, in
     * case someone tries to PQreset() the PGconn.)
     */
    conn->options_valid = true;
 
    return true;
 
oom_error:
    conn->status = CONNECTION_BAD;
    libpq_append_conn_error(conn, "out of memory");
    return false;
}
 
/*
 *      PQconndefaults
 *
 * Construct a default connection options array, which identifies all the
 * available options and shows any default values that are available from the
 * environment etc.  On error (eg out of memory), NULL is returned.
 *
 * Using this function, an application may determine all possible options
 * and their current default values.
 *
 * NOTE: as of PostgreSQL 7.0, the returned array is dynamically allocated
 * and should be freed when no longer needed via PQconninfoFree().  (In prior
 * versions, the returned array was static, but that's not thread-safe.)
 * Pre-7.0 applications that use this function will see a small memory leak
 * until they are updated to call PQconninfoFree.
 */
PQconninfoOption *
PQconndefaults(void)
{
    PQExpBufferData errorBuf;
    PQconninfoOption *connOptions;
 
    /* We don't actually report any errors here, but callees want a buffer */
    initPQExpBuffer(&errorBuf);
    if (PQExpBufferDataBroken(errorBuf))
        return NULL;            /* out of memory already :-( */
 
    connOptions = conninfo_init(&errorBuf);
    if (connOptions != NULL)
    {
        /* pass NULL errorBuf to ignore errors */
        if (!conninfo_add_defaults(connOptions, NULL))
        {
            PQconninfoFree(connOptions);
            connOptions = NULL;
        }
    }
 
    termPQExpBuffer(&errorBuf);
    return connOptions;
}
 
/* ----------------
 *      PQsetdbLogin
 *
 * establishes a connection to a postgres backend through the postmaster
 * at the specified host and port.
 *
 * returns a PGconn* which is needed for all subsequent libpq calls
 *
 * if the status field of the connection returned is CONNECTION_BAD,
 * then only the errorMessage is likely to be useful.
 * ----------------
 */
PGconn *
PQsetdbLogin(const char *pghost, const char *pgport, const char *pgoptions,
             const char *pgtty, const char *dbName, const char *login,
             const char *pwd)
{
    PGconn     *conn;
 
    /*
     * Allocate memory for the conn structure.  Note that we also expect this
     * to initialize conn->errorMessage to empty.  All subsequent steps during
     * connection initialization will only append to that buffer.
     */
    conn = pqMakeEmptyPGconn();
    if (conn == NULL)
        return NULL;
 
    /*
     * If the dbName parameter contains what looks like a connection string,
     * parse it into conn struct using connectOptions1.
     */
    if (dbName && recognized_connection_string(dbName))
    {
        if (!connectOptions1(conn, dbName))
            return conn;
    }
    else
    {
        /*
         * Old-style path: first, parse an empty conninfo string in order to
         * set up the same defaults that PQconnectdb() would use.
         */
        if (!connectOptions1(conn, ""))
            return conn;
 
        /* Insert dbName parameter value into struct */
        if (dbName && dbName[0] != '\0')
        {
            free(conn->dbName);
            conn->dbName = strdup(dbName);
            if (!conn->dbName)
                goto oom_error;
        }
    }
 
    /*
     * Insert remaining parameters into struct, overriding defaults (as well
     * as any conflicting data from dbName taken as a conninfo).
     */
    if (pghost && pghost[0] != '\0')
    {
        free(conn->pghost);
        conn->pghost = strdup(pghost);
        if (!conn->pghost)
            goto oom_error;
    }
 
    if (pgport && pgport[0] != '\0')
    {
        free(conn->pgport);
        conn->pgport = strdup(pgport);
        if (!conn->pgport)
            goto oom_error;
    }
 
    if (pgoptions && pgoptions[0] != '\0')
    {
        free(conn->pgoptions);
        conn->pgoptions = strdup(pgoptions);
        if (!conn->pgoptions)
            goto oom_error;
    }
 
    if (login && login[0] != '\0')
    {
        free(conn->pguser);
        conn->pguser = strdup(login);
        if (!conn->pguser)
            goto oom_error;
    }
 
    if (pwd && pwd[0] != '\0')
    {
        free(conn->pgpass);
        conn->pgpass = strdup(pwd);
        if (!conn->pgpass)
            goto oom_error;
    }
 
    /*
     * Compute derived options
     */
    if (!pqConnectOptions2(conn))
        return conn;
 
    /*
     * Connect to the database
     */
    if (pqConnectDBStart(conn))
        (void) pqConnectDBComplete(conn);
 
    return conn;
 
oom_error:
    conn->status = CONNECTION_BAD;
    libpq_append_conn_error(conn, "out of memory");
    return conn;
}
 
 
/* ----------
 * connectNoDelay -
 * Sets the TCP_NODELAY socket option.
 * Returns 1 if successful, 0 if not.
 * ----------
 */
static int
connectNoDelay(PGconn *conn)
{
#ifdef  TCP_NODELAY
    int         on = 1;
 
    if (setsockopt(conn->sock, IPPROTO_TCP, TCP_NODELAY,
                   (char *) &on,
                   sizeof(on)) < 0)
    {
        char        sebuf[PG_STRERROR_R_BUFLEN];
 
        libpq_append_conn_error(conn, "could not set socket to TCP no delay mode: %s",
                                SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#endif
 
    return 1;
}
 
/* ----------
 * Write currently connected IP address into host_addr (of len host_addr_len).
 * If unable to, set it to the empty string.
 * ----------
 */
static void
getHostaddr(PGconn *conn, char *host_addr, int host_addr_len)
{
    struct sockaddr_storage *addr = &conn->raddr.addr;
 
    if (addr->ss_family == AF_INET)
    {
        if (pg_inet_net_ntop(AF_INET,
                             &((struct sockaddr_in *) addr)->sin_addr.s_addr,
                             32,
                             host_addr, host_addr_len) == NULL)
            host_addr[0] = '\0';
    }
    else if (addr->ss_family == AF_INET6)
    {
        if (pg_inet_net_ntop(AF_INET6,
                             &((struct sockaddr_in6 *) addr)->sin6_addr.s6_addr,
                             128,
                             host_addr, host_addr_len) == NULL)
            host_addr[0] = '\0';
    }
    else
        host_addr[0] = '\0';
}
 
/*
 * emitHostIdentityInfo -
 * Speculatively append "connection to server so-and-so failed: " to
 * conn->errorMessage once we've identified the current connection target
 * address.  This ensures that any subsequent error message will be properly
 * attributed to the server we couldn't connect to.  conn->raddr must be
 * valid, and the result of getHostaddr() must be supplied.
 */
static void
emitHostIdentityInfo(PGconn *conn, const char *host_addr)
{
    if (conn->raddr.addr.ss_family == AF_UNIX)
    {
        char        service[NI_MAXHOST];
 
        pg_getnameinfo_all(&conn->raddr.addr, conn->raddr.salen,
                           NULL, 0,
                           service, sizeof(service),
                           NI_NUMERICSERV);
        appendPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("connection to server on socket \"%s\" failed: "),
                          service);
    }
    else
    {
        const char *displayed_host;
        const char *displayed_port;
 
        /* To which host and port were we actually connecting? */
        if (conn->connhost[conn->whichhost].type == CHT_HOST_ADDRESS)
            displayed_host = conn->connhost[conn->whichhost].hostaddr;
        else
            displayed_host = conn->connhost[conn->whichhost].host;
        displayed_port = conn->connhost[conn->whichhost].port;
        if (displayed_port == NULL || displayed_port[0] == '\0')
            displayed_port = DEF_PGPORT_STR;
 
        /*
         * If the user did not supply an IP address using 'hostaddr', and
         * 'host' was missing or does not match our lookup, display the
         * looked-up IP address.
         */
        if (conn->connhost[conn->whichhost].type != CHT_HOST_ADDRESS &&
            host_addr[0] &&
            strcmp(displayed_host, host_addr) != 0)
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("connection to server at \"%s\" (%s), port %s failed: "),
                              displayed_host, host_addr,
                              displayed_port);
        else
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("connection to server at \"%s\", port %s failed: "),
                              displayed_host,
                              displayed_port);
    }
}
 
/* ----------
 * connectFailureMessage -
 * create a friendly error message on connection failure,
 * using the given errno value.  Use this for error cases that
 * imply that there's no server there.
 * ----------
 */
static void
connectFailureMessage(PGconn *conn, int errorno)
{
    char        sebuf[PG_STRERROR_R_BUFLEN];
 
    appendPQExpBuffer(&conn->errorMessage,
                      "%s\n",
                      SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
 
    if (conn->raddr.addr.ss_family == AF_UNIX)
        libpq_append_conn_error(conn, "\tIs the server running locally and accepting connections on that socket?");
    else
        libpq_append_conn_error(conn, "\tIs the server running on that host and accepting TCP/IP connections?");
}
 
/*
 * Should we use keepalives?  Returns 1 if yes, 0 if no, and -1 if
 * conn->keepalives is set to a value which is not parseable as an
 * integer.
 */
static int
useKeepalives(PGconn *conn)
{
    int         val;
 
    if (conn->keepalives == NULL)
        return 1;
 
    if (!pqParseIntParam(conn->keepalives, &val, conn, "keepalives"))
        return -1;
 
    return val != 0 ? 1 : 0;
}
 
#ifndef WIN32
/*
 * Set the keepalive idle timer.
 */
static int
setKeepalivesIdle(PGconn *conn)
{
    int         idle;
 
    if (conn->keepalives_idle == NULL)
        return 1;
 
    if (!pqParseIntParam(conn->keepalives_idle, &idle, conn,
                         "keepalives_idle"))
        return 0;
    if (idle < 0)
        idle = 0;
 
#ifdef PG_TCP_KEEPALIVE_IDLE
    if (setsockopt(conn->sock, IPPROTO_TCP, PG_TCP_KEEPALIVE_IDLE,
                   (char *) &idle, sizeof(idle)) < 0)
    {
        char        sebuf[PG_STRERROR_R_BUFLEN];
 
        libpq_append_conn_error(conn, "%s(%s) failed: %s",
                                "setsockopt",
                                PG_TCP_KEEPALIVE_IDLE_STR,
                                SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#endif
 
    return 1;
}
 
/*
 * Set the keepalive interval.
 */
static int
setKeepalivesInterval(PGconn *conn)
{
    int         interval;
 
    if (conn->keepalives_interval == NULL)
        return 1;
 
    if (!pqParseIntParam(conn->keepalives_interval, &interval, conn,
                         "keepalives_interval"))
        return 0;
    if (interval < 0)
        interval = 0;
 
#ifdef TCP_KEEPINTVL
    if (setsockopt(conn->sock, IPPROTO_TCP, TCP_KEEPINTVL,
                   (char *) &interval, sizeof(interval)) < 0)
    {
        char        sebuf[PG_STRERROR_R_BUFLEN];
 
        libpq_append_conn_error(conn, "%s(%s) failed: %s",
                                "setsockopt",
                                "TCP_KEEPINTVL",
                                SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#endif
 
    return 1;
}
 
/*
 * Set the count of lost keepalive packets that will trigger a connection
 * break.
 */
static int
setKeepalivesCount(PGconn *conn)
{
    int         count;
 
    if (conn->keepalives_count == NULL)
        return 1;
 
    if (!pqParseIntParam(conn->keepalives_count, &count, conn,
                         "keepalives_count"))
        return 0;
    if (count < 0)
        count = 0;
 
#ifdef TCP_KEEPCNT
    if (setsockopt(conn->sock, IPPROTO_TCP, TCP_KEEPCNT,
                   (char *) &count, sizeof(count)) < 0)
    {
        char        sebuf[PG_STRERROR_R_BUFLEN];
 
        libpq_append_conn_error(conn, "%s(%s) failed: %s",
                                "setsockopt",
                                "TCP_KEEPCNT",
                                SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#endif
 
    return 1;
}
#else                           /* WIN32 */
#ifdef SIO_KEEPALIVE_VALS
/*
 * Enable keepalives and set the keepalive values on Win32,
 * where they are always set in one batch.
 *
 * CAUTION: This needs to be signal safe, since it's used by PQcancel.
 */
int
pqSetKeepalivesWin32(pgsocket sock, int idle, int interval)
{
    struct tcp_keepalive ka;
    DWORD       retsize;
 
    if (idle <= 0)
        idle = 2 * 60 * 60;     /* 2 hours = default */
    if (interval <= 0)
        interval = 1;           /* 1 second = default */
 
    ka.onoff = 1;
    ka.keepalivetime = idle * 1000;
    ka.keepaliveinterval = interval * 1000;
 
    if (WSAIoctl(sock,
                 SIO_KEEPALIVE_VALS,
                 (LPVOID) &ka,
                 sizeof(ka),
                 NULL,
                 0,
                 &retsize,
                 NULL,
                 NULL)
        != 0)
        return 0;
    return 1;
}
 
static int
prepKeepalivesWin32(PGconn *conn)
{
    int         idle = -1;
    int         interval = -1;
 
    if (conn->keepalives_idle &&
        !pqParseIntParam(conn->keepalives_idle, &idle, conn,
                         "keepalives_idle"))
        return 0;
    if (conn->keepalives_interval &&
        !pqParseIntParam(conn->keepalives_interval, &interval, conn,
                         "keepalives_interval"))
        return 0;
 
    if (!pqSetKeepalivesWin32(conn->sock, idle, interval))
    {
        libpq_append_conn_error(conn, "%s(%s) failed: error code %d",
                                "WSAIoctl", "SIO_KEEPALIVE_VALS",
                                WSAGetLastError());
        return 0;
    }
    return 1;
}
#endif                          /* SIO_KEEPALIVE_VALS */
#endif                          /* WIN32 */
 
/*
 * Set the TCP user timeout.
 */
static int
setTCPUserTimeout(PGconn *conn)
{
    int         timeout;
 
    if (conn->pgtcp_user_timeout == NULL)
        return 1;
 
    if (!pqParseIntParam(conn->pgtcp_user_timeout, &timeout, conn,
                         "tcp_user_timeout"))
        return 0;
 
    if (timeout < 0)
        timeout = 0;
 
#ifdef TCP_USER_TIMEOUT
    if (setsockopt(conn->sock, IPPROTO_TCP, TCP_USER_TIMEOUT,
                   (char *) &timeout, sizeof(timeout)) < 0)
    {
        char        sebuf[256];
 
        libpq_append_conn_error(conn, "%s(%s) failed: %s",
                                "setsockopt",
                                "TCP_USER_TIMEOUT",
                                SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#endif
 
    return 1;
}
 
/* ----------
 * pqConnectDBStart -
 *      Begin the process of making a connection to the backend.
 *
 * Returns 1 if successful, 0 if not.
 * ----------
 */
int
pqConnectDBStart(PGconn *conn)
{
    if (!conn)
        return 0;
 
    if (!conn->options_valid)
        goto connect_errReturn;
 
    /*
     * Check for bad linking to backend-internal versions of src/common
     * functions (see comments in link-canary.c for the reason we need this).
     * Nobody but developers should see this message, so we don't bother
     * translating it.
     */
    if (!pg_link_canary_is_frontend())
    {
        appendPQExpBufferStr(&conn->errorMessage,
                             "libpq is incorrectly linked to backend functions\n");
        goto connect_errReturn;
    }
 
    /* Ensure our buffers are empty */
    conn->inStart = conn->inCursor = conn->inEnd = 0;
    conn->outCount = 0;
 
    /*
     * Set up to try to connect to the first host.  (Setting whichhost = -1 is
     * a bit of a cheat, but PQconnectPoll will advance it to 0 before
     * anything else looks at it.)
     *
     * Cancel requests are special though, they should only try one host and
     * address, and these fields have already been set up in PQcancelCreate,
     * so leave these fields alone for cancel requests.
     */
    if (!conn->cancelRequest)
    {
        conn->whichhost = -1;
        conn->try_next_host = true;
        conn->try_next_addr = false;
    }
 
    conn->status = CONNECTION_NEEDED;
 
    /* Also reset the target_server_type state if needed */
    if (conn->target_server_type == SERVER_TYPE_PREFER_STANDBY_PASS2)
        conn->target_server_type = SERVER_TYPE_PREFER_STANDBY;
 
    /*
     * The code for processing CONNECTION_NEEDED state is in PQconnectPoll(),
     * so that it can easily be re-executed if needed again during the
     * asynchronous startup process.  However, we must run it once here,
     * because callers expect a success return from this routine to mean that
     * we are in PGRES_POLLING_WRITING connection state.
     */
    if (PQconnectPoll(conn) == PGRES_POLLING_WRITING)
        return 1;
 
connect_errReturn:
 
    /*
     * If we managed to open a socket, close it immediately rather than
     * waiting till PQfinish.  (The application cannot have gotten the socket
     * from PQsocket yet, so this doesn't risk breaking anything.)
     */
    pqDropConnection(conn, true);
    conn->status = CONNECTION_BAD;
    return 0;
}
 
 
/*
 *      pqConnectDBComplete
 *
 * Block and complete a connection.
 *
 * Returns 1 on success, 0 on failure.
 */
int
pqConnectDBComplete(PGconn *conn)
{
    PostgresPollingStatusType flag = PGRES_POLLING_WRITING;
    pg_usec_time_t end_time = -1;
    int         timeout = 0;
    int         last_whichhost = -2;    /* certainly different from whichhost */
    int         last_whichaddr = -2;    /* certainly different from whichaddr */
 
    if (conn == NULL || conn->status == CONNECTION_BAD)
        return 0;
 
    /*
     * Set up a time limit, if connect_timeout is greater than zero.
     */
    if (conn->connect_timeout != NULL)
    {
        if (!pqParseIntParam(conn->connect_timeout, &timeout, conn,
                             "connect_timeout"))
        {
            /* mark the connection as bad to report the parsing failure */
            conn->status = CONNECTION_BAD;
            return 0;
        }
    }
 
    for (;;)
    {
        int         ret = 0;
 
        /*
         * (Re)start the connect_timeout timer if it's active and we are
         * considering a different host than we were last time through.  If
         * we've already succeeded, though, needn't recalculate.
         */
        if (flag != PGRES_POLLING_OK &&
            timeout > 0 &&
            (conn->whichhost != last_whichhost ||
             conn->whichaddr != last_whichaddr))
        {
            end_time = PQgetCurrentTimeUSec() + (pg_usec_time_t) timeout * 1000000;
            last_whichhost = conn->whichhost;
            last_whichaddr = conn->whichaddr;
        }
 
        /*
         * Wait, if necessary.  Note that the initial state (just after
         * PQconnectStart) is to wait for the socket to select for writing.
         */
        switch (flag)
        {
            case PGRES_POLLING_OK:
                return 1;       /* success! */
 
            case PGRES_POLLING_READING:
                ret = pqWaitTimed(1, 0, conn, end_time);
                if (ret == -1)
                {
                    /* hard failure, eg select() problem, aborts everything */
                    conn->status = CONNECTION_BAD;
                    return 0;
                }
                break;
 
            case PGRES_POLLING_WRITING:
                ret = pqWaitTimed(0, 1, conn, end_time);
                if (ret == -1)
                {
                    /* hard failure, eg select() problem, aborts everything */
                    conn->status = CONNECTION_BAD;
                    return 0;
                }
                break;
 
            default:
                /* Just in case we failed to set it in PQconnectPoll */
                conn->status = CONNECTION_BAD;
                return 0;
        }
 
        if (ret == 1)           /* connect_timeout elapsed */
        {
            /*
             * Give up on current server/address, try the next one.
             */
            conn->try_next_addr = true;
            conn->status = CONNECTION_NEEDED;
        }
 
        /*
         * Now try to advance the state machine.
         */
        if (conn->cancelRequest)
            flag = PQcancelPoll((PGcancelConn *) conn);
        else
            flag = PQconnectPoll(conn);
    }
}
 
/* ----------------
 *      PQconnectPoll
 *
 * Poll an asynchronous connection.
 *
 * Returns a PostgresPollingStatusType.
 * Before calling this function, use select(2) to determine when data
 * has arrived..
 *
 * You must call PQfinish whether or not this fails.
 *
 * This function and PQconnectStart are intended to allow connections to be
 * made without blocking the execution of your program on remote I/O. However,
 * there are a number of caveats:
 *
 *   o  If you call PQtrace, ensure that the stream object into which you trace
 *      will not block.
 *   o  If you do not supply an IP address for the remote host (i.e. you
 *      supply a host name instead) then PQconnectStart will block on
 *      getaddrinfo.  You will be fine if using Unix sockets (i.e. by
 *      supplying neither a host name nor a host address).
 *   o  If your backend wants to use Kerberos authentication then you must
 *      supply both a host name and a host address, otherwise this function
 *      may block on gethostname.
 *
 * ----------------
 */
PostgresPollingStatusType
PQconnectPoll(PGconn *conn)
{
    bool        reset_connection_state_machine = false;
    bool        need_new_connection = false;
    PGresult   *res;
    char        sebuf[PG_STRERROR_R_BUFLEN];
    int         optval;
 
    if (conn == NULL)
        return PGRES_POLLING_FAILED;
 
    /* Get the new data */
    switch (conn->status)
    {
            /*
             * We really shouldn't have been polled in these two cases, but we
             * can handle it.
             */
        case CONNECTION_BAD:
            return PGRES_POLLING_FAILED;
        case CONNECTION_OK:
            return PGRES_POLLING_OK;
 
            /* These are reading states */
        case CONNECTION_AWAITING_RESPONSE:
        case CONNECTION_AUTH_OK:
        case CONNECTION_CHECK_WRITABLE:
        case CONNECTION_CONSUME:
        case CONNECTION_CHECK_STANDBY:
            {
                /* Load waiting data */
                int         n = pqReadData(conn);
 
                if (n < 0)
                    goto error_return;
                if (n == 0)
                    return PGRES_POLLING_READING;
 
                break;
            }
 
            /* These are writing states, so we just proceed. */
        case CONNECTION_STARTED:
        case CONNECTION_MADE:
            break;
 
            /* Special cases: proceed without waiting. */
        case CONNECTION_SSL_STARTUP:
        case CONNECTION_NEEDED:
        case CONNECTION_GSS_STARTUP:
        case CONNECTION_CHECK_TARGET:
        case CONNECTION_AUTHENTICATING:
            break;
 
        default:
            libpq_append_conn_error(conn, "invalid connection state, probably indicative of memory corruption");
            goto error_return;
    }
 
 
keep_going:                     /* We will come back to here until there is
                                 * nothing left to do. */
 
    /* Time to advance to next address, or next host if no more addresses? */
    if (conn->try_next_addr)
    {
        if (conn->whichaddr < conn->naddr)
        {
            conn->whichaddr++;
            reset_connection_state_machine = true;
        }
        else
            conn->try_next_host = true;
        conn->try_next_addr = false;
    }
 
    /* Time to advance to next connhost[] entry? */
    if (conn->try_next_host)
    {
        pg_conn_host *ch;
        struct addrinfo hint;
        struct addrinfo *addrlist;
        int         thisport;
        int         ret;
        char        portstr[MAXPGPATH];
 
        if (conn->whichhost + 1 < conn->nconnhost)
            conn->whichhost++;
        else
        {
            /*
             * Oops, no more hosts.
             *
             * If we are trying to connect in "prefer-standby" mode, then drop
             * the standby requirement and start over. Don't do this for
             * cancel requests though, since we are certain the list of
             * servers won't change as the target_server_type option is not
             * applicable to those connections.
             *
             * Otherwise, an appropriate error message is already set up, so
             * we just need to set the right status.
             */
            if (conn->target_server_type == SERVER_TYPE_PREFER_STANDBY &&
                conn->nconnhost > 0 &&
                !conn->cancelRequest)
            {
                conn->target_server_type = SERVER_TYPE_PREFER_STANDBY_PASS2;
                conn->whichhost = 0;
            }
            else
                goto error_return;
        }
 
        /* Drop any address info for previous host */
        release_conn_addrinfo(conn);
 
        /*
         * Look up info for the new host.  On failure, log the problem in
         * conn->errorMessage, then loop around to try the next host.  (Note
         * we don't clear try_next_host until we've succeeded.)
         */
        ch = &conn->connhost[conn->whichhost];
 
        /* Initialize hint structure */
        MemSet(&hint, 0, sizeof(hint));
        hint.ai_socktype = SOCK_STREAM;
        hint.ai_family = AF_UNSPEC;
 
        /* Figure out the port number we're going to use. */
        if (ch->port == NULL || ch->port[0] == '\0')
            thisport = DEF_PGPORT;
        else
        {
            if (!pqParseIntParam(ch->port, &thisport, conn, "port"))
                goto error_return;
 
            if (thisport < 1 || thisport > 65535)
            {
                libpq_append_conn_error(conn, "invalid port number: \"%s\"", ch->port);
                goto keep_going;
            }
        }
        snprintf(portstr, sizeof(portstr), "%d", thisport);
 
        /* Use pg_getaddrinfo_all() to resolve the address */
        switch (ch->type)
        {
            case CHT_HOST_NAME:
                ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
                                         &addrlist);
                if (ret || !addrlist)
                {
                    libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
                                            ch->host, gai_strerror(ret));
                    goto keep_going;
                }
                break;
 
            case CHT_HOST_ADDRESS:
                hint.ai_flags = AI_NUMERICHOST;
                ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
                                         &addrlist);
                if (ret || !addrlist)
                {
                    libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
                                            ch->hostaddr, gai_strerror(ret));
                    goto keep_going;
                }
                break;
 
            case CHT_UNIX_SOCKET:
                hint.ai_family = AF_UNIX;
                UNIXSOCK_PATH(portstr, thisport, ch->host);
                if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
                {
                    libpq_append_conn_error(conn, "Unix-domain socket path \"%s\" is too long (maximum %zu bytes)",
                                            portstr,
                                            (UNIXSOCK_PATH_BUFLEN - 1));
                    goto keep_going;
                }
 
                /*
                 * NULL hostname tells pg_getaddrinfo_all to parse the service
                 * name as a Unix-domain socket path.
                 */
                ret = pg_getaddrinfo_all(NULL, portstr, &hint,
                                         &addrlist);
                if (ret || !addrlist)
                {
                    libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
                                            portstr, gai_strerror(ret));
                    goto keep_going;
                }
                break;
        }
 
        /*
         * Store a copy of the addrlist in private memory so we can perform
         * randomization for load balancing.
         */
        ret = store_conn_addrinfo(conn, addrlist);
        pg_freeaddrinfo_all(hint.ai_family, addrlist);
        if (ret)
            goto error_return;  /* message already logged */
 
        /*
         * If random load balancing is enabled we shuffle the addresses.
         */
        if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
        {
            /*
             * This is the "inside-out" variant of the Fisher-Yates shuffle
             * algorithm. Notionally, we append each new value to the array
             * and then swap it with a randomly-chosen array element (possibly
             * including itself, else we fail to generate permutations with
             * the last integer last).  The swap step can be optimized by
             * combining it with the insertion.
             *
             * We don't need to initialize conn->prng_state here, because that
             * already happened in pqConnectOptions2.
             */
            for (int i = 1; i < conn->naddr; i++)
            {
                int         j = pg_prng_uint64_range(&conn->prng_state, 0, i);
                AddrInfo    temp = conn->addr[j];
 
                conn->addr[j] = conn->addr[i];
                conn->addr[i] = temp;
            }
        }
 
        reset_connection_state_machine = true;
        conn->try_next_host = false;
    }
 
    /* Reset connection state machine? */
    if (reset_connection_state_machine)
    {
        /*
         * (Re) initialize our connection control variables for a set of
         * connection attempts to a single server address.  These variables
         * must persist across individual connection attempts, but we must
         * reset them when we start to consider a new server.
         */
        conn->pversion = conn->max_pversion;
        conn->send_appname = true;
        conn->failed_enc_methods = 0;
        conn->current_enc_method = 0;
        conn->allowed_enc_methods = 0;
        reset_connection_state_machine = false;
        need_new_connection = true;
    }
 
    /* Force a new connection (perhaps to the same server as before)? */
    if (need_new_connection)
    {
        /* Drop any existing connection */
        pqDropConnection(conn, true);
 
        /* Reset all state obtained from old server */
        pqDropServerData(conn);
 
        /* Drop any PGresult we might have, too */
        conn->asyncStatus = PGASYNC_IDLE;
        conn->xactStatus = PQTRANS_IDLE;
        conn->pipelineStatus = PQ_PIPELINE_OFF;
        pqClearAsyncResult(conn);
 
        /* Reset conn->status to put the state machine in the right state */
        conn->status = CONNECTION_NEEDED;
 
        need_new_connection = false;
    }
 
    /*
     * Decide what to do next, if server rejects SSL or GSS negotiation, but
     * the connection is still valid.  If there are no options left, error out
     * with 'msg'.
     */
#define ENCRYPTION_NEGOTIATION_FAILED(msg) \
    do { \
        switch (encryption_negotiation_failed(conn)) \
        { \
            case 0: \
                libpq_append_conn_error(conn, (msg)); \
                goto error_return; \
            case 1: \
                conn->status = CONNECTION_MADE; \
                return PGRES_POLLING_WRITING; \
            case 2: \
                need_new_connection = true; \
                goto keep_going; \
        } \
    } while(0);
 
    /*
     * Decide what to do next, if connection fails.  If there are no options
     * left, return with an error.  The error message has already been written
     * to the connection's error buffer.
     */
#define CONNECTION_FAILED() \
    do { \
        if (connection_failed(conn)) \
        { \
            need_new_connection = true; \
            goto keep_going; \
        } \
        else \
            goto error_return; \
    } while(0);
 
    /* Now try to advance the state machine for this connection */
    switch (conn->status)
    {
        case CONNECTION_NEEDED:
            {
                /*
                 * Try to initiate a connection to one of the addresses
                 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
                 * next one to try.
                 *
                 * The extra level of braces here is historical.  It's not
                 * worth reindenting this whole switch case to remove 'em.
                 */
                {
                    char        host_addr[NI_MAXHOST];
                    int         sock_type;
                    AddrInfo   *addr_cur;
 
                    /*
                     * Advance to next possible host, if we've tried all of
                     * the addresses for the current host.
                     */
                    if (conn->whichaddr == conn->naddr)
                    {
                        conn->try_next_host = true;
                        goto keep_going;
                    }
                    addr_cur = &conn->addr[conn->whichaddr];
 
                    /* Remember current address for possible use later */
                    memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
#ifdef ENABLE_GSS
 
                    /*
                     * Before establishing the connection, check if it's
                     * doomed to fail because gssencmode='require' but GSSAPI
                     * is not available.
                     */
                    if (conn->gssencmode[0] == 'r')
                    {
                        if (conn->raddr.addr.ss_family == AF_UNIX)
                        {
                            libpq_append_conn_error(conn,
                                                    "GSSAPI encryption required but it is not supported over a local socket");
                            goto error_return;
                        }
                        if (conn->gcred == GSS_C_NO_CREDENTIAL)
                        {
                            if (!pg_GSS_have_cred_cache(&conn->gcred))
                            {
                                libpq_append_conn_error(conn,
                                                        "GSSAPI encryption required but no credential cache");
                                goto error_return;
                            }
                        }
                    }
#endif
 
                    /*
                     * Choose the encryption method to try first.  Do this
                     * before establishing the connection, so that if none of
                     * the modes allowed by the connections options are
                     * available, we can error out before establishing the
                     * connection.
                     */
                    if (!init_allowed_encryption_methods(conn))
                        goto error_return;
 
                    /*
                     * Set connip, too.  Note we purposely ignore strdup
                     * failure; not a big problem if it fails.
                     */
                    if (conn->connip != NULL)
                    {
                        free(conn->connip);
                        conn->connip = NULL;
                    }
                    getHostaddr(conn, host_addr, NI_MAXHOST);
                    if (host_addr[0])
                        conn->connip = strdup(host_addr);
 
                    /* Try to create the socket */
                    sock_type = SOCK_STREAM;
#ifdef SOCK_CLOEXEC
 
                    /*
                     * Atomically mark close-on-exec, if possible on this
                     * platform, so that there isn't a window where a
                     * subprogram executed by another thread inherits the
                     * socket.  See fallback code below.
                     */
                    sock_type |= SOCK_CLOEXEC;
#endif
#ifdef SOCK_NONBLOCK
 
                    /*
                     * We might as well skip a system call for nonblocking
                     * mode too, if we can.
                     */
                    sock_type |= SOCK_NONBLOCK;
#endif
                    conn->sock = socket(addr_cur->family, sock_type, 0);
                    if (conn->sock == PGINVALID_SOCKET)
                    {
                        int         errorno = SOCK_ERRNO;
 
                        /*
                         * Silently ignore socket() failure if we have more
                         * addresses to try; this reduces useless chatter in
                         * cases where the address list includes both IPv4 and
                         * IPv6 but kernel only accepts one family.
                         */
                        if (conn->whichaddr < conn->naddr ||
                            conn->whichhost + 1 < conn->nconnhost)
                        {
                            conn->try_next_addr = true;
                            goto keep_going;
                        }
                        emitHostIdentityInfo(conn, host_addr);
                        libpq_append_conn_error(conn, "could not create socket: %s",
                                                SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
                        goto error_return;
                    }
 
                    /*
                     * Once we've identified a target address, all errors
                     * except the preceding socket()-failure case should be
                     * prefixed with host-identity information.  (If the
                     * connection succeeds, the contents of conn->errorMessage
                     * won't matter, so this is harmless.)
                     */
                    emitHostIdentityInfo(conn, host_addr);
 
                    /*
                     * Select socket options: no delay of outgoing data for
                     * TCP sockets, nonblock mode, close-on-exec.  Try the
                     * next address if any of this fails.
                     */
                    if (addr_cur->family != AF_UNIX)
                    {
                        if (!connectNoDelay(conn))
                        {
                            /* error message already created */
                            conn->try_next_addr = true;
                            goto keep_going;
                        }
                    }
#ifndef SOCK_NONBLOCK
                    if (!pg_set_noblock(conn->sock))
                    {
                        libpq_append_conn_error(conn, "could not set socket to nonblocking mode: %s",
                                                SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        conn->try_next_addr = true;
                        goto keep_going;
                    }
#endif
 
#ifndef SOCK_CLOEXEC
#ifdef F_SETFD
                    if (fcntl(conn->sock, F_SETFD, FD_CLOEXEC) == -1)
                    {
                        libpq_append_conn_error(conn, "could not set socket to close-on-exec mode: %s",
                                                SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        conn->try_next_addr = true;
                        goto keep_going;
                    }
#endif                          /* F_SETFD */
#endif
 
                    if (addr_cur->family != AF_UNIX)
                    {
#ifndef WIN32
                        int         on = 1;
#endif
                        int         usekeepalives = useKeepalives(conn);
                        int         err = 0;
 
                        if (usekeepalives < 0)
                        {
                            /* error is already reported */
                            err = 1;
                        }
                        else if (usekeepalives == 0)
                        {
                            /* Do nothing */
                        }
#ifndef WIN32
                        else if (setsockopt(conn->sock,
                                            SOL_SOCKET, SO_KEEPALIVE,
                                            (char *) &on, sizeof(on)) < 0)
                        {
                            libpq_append_conn_error(conn, "%s(%s) failed: %s",
                                                    "setsockopt",
                                                    "SO_KEEPALIVE",
                                                    SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                            err = 1;
                        }
                        else if (!setKeepalivesIdle(conn)
                                 || !setKeepalivesInterval(conn)
                                 || !setKeepalivesCount(conn))
                            err = 1;
#else                           /* WIN32 */
#ifdef SIO_KEEPALIVE_VALS
                        else if (!prepKeepalivesWin32(conn))
                            err = 1;
#endif                          /* SIO_KEEPALIVE_VALS */
#endif                          /* WIN32 */
                        else if (!setTCPUserTimeout(conn))
                            err = 1;
 
                        if (err)
                        {
                            conn->try_next_addr = true;
                            goto keep_going;
                        }
                    }
 
                    /*----------
                     * We have three methods of blocking SIGPIPE during
                     * send() calls to this socket:
                     *
                     *  - setsockopt(sock, SO_NOSIGPIPE)
                     *  - send(sock, ..., MSG_NOSIGNAL)
                     *  - setting the signal mask to SIG_IGN during send()
                     *
                     * The third method requires three syscalls per send,
                     * so we prefer either of the first two, but they are
                     * less portable.  The state is tracked in the following
                     * members of PGconn:
                     *
                     * conn->sigpipe_so     - we have set up SO_NOSIGPIPE
                     * conn->sigpipe_flag   - we're specifying MSG_NOSIGNAL
                     *
                     * If we can use SO_NOSIGPIPE, then set sigpipe_so here
                     * and we're done.  Otherwise, set sigpipe_flag so that
                     * we will try MSG_NOSIGNAL on sends.  If we get an error
                     * with MSG_NOSIGNAL, we'll clear that flag and revert to
                     * signal masking.
                     *----------
                     */
                    conn->sigpipe_so = false;
#ifdef MSG_NOSIGNAL
                    conn->sigpipe_flag = true;
#else
                    conn->sigpipe_flag = false;
#endif                          /* MSG_NOSIGNAL */
 
#ifdef SO_NOSIGPIPE
                    optval = 1;
                    if (setsockopt(conn->sock, SOL_SOCKET, SO_NOSIGPIPE,
                                   (char *) &optval, sizeof(optval)) == 0)
                    {
                        conn->sigpipe_so = true;
                        conn->sigpipe_flag = false;
                    }
#endif                          /* SO_NOSIGPIPE */
 
                    /*
                     * Start/make connection.  This should not block, since we
                     * are in nonblock mode.  If it does, well, too bad.
                     */
                    if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
                                addr_cur->addr.salen) < 0)
                    {
                        if (SOCK_ERRNO == EINPROGRESS ||
#ifdef WIN32
                            SOCK_ERRNO == EWOULDBLOCK ||
#endif
                            SOCK_ERRNO == EINTR)
                        {
                            /*
                             * This is fine - we're in non-blocking mode, and
                             * the connection is in progress.  Tell caller to
                             * wait for write-ready on socket.
                             */
                            conn->status = CONNECTION_STARTED;
                            return PGRES_POLLING_WRITING;
                        }
                        /* otherwise, trouble */
                    }
                    else
                    {
                        /*
                         * Hm, we're connected already --- seems the "nonblock
                         * connection" wasn't.  Advance the state machine and
                         * go do the next stuff.
                         */
                        conn->status = CONNECTION_STARTED;
                        goto keep_going;
                    }
 
                    /*
                     * This connection failed.  Add the error report to
                     * conn->errorMessage, then try the next address if any.
                     */
                    connectFailureMessage(conn, SOCK_ERRNO);
                    conn->try_next_addr = true;
                    goto keep_going;
                }
            }
 
        case CONNECTION_STARTED:
            {
                socklen_t   optlen = sizeof(optval);
 
                /*
                 * Write ready, since we've made it here, so the connection
                 * has been made ... or has failed.
                 */
 
                /*
                 * Now check (using getsockopt) that there is not an error
                 * state waiting for us on the socket.
                 */
 
                if (getsockopt(conn->sock, SOL_SOCKET, SO_ERROR,
                               (char *) &optval, &optlen) == -1)
                {
                    libpq_append_conn_error(conn, "could not get socket error status: %s",
                                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                    goto error_return;
                }
                else if (optval != 0)
                {
                    /*
                     * When using a nonblocking connect, we will typically see
                     * connect failures at this point, so provide a friendly
                     * error message.
                     */
                    connectFailureMessage(conn, optval);
 
                    /*
                     * Try the next address if any, just as in the case where
                     * connect() returned failure immediately.
                     */
                    conn->try_next_addr = true;
                    goto keep_going;
                }
 
                /* Fill in the client address */
                conn->laddr.salen = sizeof(conn->laddr.addr);
                if (getsockname(conn->sock,
                                (struct sockaddr *) &conn->laddr.addr,
                                &conn->laddr.salen) < 0)
                {
                    libpq_append_conn_error(conn, "could not get client address from socket: %s",
                                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                    goto error_return;
                }
 
                /*
                 * Implement requirepeer check, if requested and it's a
                 * Unix-domain socket.
                 */
                if (conn->requirepeer && conn->requirepeer[0] &&
                    conn->raddr.addr.ss_family == AF_UNIX)
                {
#ifndef WIN32
                    char       *remote_username;
#endif
                    uid_t       uid;
                    gid_t       gid;
 
                    errno = 0;
                    if (getpeereid(conn->sock, &uid, &gid) != 0)
                    {
                        /*
                         * Provide special error message if getpeereid is a
                         * stub
                         */
                        if (errno == ENOSYS)
                            libpq_append_conn_error(conn, "requirepeer parameter is not supported on this platform");
                        else
                            libpq_append_conn_error(conn, "could not get peer credentials: %s",
                                                    strerror_r(errno, sebuf, sizeof(sebuf)));
                        goto error_return;
                    }
 
#ifndef WIN32
                    remote_username = pg_fe_getusername(uid,
                                                        &conn->errorMessage);
                    if (remote_username == NULL)
                        goto error_return;  /* message already logged */
 
                    if (strcmp(remote_username, conn->requirepeer) != 0)
                    {
                        libpq_append_conn_error(conn, "requirepeer specifies \"%s\", but actual peer user name is \"%s\"",
                                                conn->requirepeer, remote_username);
                        free(remote_username);
                        goto error_return;
                    }
                    free(remote_username);
#else                           /* WIN32 */
                    /* should have failed with ENOSYS above */
                    Assert(false);
#endif                          /* WIN32 */
                }
 
                /*
                 * Make sure we can write before advancing to next step.
                 */
                conn->status = CONNECTION_MADE;
                return PGRES_POLLING_WRITING;
            }
 
        case CONNECTION_MADE:
            {
                char       *startpacket;
                int         packetlen;
 
#ifdef ENABLE_GSS
 
                /*
                 * If GSSAPI encryption is enabled, send a packet to the
                 * server asking for GSSAPI Encryption and proceed with GSSAPI
                 * handshake.  We will come back here after GSSAPI encryption
                 * has been established, with conn->gctx set.
                 */
                if (conn->current_enc_method == ENC_GSSAPI && !conn->gctx)
                {
                    ProtocolVersion pv = pg_hton32(NEGOTIATE_GSS_CODE);
 
                    if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
                    {
                        libpq_append_conn_error(conn, "could not send GSSAPI negotiation packet: %s",
                                                SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        goto error_return;
                    }
 
                    /* Ok, wait for response */
                    conn->status = CONNECTION_GSS_STARTUP;
                    return PGRES_POLLING_READING;
                }
#endif
 
#ifdef USE_SSL
 
                /*
                 * If SSL is enabled, start the SSL negotiation. We will come
                 * back here after SSL encryption has been established, with
                 * ssl_in_use set.
                 */
                if (conn->current_enc_method == ENC_SSL && !conn->ssl_in_use)
                {
                    /*
                     * If traditional postgres SSL negotiation is used, send
                     * the SSL request.  In direct negotiation, jump straight
                     * into the SSL handshake.
                     */
                    if (conn->sslnegotiation[0] == 'p')
                    {
                        ProtocolVersion pv;
 
                        /*
                         * Send the SSL request packet.
                         *
                         * Theoretically, this could block, but it really
                         * shouldn't since we only got here if the socket is
                         * write-ready.
                         */
                        pv = pg_hton32(NEGOTIATE_SSL_CODE);
                        if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
                        {
                            libpq_append_conn_error(conn, "could not send SSL negotiation packet: %s",
                                                    SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                            goto error_return;
                        }
                        /* Ok, wait for response */
                        conn->status = CONNECTION_SSL_STARTUP;
                        return PGRES_POLLING_READING;
                    }
                    else
                    {
                        Assert(conn->sslnegotiation[0] == 'd');
                        conn->status = CONNECTION_SSL_STARTUP;
                        return PGRES_POLLING_WRITING;
                    }
                }
#endif                          /* USE_SSL */
 
                /*
                 * For cancel requests this is as far as we need to go in the
                 * connection establishment. Now we can actually send our
                 * cancellation request.
                 */
                if (conn->cancelRequest)
                {
                    if (PQsendCancelRequest(conn) != STATUS_OK)
                    {
                        libpq_append_conn_error(conn, "could not send cancel packet: %s",
                                                SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        goto error_return;
                    }
                    conn->status = CONNECTION_AWAITING_RESPONSE;
                    return PGRES_POLLING_READING;
                }
 
                /*
                 * We have now established encryption, or we are happy to
                 * proceed without.
                 */
 
                /* Build the startup packet. */
                startpacket = pqBuildStartupPacket3(conn, &packetlen,
                                                    EnvironmentOptions);
                if (!startpacket)
                {
                    libpq_append_conn_error(conn, "out of memory");
                    goto error_return;
                }
 
                /*
                 * Send the startup packet.
                 *
                 * Theoretically, this could block, but it really shouldn't
                 * since we only got here if the socket is write-ready.
                 */
                if (pqPacketSend(conn, 0, startpacket, packetlen) != STATUS_OK)
                {
                    libpq_append_conn_error(conn, "could not send startup packet: %s",
                                            SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                    free(startpacket);
                    goto error_return;
                }
 
                free(startpacket);
 
                conn->status = CONNECTION_AWAITING_RESPONSE;
                return PGRES_POLLING_READING;
            }
 
            /*
             * Handle SSL negotiation: wait for postmaster messages and
             * respond as necessary.
             */
        case CONNECTION_SSL_STARTUP:
            {
#ifdef USE_SSL
                PostgresPollingStatusType pollres;
 
                /*
                 * On first time through with traditional SSL negotiation, get
                 * the postmaster's response to our SSLRequest packet. With
                 * sslnegotiation='direct', go straight to initiating SSL.
                 */
                if (!conn->ssl_in_use && conn->sslnegotiation[0] == 'p')
                {
                    /*
                     * We use pqReadData here since it has the logic to
                     * distinguish no-data-yet from connection closure. Since
                     * conn->ssl isn't set, a plain recv() will occur.
                     */
                    char        SSLok;
                    int         rdresult;
 
                    rdresult = pqReadData(conn);
                    if (rdresult < 0)
                    {
                        /* errorMessage is already filled in */
                        goto error_return;
                    }
                    if (rdresult == 0)
                    {
                        /* caller failed to wait for data */
                        return PGRES_POLLING_READING;
                    }
                    if (pqGetc(&SSLok, conn) < 0)
                    {
                        /* should not happen really */
                        return PGRES_POLLING_READING;
                    }
                    if (SSLok == 'S')
                    {
                        if (conn->Pfdebug)
                            pqTraceOutputCharResponse(conn, "SSLResponse",
                                                      SSLok);
                        /* mark byte consumed */
                        conn->inStart = conn->inCursor;
                    }
                    else if (SSLok == 'N')
                    {
                        if (conn->Pfdebug)
                            pqTraceOutputCharResponse(conn, "SSLResponse",
                                                      SSLok);
                        /* mark byte consumed */
                        conn->inStart = conn->inCursor;
 
                        /*
                         * The connection is still valid, so if it's OK to
                         * continue without SSL, we can proceed using this
                         * connection.  Otherwise return with an error.
                         */
                        ENCRYPTION_NEGOTIATION_FAILED(libpq_gettext("server does not support SSL, but SSL was required"));
                    }
                    else if (SSLok == 'E')
                    {
                        /*
                         * Server failure of some sort, such as failure to
                         * fork a backend process.  Don't bother retrieving
                         * the error message; we should not trust it as the
                         * server has not been authenticated yet.
                         */
                        libpq_append_conn_error(conn, "server sent an error response during SSL exchange");
                        goto error_return;
                    }
                    else
                    {
                        libpq_append_conn_error(conn, "received invalid response to SSL negotiation: %c",
                                                SSLok);
                        goto error_return;
                    }
                }
 
                /*
                 * Begin or continue the SSL negotiation process.
                 */
                pollres = pqsecure_open_client(conn);
                if (pollres == PGRES_POLLING_OK)
                {
                    /*
                     * At this point we should have no data already buffered.
                     * If we do, it was received before we performed the SSL
                     * handshake, so it wasn't encrypted and indeed may have
                     * been injected by a man-in-the-middle.
                     */
                    if (conn->inCursor != conn->inEnd)
                    {
                        libpq_append_conn_error(conn, "received unencrypted data after SSL response");
                        goto error_return;
                    }
 
                    /* SSL handshake done, ready to send startup packet */
                    conn->status = CONNECTION_MADE;
                    return PGRES_POLLING_WRITING;
                }
                if (pollres == PGRES_POLLING_FAILED)
                {
                    /*
                     * SSL handshake failed.  We will retry with a plaintext
                     * connection, if permitted by sslmode.
                     */
                    CONNECTION_FAILED();
                }
                /* Else, return POLLING_READING or POLLING_WRITING status */
                return pollres;
#else                           /* !USE_SSL */
                /* can't get here */
                goto error_return;
#endif                          /* USE_SSL */
            }
 
        case CONNECTION_GSS_STARTUP:
            {
#ifdef ENABLE_GSS
                PostgresPollingStatusType pollres;
 
                /*
                 * If we haven't yet, get the postmaster's response to our
                 * negotiation packet
                 */
                if (!conn->gctx)
                {
                    char        gss_ok;
                    int         rdresult = pqReadData(conn);
 
                    if (rdresult < 0)
                        /* pqReadData fills in error message */
                        goto error_return;
                    else if (rdresult == 0)
                        /* caller failed to wait for data */
                        return PGRES_POLLING_READING;
                    if (pqGetc(&gss_ok, conn) < 0)
                        /* shouldn't happen... */
                        return PGRES_POLLING_READING;
 
                    if (gss_ok == 'E')
                    {
                        /*
                         * Server failure of some sort, possibly protocol
                         * version support failure.  Don't bother retrieving
                         * the error message; we should not trust it anyway as
                         * the server has not authenticated yet.
                         *
                         * Note that unlike on an error response to
                         * SSLRequest, we allow falling back to SSL or
                         * plaintext connection here.  GSS support was
                         * introduced in PostgreSQL version 12, so an error
                         * response might mean that we are connecting to a
                         * pre-v12 server.
                         */
                        libpq_append_conn_error(conn, "server sent an error response during GSS encryption exchange");
                        CONNECTION_FAILED();
                    }
 
                    /* mark byte consumed */
                    conn->inStart = conn->inCursor;
 
                    if (gss_ok == 'N')
                    {
                        if (conn->Pfdebug)
                            pqTraceOutputCharResponse(conn, "GSSENCResponse",
                                                      gss_ok);
 
                        /*
                         * The connection is still valid, so if it's OK to
                         * continue without GSS, we can proceed using this
                         * connection.  Otherwise return with an error.
                         */
                        ENCRYPTION_NEGOTIATION_FAILED(libpq_gettext("server doesn't support GSSAPI encryption, but it was required"));
                    }
                    else if (gss_ok != 'G')
                    {
                        libpq_append_conn_error(conn, "received invalid response to GSSAPI negotiation: %c",
                                                gss_ok);
                        goto error_return;
                    }
 
                    if (conn->Pfdebug)
                        pqTraceOutputCharResponse(conn, "GSSENCResponse",
                                                  gss_ok);
                }
 
                /* Begin or continue GSSAPI negotiation */
                pollres = pqsecure_open_gss(conn);
                if (pollres == PGRES_POLLING_OK)
                {
                    /*
                     * At this point we should have no data already buffered.
                     * If we do, it was received before we performed the GSS
                     * handshake, so it wasn't encrypted and indeed may have
                     * been injected by a man-in-the-middle.
                     */
                    if (conn->inCursor != conn->inEnd)
                    {
                        libpq_append_conn_error(conn, "received unencrypted data after GSSAPI encryption response");
                        goto error_return;
                    }
 
                    /* All set for startup packet */
                    conn->status = CONNECTION_MADE;
                    return PGRES_POLLING_WRITING;
                }
                else if (pollres == PGRES_POLLING_FAILED)
                {
                    /*
                     * GSS handshake failed.  We will retry with an SSL or
                     * plaintext connection, if permitted by the options.
                     */
                    CONNECTION_FAILED();
                }
                /* Else, return POLLING_READING or POLLING_WRITING status */
                return pollres;
#else                           /* !ENABLE_GSS */
                /* unreachable */
                goto error_return;
#endif                          /* ENABLE_GSS */
            }
 
            /*
             * Handle authentication exchange: wait for postmaster messages
             * and respond as necessary.
             */
        case CONNECTION_AWAITING_RESPONSE:
            {
                char        beresp;
                int         msgLength;
                int         avail;
                AuthRequest areq;
                int         res;
                bool        async;
 
                /*
                 * Scan the message from current point (note that if we find
                 * the message is incomplete, we will return without advancing
                 * inStart, and resume here next time).
                 */
                conn->inCursor = conn->inStart;
 
                /* Read type byte */
                if (pqGetc(&beresp, conn))
                {
                    /* We'll come back when there is more data */
                    return PGRES_POLLING_READING;
                }
 
                /*
                 * Validate message type: we expect only an authentication
                 * request, NegotiateProtocolVersion, or an error here.
                 * Anything else probably means it's not Postgres on the other
                 * end at all.
                 */
                if (beresp != PqMsg_AuthenticationRequest &&
                    beresp != PqMsg_ErrorResponse &&
                    beresp != PqMsg_NegotiateProtocolVersion)
                {
                    libpq_append_conn_error(conn, "expected authentication request from server, but received %c",
                                            beresp);
                    goto error_return;
                }
 
                /* Read message length word */
                if (pqGetInt(&msgLength, 4, conn))
                {
                    /* We'll come back when there is more data */
                    return PGRES_POLLING_READING;
                }
 
                /*
                 * Try to validate message length before using it.
                 *
                 * Authentication requests can't be very large, although GSS
                 * auth requests may not be that small.  Same for
                 * NegotiateProtocolVersion.
                 *
                 * Errors can be a little larger, but not huge.  If we see a
                 * large apparent length in an error, it means we're really
                 * talking to a pre-3.0-protocol server; cope.  (Before
                 * version 14, the server also used the old protocol for
                 * errors that happened before processing the startup packet.)
                 */
                if (beresp == PqMsg_AuthenticationRequest &&
                    (msgLength < 8 || msgLength > 2000))
                {
                    libpq_append_conn_error(conn, "received invalid authentication request");
                    goto error_return;
                }
                if (beresp == PqMsg_NegotiateProtocolVersion &&
                    (msgLength < 8 || msgLength > 2000))
                {
                    libpq_append_conn_error(conn, "received invalid protocol negotiation message");
                    goto error_return;
                }
 
#define MAX_ERRLEN 30000
                if (beresp == PqMsg_ErrorResponse &&
                    (msgLength < 8 || msgLength > MAX_ERRLEN))
                {
                    /* Handle error from a pre-3.0 server */
                    conn->inCursor = conn->inStart + 1; /* reread data */
                    if (pqGets_append(&conn->errorMessage, conn))
                    {
                        /*
                         * We may not have authenticated the server yet, so
                         * don't let the buffer grow forever.
                         */
                        avail = conn->inEnd - conn->inCursor;
                        if (avail > MAX_ERRLEN)
                        {
                            libpq_append_conn_error(conn, "received invalid error message");
                            goto error_return;
                        }
 
                        /* We'll come back when there is more data */
                        return PGRES_POLLING_READING;
                    }
                    /* OK, we read the message; mark data consumed */
                    pqParseDone(conn, conn->inCursor);
 
                    /*
                     * Before 7.2, the postmaster didn't always end its
                     * messages with a newline, so add one if needed to
                     * conform to libpq conventions.
                     */
                    if (conn->errorMessage.len == 0 ||
                        conn->errorMessage.data[conn->errorMessage.len - 1] != '\n')
                    {
                        appendPQExpBufferChar(&conn->errorMessage, '\n');
                    }
 
                    goto error_return;
                }
#undef MAX_ERRLEN
 
                /*
                 * Can't process if message body isn't all here yet.
                 *
                 * After this check passes, any further EOF during parsing
                 * implies that the server sent a bad/truncated message.
                 * Reading more bytes won't help in that case, so don't return
                 * PGRES_POLLING_READING after this point.
                 */
                msgLength -= 4;
                avail = conn->inEnd - conn->inCursor;
                if (avail < msgLength)
                {
                    /*
                     * Before returning, try to enlarge the input buffer if
                     * needed to hold the whole message; see notes in
                     * pqParseInput3.
                     */
                    if (pqCheckInBufferSpace(conn->inCursor + (size_t) msgLength,
                                             conn))
                        goto error_return;
                    /* We'll come back when there is more data */
                    return PGRES_POLLING_READING;
                }
 
                /* Handle errors. */
                if (beresp == PqMsg_ErrorResponse)
                {
                    if (pqGetErrorNotice3(conn, true))
                    {
                        libpq_append_conn_error(conn, "received invalid error message");
                        goto error_return;
                    }
                    /* OK, we read the message; mark data consumed */
                    pqParseDone(conn, conn->inCursor);
 
                    /*
                     * If error is "cannot connect now", try the next host if
                     * any (but we don't want to consider additional addresses
                     * for this host, nor is there much point in changing SSL
                     * or GSS mode).  This is helpful when dealing with
                     * standby servers that might not be in hot-standby state.
                     */
                    if (strcmp(conn->last_sqlstate,
                               ERRCODE_CANNOT_CONNECT_NOW) == 0)
                    {
                        conn->try_next_host = true;
                        goto keep_going;
                    }
 
                    /* Check to see if we should mention pgpassfile */
                    pgpassfileWarning(conn);
 
                    /*
                     * ...and whether we should mention grease. If the error
                     * message contains the PG_PROTOCOL_GREASE number (in
                     * major.minor, decimal, or hex format) or a complaint
                     * about a protocol violation before we've even started an
                     * authentication exchange, it's probably caused by a
                     * grease interaction.
                     */
                    if (conn->max_pversion == PG_PROTOCOL_GREASE &&
                        !conn->auth_req_received)
                    {
                        const char *sqlstate = PQresultErrorField(conn->result,
                                                                  PG_DIAG_SQLSTATE);
 
                        if ((sqlstate &&
                             strcmp(sqlstate, ERRCODE_PROTOCOL_VIOLATION) == 0) ||
                            (conn->errorMessage.len > 0 &&
                             (strstr(conn->errorMessage.data, "3.9999") ||
                              strstr(conn->errorMessage.data, "206607") ||
                              strstr(conn->errorMessage.data, "3270F") ||
                              strstr(conn->errorMessage.data, "3270f"))))
                        {
                            libpq_append_grease_info(conn);
                        }
                    }
 
                    CONNECTION_FAILED();
                }
                /* Handle NegotiateProtocolVersion */
                else if (beresp == PqMsg_NegotiateProtocolVersion)
                {
                    if (conn->pversion_negotiated)
                    {
                        libpq_append_conn_error(conn, "received duplicate protocol negotiation message");
                        goto error_return;
                    }
                    if (pqGetNegotiateProtocolVersion3(conn))
                    {
                        /* pqGetNegotiateProtocolVersion3 set error already */
                        goto error_return;
                    }
                    conn->pversion_negotiated = true;
 
                    /* OK, we read the message; mark data consumed */
                    pqParseDone(conn, conn->inCursor);
 
                    goto keep_going;
                }
 
                /* It is an authentication request. */
                conn->auth_req_received = true;
 
                /* Get the type of request. */
                if (pqGetInt((int *) &areq, 4, conn))
                {
                    /* can't happen because we checked the length already */
                    libpq_append_conn_error(conn, "received invalid authentication request");
                    goto error_return;
                }
                msgLength -= 4;
 
                /*
                 * Process the rest of the authentication request message, and
                 * respond to it if necessary.
                 *
                 * Note that conn->pghost must be non-NULL if we are going to
                 * avoid the Kerberos code doing a hostname look-up.
                 */
                res = pg_fe_sendauth(areq, msgLength, conn, &async);
 
                if (async && (res == STATUS_OK))
                {
                    /*
                     * We'll come back later once we're ready to respond.
                     * Don't consume the request yet.
                     */
                    conn->status = CONNECTION_AUTHENTICATING;
                    goto keep_going;
                }
 
                /*
                 * OK, we have processed the message; mark data consumed.  We
                 * don't call pqParseDone here because we already traced this
                 * message inside pg_fe_sendauth.
                 */
                conn->inStart = conn->inCursor;
 
                if (res != STATUS_OK)
                {
                    /*
                     * OAuth connections may perform two-step discovery, where
                     * the first connection is a dummy.
                     */
                    if (conn->sasl == &pg_oauth_mech && conn->oauth_want_retry)
                    {
                        need_new_connection = true;
                        goto keep_going;
                    }
 
                    goto error_return;
                }
 
                /*
                 * Just make sure that any data sent by pg_fe_sendauth is
                 * flushed out.  Although this theoretically could block, it
                 * really shouldn't since we don't send large auth responses.
                 */
                if (pqFlush(conn))
                    goto error_return;
 
                if (areq == AUTH_REQ_OK)
                {
                    /* We are done with authentication exchange */
                    conn->status = CONNECTION_AUTH_OK;
 
                    /*
                     * Set asyncStatus so that PQgetResult will think that
                     * what comes back next is the result of a query.  See
                     * below.
                     */
                    conn->asyncStatus = PGASYNC_BUSY;
                }
 
                /* Look to see if we have more data yet. */
                goto keep_going;
            }
 
        case CONNECTION_AUTHENTICATING:
            {
                PostgresPollingStatusType status;
 
                if (!conn->async_auth || !conn->cleanup_async_auth)
                {
                    /* programmer error; should not happen */
                    libpq_append_conn_error(conn,
                                            "internal error: async authentication has no handler");
                    goto error_return;
                }
 
                /* Drive some external authentication work. */
                status = conn->async_auth(conn);
 
                if (status == PGRES_POLLING_FAILED)
                    goto error_return;
 
                if (status == PGRES_POLLING_OK)
                {
                    /* Done. Tear down the async implementation. */
                    conn->cleanup_async_auth(conn);
                    conn->cleanup_async_auth = NULL;
 
                    /*
                     * Cleanup must unset altsock, both as an indication that
                     * it's been released, and to stop pqSocketCheck from
                     * looking at the wrong socket after async auth is done.
                     */
                    if (conn->altsock != PGINVALID_SOCKET)
                    {
                        Assert(false);
                        libpq_append_conn_error(conn,
                                                "internal error: async cleanup did not release polling socket");
                        goto error_return;
                    }
 
                    /*
                     * Reenter the authentication exchange with the server. We
                     * didn't consume the message that started external
                     * authentication, so it'll be reprocessed as if we just
                     * received it.
                     */
                    conn->status = CONNECTION_AWAITING_RESPONSE;
 
                    goto keep_going;
                }
 
                /*
                 * Caller needs to poll some more. conn->async_auth() should
                 * have assigned an altsock to poll on.
                 */
                if (conn->altsock == PGINVALID_SOCKET)
                {
                    Assert(false);
                    libpq_append_conn_error(conn,
                                            "internal error: async authentication did not set a socket for polling");
                    goto error_return;
                }
 
                return status;
            }
 
        case CONNECTION_AUTH_OK:
            {
                /*
                 * Now we expect to hear from the backend. A ReadyForQuery
                 * message indicates that startup is successful, but we might
                 * also get an Error message indicating failure. (Notice
                 * messages indicating nonfatal warnings are also allowed by
                 * the protocol, as are ParameterStatus and BackendKeyData
                 * messages.) Easiest way to handle this is to let
                 * PQgetResult() read the messages. We just have to fake it
                 * out about the state of the connection, by setting
                 * asyncStatus = PGASYNC_BUSY (done above).
                 */
 
                if (PQisBusy(conn))
                    return PGRES_POLLING_READING;
 
                res = PQgetResult(conn);
 
                /*
                 * NULL return indicating we have gone to IDLE state is
                 * expected
                 */
                if (res)
                {
                    if (res->resultStatus != PGRES_FATAL_ERROR)
                        libpq_append_conn_error(conn, "unexpected message from server during startup");
                    else if (conn->send_appname &&
                             (conn->appname || conn->fbappname))
                    {
                        /*
                         * If we tried to send application_name, check to see
                         * if the error is about that --- pre-9.0 servers will
                         * reject it at this stage of the process.  If so,
                         * close the connection and retry without sending
                         * application_name.  We could possibly get a false
                         * SQLSTATE match here and retry uselessly, but there
                         * seems no great harm in that; we'll just get the
                         * same error again if it's unrelated.
                         */
                        const char *sqlstate;
 
                        sqlstate = PQresultErrorField(res, PG_DIAG_SQLSTATE);
                        if (sqlstate &&
                            strcmp(sqlstate, ERRCODE_APPNAME_UNKNOWN) == 0)
                        {
                            PQclear(res);
                            conn->send_appname = false;
                            need_new_connection = true;
                            goto keep_going;
                        }
                    }
 
                    /*
                     * if the resultStatus is FATAL, then conn->errorMessage
                     * already has a copy of the error; needn't copy it back.
                     * But add a newline if it's not there already, since
                     * postmaster error messages may not have one.
                     */
                    if (conn->errorMessage.len <= 0 ||
                        conn->errorMessage.data[conn->errorMessage.len - 1] != '\n')
                        appendPQExpBufferChar(&conn->errorMessage, '\n');
                    PQclear(res);
                    goto error_return;
                }
 
                if (conn->max_pversion == PG_PROTOCOL_GREASE &&
                    conn->pversion == PG_PROTOCOL_GREASE)
                {
                    libpq_append_conn_error(conn, "server incorrectly accepted \"grease\" protocol version 3.9999 without negotiation");
                    libpq_append_grease_info(conn);
                    goto error_return;
                }
 
                /* Almost there now ... */
                conn->status = CONNECTION_CHECK_TARGET;
                goto keep_going;
            }
 
        case CONNECTION_CHECK_TARGET:
            {
                /*
                 * If a read-write, read-only, primary, or standby connection
                 * is required, see if we have one.
                 */
                if (conn->target_server_type == SERVER_TYPE_READ_WRITE ||
                    conn->target_server_type == SERVER_TYPE_READ_ONLY)
                {
                    bool        read_only_server;
 
                    /*
                     * If the server didn't report
                     * "default_transaction_read_only" or "in_hot_standby" at
                     * startup, we must determine its state by sending the
                     * query "SHOW transaction_read_only".  This GUC exists in
                     * all server versions that support 3.0 protocol.
                     */
                    if (conn->default_transaction_read_only == PG_BOOL_UNKNOWN ||
                        conn->in_hot_standby == PG_BOOL_UNKNOWN)
                    {
                        /*
                         * We use PQsendQueryContinue so that
                         * conn->errorMessage does not get cleared.  We need
                         * to preserve any error messages related to previous
                         * hosts we have tried and failed to connect to.
                         */
                        conn->status = CONNECTION_OK;
                        if (!PQsendQueryContinue(conn,
                                                 "SHOW transaction_read_only"))
                            goto error_return;
                        /* We'll return to this state when we have the answer */
                        conn->status = CONNECTION_CHECK_WRITABLE;
                        return PGRES_POLLING_READING;
                    }
 
                    /* OK, we can make the test */
                    read_only_server =
                        (conn->default_transaction_read_only == PG_BOOL_YES ||
                         conn->in_hot_standby == PG_BOOL_YES);
 
                    if ((conn->target_server_type == SERVER_TYPE_READ_WRITE) ?
                        read_only_server : !read_only_server)
                    {
                        /* Wrong server state, reject and try the next host */
                        if (conn->target_server_type == SERVER_TYPE_READ_WRITE)
                            libpq_append_conn_error(conn, "session is read-only");
                        else
                            libpq_append_conn_error(conn, "session is not read-only");
 
                        /* Close connection politely. */
                        conn->status = CONNECTION_OK;
                        sendTerminateConn(conn);
 
                        /*
                         * Try next host if any, but we don't want to consider
                         * additional addresses for this host.
                         */
                        conn->try_next_host = true;
                        goto keep_going;
                    }
                }
                else if (conn->target_server_type == SERVER_TYPE_PRIMARY ||
                         conn->target_server_type == SERVER_TYPE_STANDBY ||
                         conn->target_server_type == SERVER_TYPE_PREFER_STANDBY)
                {
                    /*
                     * If the server didn't report "in_hot_standby" at
                     * startup, we must determine its state by sending the
                     * query "SELECT pg_catalog.pg_is_in_recovery()".  Servers
                     * before 9.0 don't have that function, but by the same
                     * token they don't have any standby mode, so we may just
                     * assume the result.
                     */
                    if (conn->sversion < 90000)
                        conn->in_hot_standby = PG_BOOL_NO;
 
                    if (conn->in_hot_standby == PG_BOOL_UNKNOWN)
                    {
                        /*
                         * We use PQsendQueryContinue so that
                         * conn->errorMessage does not get cleared.  We need
                         * to preserve any error messages related to previous
                         * hosts we have tried and failed to connect to.
                         */
                        conn->status = CONNECTION_OK;
                        if (!PQsendQueryContinue(conn,
                                                 "SELECT pg_catalog.pg_is_in_recovery()"))
                            goto error_return;
                        /* We'll return to this state when we have the answer */
                        conn->status = CONNECTION_CHECK_STANDBY;
                        return PGRES_POLLING_READING;
                    }
 
                    /* OK, we can make the test */
                    if ((conn->target_server_type == SERVER_TYPE_PRIMARY) ?
                        (conn->in_hot_standby == PG_BOOL_YES) :
                        (conn->in_hot_standby == PG_BOOL_NO))
                    {
                        /* Wrong server state, reject and try the next host */
                        if (conn->target_server_type == SERVER_TYPE_PRIMARY)
                            libpq_append_conn_error(conn, "server is in hot standby mode");
                        else
                            libpq_append_conn_error(conn, "server is not in hot standby mode");
 
                        /* Close connection politely. */
                        conn->status = CONNECTION_OK;
                        sendTerminateConn(conn);
 
                        /*
                         * Try next host if any, but we don't want to consider
                         * additional addresses for this host.
                         */
                        conn->try_next_host = true;
                        goto keep_going;
                    }
                }
 
                /* Don't hold onto any OAuth tokens longer than necessary. */
                pqClearOAuthToken(conn);
 
                /*
                 * For non cancel requests we can release the address list
                 * now. For cancel requests we never actually resolve
                 * addresses and instead the addrinfo exists for the lifetime
                 * of the connection.
                 */
                if (!conn->cancelRequest)
                    release_conn_addrinfo(conn);
 
                /*
                 * Contents of conn->errorMessage are no longer interesting
                 * (and it seems some clients expect it to be empty after a
                 * successful connection).
                 */
                pqClearConnErrorState(conn);
 
                /* We are open for business! */
                conn->status = CONNECTION_OK;
                return PGRES_POLLING_OK;
            }
 
        case CONNECTION_CONSUME:
            {
                /*
                 * This state just makes sure the connection is idle after
                 * we've obtained the result of a SHOW or SELECT query.  Once
                 * we're clear, return to CONNECTION_CHECK_TARGET state to
                 * decide what to do next.  We must transiently set status =
                 * CONNECTION_OK in order to use the result-consuming
                 * subroutines.
                 */
                conn->status = CONNECTION_OK;
                if (!PQconsumeInput(conn))
                    goto error_return;
 
                if (PQisBusy(conn))
                {
                    conn->status = CONNECTION_CONSUME;
                    return PGRES_POLLING_READING;
                }
 
                /* Call PQgetResult() again until we get a NULL result */
                res = PQgetResult(conn);
                if (res != NULL)
                {
                    PQclear(res);
                    conn->status = CONNECTION_CONSUME;
                    return PGRES_POLLING_READING;
                }
 
                conn->status = CONNECTION_CHECK_TARGET;
                goto keep_going;
            }
 
        case CONNECTION_CHECK_WRITABLE:
            {
                /*
                 * Waiting for result of "SHOW transaction_read_only".  We
                 * must transiently set status = CONNECTION_OK in order to use
                 * the result-consuming subroutines.
                 */
                conn->status = CONNECTION_OK;
                if (!PQconsumeInput(conn))
                    goto error_return;
 
                if (PQisBusy(conn))
                {
                    conn->status = CONNECTION_CHECK_WRITABLE;
                    return PGRES_POLLING_READING;
                }
 
                res = PQgetResult(conn);
                if (res && PQresultStatus(res) == PGRES_TUPLES_OK &&
                    PQntuples(res) == 1)
                {
                    char       *val = PQgetvalue(res, 0, 0);
 
                    /*
                     * "transaction_read_only = on" proves that at least one
                     * of default_transaction_read_only and in_hot_standby is
                     * on, but we don't actually know which.  We don't care
                     * though for the purpose of identifying a read-only
                     * session, so satisfy the CONNECTION_CHECK_TARGET code by
                     * claiming they are both on.  On the other hand, if it's
                     * a read-write session, they are certainly both off.
                     */
                    if (strncmp(val, "on", 2) == 0)
                    {
                        conn->default_transaction_read_only = PG_BOOL_YES;
                        conn->in_hot_standby = PG_BOOL_YES;
                    }
                    else
                    {
                        conn->default_transaction_read_only = PG_BOOL_NO;
                        conn->in_hot_standby = PG_BOOL_NO;
                    }
                    PQclear(res);
 
                    /* Finish reading messages before continuing */
                    conn->status = CONNECTION_CONSUME;
                    goto keep_going;
                }
 
                /* Something went wrong with "SHOW transaction_read_only". */
                PQclear(res);
 
                /* Append error report to conn->errorMessage. */
                libpq_append_conn_error(conn, "\"%s\" failed",
                                        "SHOW transaction_read_only");
 
                /* Close connection politely. */
                conn->status = CONNECTION_OK;
                sendTerminateConn(conn);
 
                /* Try next host. */
                conn->try_next_host = true;
                goto keep_going;
            }
 
        case CONNECTION_CHECK_STANDBY:
            {
                /*
                 * Waiting for result of "SELECT pg_is_in_recovery()".  We
                 * must transiently set status = CONNECTION_OK in order to use
                 * the result-consuming subroutines.
                 */
                conn->status = CONNECTION_OK;
                if (!PQconsumeInput(conn))
                    goto error_return;
 
                if (PQisBusy(conn))
                {
                    conn->status = CONNECTION_CHECK_STANDBY;
                    return PGRES_POLLING_READING;
                }
 
                res = PQgetResult(conn);
                if (res && PQresultStatus(res) == PGRES_TUPLES_OK &&
                    PQntuples(res) == 1)
                {
                    char       *val = PQgetvalue(res, 0, 0);
 
                    if (strncmp(val, "t", 1) == 0)
                        conn->in_hot_standby = PG_BOOL_YES;
                    else
                        conn->in_hot_standby = PG_BOOL_NO;
                    PQclear(res);
 
                    /* Finish reading messages before continuing */
                    conn->status = CONNECTION_CONSUME;
                    goto keep_going;
                }
 
                /* Something went wrong with "SELECT pg_is_in_recovery()". */
                PQclear(res);
 
                /* Append error report to conn->errorMessage. */
                libpq_append_conn_error(conn, "\"%s\" failed",
                                        "SELECT pg_is_in_recovery()");
 
                /* Close connection politely. */
                conn->status = CONNECTION_OK;
                sendTerminateConn(conn);
 
                /* Try next host. */
                conn->try_next_host = true;
                goto keep_going;
            }
 
        default:
            libpq_append_conn_error(conn,
                                    "invalid connection state %d, probably indicative of memory corruption",
                                    conn->status);
            goto error_return;
    }
 
    /* Unreachable */
 
error_return:
 
    /*
     * We used to close the socket at this point, but that makes it awkward
     * for those above us if they wish to remove this socket from their own
     * records (an fd_set for example).  We'll just have this socket closed
     * when PQfinish is called (which is compulsory even after an error, since
     * the connection structure must be freed).
     */
    conn->status = CONNECTION_BAD;
    return PGRES_POLLING_FAILED;
}
 
/*
 * Initialize the state machine for negotiating encryption
 */
static bool
init_allowed_encryption_methods(PGconn *conn)
{
    if (conn->raddr.addr.ss_family == AF_UNIX)
    {
        /* Don't request SSL or GSSAPI over Unix sockets */
        conn->allowed_enc_methods &= ~(ENC_SSL | ENC_GSSAPI);
 
        /*
         * XXX: we probably should not do this. sslmode=require works
         * differently
         */
        if (conn->gssencmode[0] == 'r')
        {
            libpq_append_conn_error(conn,
                                    "GSSAPI encryption required but it is not supported over a local socket");
            conn->allowed_enc_methods = 0;
            conn->current_enc_method = ENC_ERROR;
            return false;
        }
 
        conn->allowed_enc_methods = ENC_PLAINTEXT;
        conn->current_enc_method = ENC_PLAINTEXT;
        return true;
    }
 
    /* initialize based on sslmode and gssencmode */
    conn->allowed_enc_methods = 0;
 
#ifdef USE_SSL
    /* sslmode anything but 'disable', and GSSAPI not required */
    if (conn->sslmode[0] != 'd' && conn->gssencmode[0] != 'r')
    {
        conn->allowed_enc_methods |= ENC_SSL;
    }
#endif
 
#ifdef ENABLE_GSS
    if (conn->gssencmode[0] != 'd')
        conn->allowed_enc_methods |= ENC_GSSAPI;
#endif
 
    if ((conn->sslmode[0] == 'd' || conn->sslmode[0] == 'p' || conn->sslmode[0] == 'a') &&
        (conn->gssencmode[0] == 'd' || conn->gssencmode[0] == 'p'))
    {
        conn->allowed_enc_methods |= ENC_PLAINTEXT;
    }
 
    return select_next_encryption_method(conn, false);
}
 
/*
 * Out-of-line portion of the ENCRYPTION_NEGOTIATION_FAILED() macro in the
 * PQconnectPoll state machine.
 *
 * Return value:
 *  0: connection failed and we are out of encryption methods to try. return an error
 *  1: Retry with next connection method. The TCP connection is still valid and in
 *     known state, so we can proceed with the negotiating next method without
 *     reconnecting.
 *  2: Disconnect, and retry with next connection method.
 *
 * conn->current_enc_method is updated to the next method to try.
 */
#if defined(USE_SSL) || defined(ENABLE_GSS)
static int
encryption_negotiation_failed(PGconn *conn)
{
    Assert((conn->failed_enc_methods & conn->current_enc_method) == 0);
    conn->failed_enc_methods |= conn->current_enc_method;
 
    if (select_next_encryption_method(conn, true))
    {
        /* An existing connection cannot be reused for direct SSL */
        if (conn->current_enc_method == ENC_SSL && conn->sslnegotiation[0] == 'd')
            return 2;
        else
            return 1;
    }
    else
        return 0;
}
#endif
 
/*
 * Out-of-line portion of the CONNECTION_FAILED() macro
 *
 * Returns true, if we should reconnect and retry with a different encryption
 * method.  conn->current_enc_method is updated to the next method to try.
 */
static bool
connection_failed(PGconn *conn)
{
    Assert((conn->failed_enc_methods & conn->current_enc_method) == 0);
    conn->failed_enc_methods |= conn->current_enc_method;
 
    return select_next_encryption_method(conn, false);
}
 
/*
 * Choose the next encryption method to try. If this is a retry,
 * conn->failed_enc_methods has already been updated. The function sets
 * conn->current_enc_method to the next method to try. Returns false if no
 * encryption methods remain.
 */
static bool
select_next_encryption_method(PGconn *conn, bool have_valid_connection)
{
    int         remaining_methods;
 
#define SELECT_NEXT_METHOD(method) \
    do { \
        if ((remaining_methods & method) != 0) \
        { \
            conn->current_enc_method = method; \
            return true; \
        } \
    } while (false)
 
    remaining_methods = conn->allowed_enc_methods & ~conn->failed_enc_methods;
 
    /*
     * Try GSSAPI before SSL
     */
#ifdef ENABLE_GSS
    if ((remaining_methods & ENC_GSSAPI) != 0)
    {
        /*
         * If GSSAPI encryption is enabled, then call pg_GSS_have_cred_cache()
         * which will return true if we can acquire credentials (and give us a
         * handle to use in conn->gcred), and then send a packet to the server
         * asking for GSSAPI Encryption (and skip past SSL negotiation and
         * regular startup below).
         */
        if (!conn->gctx)
        {
            if (!pg_GSS_have_cred_cache(&conn->gcred))
            {
                conn->allowed_enc_methods &= ~ENC_GSSAPI;
                remaining_methods &= ~ENC_GSSAPI;
 
                if (conn->gssencmode[0] == 'r')
                {
                    libpq_append_conn_error(conn,
                                            "GSSAPI encryption required but no credential cache");
                }
            }
        }
    }
 
    SELECT_NEXT_METHOD(ENC_GSSAPI);
#endif
 
    /*
     * The order between SSL encryption and plaintext depends on sslmode. With
     * sslmode=allow, try plaintext connection before SSL. With
     * sslmode=prefer, it's the other way round. With other modes, we only try
     * plaintext or SSL connections so the order they're listed here doesn't
     * matter.
     */
    if (conn->sslmode[0] == 'a')
        SELECT_NEXT_METHOD(ENC_PLAINTEXT);
 
    SELECT_NEXT_METHOD(ENC_SSL);
 
    if (conn->sslmode[0] != 'a')
        SELECT_NEXT_METHOD(ENC_PLAINTEXT);
 
    /* No more options */
    conn->current_enc_method = ENC_ERROR;
    return false;
#undef SELECT_NEXT_METHOD
}
 
/*
 * internal_ping
 *      Determine if a server is running and if we can connect to it.
 *
 * The argument is a connection that's been started, but not completed.
 */
static PGPing
internal_ping(PGconn *conn)
{
    /* Say "no attempt" if we never got to PQconnectPoll */
    if (!conn || !conn->options_valid)
        return PQPING_NO_ATTEMPT;
 
    /* Attempt to complete the connection */
    if (conn->status != CONNECTION_BAD)
        (void) pqConnectDBComplete(conn);
 
    /* Definitely OK if we succeeded */
    if (conn->status != CONNECTION_BAD)
        return PQPING_OK;
 
    /*
     * Here begins the interesting part of "ping": determine the cause of the
     * failure in sufficient detail to decide what to return.  We do not want
     * to report that the server is not up just because we didn't have a valid
     * password, for example.  In fact, any sort of authentication request
     * implies the server is up.  (We need this check since the libpq side of
     * things might have pulled the plug on the connection before getting an
     * error as such from the postmaster.)
     */
    if (conn->auth_req_received)
        return PQPING_OK;
 
    /*
     * If we failed to get any ERROR response from the postmaster, report
     * PQPING_NO_RESPONSE.  This result could be somewhat misleading for a
     * pre-7.4 server, since it won't send back a SQLSTATE, but those are long
     * out of support.  Another corner case where the server could return a
     * failure without a SQLSTATE is fork failure, but PQPING_NO_RESPONSE
     * isn't totally unreasonable for that anyway.  We expect that every other
     * failure case in a modern server will produce a report with a SQLSTATE.
     *
     * NOTE: whenever we get around to making libpq generate SQLSTATEs for
     * client-side errors, we should either not store those into
     * last_sqlstate, or add an extra flag so we can tell client-side errors
     * apart from server-side ones.
     */
    if (strlen(conn->last_sqlstate) != 5)
        return PQPING_NO_RESPONSE;
 
    /*
     * Report PQPING_REJECT if server says it's not accepting connections.
     */
    if (strcmp(conn->last_sqlstate, ERRCODE_CANNOT_CONNECT_NOW) == 0)
        return PQPING_REJECT;
 
    /*
     * Any other SQLSTATE can be taken to indicate that the server is up.
     * Presumably it didn't like our username, password, or database name; or
     * perhaps it had some transient failure, but that should not be taken as
     * meaning "it's down".
     */
    return PQPING_OK;
}
 
 
/*
 * pqMakeEmptyPGconn
 *   - create a PGconn data structure with (as yet) no interesting data
 */
PGconn *
pqMakeEmptyPGconn(void)
{
    PGconn     *conn;
 
#ifdef WIN32
 
    /*
     * Make sure socket support is up and running in this process.
     *
     * Note: the Windows documentation says that we should eventually do a
     * matching WSACleanup() call, but experience suggests that that is at
     * least as likely to cause problems as fix them.  So we don't.
     */
    static bool wsastartup_done = false;
 
    if (!wsastartup_done)
    {
        WSADATA     wsaData;
 
        if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
            return NULL;
        wsastartup_done = true;
    }
 
    /* Forget any earlier error */
    WSASetLastError(0);
#endif                          /* WIN32 */
 
    conn = (PGconn *) malloc(sizeof(PGconn));
    if (conn == NULL)
        return conn;
 
    /* Zero all pointers and booleans */
    MemSet(conn, 0, sizeof(PGconn));
 
    /* install default notice hooks */
    conn->noticeHooks.noticeRec = defaultNoticeReceiver;
    conn->noticeHooks.noticeProc = defaultNoticeProcessor;
 
    conn->status = CONNECTION_BAD;
    conn->asyncStatus = PGASYNC_IDLE;
    conn->pipelineStatus = PQ_PIPELINE_OFF;
    conn->xactStatus = PQTRANS_IDLE;
    conn->options_valid = false;
    conn->nonblocking = false;
    conn->client_encoding = PG_SQL_ASCII;
    conn->std_strings = false;  /* unless server says differently */
    conn->default_transaction_read_only = PG_BOOL_UNKNOWN;
    conn->in_hot_standby = PG_BOOL_UNKNOWN;
    conn->scram_sha_256_iterations = SCRAM_SHA_256_DEFAULT_ITERATIONS;
    conn->verbosity = PQERRORS_DEFAULT;
    conn->show_context = PQSHOW_CONTEXT_ERRORS;
    conn->sock = PGINVALID_SOCKET;
    conn->altsock = PGINVALID_SOCKET;
    conn->Pfdebug = NULL;
 
    /*
     * We try to send at least 8K at a time, which is the usual size of pipe
     * buffers on Unix systems.  That way, when we are sending a large amount
     * of data, we avoid incurring extra kernel context swaps for partial
     * bufferloads.  The output buffer is initially made 16K in size, and we
     * try to dump it after accumulating 8K.
     *
     * With the same goal of minimizing context swaps, the input buffer will
     * be enlarged anytime it has less than 8K free, so we initially allocate
     * twice that.
     */
    conn->inBufSize = 16 * 1024;
    conn->inBuffer = (char *) malloc(conn->inBufSize);
    conn->outBufSize = 16 * 1024;
    conn->outBuffer = (char *) malloc(conn->outBufSize);
    conn->rowBufLen = 32;
    conn->rowBuf = (PGdataValue *) malloc(conn->rowBufLen * sizeof(PGdataValue));
    initPQExpBuffer(&conn->errorMessage);
    initPQExpBuffer(&conn->workBuffer);
 
    if (conn->inBuffer == NULL ||
        conn->outBuffer == NULL ||
        conn->rowBuf == NULL ||
        PQExpBufferBroken(&conn->errorMessage) ||
        PQExpBufferBroken(&conn->workBuffer))
    {
        /* out of memory already :-( */
        freePGconn(conn);
        conn = NULL;
    }
 
    return conn;
}
 
/*
 * freePGconn
 *   - free an idle (closed) PGconn data structure
 *
 * NOTE: this should not overlap any functionality with pqClosePGconn().
 * Clearing/resetting of transient state belongs there; what we do here is
 * release data that is to be held for the life of the PGconn structure.
 * If a value ought to be cleared/freed during PQreset(), do it there not here.
 */
static void
freePGconn(PGconn *conn)
{
    /* let any event procs clean up their state data */
    for (int i = 0; i < conn->nEvents; i++)
    {
        PGEventConnDestroy evt;
 
        evt.conn = conn;
        (void) conn->events[i].proc(PGEVT_CONNDESTROY, &evt,
                                    conn->events[i].passThrough);
        free(conn->events[i].name);
    }
 
    /* free everything not freed in pqClosePGconn */
    free(conn->pghost);
    free(conn->pghostaddr);
    free(conn->pgport);
    free(conn->connect_timeout);
    free(conn->pgtcp_user_timeout);
    free(conn->client_encoding_initial);
    free(conn->pgoptions);
    free(conn->appname);
    free(conn->fbappname);
    free(conn->dbName);
    free(conn->replication);
    free(conn->pgservice);
    free(conn->pgservicefile);
    free(conn->pguser);
    if (conn->pgpass)
    {
        explicit_bzero(conn->pgpass, strlen(conn->pgpass));
        free(conn->pgpass);
    }
    free(conn->pgpassfile);
    free(conn->channel_binding);
    free(conn->keepalives);
    free(conn->keepalives_idle);
    free(conn->keepalives_interval);
    free(conn->keepalives_count);
    free(conn->sslmode);
    free(conn->sslnegotiation);
    free(conn->sslcompression);
    free(conn->sslkey);
    free(conn->sslcert);
    if (conn->sslpassword)
    {
        explicit_bzero(conn->sslpassword, strlen(conn->sslpassword));
        free(conn->sslpassword);
    }
    free(conn->sslcertmode);
    free(conn->sslrootcert);
    free(conn->sslcrl);
    free(conn->sslcrldir);
    free(conn->sslsni);
    free(conn->requirepeer);
    free(conn->gssencmode);
    free(conn->krbsrvname);
    free(conn->gsslib);
    free(conn->gssdelegation);
    free(conn->min_protocol_version);
    free(conn->max_protocol_version);
    free(conn->ssl_min_protocol_version);
    free(conn->ssl_max_protocol_version);
    free(conn->target_session_attrs);
    free(conn->require_auth);
    free(conn->load_balance_hosts);
    free(conn->scram_client_key);
    free(conn->scram_server_key);
    free(conn->sslkeylogfile);
    free(conn->oauth_issuer);
    free(conn->oauth_issuer_id);
    free(conn->oauth_discovery_uri);
    free(conn->oauth_client_id);
    free(conn->oauth_client_secret);
    free(conn->oauth_scope);
    /* Note that conn->Pfdebug is not ours to close or free */
    free(conn->events);
    pqReleaseConnHosts(conn);
    free(conn->connip);
    release_conn_addrinfo(conn);
    free(conn->scram_client_key_binary);
    free(conn->scram_server_key_binary);
    /* if this is a cancel connection, be_cancel_key may still be allocated */
    free(conn->be_cancel_key);
    free(conn->inBuffer);
    free(conn->outBuffer);
    free(conn->rowBuf);
    termPQExpBuffer(&conn->errorMessage);
    termPQExpBuffer(&conn->workBuffer);
 
    free(conn);
}
 
/*
 * pqReleaseConnHosts
 *   - Free the host list in the PGconn.
 */
void
pqReleaseConnHosts(PGconn *conn)
{
    if (conn->connhost)
    {
        for (int i = 0; i < conn->nconnhost; ++i)
        {
            free(conn->connhost[i].host);
            free(conn->connhost[i].hostaddr);
            free(conn->connhost[i].port);
            if (conn->connhost[i].password != NULL)
            {
                explicit_bzero(conn->connhost[i].password,
                               strlen(conn->connhost[i].password));
                free(conn->connhost[i].password);
            }
        }
        free(conn->connhost);
        conn->connhost = NULL;
    }
}
 
/*
 * store_conn_addrinfo
 *   - copy addrinfo to PGconn object
 *
 * Copies the addrinfos from addrlist to the PGconn object such that the
 * addrinfos can be manipulated by libpq. Returns a positive integer on
 * failure, otherwise zero.
 */
static int
store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
{
    struct addrinfo *ai = addrlist;
 
    conn->whichaddr = 0;
 
    conn->naddr = 0;
    while (ai)
    {
        ai = ai->ai_next;
        conn->naddr++;
    }
 
    conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
    if (conn->addr == NULL)
    {
        libpq_append_conn_error(conn, "out of memory");
        return 1;
    }
 
    ai = addrlist;
    for (int i = 0; i < conn->naddr; i++)
    {
        conn->addr[i].family = ai->ai_family;
 
        memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
               ai->ai_addrlen);
        conn->addr[i].addr.salen = ai->ai_addrlen;
        ai = ai->ai_next;
    }
 
    return 0;
}
 
/*
 * release_conn_addrinfo
 *   - Free any addrinfo list in the PGconn.
 */
static void
release_conn_addrinfo(PGconn *conn)
{
    if (conn->addr)
    {
        free(conn->addr);
        conn->addr = NULL;
    }
}
 
/*
 * sendTerminateConn
 *   - Send a terminate message to backend.
 */
static void
sendTerminateConn(PGconn *conn)
{
    /*
     * The Postgres cancellation protocol does not have a notion of a
     * Terminate message, so don't send one.
     */
    if (conn->cancelRequest)
        return;
 
    /*
     * Note that the protocol doesn't allow us to send Terminate messages
     * during the startup phase.
     */
    if (conn->sock != PGINVALID_SOCKET && conn->status == CONNECTION_OK)
    {
        /*
         * Try to send "close connection" message to backend. Ignore any
         * error.
         */
        pqPutMsgStart(PqMsg_Terminate, conn);
        pqPutMsgEnd(conn);
        (void) pqFlush(conn);
    }
}
 
/*
 * pqClosePGconn
 *   - properly close a connection to the backend
 *
 * This should reset or release all transient state, but NOT the connection
 * parameters.  On exit, the PGconn should be in condition to start a fresh
 * connection with the same parameters (see PQreset()).
 */
void
pqClosePGconn(PGconn *conn)
{
    /*
     * If possible, send Terminate message to close the connection politely.
     */
    sendTerminateConn(conn);
 
    /*
     * Must reset the blocking status so a possible reconnect will work.
     *
     * Don't call PQsetnonblocking() because it will fail if it's unable to
     * flush the connection.
     */
    conn->nonblocking = false;
 
    /*
     * Close the connection, reset all transient state, flush I/O buffers.
     * Note that this includes clearing conn's error state; we're no longer
     * interested in any failures associated with the old connection, and we
     * want a clean slate for any new connection attempt.
     */
    pqDropConnection(conn, true);
    conn->status = CONNECTION_BAD;  /* Well, not really _bad_ - just absent */
    conn->asyncStatus = PGASYNC_IDLE;
    conn->xactStatus = PQTRANS_IDLE;
    conn->pipelineStatus = PQ_PIPELINE_OFF;
    pqClearOAuthToken(conn);
    pqClearAsyncResult(conn);   /* deallocate result */
    pqClearConnErrorState(conn);
 
    /*
     * Release addrinfo, but since cancel requests never change their addrinfo
     * we don't do that. Otherwise we would have to rebuild it during a
     * PQcancelReset.
     */
    if (!conn->cancelRequest)
        release_conn_addrinfo(conn);
 
    /* Reset all state obtained from server, too */
    pqDropServerData(conn);
}
 
/*
 * PQfinish: properly close a connection to the backend. Also frees
 * the PGconn data structure so it shouldn't be re-used after this.
 */
void
PQfinish(PGconn *conn)
{
    if (conn)
    {
        pqClosePGconn(conn);
        freePGconn(conn);
    }
}
 
/*
 * PQreset: resets the connection to the backend by closing the
 * existing connection and creating a new one.
 */
void
PQreset(PGconn *conn)
{
    if (conn)
    {
        pqClosePGconn(conn);
 
        if (pqConnectDBStart(conn) && pqConnectDBComplete(conn))
        {
            /*
             * Notify event procs of successful reset.
             */
            int         i;
 
            for (i = 0; i < conn->nEvents; i++)
            {
                PGEventConnReset evt;
 
                evt.conn = conn;
                (void) conn->events[i].proc(PGEVT_CONNRESET, &evt,
                                            conn->events[i].passThrough);
            }
        }
    }
}
 
 
/*
 * PQresetStart:
 * resets the connection to the backend
 * closes the existing connection and makes a new one
 * Returns 1 on success, 0 on failure.
 */
int
PQresetStart(PGconn *conn)
{
    if (conn)
    {
        pqClosePGconn(conn);
 
        return pqConnectDBStart(conn);
    }
 
    return 0;
}
 
 
/*
 * PQresetPoll:
 * resets the connection to the backend
 * closes the existing connection and makes a new one
 */
PostgresPollingStatusType
PQresetPoll(PGconn *conn)
{
    if (conn)
    {
        PostgresPollingStatusType status = PQconnectPoll(conn);
 
        if (status == PGRES_POLLING_OK)
        {
            /*
             * Notify event procs of successful reset.
             */
            int         i;
 
            for (i = 0; i < conn->nEvents; i++)
            {
                PGEventConnReset evt;
 
                evt.conn = conn;
                (void) conn->events[i].proc(PGEVT_CONNRESET, &evt,
                                            conn->events[i].passThrough);
            }
        }
 
        return status;
    }
 
    return PGRES_POLLING_FAILED;
}
 
/*
 * pqPacketSend() -- convenience routine to send a message to server.
 *
 * pack_type: the single-byte message type code.  (Pass zero for startup
 * packets, which have no message type code.)
 *
 * buf, buf_len: contents of message.  The given length includes only what
 * is in buf; the message type and message length fields are added here.
 *
 * RETURNS: STATUS_ERROR if the write fails, STATUS_OK otherwise.
 * SIDE_EFFECTS: may block.
 */
int
pqPacketSend(PGconn *conn, char pack_type,
             const void *buf, size_t buf_len)
{
    /* Start the message. */
    if (pqPutMsgStart(pack_type, conn))
        return STATUS_ERROR;
 
    /* Send the message body. */
    if (pqPutnchar(buf, buf_len, conn))
        return STATUS_ERROR;
 
    /* Finish the message. */
    if (pqPutMsgEnd(conn))
        return STATUS_ERROR;
 
    /* Flush to ensure backend gets it. */
    if (pqFlush(conn))
        return STATUS_ERROR;
 
    return STATUS_OK;
}
 
#ifdef USE_LDAP
 
#define LDAP_URL    "ldap://"
#define LDAP_DEF_PORT   389
#define PGLDAP_TIMEOUT 2
 
#define ld_is_sp_tab(x) ((x) == ' ' || (x) == '\t')
#define ld_is_nl_cr(x) ((x) == '\r' || (x) == '\n')
 
 
/*
 *      ldapServiceLookup
 *
 * Search the LDAP URL passed as first argument, treat the result as a
 * string of connection options that are parsed and added to the array of
 * options passed as second argument.
 *
 * LDAP URLs must conform to RFC 1959 without escape sequences.
 *  ldap://host:port/dn?attributes?scope?filter?extensions
 *
 * Returns
 *  0 if the lookup was successful,
 *  1 if the connection to the LDAP server could be established but
 *    the search was unsuccessful,
 *  2 if a connection could not be established, and
 *  3 if a fatal error occurred.
 *
 * An error message is appended to *errorMessage for return codes 1 and 3.
 */
static int
ldapServiceLookup(const char *purl, PQconninfoOption *options,
                  PQExpBuffer errorMessage)
{
    int         port = LDAP_DEF_PORT,
                scope,
                rc,
                size,
                state,
                oldstate,
                i;
#ifndef WIN32
    int         msgid;
#endif
    bool        found_keyword;
    char       *url,
               *hostname,
               *portstr,
               *endptr,
               *dn,
               *scopestr,
               *filter,
               *result,
               *p,
               *p1 = NULL,
               *optname = NULL,
               *optval = NULL;
    char       *attrs[2] = {NULL, NULL};
    LDAP       *ld = NULL;
    LDAPMessage *res,
               *entry;
    struct berval **values;
    LDAP_TIMEVAL time = {PGLDAP_TIMEOUT, 0};
    int         ldapversion = LDAP_VERSION3;
 
    if ((url = strdup(purl)) == NULL)
    {
        libpq_append_error(errorMessage, "out of memory");
        return 3;
    }
 
    /*
     * Parse URL components, check for correctness.  Basically, url has '\0'
     * placed at component boundaries and variables are pointed at each
     * component.
     */
 
    if (pg_strncasecmp(url, LDAP_URL, strlen(LDAP_URL)) != 0)
    {
        libpq_append_error(errorMessage,
                           "invalid LDAP URL \"%s\": scheme must be ldap://", purl);
        free(url);
        return 3;
    }
 
    /* hostname */
    hostname = url + strlen(LDAP_URL);
    if (*hostname == '/')       /* no hostname? */
        hostname = DefaultHost; /* the default */
 
    /* dn, "distinguished name" */
    p = strchr(url + strlen(LDAP_URL), '/');
    if (p == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        libpq_append_error(errorMessage,
                           "invalid LDAP URL \"%s\": missing distinguished name",
                           purl);
        free(url);
        return 3;
    }
    *p = '\0';                  /* terminate hostname */
    dn = p + 1;
 
    /* attribute */
    if ((p = strchr(dn, '?')) == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        libpq_append_error(errorMessage,
                           "invalid LDAP URL \"%s\": must have exactly one attribute",
                           purl);
        free(url);
        return 3;
    }
    *p = '\0';
    attrs[0] = p + 1;
 
    /* scope */
    if ((p = strchr(attrs[0], '?')) == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        libpq_append_error(errorMessage,
                           "invalid LDAP URL \"%s\": must have search scope (base/one/sub)",
                           purl);
        free(url);
        return 3;
    }
    *p = '\0';
    scopestr = p + 1;
 
    /* filter */
    if ((p = strchr(scopestr, '?')) == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        libpq_append_error(errorMessage,
                           "invalid LDAP URL \"%s\": no filter",
                           purl);
        free(url);
        return 3;
    }
    *p = '\0';
    filter = p + 1;
    if ((p = strchr(filter, '?')) != NULL)
        *p = '\0';
 
    /* port number? */
    if ((p1 = strchr(hostname, ':')) != NULL)
    {
        long        lport;
 
        *p1 = '\0';
        portstr = p1 + 1;
        errno = 0;
        lport = strtol(portstr, &endptr, 10);
        if (*portstr == '\0' || *endptr != '\0' || errno || lport < 0 || lport > 65535)
        {
            libpq_append_error(errorMessage,
                               "invalid LDAP URL \"%s\": invalid port number",
                               purl);
            free(url);
            return 3;
        }
        port = (int) lport;
    }
 
    /* Allow only one attribute */
    if (strchr(attrs[0], ',') != NULL)
    {
        libpq_append_error(errorMessage,
                           "invalid LDAP URL \"%s\": must have exactly one attribute",
                           purl);
        free(url);
        return 3;
    }
 
    /* set scope */
    if (pg_strcasecmp(scopestr, "base") == 0)
        scope = LDAP_SCOPE_BASE;
    else if (pg_strcasecmp(scopestr, "one") == 0)
        scope = LDAP_SCOPE_ONELEVEL;
    else if (pg_strcasecmp(scopestr, "sub") == 0)
        scope = LDAP_SCOPE_SUBTREE;
    else
    {
        libpq_append_error(errorMessage,
                           "invalid LDAP URL \"%s\": must have search scope (base/one/sub)",
                           purl);
        free(url);
        return 3;
    }
 
    /* initialize LDAP structure */
    if ((ld = ldap_init(hostname, port)) == NULL)
    {
        libpq_append_error(errorMessage, "could not create LDAP structure");
        free(url);
        return 3;
    }
 
    if ((rc = ldap_set_option(ld, LDAP_OPT_PROTOCOL_VERSION, &ldapversion)) != LDAP_SUCCESS)
    {
        libpq_append_error(errorMessage, "could not set LDAP protocol version: %s",
                           ldap_err2string(rc));
        free(url);
        ldap_unbind(ld);
        return 3;
    }
 
    /*
     * Perform an explicit anonymous bind.
     *
     * LDAP does not require that an anonymous bind is performed explicitly,
     * but we want to distinguish between the case where LDAP bind does not
     * succeed within PGLDAP_TIMEOUT seconds (return 2 to continue parsing the
     * service control file) and the case where querying the LDAP server fails
     * (return 1 to end parsing).
     *
     * Unfortunately there is no way of setting a timeout that works for both
     * Windows and OpenLDAP.
     */
#ifdef WIN32
    /* the nonstandard ldap_connect function performs an anonymous bind */
    if (ldap_connect(ld, &time) != LDAP_SUCCESS)
    {
        /* error or timeout in ldap_connect */
        free(url);
        ldap_unbind(ld);
        return 2;
    }
#else                           /* !WIN32 */
    /* in OpenLDAP, use the LDAP_OPT_NETWORK_TIMEOUT option */
    if (ldap_set_option(ld, LDAP_OPT_NETWORK_TIMEOUT, &time) != LDAP_SUCCESS)
    {
        free(url);
        ldap_unbind(ld);
        return 3;
    }
 
    /* anonymous bind */
    if ((msgid = ldap_simple_bind(ld, NULL, NULL)) == -1)
    {
        /* error or network timeout */
        free(url);
        ldap_unbind(ld);
        return 2;
    }
 
    /* wait some time for the connection to succeed */
    res = NULL;
    if ((rc = ldap_result(ld, msgid, LDAP_MSG_ALL, &time, &res)) == -1 ||
        res == NULL)
    {
        /* error or timeout */
        if (res != NULL)
            ldap_msgfree(res);
        free(url);
        ldap_unbind(ld);
        return 2;
    }
    ldap_msgfree(res);
 
    /* reset timeout */
    time.tv_sec = -1;
    if (ldap_set_option(ld, LDAP_OPT_NETWORK_TIMEOUT, &time) != LDAP_SUCCESS)
    {
        free(url);
        ldap_unbind(ld);
        return 3;
    }
#endif                          /* WIN32 */
 
    /* search */
    res = NULL;
    if ((rc = ldap_search_st(ld, dn, scope, filter, attrs, 0, &time, &res))
        != LDAP_SUCCESS)
    {
        if (res != NULL)
            ldap_msgfree(res);
        libpq_append_error(errorMessage, "lookup on LDAP server failed: %s", ldap_err2string(rc));
        ldap_unbind(ld);
        free(url);
        return 1;
    }
 
    /* complain if there was not exactly one result */
    if ((rc = ldap_count_entries(ld, res)) != 1)
    {
        if (rc > 1)
            libpq_append_error(errorMessage, "more than one entry found on LDAP lookup");
        else
            libpq_append_error(errorMessage, "no entry found on LDAP lookup");
        ldap_msgfree(res);
        ldap_unbind(ld);
        free(url);
        return 1;
    }
 
    /* get entry */
    if ((entry = ldap_first_entry(ld, res)) == NULL)
    {
        /* should never happen */
        libpq_append_error(errorMessage, "no entry found on LDAP lookup");
        ldap_msgfree(res);
        ldap_unbind(ld);
        free(url);
        return 1;
    }
 
    /* get values */
    if ((values = ldap_get_values_len(ld, entry, attrs[0])) == NULL)
    {
        libpq_append_error(errorMessage, "attribute has no values on LDAP lookup");
        ldap_msgfree(res);
        ldap_unbind(ld);
        free(url);
        return 1;
    }
 
    ldap_msgfree(res);
    free(url);
 
    if (values[0] == NULL)
    {
        libpq_append_error(errorMessage, "attribute has no values on LDAP lookup");
        ldap_value_free_len(values);
        ldap_unbind(ld);
        return 1;
    }
 
    /* concatenate values into a single string with newline terminators */
    size = 1;                   /* for the trailing null */
    for (i = 0; values[i] != NULL; i++)
    {
        if (values[i]->bv_len >= INT_MAX ||
            size > (INT_MAX - (values[i]->bv_len + 1)))
        {
            libpq_append_error(errorMessage,
                               "connection info string size exceeds the maximum allowed (%d)",
                               INT_MAX);
            ldap_value_free_len(values);
            ldap_unbind(ld);
            return 3;
        }
 
        size += values[i]->bv_len + 1;
    }
 
    if ((result = malloc(size)) == NULL)
    {
        libpq_append_error(errorMessage, "out of memory");
        ldap_value_free_len(values);
        ldap_unbind(ld);
        return 3;
    }
    p = result;
    for (i = 0; values[i] != NULL; i++)
    {
        memcpy(p, values[i]->bv_val, values[i]->bv_len);
        p += values[i]->bv_len;
        *(p++) = '\n';
    }
    *p = '\0';
 
    ldap_value_free_len(values);
    ldap_unbind(ld);
 
    /* parse result string */
    oldstate = state = 0;
    for (p = result; *p != '\0'; ++p)
    {
        switch (state)
        {
            case 0:             /* between entries */
                if (!ld_is_sp_tab(*p) && !ld_is_nl_cr(*p))
                {
                    optname = p;
                    state = 1;
                }
                break;
            case 1:             /* in option name */
                if (ld_is_sp_tab(*p))
                {
                    *p = '\0';
                    state = 2;
                }
                else if (ld_is_nl_cr(*p))
                {
                    libpq_append_error(errorMessage,
                                       "missing \"=\" after \"%s\" in connection info string",
                                       optname);
                    free(result);
                    return 3;
                }
                else if (*p == '=')
                {
                    *p = '\0';
                    state = 3;
                }
                break;
            case 2:             /* after option name */
                if (*p == '=')
                {
                    state = 3;
                }
                else if (!ld_is_sp_tab(*p))
                {
                    libpq_append_error(errorMessage,
                                       "missing \"=\" after \"%s\" in connection info string",
                                       optname);
                    free(result);
                    return 3;
                }
                break;
            case 3:             /* before option value */
                if (*p == '\'')
                {
                    optval = p + 1;
                    p1 = p + 1;
                    state = 5;
                }
                else if (ld_is_nl_cr(*p))
                {
                    optval = optname + strlen(optname); /* empty */
                    state = 0;
                }
                else if (!ld_is_sp_tab(*p))
                {
                    optval = p;
                    state = 4;
                }
                break;
            case 4:             /* in unquoted option value */
                if (ld_is_sp_tab(*p) || ld_is_nl_cr(*p))
                {
                    *p = '\0';
                    state = 0;
                }
                break;
            case 5:             /* in quoted option value */
                if (*p == '\'')
                {
                    *p1 = '\0';
                    state = 0;
                }
                else if (*p == '\\')
                    state = 6;
                else
                    *(p1++) = *p;
                break;
            case 6:             /* in quoted option value after escape */
                *(p1++) = *p;
                state = 5;
                break;
        }
 
        if (state == 0 && oldstate != 0)
        {
            found_keyword = false;
            for (i = 0; options[i].keyword; i++)
            {
                if (strcmp(options[i].keyword, optname) == 0)
                {
                    if (options[i].val == NULL)
                    {
                        options[i].val = strdup(optval);
                        if (!options[i].val)
                        {
                            libpq_append_error(errorMessage, "out of memory");
                            free(result);
                            return 3;
                        }
                    }
                    found_keyword = true;
                    break;
                }
            }
            if (!found_keyword)
            {
                libpq_append_error(errorMessage, "invalid connection option \"%s\"", optname);
                free(result);
                return 1;
            }
            optname = NULL;
            optval = NULL;
        }
        oldstate = state;
    }
 
    free(result);
 
    if (state == 5 || state == 6)
    {
        libpq_append_error(errorMessage,
                           "unterminated quoted string in connection info string");
        return 3;
    }
 
    return 0;
}
 
#endif                          /* USE_LDAP */
 
/*
 * parseServiceInfo: if a service name has been given, look it up and absorb
 * connection options from it into *options.
 *
 * Returns 0 on success, nonzero on failure.  On failure, if errorMessage
 * isn't null, also store an error message there.  (Note: the only reason
 * this function and related ones don't dump core on errorMessage == NULL
 * is the undocumented fact that appendPQExpBuffer does nothing when passed
 * a null PQExpBuffer pointer.)
 */
static int
parseServiceInfo(PQconninfoOption *options, PQExpBuffer errorMessage)
{
    const char *service = conninfo_getval(options, "service");
    const char *service_fname = conninfo_getval(options, "servicefile");
    char        serviceFile[MAXPGPATH];
    char       *env;
    bool        group_found = false;
    int         status;
    struct stat stat_buf;
 
    /*
     * We have to special-case the environment variable PGSERVICE here, since
     * this is and should be called before inserting environment defaults for
     * other connection options.
     */
    if (service == NULL)
        service = getenv("PGSERVICE");
 
    /* If no service name given, nothing to do */
    if (service == NULL)
        return 0;
 
    /*
     * First, try the "servicefile" option in connection string.  Then, try
     * the PGSERVICEFILE environment variable.  Finally, check
     * ~/.pg_service.conf (if that exists).
     */
    if (service_fname != NULL)
        strlcpy(serviceFile, service_fname, sizeof(serviceFile));
    else if ((env = getenv("PGSERVICEFILE")) != NULL)
        strlcpy(serviceFile, env, sizeof(serviceFile));
    else
    {
        char        homedir[MAXPGPATH];
 
        if (!pqGetHomeDirectory(homedir, sizeof(homedir)))
            goto next_file;
        snprintf(serviceFile, MAXPGPATH, "%s/%s", homedir, ".pg_service.conf");
        if (stat(serviceFile, &stat_buf) != 0)
            goto next_file;
    }
 
    status = parseServiceFile(serviceFile, service, options, errorMessage, &group_found);
    if (group_found || status != 0)
        return status;
 
next_file:
 
    /*
     * This could be used by any application so we can't use the binary
     * location to find our config files.
     */
    snprintf(serviceFile, MAXPGPATH, "%s/pg_service.conf",
             getenv("PGSYSCONFDIR") ? getenv("PGSYSCONFDIR") : SYSCONFDIR);
    if (stat(serviceFile, &stat_buf) != 0)
        goto last_file;
 
    status = parseServiceFile(serviceFile, service, options, errorMessage, &group_found);
    if (status != 0)
        return status;
 
last_file:
    if (!group_found)
    {
        libpq_append_error(errorMessage, "definition of service \"%s\" not found", service);
        return 3;
    }
 
    return 0;
}
 
static int
parseServiceFile(const char *serviceFile,
                 const char *service,
                 PQconninfoOption *options,
                 PQExpBuffer errorMessage,
                 bool *group_found)
{
    int         result = 0,
                linenr = 0,
                i;
    FILE       *f;
    char       *line;
    char        buf[1024];
 
    *group_found = false;
 
    f = fopen(serviceFile, "r");
    if (f == NULL)
    {
        libpq_append_error(errorMessage, "service file \"%s\" not found", serviceFile);
        return 1;
    }
 
    while ((line = fgets(buf, sizeof(buf), f)) != NULL)
    {
        int         len;
 
        linenr++;
 
        if (strlen(line) >= sizeof(buf) - 1)
        {
            libpq_append_error(errorMessage,
                               "line %d too long in service file \"%s\"",
                               linenr,
                               serviceFile);
            result = 2;
            goto exit;
        }
 
        /* ignore whitespace at end of line, especially the newline */
        len = strlen(line);
        while (len > 0 && isspace((unsigned char) line[len - 1]))
            line[--len] = '\0';
 
        /* ignore leading whitespace too */
        while (*line && isspace((unsigned char) line[0]))
            line++;
 
        /* ignore comments and empty lines */
        if (line[0] == '\0' || line[0] == '#')
            continue;
 
        /* Check for right groupname */
        if (line[0] == '[')
        {
            if (*group_found)
            {
                /* end of desired group reached; return success */
                goto exit;
            }
 
            if (strncmp(line + 1, service, strlen(service)) == 0 &&
                line[strlen(service) + 1] == ']')
                *group_found = true;
            else
                *group_found = false;
        }
        else
        {
            if (*group_found)
            {
                /*
                 * Finally, we are in the right group and can parse the line
                 */
                char       *key,
                           *val;
                bool        found_keyword;
 
#ifdef USE_LDAP
                if (strncmp(line, "ldap", 4) == 0)
                {
                    int         rc = ldapServiceLookup(line, options, errorMessage);
 
                    /* if rc = 2, go on reading for fallback */
                    switch (rc)
                    {
                        case 0:
                            goto exit;
                        case 1:
                        case 3:
                            result = 3;
                            goto exit;
                        case 2:
                            continue;
                    }
                }
#endif
 
                key = line;
                val = strchr(line, '=');
                if (val == NULL)
                {
                    libpq_append_error(errorMessage,
                                       "syntax error in service file \"%s\", line %d",
                                       serviceFile,
                                       linenr);
                    result = 3;
                    goto exit;
                }
                *val++ = '\0';
 
                if (strcmp(key, "service") == 0)
                {
                    libpq_append_error(errorMessage,
                                       "nested \"service\" specifications not supported in service file \"%s\", line %d",
                                       serviceFile,
                                       linenr);
                    result = 3;
                    goto exit;
                }
 
                if (strcmp(key, "servicefile") == 0)
                {
                    libpq_append_error(errorMessage,
                                       "nested \"servicefile\" specifications not supported in service file \"%s\", line %d",
                                       serviceFile,
                                       linenr);
                    result = 3;
                    goto exit;
                }
 
                /*
                 * Set the parameter --- but don't override any previous
                 * explicit setting.
                 */
                found_keyword = false;
                for (i = 0; options[i].keyword; i++)
                {
                    if (strcmp(options[i].keyword, key) == 0)
                    {
                        if (options[i].val == NULL)
                            options[i].val = strdup(val);
                        if (!options[i].val)
                        {
                            libpq_append_error(errorMessage, "out of memory");
                            result = 3;
                            goto exit;
                        }
                        found_keyword = true;
                        break;
                    }
                }
 
                if (!found_keyword)
                {
                    libpq_append_error(errorMessage,
                                       "syntax error in service file \"%s\", line %d",
                                       serviceFile,
                                       linenr);
                    result = 3;
                    goto exit;
                }
            }
        }
    }
 
exit:
 
    /*
     * If a service has been successfully found, set the "servicefile" option
     * if not already set.  This matters when we use a default service file or
     * PGSERVICEFILE, where we want to be able track the value.
     */
    if (*group_found && result == 0)
    {
        for (i = 0; options[i].keyword; i++)
        {
            if (strcmp(options[i].keyword, "servicefile") != 0)
                continue;
 
            /* If value is already set, nothing to do */
            if (options[i].val != NULL)
                break;
 
            options[i].val = strdup(serviceFile);
            if (options[i].val == NULL)
            {
                libpq_append_error(errorMessage, "out of memory");
                result = 3;
            }
            break;
        }
    }
 
    fclose(f);
 
    return result;
}
 
 
/*
 *      PQconninfoParse
 *
 * Parse a string like PQconnectdb() would do and return the
 * resulting connection options array.  NULL is returned on failure.
 * The result contains only options specified directly in the string,
 * not any possible default values.
 *
 * If errmsg isn't NULL, *errmsg is set to NULL on success, or a malloc'd
 * string on failure (use PQfreemem to free it).  In out-of-memory conditions
 * both *errmsg and the result could be NULL.
 *
 * NOTE: the returned array is dynamically allocated and should
 * be freed when no longer needed via PQconninfoFree().
 */
PQconninfoOption *
PQconninfoParse(const char *conninfo, char **errmsg)
{
    PQExpBufferData errorBuf;
    PQconninfoOption *connOptions;
 
    if (errmsg)
        *errmsg = NULL;         /* default */
    initPQExpBuffer(&errorBuf);
    if (PQExpBufferDataBroken(errorBuf))
        return NULL;            /* out of memory already :-( */
    connOptions = parse_connection_string(conninfo, &errorBuf, false);
    if (connOptions == NULL && errmsg)
        *errmsg = errorBuf.data;
    else
        termPQExpBuffer(&errorBuf);
    return connOptions;
}
 
/*
 * Build a working copy of the constant PQconninfoOptions array.
 */
static PQconninfoOption *
conninfo_init(PQExpBuffer errorMessage)
{
    PQconninfoOption *options;
    PQconninfoOption *opt_dest;
    const internalPQconninfoOption *cur_opt;
 
    /*
     * Get enough memory for all options in PQconninfoOptions, even if some
     * end up being filtered out.
     */
    options = (PQconninfoOption *) malloc(sizeof(PQconninfoOption) * sizeof(PQconninfoOptions) / sizeof(PQconninfoOptions[0]));
    if (options == NULL)
    {
        libpq_append_error(errorMessage, "out of memory");
        return NULL;
    }
    opt_dest = options;
 
    for (cur_opt = PQconninfoOptions; cur_opt->keyword; cur_opt++)
    {
        /* Only copy the public part of the struct, not the full internal */
        memcpy(opt_dest, cur_opt, sizeof(PQconninfoOption));
        opt_dest++;
    }
    MemSet(opt_dest, 0, sizeof(PQconninfoOption));
 
    return options;
}
 
/*
 * Connection string parser
 *
 * Returns a malloc'd PQconninfoOption array, if parsing is successful.
 * Otherwise, NULL is returned and an error message is added to errorMessage.
 *
 * If use_defaults is true, default values are filled in (from a service file,
 * environment variables, etc).
 */
static PQconninfoOption *
parse_connection_string(const char *connstr, PQExpBuffer errorMessage,
                        bool use_defaults)
{
    /* Parse as URI if connection string matches URI prefix */
    if (uri_prefix_length(connstr) != 0)
        return conninfo_uri_parse(connstr, errorMessage, use_defaults);
 
    /* Parse as default otherwise */
    return conninfo_parse(connstr, errorMessage, use_defaults);
}
 
/*
 * Checks if connection string starts with either of the valid URI prefix
 * designators.
 *
 * Returns the URI prefix length, 0 if the string doesn't contain a URI prefix.
 *
 * XXX this is duplicated in psql/common.c.
 */
static int
uri_prefix_length(const char *connstr)
{
    if (strncmp(connstr, uri_designator,
                sizeof(uri_designator) - 1) == 0)
        return sizeof(uri_designator) - 1;
 
    if (strncmp(connstr, short_uri_designator,
                sizeof(short_uri_designator) - 1) == 0)
        return sizeof(short_uri_designator) - 1;
 
    return 0;
}
 
/*
 * Recognized connection string either starts with a valid URI prefix or
 * contains a "=" in it.
 *
 * Must be consistent with parse_connection_string: anything for which this
 * returns true should at least look like it's parseable by that routine.
 *
 * XXX this is duplicated in psql/common.c
 */
static bool
recognized_connection_string(const char *connstr)
{
    return uri_prefix_length(connstr) != 0 || strchr(connstr, '=') != NULL;
}
 
/*
 * Subroutine for parse_connection_string
 *
 * Deal with a string containing key=value pairs.
 */
static PQconninfoOption *
conninfo_parse(const char *conninfo, PQExpBuffer errorMessage,
               bool use_defaults)
{
    char       *pname;
    char       *pval;
    char       *buf;
    char       *cp;
    char       *cp2;
    PQconninfoOption *options;
 
    /* Make a working copy of PQconninfoOptions */
    options = conninfo_init(errorMessage);
    if (options == NULL)
        return NULL;
 
    /* Need a modifiable copy of the input string */
    if ((buf = strdup(conninfo)) == NULL)
    {
        libpq_append_error(errorMessage, "out of memory");
        PQconninfoFree(options);
        return NULL;
    }
    cp = buf;
 
    while (*cp)
    {
        /* Skip blanks before the parameter name */
        if (isspace((unsigned char) *cp))
        {
            cp++;
            continue;
        }
 
        /* Get the parameter name */
        pname = cp;
        while (*cp)
        {
            if (*cp == '=')
                break;
            if (isspace((unsigned char) *cp))
            {
                *cp++ = '\0';
                while (*cp)
                {
                    if (!isspace((unsigned char) *cp))
                        break;
                    cp++;
                }
                break;
            }
            cp++;
        }
 
        /* Check that there is a following '=' */
        if (*cp != '=')
        {
            libpq_append_error(errorMessage,
                               "missing \"=\" after \"%s\" in connection info string",
                               pname);
            PQconninfoFree(options);
            free(buf);
            return NULL;
        }
        *cp++ = '\0';
 
        /* Skip blanks after the '=' */
        while (*cp)
        {
            if (!isspace((unsigned char) *cp))
                break;
            cp++;
        }
 
        /* Get the parameter value */
        pval = cp;
 
        if (*cp != '\'')
        {
            cp2 = pval;
            while (*cp)
            {
                if (isspace((unsigned char) *cp))
                {
                    *cp++ = '\0';
                    break;
                }
                if (*cp == '\\')
                {
                    cp++;
                    if (*cp != '\0')
                        *cp2++ = *cp++;
                }
                else
                    *cp2++ = *cp++;
            }
            *cp2 = '\0';
        }
        else
        {
            cp2 = pval;
            cp++;
            for (;;)
            {
                if (*cp == '\0')
                {
                    libpq_append_error(errorMessage, "unterminated quoted string in connection info string");
                    PQconninfoFree(options);
                    free(buf);
                    return NULL;
                }
                if (*cp == '\\')
                {
                    cp++;
                    if (*cp != '\0')
                        *cp2++ = *cp++;
                    continue;
                }
                if (*cp == '\'')
                {
                    *cp2 = '\0';
                    cp++;
                    break;
                }
                *cp2++ = *cp++;
            }
        }
 
        /*
         * Now that we have the name and the value, store the record.
         */
        if (!conninfo_storeval(options, pname, pval, errorMessage, false, false))
        {
            PQconninfoFree(options);
            free(buf);
            return NULL;
        }
    }
 
    /* Done with the modifiable input string */
    free(buf);
 
    /*
     * Add in defaults if the caller wants that.
     */
    if (use_defaults)
    {
        if (!conninfo_add_defaults(options, errorMessage))
        {
            PQconninfoFree(options);
            return NULL;
        }
    }
 
    return options;
}
 
/*
 * Conninfo array parser routine
 *
 * If successful, a malloc'd PQconninfoOption array is returned.
 * If not successful, NULL is returned and an error message is
 * appended to errorMessage.
 * Defaults are supplied (from a service file, environment variables, etc)
 * for unspecified options, but only if use_defaults is true.
 *
 * If expand_dbname is non-zero, and the value passed for the first occurrence
 * of "dbname" keyword is a connection string (as indicated by
 * recognized_connection_string) then parse and process it, overriding any
 * previously processed conflicting keywords. Subsequent keywords will take
 * precedence, however. In-tree programs generally specify expand_dbname=true,
 * so command-line arguments naming a database can use a connection string.
 * Some code acquires arbitrary database names from known-literal sources like
 * PQdb(), PQconninfoParse() and pg_database.datname.  When connecting to such
 * a database, in-tree code first wraps the name in a connection string.
 */
static PQconninfoOption *
conninfo_array_parse(const char *const *keywords, const char *const *values,
                     PQExpBuffer errorMessage, bool use_defaults,
                     int expand_dbname)
{
    PQconninfoOption *options;
    PQconninfoOption *dbname_options = NULL;
    PQconninfoOption *option;
    int         i = 0;
 
    /*
     * If expand_dbname is non-zero, check keyword "dbname" to see if val is
     * actually a recognized connection string.
     */
    while (expand_dbname && keywords[i])
    {
        const char *pname = keywords[i];
        const char *pvalue = values[i];
 
        /* first find "dbname" if any */
        if (strcmp(pname, "dbname") == 0 && pvalue)
        {
            /*
             * If value is a connection string, parse it, but do not use
             * defaults here -- those get picked up later. We only want to
             * override for those parameters actually passed.
             */
            if (recognized_connection_string(pvalue))
            {
                dbname_options = parse_connection_string(pvalue, errorMessage, false);
                if (dbname_options == NULL)
                    return NULL;
            }
            break;
        }
        ++i;
    }
 
    /* Make a working copy of PQconninfoOptions */
    options = conninfo_init(errorMessage);
    if (options == NULL)
    {
        PQconninfoFree(dbname_options);
        return NULL;
    }
 
    /* Parse the keywords/values arrays */
    i = 0;
    while (keywords[i])
    {
        const char *pname = keywords[i];
        const char *pvalue = values[i];
 
        if (pvalue != NULL && pvalue[0] != '\0')
        {
            /* Search for the param record */
            for (option = options; option->keyword != NULL; option++)
            {
                if (strcmp(option->keyword, pname) == 0)
                    break;
            }
 
            /* Check for invalid connection option */
            if (option->keyword == NULL)
            {
                libpq_append_error(errorMessage, "invalid connection option \"%s\"", pname);
                PQconninfoFree(options);
                PQconninfoFree(dbname_options);
                return NULL;
            }
 
            /*
             * If we are on the first dbname parameter, and we have a parsed
             * connection string, copy those parameters across, overriding any
             * existing previous settings.
             */
            if (strcmp(pname, "dbname") == 0 && dbname_options)
            {
                PQconninfoOption *str_option;
 
                for (str_option = dbname_options; str_option->keyword != NULL; str_option++)
                {
                    if (str_option->val != NULL)
                    {
                        int         k;
 
                        for (k = 0; options[k].keyword; k++)
                        {
                            if (strcmp(options[k].keyword, str_option->keyword) == 0)
                            {
                                free(options[k].val);
                                options[k].val = strdup(str_option->val);
                                if (!options[k].val)
                                {
                                    libpq_append_error(errorMessage, "out of memory");
                                    PQconninfoFree(options);
                                    PQconninfoFree(dbname_options);
                                    return NULL;
                                }
                                break;
                            }
                        }
                    }
                }
 
                /*
                 * Forget the parsed connection string, so that any subsequent
                 * dbname parameters will not be expanded.
                 */
                PQconninfoFree(dbname_options);
                dbname_options = NULL;
            }
            else
            {
                /*
                 * Store the value, overriding previous settings
                 */
                free(option->val);
                option->val = strdup(pvalue);
                if (!option->val)
                {
                    libpq_append_error(errorMessage, "out of memory");
                    PQconninfoFree(options);
                    PQconninfoFree(dbname_options);
                    return NULL;
                }
            }
        }
        ++i;
    }
    PQconninfoFree(dbname_options);
 
    /*
     * Add in defaults if the caller wants that.
     */
    if (use_defaults)
    {
        if (!conninfo_add_defaults(options, errorMessage))
        {
            PQconninfoFree(options);
            return NULL;
        }
    }
 
    return options;
}
 
/*
 * Add the default values for any unspecified options to the connection
 * options array.
 *
 * Defaults are obtained from a service file, environment variables, etc.
 *
 * Returns true if successful, otherwise false; errorMessage, if supplied,
 * is filled in upon failure.  Note that failure to locate a default value
 * is not an error condition here --- we just leave the option's value as
 * NULL.
 */
static bool
conninfo_add_defaults(PQconninfoOption *options, PQExpBuffer errorMessage)
{
    PQconninfoOption *option;
    PQconninfoOption *sslmode_default = NULL,
               *sslrootcert = NULL;
    char       *tmp;
 
    /*
     * If there's a service spec, use it to obtain any not-explicitly-given
     * parameters.  Ignore error if no error message buffer is passed because
     * there is no way to pass back the failure message.
     */
    if (parseServiceInfo(options, errorMessage) != 0 && errorMessage)
        return false;
 
    /*
     * Get the fallback resources for parameters not specified in the conninfo
     * string nor the service.
     */
    for (option = options; option->keyword != NULL; option++)
    {
        if (strcmp(option->keyword, "sslrootcert") == 0)
            sslrootcert = option;   /* save for later */
 
        if (option->val != NULL)
            continue;           /* Value was in conninfo or service */
 
        /*
         * Try to get the environment variable fallback
         */
        if (option->envvar != NULL)
        {
            if ((tmp = getenv(option->envvar)) != NULL)
            {
                option->val = strdup(tmp);
                if (!option->val)
                {
                    if (errorMessage)
                        libpq_append_error(errorMessage, "out of memory");
                    return false;
                }
                continue;
            }
        }
 
        /*
         * Interpret the deprecated PGREQUIRESSL environment variable.  Per
         * tradition, translate values starting with "1" to sslmode=require,
         * and ignore other values.  Given both PGREQUIRESSL=1 and PGSSLMODE,
         * PGSSLMODE takes precedence; the opposite was true before v9.3.
         */
        if (strcmp(option->keyword, "sslmode") == 0)
        {
            const char *requiresslenv = getenv("PGREQUIRESSL");
 
            if (requiresslenv != NULL && requiresslenv[0] == '1')
            {
                option->val = strdup("require");
                if (!option->val)
                {
                    if (errorMessage)
                        libpq_append_error(errorMessage, "out of memory");
                    return false;
                }
                continue;
            }
 
            /*
             * sslmode is not specified. Let it be filled in with the compiled
             * default for now, but if sslrootcert=system, we'll override the
             * default later before returning.
             */
            sslmode_default = option;
        }
 
        /*
         * No environment variable specified or the variable isn't set - try
         * compiled-in default
         */
        if (option->compiled != NULL)
        {
            option->val = strdup(option->compiled);
            if (!option->val)
            {
                if (errorMessage)
                    libpq_append_error(errorMessage, "out of memory");
                return false;
            }
            continue;
        }
 
        /*
         * Special handling for "user" option.  Note that if pg_fe_getauthname
         * fails, we just leave the value as NULL; there's no need for this to
         * be an error condition if the caller provides a user name.  The only
         * reason we do this now at all is so that callers of PQconndefaults
         * will see a correct default (barring error, of course).
         */
        if (strcmp(option->keyword, "user") == 0)
        {
            option->val = pg_fe_getauthname(NULL);
            continue;
        }
    }
 
    /*
     * Special handling for sslrootcert=system with no sslmode explicitly
     * defined. In this case we want to strengthen the default sslmode to
     * verify-full.
     */
    if (sslmode_default && sslrootcert)
    {
        if (sslrootcert->val && strcmp(sslrootcert->val, "system") == 0)
        {
            free(sslmode_default->val);
 
            sslmode_default->val = strdup("verify-full");
            if (!sslmode_default->val)
            {
                if (errorMessage)
                    libpq_append_error(errorMessage, "out of memory");
                return false;
            }
        }
    }
 
    return true;
}
 
/*
 * Subroutine for parse_connection_string
 *
 * Deal with a URI connection string.
 */
static PQconninfoOption *
conninfo_uri_parse(const char *uri, PQExpBuffer errorMessage,
                   bool use_defaults)
{
    PQconninfoOption *options;
 
    /* Make a working copy of PQconninfoOptions */
    options = conninfo_init(errorMessage);
    if (options == NULL)
        return NULL;
 
    if (!conninfo_uri_parse_options(options, uri, errorMessage))
    {
        PQconninfoFree(options);
        return NULL;
    }
 
    /*
     * Add in defaults if the caller wants that.
     */
    if (use_defaults)
    {
        if (!conninfo_add_defaults(options, errorMessage))
        {
            PQconninfoFree(options);
            return NULL;
        }
    }
 
    return options;
}
 
/*
 * conninfo_uri_parse_options
 *      Actual URI parser.
 *
 * If successful, returns true while the options array is filled with parsed
 * options from the URI.
 * If not successful, returns false and fills errorMessage accordingly.
 *
 * Parses the connection URI string in 'uri' according to the URI syntax (RFC
 * 3986):
 *
 * postgresql://[user[:password]@][netloc][:port][/dbname][?param1=value1&...]
 *
 * where "netloc" is a hostname, an IPv4 address, or an IPv6 address surrounded
 * by literal square brackets.  As an extension, we also allow multiple
 * netloc[:port] specifications, separated by commas:
 *
 * postgresql://[user[:password]@][netloc][:port][,...][/dbname][?param1=value1&...]
 *
 * Any of the URI parts might use percent-encoding (%xy).
 */
static bool
conninfo_uri_parse_options(PQconninfoOption *options, const char *uri,
                           PQExpBuffer errorMessage)
{
    int         prefix_len;
    char       *p;
    char       *buf = NULL;
    char       *start;
    char        prevchar = '\0';
    char       *user = NULL;
    char       *host = NULL;
    bool        retval = false;
    PQExpBufferData hostbuf;
    PQExpBufferData portbuf;
 
    initPQExpBuffer(&hostbuf);
    initPQExpBuffer(&portbuf);
    if (PQExpBufferDataBroken(hostbuf) || PQExpBufferDataBroken(portbuf))
    {
        libpq_append_error(errorMessage, "out of memory");
        goto cleanup;
    }
 
    /* need a modifiable copy of the input URI */
    buf = strdup(uri);
    if (buf == NULL)
    {
        libpq_append_error(errorMessage, "out of memory");
        goto cleanup;
    }
    start = buf;
 
    /* Skip the URI prefix */
    prefix_len = uri_prefix_length(uri);
    if (prefix_len == 0)
    {
        /* Should never happen */
        libpq_append_error(errorMessage,
                           "invalid URI propagated to internal parser routine: \"%s\"",
                           uri);
        goto cleanup;
    }
    start += prefix_len;
    p = start;
 
    /* Look ahead for possible user credentials designator */
    while (*p && *p != '@' && *p != '/')
        ++p;
    if (*p == '@')
    {
        /*
         * Found username/password designator, so URI should be of the form
         * "scheme://user[:password]@[netloc]".
         */
        user = start;
 
        p = user;
        while (*p != ':' && *p != '@')
            ++p;
 
        /* Save last char and cut off at end of user name */
        prevchar = *p;
        *p = '\0';
 
        if (*user &&
            !conninfo_storeval(options, "user", user,
                               errorMessage, false, true))
            goto cleanup;
 
        if (prevchar == ':')
        {
            const char *password = p + 1;
 
            while (*p != '@')
                ++p;
            *p = '\0';
 
            if (*password &&
                !conninfo_storeval(options, "password", password,
                                   errorMessage, false, true))
                goto cleanup;
        }
 
        /* Advance past end of parsed user name or password token */
        ++p;
    }
    else
    {
        /*
         * No username/password designator found.  Reset to start of URI.
         */
        p = start;
    }
 
    /*
     * There may be multiple netloc[:port] pairs, each separated from the next
     * by a comma.  When we initially enter this loop, "p" has been
     * incremented past optional URI credential information at this point and
     * now points at the "netloc" part of the URI.  On subsequent loop
     * iterations, "p" has been incremented past the comma separator and now
     * points at the start of the next "netloc".
     */
    for (;;)
    {
        /*
         * Look for IPv6 address.
         */
        if (*p == '[')
        {
            host = ++p;
            while (*p && *p != ']')
                ++p;
            if (!*p)
            {
                libpq_append_error(errorMessage,
                                   "end of string reached when looking for matching \"]\" in IPv6 host address in URI: \"%s\"",
                                   uri);
                goto cleanup;
            }
            if (p == host)
            {
                libpq_append_error(errorMessage,
                                   "IPv6 host address may not be empty in URI: \"%s\"",
                                   uri);
                goto cleanup;
            }
 
            /* Cut off the bracket and advance */
            *(p++) = '\0';
 
            /*
             * The address may be followed by a port specifier or a slash or a
             * query or a separator comma.
             */
            if (*p && *p != ':' && *p != '/' && *p != '?' && *p != ',')
            {
                libpq_append_error(errorMessage,
                                   "unexpected character \"%c\" at position %d in URI (expected \":\" or \"/\"): \"%s\"",
                                   *p, (int) (p - buf + 1), uri);
                goto cleanup;
            }
        }
        else
        {
            /* not an IPv6 address: DNS-named or IPv4 netloc */
            host = p;
 
            /*
             * Look for port specifier (colon) or end of host specifier
             * (slash) or query (question mark) or host separator (comma).
             */
            while (*p && *p != ':' && *p != '/' && *p != '?' && *p != ',')
                ++p;
        }
 
        /* Save the hostname terminator before we null it */
        prevchar = *p;
        *p = '\0';
 
        appendPQExpBufferStr(&hostbuf, host);
 
        if (prevchar == ':')
        {
            const char *port = ++p; /* advance past host terminator */
 
            while (*p && *p != '/' && *p != '?' && *p != ',')
                ++p;
 
            prevchar = *p;
            *p = '\0';
 
            appendPQExpBufferStr(&portbuf, port);
        }
 
        if (prevchar != ',')
            break;
        ++p;                    /* advance past comma separator */
        appendPQExpBufferChar(&hostbuf, ',');
        appendPQExpBufferChar(&portbuf, ',');
    }
 
    /* Save final values for host and port. */
    if (PQExpBufferDataBroken(hostbuf) || PQExpBufferDataBroken(portbuf))
        goto cleanup;
    if (hostbuf.data[0] &&
        !conninfo_storeval(options, "host", hostbuf.data,
                           errorMessage, false, true))
        goto cleanup;
    if (portbuf.data[0] &&
        !conninfo_storeval(options, "port", portbuf.data,
                           errorMessage, false, true))
        goto cleanup;
 
    if (prevchar && prevchar != '?')
    {
        const char *dbname = ++p;   /* advance past host terminator */
 
        /* Look for query parameters */
        while (*p && *p != '?')
            ++p;
 
        prevchar = *p;
        *p = '\0';
 
        /*
         * Avoid setting dbname to an empty string, as it forces the default
         * value (username) and ignores $PGDATABASE, as opposed to not setting
         * it at all.
         */
        if (*dbname &&
            !conninfo_storeval(options, "dbname", dbname,
                               errorMessage, false, true))
            goto cleanup;
    }
 
    if (prevchar)
    {
        ++p;                    /* advance past terminator */
 
        if (!conninfo_uri_parse_params(p, options, errorMessage))
            goto cleanup;
    }
 
    /* everything parsed okay */
    retval = true;
 
cleanup:
    termPQExpBuffer(&hostbuf);
    termPQExpBuffer(&portbuf);
    free(buf);
    return retval;
}
 
/*
 * Connection URI parameters parser routine
 *
 * If successful, returns true while connOptions is filled with parsed
 * parameters.  Otherwise, returns false and fills errorMessage appropriately.
 *
 * Destructively modifies 'params' buffer.
 */
static bool
conninfo_uri_parse_params(char *params,
                          PQconninfoOption *connOptions,
                          PQExpBuffer errorMessage)
{
    while (*params)
    {
        char       *keyword = params;
        char       *value = NULL;
        char       *p = params;
        bool        malloced = false;
        int         oldmsglen;
 
        /*
         * Scan the params string for '=' and '&', marking the end of keyword
         * and value respectively.
         */
        for (;;)
        {
            if (*p == '=')
            {
                /* Was there '=' already? */
                if (value != NULL)
                {
                    libpq_append_error(errorMessage,
                                       "extra key/value separator \"=\" in URI query parameter: \"%s\"",
                                       keyword);
                    return false;
                }
                /* Cut off keyword, advance to value */
                *p++ = '\0';
                value = p;
            }
            else if (*p == '&' || *p == '\0')
            {
                /*
                 * If not at the end, cut off value and advance; leave p
                 * pointing to start of the next parameter, if any.
                 */
                if (*p != '\0')
                    *p++ = '\0';
                /* Was there '=' at all? */
                if (value == NULL)
                {
                    libpq_append_error(errorMessage,
                                       "missing key/value separator \"=\" in URI query parameter: \"%s\"",
                                       keyword);
                    return false;
                }
                /* Got keyword and value, go process them. */
                break;
            }
            else
                ++p;            /* Advance over all other bytes. */
        }
 
        keyword = conninfo_uri_decode(keyword, errorMessage);
        if (keyword == NULL)
        {
            /* conninfo_uri_decode already set an error message */
            return false;
        }
        value = conninfo_uri_decode(value, errorMessage);
        if (value == NULL)
        {
            /* conninfo_uri_decode already set an error message */
            free(keyword);
            return false;
        }
        malloced = true;
 
        /*
         * Special keyword handling for improved JDBC compatibility.
         */
        if (strcmp(keyword, "ssl") == 0 &&
            strcmp(value, "true") == 0)
        {
            free(keyword);
            free(value);
            malloced = false;
 
            keyword = "sslmode";
            value = "require";
        }
 
        /*
         * Store the value if the corresponding option exists; ignore
         * otherwise.  At this point both keyword and value are not
         * URI-encoded.
         */
        oldmsglen = errorMessage->len;
        if (!conninfo_storeval(connOptions, keyword, value,
                               errorMessage, true, false))
        {
            /* Insert generic message if conninfo_storeval didn't give one. */
            if (errorMessage->len == oldmsglen)
                libpq_append_error(errorMessage,
                                   "invalid URI query parameter: \"%s\"",
                                   keyword);
            /* And fail. */
            if (malloced)
            {
                free(keyword);
                free(value);
            }
            return false;
        }
 
        if (malloced)
        {
            free(keyword);
            free(value);
        }
 
        /* Proceed to next key=value pair, if any */
        params = p;
    }
 
    return true;
}
 
/*
 * Connection URI decoder routine
 *
 * If successful, returns the malloc'd decoded string.
 * If not successful, returns NULL and fills errorMessage accordingly.
 *
 * The string is decoded by replacing any percent-encoded tokens with
 * corresponding characters, while preserving any non-encoded characters.  A
 * percent-encoded token is a character triplet: a percent sign, followed by a
 * pair of hexadecimal digits (0-9A-F), where lower- and upper-case letters are
 * treated identically.
 */
static char *
conninfo_uri_decode(const char *str, PQExpBuffer errorMessage)
{
    char       *buf;            /* result */
    char       *p;              /* output location */
    const char *q = str;        /* input location */
 
    buf = malloc(strlen(str) + 1);
    if (buf == NULL)
    {
        libpq_append_error(errorMessage, "out of memory");
        return NULL;
    }
    p = buf;
 
    /* skip leading whitespaces */
    for (const char *s = q; *s == ' '; s++)
    {
        q++;
        continue;
    }
 
    for (;;)
    {
        if (*q != '%')
        {
            /* if found a whitespace or NUL, the string ends */
            if (*q == ' ' || *q == '\0')
                goto end;
 
            /* copy character */
            *(p++) = *(q++);
        }
        else
        {
            int         hi;
            int         lo;
            int         c;
 
            ++q;                /* skip the percent sign itself */
 
            /*
             * Possible EOL will be caught by the first call to
             * get_hexdigit(), so we never dereference an invalid q pointer.
             */
            if (!(get_hexdigit(*q++, &hi) && get_hexdigit(*q++, &lo)))
            {
                libpq_append_error(errorMessage,
                                   "invalid percent-encoded token: \"%s\"",
                                   str);
                free(buf);
                return NULL;
            }
 
            c = (hi << 4) | lo;
            if (c == 0)
            {
                libpq_append_error(errorMessage,
                                   "forbidden value %%00 in percent-encoded value: \"%s\"",
                                   str);
                free(buf);
                return NULL;
            }
            *(p++) = c;
        }
    }
 
end:
 
    /* skip trailing whitespaces */
    for (const char *s = q; *s == ' '; s++)
    {
        q++;
        continue;
    }
 
    /* Not at the end of the string yet?  Fail. */
    if (*q != '\0')
    {
        libpq_append_error(errorMessage,
                           "unexpected spaces found in \"%s\", use percent-encoded spaces (%%20) instead",
                           str);
        free(buf);
        return NULL;
    }
 
    /* Copy NUL terminator */
    *p = '\0';
 
    return buf;
}
 
/*
 * Convert hexadecimal digit character to its integer value.
 *
 * If successful, returns true and value is filled with digit's base 16 value.
 * If not successful, returns false.
 *
 * Lower- and upper-case letters in the range A-F are treated identically.
 */
static bool
get_hexdigit(char digit, int *value)
{
    if ('0' <= digit && digit <= '9')
        *value = digit - '0';
    else if ('A' <= digit && digit <= 'F')
        *value = digit - 'A' + 10;
    else if ('a' <= digit && digit <= 'f')
        *value = digit - 'a' + 10;
    else
        return false;
 
    return true;
}
 
/*
 * Find an option value corresponding to the keyword in the connOptions array.
 *
 * If successful, returns a pointer to the corresponding option's value.
 * If not successful, returns NULL.
 */
static const char *
conninfo_getval(PQconninfoOption *connOptions,
                const char *keyword)
{
    PQconninfoOption *option;
 
    option = conninfo_find(connOptions, keyword);
 
    return option ? option->val : NULL;
}
 
/*
 * Store a (new) value for an option corresponding to the keyword in
 * connOptions array.
 *
 * If uri_decode is true, the value is URI-decoded.  The keyword is always
 * assumed to be non URI-encoded.
 *
 * If successful, returns a pointer to the corresponding PQconninfoOption,
 * which value is replaced with a strdup'd copy of the passed value string.
 * The existing value for the option is free'd before replacing, if any.
 *
 * If not successful, returns NULL and fills errorMessage accordingly.
 * However, if the reason of failure is an invalid keyword being passed and
 * ignoreMissing is true, errorMessage will be left untouched.
 */
static PQconninfoOption *
conninfo_storeval(PQconninfoOption *connOptions,
                  const char *keyword, const char *value,
                  PQExpBuffer errorMessage, bool ignoreMissing,
                  bool uri_decode)
{
    PQconninfoOption *option;
    char       *value_copy;
 
    /*
     * For backwards compatibility, requiressl=1 gets translated to
     * sslmode=require, and requiressl=0 gets translated to sslmode=prefer
     * (which is the default for sslmode).
     */
    if (strcmp(keyword, "requiressl") == 0)
    {
        keyword = "sslmode";
        if (value[0] == '1')
            value = "require";
        else
            value = "prefer";
    }
 
    option = conninfo_find(connOptions, keyword);
    if (option == NULL)
    {
        if (!ignoreMissing)
            libpq_append_error(errorMessage,
                               "invalid connection option \"%s\"",
                               keyword);
        return NULL;
    }
 
    if (uri_decode)
    {
        value_copy = conninfo_uri_decode(value, errorMessage);
        if (value_copy == NULL)
            /* conninfo_uri_decode already set an error message */
            return NULL;
    }
    else
    {
        value_copy = strdup(value);
        if (value_copy == NULL)
        {
            libpq_append_error(errorMessage, "out of memory");
            return NULL;
        }
    }
 
    free(option->val);
    option->val = value_copy;
 
    return option;
}
 
/*
 * Find a PQconninfoOption option corresponding to the keyword in the
 * connOptions array.
 *
 * If successful, returns a pointer to the corresponding PQconninfoOption
 * structure.
 * If not successful, returns NULL.
 */
static PQconninfoOption *
conninfo_find(PQconninfoOption *connOptions, const char *keyword)
{
    PQconninfoOption *option;
 
    for (option = connOptions; option->keyword != NULL; option++)
    {
        if (strcmp(option->keyword, keyword) == 0)
            return option;
    }
 
    return NULL;
}
 
 
/*
 * Return the connection options used for the connection
 */
PQconninfoOption *
PQconninfo(PGconn *conn)
{
    PQExpBufferData errorBuf;
    PQconninfoOption *connOptions;
 
    if (conn == NULL)
        return NULL;
 
    /*
     * We don't actually report any errors here, but callees want a buffer,
     * and we prefer not to trash the conn's errorMessage.
     */
    initPQExpBuffer(&errorBuf);
    if (PQExpBufferDataBroken(errorBuf))
        return NULL;            /* out of memory already :-( */
 
    connOptions = conninfo_init(&errorBuf);
 
    if (connOptions != NULL)
    {
        const internalPQconninfoOption *option;
 
        for (option = PQconninfoOptions; option->keyword; option++)
        {
            char      **connmember;
 
            if (option->connofs < 0)
                continue;
 
            connmember = (char **) ((char *) conn + option->connofs);
 
            if (*connmember)
                conninfo_storeval(connOptions, option->keyword, *connmember,
                                  &errorBuf, true, false);
        }
    }
 
    termPQExpBuffer(&errorBuf);
 
    return connOptions;
}
 
 
void
PQconninfoFree(PQconninfoOption *connOptions)
{
    if (connOptions == NULL)
        return;
 
    for (PQconninfoOption *option = connOptions; option->keyword != NULL; option++)
        free(option->val);
    free(connOptions);
}
 
 
/* =========== accessor functions for PGconn ========= */
char *
PQdb(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return conn->dbName;
}
 
char *
PQuser(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return conn->pguser;
}
 
char *
PQpass(const PGconn *conn)
{
    char       *password = NULL;
 
    if (!conn)
        return NULL;
    if (conn->connhost != NULL)
        password = conn->connhost[conn->whichhost].password;
    if (password == NULL)
        password = conn->pgpass;
    /* Historically we've returned "" not NULL for no password specified */
    if (password == NULL)
        password = "";
    return password;
}
 
char *
PQhost(const PGconn *conn)
{
    if (!conn)
        return NULL;
 
    if (conn->connhost != NULL)
    {
        /*
         * Return the verbatim host value provided by user, or hostaddr in its
         * lack.
         */
        if (conn->connhost[conn->whichhost].host != NULL &&
            conn->connhost[conn->whichhost].host[0] != '\0')
            return conn->connhost[conn->whichhost].host;
        else if (conn->connhost[conn->whichhost].hostaddr != NULL &&
                 conn->connhost[conn->whichhost].hostaddr[0] != '\0')
            return conn->connhost[conn->whichhost].hostaddr;
    }
 
    return "";
}
 
char *
PQhostaddr(const PGconn *conn)
{
    if (!conn)
        return NULL;
 
    /* Return the parsed IP address */
    if (conn->connhost != NULL && conn->connip != NULL)
        return conn->connip;
 
    return "";
}
 
char *
PQport(const PGconn *conn)
{
    if (!conn)
        return NULL;
 
    if (conn->connhost != NULL &&
        conn->connhost[conn->whichhost].port != NULL &&
        conn->connhost[conn->whichhost].port[0] != '\0')
        return conn->connhost[conn->whichhost].port;
 
    return DEF_PGPORT_STR;
}
 
/*
 * No longer does anything, but the function remains for API backwards
 * compatibility.
 */
char *
PQtty(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return "";
}
 
char *
PQoptions(const PGconn *conn)
{
    if (!conn)
        return NULL;
    return conn->pgoptions;
}
 
ConnStatusType
PQstatus(const PGconn *conn)
{
    if (!conn)
        return CONNECTION_BAD;
    return conn->status;
}
 
PGTransactionStatusType
PQtransactionStatus(const PGconn *conn)
{
    if (!conn || conn->status != CONNECTION_OK)
        return PQTRANS_UNKNOWN;
    if (conn->asyncStatus != PGASYNC_IDLE)
        return PQTRANS_ACTIVE;
    return conn->xactStatus;
}
 
const char *
PQparameterStatus(const PGconn *conn, const char *paramName)
{
    const pgParameterStatus *pstatus;
 
    if (!conn || !paramName)
        return NULL;
    for (pstatus = conn->pstatus; pstatus != NULL; pstatus = pstatus->next)
    {
        if (strcmp(pstatus->name, paramName) == 0)
            return pstatus->value;
    }
    return NULL;
}
 
int
PQprotocolVersion(const PGconn *conn)
{
    if (!conn)
        return 0;
    if (conn->status == CONNECTION_BAD)
        return 0;
    return PG_PROTOCOL_MAJOR(conn->pversion);
}
 
int
PQfullProtocolVersion(const PGconn *conn)
{
    if (!conn)
        return 0;
    if (conn->status == CONNECTION_BAD)
        return 0;
    return PG_PROTOCOL_FULL(conn->pversion);
}
 
int
PQserverVersion(const PGconn *conn)
{
    if (!conn)
        return 0;
    if (conn->status == CONNECTION_BAD)
        return 0;
    return conn->sversion;
}
 
char *
PQerrorMessage(const PGconn *conn)
{
    if (!conn)
        return libpq_gettext("connection pointer is NULL\n");
 
    /*
     * The errorMessage buffer might be marked "broken" due to having
     * previously failed to allocate enough memory for the message.  In that
     * case, tell the application we ran out of memory.
     */
    if (PQExpBufferBroken(&conn->errorMessage))
        return libpq_gettext("out of memory\n");
 
    return conn->errorMessage.data;
}
 
/*
 * In Windows, socket values are unsigned, and an invalid socket value
 * (INVALID_SOCKET) is ~0, which equals -1 in comparisons (with no compiler
 * warning). Ideally we would return an unsigned value for PQsocket() on
 * Windows, but that would cause the function's return value to differ from
 * Unix, so we just return -1 for invalid sockets.
 * http://msdn.microsoft.com/en-us/library/windows/desktop/cc507522%28v=vs.85%29.aspx
 * http://stackoverflow.com/questions/10817252/why-is-invalid-socket-defined-as-0-in-winsock2-h-c
 */
int
PQsocket(const PGconn *conn)
{
    if (!conn)
        return -1;
    if (conn->altsock != PGINVALID_SOCKET)
        return conn->altsock;
    return (conn->sock != PGINVALID_SOCKET) ? conn->sock : -1;
}
 
int
PQbackendPID(const PGconn *conn)
{
    if (!conn || conn->status != CONNECTION_OK)
        return 0;
    return conn->be_pid;
}
 
PGpipelineStatus
PQpipelineStatus(const PGconn *conn)
{
    if (!conn)
        return PQ_PIPELINE_OFF;
 
    return conn->pipelineStatus;
}
 
int
PQconnectionNeedsPassword(const PGconn *conn)
{
    char       *password;
 
    if (!conn)
        return false;
    password = PQpass(conn);
    if (conn->password_needed &&
        (password == NULL || password[0] == '\0'))
        return true;
    else
        return false;
}
 
int
PQconnectionUsedPassword(const PGconn *conn)
{
    if (!conn)
        return false;
    if (conn->password_needed)
        return true;
    else
        return false;
}
 
int
PQconnectionUsedGSSAPI(const PGconn *conn)
{
    if (!conn)
        return false;
    if (conn->gssapi_used)
        return true;
    else
        return false;
}
 
int
PQclientEncoding(const PGconn *conn)
{
    if (!conn || conn->status != CONNECTION_OK)
        return -1;
    return conn->client_encoding;
}
 
int
PQsetClientEncoding(PGconn *conn, const char *encoding)
{
    char        qbuf[128];
    static const char query[] = "set client_encoding to '%s'";
    PGresult   *res;
    int         status;
 
    if (!conn || conn->status != CONNECTION_OK)
        return -1;
 
    if (!encoding)
        return -1;
 
    /* Resolve special "auto" value from the locale */
    if (strcmp(encoding, "auto") == 0)
        encoding = pg_encoding_to_char(pg_get_encoding_from_locale(NULL, true));
 
    /* check query buffer overflow */
    if (sizeof(qbuf) < (sizeof(query) + strlen(encoding)))
        return -1;
 
    /* ok, now send a query */
    sprintf(qbuf, query, encoding);
    res = PQexec(conn, qbuf);
 
    if (res == NULL)
        return -1;
    if (res->resultStatus != PGRES_COMMAND_OK)
        status = -1;
    else
    {
        /*
         * We rely on the backend to report the parameter value, and we'll
         * change state at that time.
         */
        status = 0;             /* everything is ok */
    }
    PQclear(res);
    return status;
}
 
PGVerbosity
PQsetErrorVerbosity(PGconn *conn, PGVerbosity verbosity)
{
    PGVerbosity old;
 
    if (!conn)
        return PQERRORS_DEFAULT;
    old = conn->verbosity;
    conn->verbosity = verbosity;
    return old;
}
 
PGContextVisibility
PQsetErrorContextVisibility(PGconn *conn, PGContextVisibility show_context)
{
    PGContextVisibility old;
 
    if (!conn)
        return PQSHOW_CONTEXT_ERRORS;
    old = conn->show_context;
    conn->show_context = show_context;
    return old;
}
 
PQnoticeReceiver
PQsetNoticeReceiver(PGconn *conn, PQnoticeReceiver proc, void *arg)
{
    PQnoticeReceiver old;
 
    if (conn == NULL)
        return NULL;
 
    old = conn->noticeHooks.noticeRec;
    if (proc)
    {
        conn->noticeHooks.noticeRec = proc;
        conn->noticeHooks.noticeRecArg = arg;
    }
    return old;
}
 
PQnoticeProcessor
PQsetNoticeProcessor(PGconn *conn, PQnoticeProcessor proc, void *arg)
{
    PQnoticeProcessor old;
 
    if (conn == NULL)
        return NULL;
 
    old = conn->noticeHooks.noticeProc;
    if (proc)
    {
        conn->noticeHooks.noticeProc = proc;
        conn->noticeHooks.noticeProcArg = arg;
    }
    return old;
}
 
/*
 * The default notice message receiver just gets the standard notice text
 * and sends it to the notice processor.  This two-level setup exists
 * mostly for backwards compatibility; perhaps we should deprecate use of
 * PQsetNoticeProcessor?
 */
static void
defaultNoticeReceiver(void *arg, const PGresult *res)
{
    (void) arg;                 /* not used */
    if (res->noticeHooks.noticeProc != NULL)
        res->noticeHooks.noticeProc(res->noticeHooks.noticeProcArg,
                                    PQresultErrorMessage(res));
}
 
/*
 * The default notice message processor just prints the
 * message on stderr.  Applications can override this if they
 * want the messages to go elsewhere (a window, for example).
 * Note that simply discarding notices is probably a bad idea.
 */
static void
defaultNoticeProcessor(void *arg, const char *message)
{
    (void) arg;                 /* not used */
    /* Note: we expect the supplied string to end with a newline already. */
    fprintf(stderr, "%s", message);
}
 
/*
 * returns a pointer to the next token or NULL if the current
 * token doesn't match
 */
static char *
pwdfMatchesString(char *buf, const char *token)
{
    char       *tbuf;
    const char *ttok;
    bool        bslash = false;
 
    if (buf == NULL || token == NULL)
        return NULL;
    tbuf = buf;
    ttok = token;
    if (tbuf[0] == '*' && tbuf[1] == ':')
        return tbuf + 2;
    while (*tbuf != 0)
    {
        if (*tbuf == '\\' && !bslash)
        {
            tbuf++;
            bslash = true;
        }
        if (*tbuf == ':' && *ttok == 0 && !bslash)
            return tbuf + 1;
        bslash = false;
        if (*ttok == 0)
            return NULL;
        if (*tbuf == *ttok)
        {
            tbuf++;
            ttok++;
        }
        else
            return NULL;
    }
    return NULL;
}
 
/*
 * Get a password from the password file. Return value is malloc'd.
 *
 * On failure, *errmsg is set to an error to be returned.  It is
 * left NULL on success, or if no password could be found.
 */
static char *
passwordFromFile(const char *hostname, const char *port,
                 const char *dbname, const char *username,
                 const char *pgpassfile, const char **errmsg)
{
    FILE       *fp;
#ifndef WIN32
    struct stat stat_buf;
#endif
    PQExpBufferData buf;
 
    *errmsg = NULL;
 
    if (dbname == NULL || dbname[0] == '\0')
        return NULL;
 
    if (username == NULL || username[0] == '\0')
        return NULL;
 
    /* 'localhost' matches pghost of '' or the default socket directory */
    if (hostname == NULL || hostname[0] == '\0')
        hostname = DefaultHost;
    else if (is_unixsock_path(hostname))
 
        /*
         * We should probably use canonicalize_path(), but then we have to
         * bring path.c into libpq, and it doesn't seem worth it.
         */
        if (strcmp(hostname, DEFAULT_PGSOCKET_DIR) == 0)
            hostname = DefaultHost;
 
    if (port == NULL || port[0] == '\0')
        port = DEF_PGPORT_STR;
 
    /* If password file cannot be opened, ignore it. */
    fp = fopen(pgpassfile, "r");
    if (fp == NULL)
        return NULL;
 
#ifndef WIN32
    if (fstat(fileno(fp), &stat_buf) != 0)
    {
        fclose(fp);
        return NULL;
    }
 
    if (!S_ISREG(stat_buf.st_mode))
    {
        fprintf(stderr,
                libpq_gettext("WARNING: password file \"%s\" is not a plain file\n"),
                pgpassfile);
        fclose(fp);
        return NULL;
    }
 
    /* If password file is insecure, alert the user and ignore it. */
    if (stat_buf.st_mode & (S_IRWXG | S_IRWXO))
    {
        fprintf(stderr,
                libpq_gettext("WARNING: password file \"%s\" has group or world access; permissions should be u=rw (0600) or less\n"),
                pgpassfile);
        fclose(fp);
        return NULL;
    }
#else
 
    /*
     * On Win32, the directory is protected, so we don't have to check the
     * file.
     */
#endif
 
    /* Use an expansible buffer to accommodate any reasonable line length */
    initPQExpBuffer(&buf);
 
    while (!feof(fp) && !ferror(fp))
    {
        /* Make sure there's a reasonable amount of room in the buffer */
        if (!enlargePQExpBuffer(&buf, 128))
        {
            *errmsg = libpq_gettext("out of memory");
            break;
        }
 
        /* Read some data, appending it to what we already have */
        if (fgets(buf.data + buf.len, buf.maxlen - buf.len, fp) == NULL)
            break;
        buf.len += strlen(buf.data + buf.len);
 
        /* If we don't yet have a whole line, loop around to read more */
        if (!(buf.len > 0 && buf.data[buf.len - 1] == '\n') && !feof(fp))
            continue;
 
        /* ignore comments */
        if (buf.data[0] != '#')
        {
            char       *t = buf.data;
            int         len;
 
            /* strip trailing newline and carriage return */
            len = pg_strip_crlf(t);
 
            if (len > 0 &&
                (t = pwdfMatchesString(t, hostname)) != NULL &&
                (t = pwdfMatchesString(t, port)) != NULL &&
                (t = pwdfMatchesString(t, dbname)) != NULL &&
                (t = pwdfMatchesString(t, username)) != NULL)
            {
                /* Found a match. */
                char       *ret,
                           *p1,
                           *p2;
 
                ret = strdup(t);
 
                fclose(fp);
                explicit_bzero(buf.data, buf.maxlen);
                termPQExpBuffer(&buf);
 
                if (!ret)
                {
                    *errmsg = libpq_gettext("out of memory");
                    return NULL;
                }
 
                /* De-escape password. */
                for (p1 = p2 = ret; *p1 != ':' && *p1 != '\0'; ++p1, ++p2)
                {
                    if (*p1 == '\\' && p1[1] != '\0')
                        ++p1;
                    *p2 = *p1;
                }
                *p2 = '\0';
 
                return ret;
            }
        }
 
        /* No match, reset buffer to prepare for next line. */
        buf.len = 0;
    }
 
    fclose(fp);
    explicit_bzero(buf.data, buf.maxlen);
    termPQExpBuffer(&buf);
    return NULL;
}
 
 
/*
 *  If the connection failed due to bad password, we should mention
 *  if we got the password from the pgpassfile.
 */
static void
pgpassfileWarning(PGconn *conn)
{
    /* If it was 'invalid authorization', add pgpassfile mention */
    /* only works with >= 9.0 servers */
    if (conn->password_needed &&
        conn->connhost[conn->whichhost].password != NULL &&
        conn->result)
    {
        const char *sqlstate = PQresultErrorField(conn->result,
                                                  PG_DIAG_SQLSTATE);
 
        if (sqlstate && strcmp(sqlstate, ERRCODE_INVALID_PASSWORD) == 0)
            libpq_append_conn_error(conn, "password retrieved from file \"%s\"",
                                    conn->pgpassfile);
    }
}
 
/*
 * Check if the SSL protocol value given in input is valid or not.
 * This is used as a sanity check routine for the connection parameters
 * ssl_min_protocol_version and ssl_max_protocol_version.
 */
static bool
sslVerifyProtocolVersion(const char *version)
{
    /*
     * An empty string and a NULL value are considered valid as it is
     * equivalent to ignoring the parameter.
     */
    if (!version || strlen(version) == 0)
        return true;
 
    if (pg_strcasecmp(version, "TLSv1") == 0 ||
        pg_strcasecmp(version, "TLSv1.1") == 0 ||
        pg_strcasecmp(version, "TLSv1.2") == 0 ||
        pg_strcasecmp(version, "TLSv1.3") == 0)
        return true;
 
    /* anything else is wrong */
    return false;
}
 
 
/*
 * Ensure that the SSL protocol range given in input is correct.  The check
 * is performed on the input string to keep it TLS backend agnostic.  Input
 * to this function is expected verified with sslVerifyProtocolVersion().
 */
static bool
sslVerifyProtocolRange(const char *min, const char *max)
{
    Assert(sslVerifyProtocolVersion(min) &&
           sslVerifyProtocolVersion(max));
 
    /* If at least one of the bounds is not set, the range is valid */
    if (min == NULL || max == NULL || strlen(min) == 0 || strlen(max) == 0)
        return true;
 
    /*
     * If the minimum version is the lowest one we accept, then all options
     * for the maximum are valid.
     */
    if (pg_strcasecmp(min, "TLSv1") == 0)
        return true;
 
    /*
     * The minimum bound is valid, and cannot be TLSv1, so using TLSv1 for the
     * maximum is incorrect.
     */
    if (pg_strcasecmp(max, "TLSv1") == 0)
        return false;
 
    /*
     * At this point we know that we have a mix of TLSv1.1 through 1.3
     * versions.
     */
    if (pg_strcasecmp(min, max) > 0)
        return false;
 
    return true;
}
 
 
/*
 * Obtain user's home directory, return in given buffer
 *
 * On Unix, this actually returns the user's home directory.  On Windows
 * it returns the PostgreSQL-specific application data folder.
 *
 * This is essentially the same as get_home_path(), but we don't use that
 * because we don't want to pull path.c into libpq (it pollutes application
 * namespace).
 *
 * Returns true on success, false on failure to obtain the directory name.
 *
 * CAUTION: although in most situations failure is unexpected, there are users
 * who like to run applications in a home-directory-less environment.  On
 * failure, you almost certainly DO NOT want to report an error.  Just act as
 * though whatever file you were hoping to find in the home directory isn't
 * there (which it isn't).
 */
bool
pqGetHomeDirectory(char *buf, int bufsize)
{
#ifndef WIN32
    const char *home;
 
    home = getenv("HOME");
    if (home && home[0])
    {
        strlcpy(buf, home, bufsize);
        return true;
    }
    else
    {
        struct passwd pwbuf;
        struct passwd *pw;
        char        tmpbuf[1024];
        int         rc;
 
        rc = getpwuid_r(geteuid(), &pwbuf, tmpbuf, sizeof tmpbuf, &pw);
        if (rc != 0 || !pw)
            return false;
        strlcpy(buf, pw->pw_dir, bufsize);
        return true;
    }
#else
    char        tmppath[MAX_PATH];
 
    ZeroMemory(tmppath, sizeof(tmppath));
    if (SHGetFolderPath(NULL, CSIDL_APPDATA, NULL, 0, tmppath) != S_OK)
        return false;
    snprintf(buf, bufsize, "%s/postgresql", tmppath);
    return true;
#endif
}
 
/*
 * Parse and try to interpret "value" as an integer value, and if successful,
 * store it in *result, complaining if there is any trailing garbage or an
 * overflow.  This allows any number of leading and trailing whitespaces.
 */
bool
pqParseIntParam(const char *value, int *result, PGconn *conn,
                const char *context)
{
    char       *end;
    long        numval;
 
    Assert(value != NULL);
 
    *result = 0;
 
    /* strtol(3) skips leading whitespaces */
    errno = 0;
    numval = strtol(value, &end, 10);
 
    /*
     * If no progress was done during the parsing or an error happened, fail.
     * This tests properly for overflows of the result.
     */
    if (value == end || errno != 0 || numval != (int) numval)
        goto error;
 
    /*
     * Skip any trailing whitespace; if anything but whitespace remains before
     * the terminating character, fail
     */
    while (*end != '\0' && isspace((unsigned char) *end))
        end++;
 
    if (*end != '\0')
        goto error;
 
    *result = numval;
    return true;
 
error:
    libpq_append_conn_error(conn, "invalid integer value \"%s\" for connection option \"%s\"",
                            value, context);
    return false;
}
 
/*
 * Parse and try to interpret "value" as a ProtocolVersion value, and if
 * successful, store it in *result.
 */
static bool
pqParseProtocolVersion(const char *value, ProtocolVersion *result, PGconn *conn,
                       const char *context)
{
    if (strcmp(value, "latest") == 0)
    {
        *result = PG_PROTOCOL_LATEST;
        return true;
    }
    if (strcmp(value, "3.0") == 0)
    {
        *result = PG_PROTOCOL(3, 0);
        return true;
    }
 
    /* 3.1 never existed, we went straight from 3.0 to 3.2 */
 
    if (strcmp(value, "3.2") == 0)
    {
        *result = PG_PROTOCOL(3, 2);
        return true;
    }
 
    libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
                            context, value);
    return false;
}
 
/*
 * To keep the API consistent, the locking stubs are always provided, even
 * if they are not required.
 *
 * Since we neglected to provide any error-return convention in the
 * pgthreadlock_t API, we can't do much except Assert upon failure of any
 * mutex primitive.  Fortunately, such failures appear to be nonexistent in
 * the field.
 */
 
static void
default_threadlock(int acquire)
{
    static pthread_mutex_t singlethread_lock = PTHREAD_MUTEX_INITIALIZER;
 
    if (acquire)
    {
        if (pthread_mutex_lock(&singlethread_lock))
            Assert(false);
    }
    else
    {
        if (pthread_mutex_unlock(&singlethread_lock))
            Assert(false);
    }
}
 
pgthreadlock_t
PQregisterThreadLock(pgthreadlock_t newhandler)
{
    pgthreadlock_t prev = pg_g_threadlock;
 
    if (newhandler)
        pg_g_threadlock = newhandler;
    else
        pg_g_threadlock = default_threadlock;
 
    return prev;
}