fe-connect.c

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/*-------------------------------------------------------------------------
 *
 * fe-connect.c
 *    functions related to setting up a connection to the backend
 *
 * Portions Copyright (c) 1996-2019, 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 <time.h>
#include <unistd.h>

#include "common/ip.h"
#include "common/link-canary.h"
#include "common/scram-common.h"
#include "common/string.h"
#include "fe-auth.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>
#ifdef _MSC_VER                 /* mstcpip.h is missing on mingw */
#include <mstcpip.h>
#endif
#else
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#ifdef HAVE_NETINET_TCP_H
#include <netinet/tcp.h>
#endif
#endif

#ifdef ENABLE_THREAD_SAFETY
#ifdef WIN32
#include "pthread-win32.h"
#else
#include <pthread.h>
#endif
#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"
/* This too */
#define ERRCODE_CANNOT_CONNECT_NOW "57P03"

/*
 * 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 DefaultTty      ""
#define DefaultOption   ""
#define DefaultAuthtype       ""
#ifdef USE_SSL
#define DefaultChannelBinding   "prefer"
#else
#define DefaultChannelBinding   "disable"
#endif
#define DefaultTargetSessionAttrs   "any"
#ifdef USE_SSL
#define DefaultSSLMode "prefer"
#else
#define DefaultSSLMode  "disable"
#endif
#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
 *
 * 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[] = {
    /*
     * "authtype" is no longer used, so mark it "don't show".  We keep it in
     * the array so as not to reject conninfo strings from old apps that might
     * still try to set it.
     */
    {"authtype", "PGAUTHTYPE", DefaultAuthtype, NULL,
    "Database-Authtype", "D", 20, -1},

    {"service", "PGSERVICE", NULL, NULL,
    "Database-Service", "", 20, -1},

    {"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", NULL, NULL,
        "Channel-Binding", "", 7,   /* sizeof("require") */
    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)},

    /*
     * "tty" is no longer used either, but keep it present for backwards
     * compatibility.
     */
    {"tty", "PGTTY", DefaultTty, NULL,
        "Backend-Debug-TTY", "D", 40,
    offsetof(struct pg_conn, pgtty)},

    {"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)},

    {"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)},

    {"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)},

    {"requirepeer", "PGREQUIREPEER", NULL, NULL,
        "Require-Peer", "", 10,
    offsetof(struct pg_conn, requirepeer)},

    /*
     * Expose gssencmode similarly to sslmode - we can still handle "disable"
     * and "prefer".
     */
    {"gssencmode", "PGGSSENCMODE", DefaultGSSMode, NULL,
        "GSSENC-Mode", "", 7,   /* sizeof("disable") == 7 */
    offsetof(struct pg_conn, gssencmode)},

#if defined(ENABLE_GSS) || defined(ENABLE_SSPI)
    /* Kerberos and GSSAPI authentication support specifying the service name */
    {"krbsrvname", "PGKRBSRVNAME", PG_KRB_SRVNAM, NULL,
        "Kerberos-service-name", "", 20,
    offsetof(struct pg_conn, krbsrvname)},
#endif

#if defined(ENABLE_GSS) && defined(ENABLE_SSPI)

    /*
     * GSSAPI and SSPI both enabled, give a way to override which is used by
     * default
     */
    {"gsslib", "PGGSSLIB", NULL, NULL,
        "GSS-library", "", 7,   /* sizeof("gssapi") = 7 */
    offsetof(struct pg_conn, gsslib)},
#endif

    {"replication", NULL, NULL, NULL,
        "Replication", "D", 5,
    offsetof(struct pg_conn, replication)},

    {"target_session_attrs", "PGTARGETSESSIONATTRS",
        DefaultTargetSessionAttrs, NULL,
        "Target-Session-Attrs", "", 11, /* sizeof("read-write") = 11 */
    offsetof(struct pg_conn, target_session_attrs)},

    /* 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
    }
};

/* 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 connectOptions2(PGconn *conn);
static int  connectDBStart(PGconn *conn);
static int  connectDBComplete(PGconn *conn);
static PGPing internal_ping(PGconn *conn);
static PGconn *makeEmptyPGconn(void);
static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
static void freePGconn(PGconn *conn);
static void closePGconn(PGconn *conn);
static void release_conn_addrinfo(PGconn *conn);
static void sendTerminateConn(PGconn *conn);
static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
static PQconninfoOption *parse_connection_string(const char *conninfo,
                                                 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);
static void pgpassfileWarning(PGconn *conn);
static void default_threadlock(int acquire);


/* 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;

    /* Free authentication state */
#ifdef ENABLE_GSS
    {
        OM_uint32   min_s;

        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);
    }
#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)
    {
        /*
         * XXX: if support for more authentication mechanisms is added, this
         * needs to call the right 'free' function.
         */
        pg_fe_scram_free(conn->sasl_state);
        conn->sasl_state = NULL;
    }
}


/*
 *      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->sversion = 0;

    /* Drop large-object lookup data */
    if (conn->lobjfuncs)
        free(conn->lobjfuncs);
    conn->lobjfuncs = NULL;

    /* Reset assorted other per-connection state */
    conn->last_sqlstate[0] = '\0';
    conn->auth_req_received = false;
    conn->password_needed = false;
    conn->write_failed = false;
    if (conn->write_err_msg)
        free(conn->write_err_msg);
    conn->write_err_msg = NULL;
    conn->be_pid = 0;
    conn->be_key = 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.
 *
 * Internally, the static functions connectDBStart, connectDBComplete
 * are part of the connection procedure.
 */

/*
 *      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) connectDBComplete(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) connectDBComplete(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
     */
    conn = makeEmptyPGconn();
    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 (!connectOptions2(conn))
        return conn;

    /*
     * Connect to the database
     */
    if (!connectDBStart(conn))
    {
        /* Just in case we failed to set it in connectDBStart */
        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
     */
    conn = makeEmptyPGconn();
    if (conn == NULL)
        return NULL;

    /*
     * Parse the conninfo string
     */
    if (!connectOptions1(conn, conninfo))
        return conn;

    /*
     * Compute derived options
     */
    if (!connectOptions2(conn))
        return conn;

    /*
     * Connect to the database
     */
    if (!connectDBStart(conn))
    {
        /* Just in case we failed to set it in connectDBStart */
        conn->status = CONNECTION_BAD;
    }

    return conn;
}

/*
 * Move option values into conn structure
 *
 * Don't put anything cute here --- intelligence should be in
 * connectOptions2 ...
 *
 * 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);

                if (*connmember)
                    free(*connmember);
                *connmember = strdup(tmp);
                if (*connmember == NULL)
                {
                    printfPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("out of memory\n"));
                    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 connectOptions2 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;
    int         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;
}

/*
 *      connectOptions2
 *
 * 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).
 */
static bool
connectOptions2(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;
            printfPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("could not match %d host names to %d hostaddr values\n"),
                              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;
#ifdef HAVE_UNIX_SOCKETS
            if (is_absolute_path(ch->host))
                ch->type = CHT_UNIX_SOCKET;
#endif
        }
        else
        {
            if (ch->host)
                free(ch->host);
#ifdef HAVE_UNIX_SOCKETS
            ch->host = strdup(DEFAULT_PGSOCKET_DIR);
            ch->type = CHT_UNIX_SOCKET;
#else
            ch->host = strdup(DefaultHost);
            ch->type = CHT_HOST_NAME;
#endif
            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;
            printfPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("could not match %d port numbers to %d hosts\n"),
                              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')
    {
        if (conn->pguser)
            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')
    {
        if (conn->dbName)
            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)))
            {
                if (conn->pgpassfile)
                    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;

                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);
            }
        }
    }

    /*
     * 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;
            printfPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("invalid channel_binding value: \"%s\"\n"),
                              conn->channel_binding);
            return false;
        }
    }
    else
    {
        conn->channel_binding = strdup(DefaultChannelBinding);
        if (!conn->channel_binding)
            goto oom_error;
    }

    /*
     * 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;
            printfPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("invalid sslmode value: \"%s\"\n"),
                              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;
                printfPQExpBuffer(&conn->errorMessage,
                                  libpq_gettext("sslmode value \"%s\" invalid when SSL support is not compiled in\n"),
                                  conn->sslmode);
                return false;
        }
#endif
    }
    else
    {
        conn->sslmode = strdup(DefaultSSLMode);
        if (!conn->sslmode)
            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;
            printfPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("invalid gssencmode value: \"%s\"\n"),
                              conn->gssencmode);
            return false;
        }
#ifndef ENABLE_GSS
        if (strcmp(conn->gssencmode, "require") == 0)
        {
            conn->status = CONNECTION_BAD;
            printfPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("gssencmode value \"%s\" invalid when GSSAPI support is not compiled in\n"),
                              conn->gssencmode);
            return false;
        }
#endif
    }
    else
    {
        conn->gssencmode = strdup(DefaultGSSMode);
        if (!conn->gssencmode)
            goto oom_error;
    }

    /*
     * 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;
    }

    /*
     * Validate target_session_attrs option.
     */
    if (conn->target_session_attrs)
    {
        if (strcmp(conn->target_session_attrs, "any") != 0
            && strcmp(conn->target_session_attrs, "read-write") != 0)
        {
            conn->status = CONNECTION_BAD;
            printfPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("invalid target_session_attrs value: \"%s\"\n"),
                              conn->target_session_attrs);
            return false;
        }
    }

    /*
     * 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;
    printfPQExpBuffer(&conn->errorMessage,
                      libpq_gettext("out of memory\n"));
    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
     */
    conn = makeEmptyPGconn();
    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')
        {
            if (conn->dbName)
                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')
    {
        if (conn->pghost)
            free(conn->pghost);
        conn->pghost = strdup(pghost);
        if (!conn->pghost)
            goto oom_error;
    }

    if (pgport && pgport[0] != '\0')
    {
        if (conn->pgport)
            free(conn->pgport);
        conn->pgport = strdup(pgport);
        if (!conn->pgport)
            goto oom_error;
    }

    if (pgoptions && pgoptions[0] != '\0')
    {
        if (conn->pgoptions)
            free(conn->pgoptions);
        conn->pgoptions = strdup(pgoptions);
        if (!conn->pgoptions)
            goto oom_error;
    }

    if (pgtty && pgtty[0] != '\0')
    {
        if (conn->pgtty)
            free(conn->pgtty);
        conn->pgtty = strdup(pgtty);
        if (!conn->pgtty)
            goto oom_error;
    }

    if (login && login[0] != '\0')
    {
        if (conn->pguser)
            free(conn->pguser);
        conn->pguser = strdup(login);
        if (!conn->pguser)
            goto oom_error;
    }

    if (pwd && pwd[0] != '\0')
    {
        if (conn->pgpass)
            free(conn->pgpass);
        conn->pgpass = strdup(pwd);
        if (!conn->pgpass)
            goto oom_error;
    }

    /*
     * Compute derived options
     */
    if (!connectOptions2(conn))
        return conn;

    /*
     * Connect to the database
     */
    if (connectDBStart(conn))
        (void) connectDBComplete(conn);

    return conn;

oom_error:
    conn->status = CONNECTION_BAD;
    printfPQExpBuffer(&conn->errorMessage,
                      libpq_gettext("out of memory\n"));
    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];

        appendPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("could not set socket to TCP no delay mode: %s\n"),
                          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';
    }
#ifdef HAVE_IPV6
    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';
    }
#endif
    else
        host_addr[0] = '\0';
}

/* ----------
 * connectFailureMessage -
 * create a friendly error message on connection failure.
 * ----------
 */
static void
connectFailureMessage(PGconn *conn, int errorno)
{
    char        sebuf[PG_STRERROR_R_BUFLEN];

#ifdef HAVE_UNIX_SOCKETS
    if (IS_AF_UNIX(conn->raddr.addr.ss_family))
    {
        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("could not connect to server: %s\n"
                                        "\tIs the server running locally and accepting\n"
                                        "\tconnections on Unix domain socket \"%s\"?\n"),
                          SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)),
                          service);
    }
    else
#endif                          /* HAVE_UNIX_SOCKETS */
    {
        char        host_addr[NI_MAXHOST];
        const char *displayed_host;
        const char *displayed_port;

        /*
         * Optionally display the network address with the hostname. This is
         * useful to distinguish between IPv4 and IPv6 connections.
         */
        getHostaddr(conn, host_addr, NI_MAXHOST);

        /* 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 &&
            strlen(host_addr) > 0 &&
            strcmp(displayed_host, host_addr) != 0)
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("could not connect to server: %s\n"
                                            "\tIs the server running on host \"%s\" (%s) and accepting\n"
                                            "\tTCP/IP connections on port %s?\n"),
                              SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)),
                              displayed_host, host_addr,
                              displayed_port);
        else
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("could not connect to server: %s\n"
                                            "\tIs the server running on host \"%s\" and accepting\n"
                                            "\tTCP/IP connections on port %s?\n"),
                              SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)),
                              displayed_host,
                              displayed_port);
    }
}

/*
 * 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)
{
    char       *ep;
    int         val;

    if (conn->keepalives == NULL)
        return 1;
    val = strtol(conn->keepalives, &ep, 10);
    if (*ep)
        return -1;
    return val != 0 ? 1 : 0;
}

/*
 * 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.
 */
static bool
parse_int_param(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:
    appendPQExpBuffer(&conn->errorMessage,
                      libpq_gettext("invalid integer value \"%s\" for connection option \"%s\"\n"),
                      value, context);
    return false;
}

#ifndef WIN32
/*
 * Set the keepalive idle timer.
 */
static int
setKeepalivesIdle(PGconn *conn)
{
    int         idle;

    if (conn->keepalives_idle == NULL)
        return 1;

    if (!parse_int_param(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];

        appendPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("setsockopt(%s) failed: %s\n"),
                          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 (!parse_int_param(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];

        appendPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("setsockopt(%s) failed: %s\n"),
                          "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 (!parse_int_param(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];

        appendPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("setsockopt(%s) failed: %s\n"),
                          "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.
 */
static int
setKeepalivesWin32(PGconn *conn)
{
    struct tcp_keepalive ka;
    DWORD       retsize;
    int         idle = 0;
    int         interval = 0;

    if (conn->keepalives_idle &&
        !parse_int_param(conn->keepalives_idle, &idle, conn,
                         "keepalives_idle"))
        return 0;
    if (idle <= 0)
        idle = 2 * 60 * 60;     /* 2 hours = default */

    if (conn->keepalives_interval &&
        !parse_int_param(conn->keepalives_interval, &interval, conn,
                         "keepalives_interval"))
        return 0;
    if (interval <= 0)
        interval = 1;           /* 1 second = default */

    ka.onoff = 1;
    ka.keepalivetime = idle * 1000;
    ka.keepaliveinterval = interval * 1000;

    if (WSAIoctl(conn->sock,
                 SIO_KEEPALIVE_VALS,
                 (LPVOID) &ka,
                 sizeof(ka),
                 NULL,
                 0,
                 &retsize,
                 NULL,
                 NULL)
        != 0)
    {
        appendPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("WSAIoctl(SIO_KEEPALIVE_VALS) failed: %ui\n"),
                          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 (!parse_int_param(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];

        appendPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("setsockopt(%s) failed: %s\n"),
                          "TCP_USER_TIMEOUT",
                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        return 0;
    }
#endif

    return 1;
}

/* ----------
 * connectDBStart -
 *      Begin the process of making a connection to the backend.
 *
 * Returns 1 if successful, 0 if not.
 * ----------
 */
static int
connectDBStart(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())
    {
        printfPQExpBuffer(&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;

    /*
     * Ensure errorMessage is empty, too.  PQconnectPoll will append messages
     * to it in the process of scanning for a working server.  Thus, if we
     * fail to connect to multiple hosts, the final error message will include
     * details about each failure.
     */
    resetPQExpBuffer(&conn->errorMessage);

#ifdef ENABLE_GSS
    if (conn->gssencmode[0] == 'd') /* "disable" */
        conn->try_gss = false;
#endif

    /*
     * 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.)
     */
    conn->whichhost = -1;
    conn->try_next_addr = false;
    conn->try_next_host = true;
    conn->status = CONNECTION_NEEDED;

    /*
     * 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;
}


/*
 *      connectDBComplete
 *
 * Block and complete a connection.
 *
 * Returns 1 on success, 0 on failure.
 */
static int
connectDBComplete(PGconn *conn)
{
    PostgresPollingStatusType flag = PGRES_POLLING_WRITING;
    time_t      finish_time = ((time_t) -1);
    int         timeout = 0;
    int         last_whichhost = -2;    /* certainly different from whichhost */
    struct addrinfo *last_addr_cur = NULL;

    if (conn == NULL || conn->status == CONNECTION_BAD)
        return 0;

    /*
     * Set up a time limit, if connect_timeout isn't zero.
     */
    if (conn->connect_timeout != NULL)
    {
        if (!parse_int_param(conn->connect_timeout, &timeout, conn,
                             "connect_timeout"))
        {
            /* mark the connection as bad to report the parsing failure */
            conn->status = CONNECTION_BAD;
            return 0;
        }

        if (timeout > 0)
        {
            /*
             * Rounding could cause connection to fail unexpectedly quickly;
             * to prevent possibly waiting hardly-at-all, insist on at least
             * two seconds.
             */
            if (timeout < 2)
                timeout = 2;
        }
        else                    /* negative means 0 */
            timeout = 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->addr_cur != last_addr_cur))
        {
            finish_time = time(NULL) + timeout;
            last_whichhost = conn->whichhost;
            last_addr_cur = conn->addr_cur;
        }

        /*
         * 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:

                /*
                 * Reset stored error messages since we now have a working
                 * connection
                 */
                resetPQExpBuffer(&conn->errorMessage);
                return 1;       /* success! */

            case PGRES_POLLING_READING:
                ret = pqWaitTimed(1, 0, conn, finish_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, finish_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.
         */
        flag = PQconnectPoll(conn);
    }
}

/*
 * This subroutine saves conn->errorMessage, which will be restored back by
 * restoreErrorMessage subroutine.  Returns false on OOM failure.
 */
static bool
saveErrorMessage(PGconn *conn, PQExpBuffer savedMessage)
{
    initPQExpBuffer(savedMessage);
    appendPQExpBufferStr(savedMessage,
                         conn->errorMessage.data);
    if (PQExpBufferBroken(savedMessage))
    {
        printfPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("out of memory\n"));
        return false;
    }
    /* Clear whatever is in errorMessage now */
    resetPQExpBuffer(&conn->errorMessage);
    return true;
}

/*
 * Restores saved error messages back to conn->errorMessage, prepending them
 * to whatever is in conn->errorMessage already.  (This does the right thing
 * if anything's been added to conn->errorMessage since saveErrorMessage.)
 */
static void
restoreErrorMessage(PGconn *conn, PQExpBuffer savedMessage)
{
    appendPQExpBufferStr(savedMessage, conn->errorMessage.data);
    resetPQExpBuffer(&conn->errorMessage);
    appendPQExpBufferStr(&conn->errorMessage, savedMessage->data);
    /* If any step above hit OOM, just report that */
    if (PQExpBufferBroken(savedMessage) ||
        PQExpBufferBroken(&conn->errorMessage))
        printfPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("out of memory\n"));
    termPQExpBuffer(savedMessage);
}

/* ----------------
 *      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
 *      gethostbyname.  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;
    PQExpBufferData savedMessage;

    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:
            {
                /* 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;

            /* We allow pqSetenvPoll to decide whether to proceed. */
        case CONNECTION_SETENV:
            break;

            /* Special cases: proceed without waiting. */
        case CONNECTION_SSL_STARTUP:
        case CONNECTION_NEEDED:
        case CONNECTION_CHECK_WRITABLE:
        case CONNECTION_CONSUME:
        case CONNECTION_GSS_STARTUP:
            break;

        default:
            appendPQExpBufferStr(&conn->errorMessage,
                                 libpq_gettext(
                                               "invalid connection state, "
                                               "probably indicative of memory corruption\n"
                                               ));
            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->addr_cur && conn->addr_cur->ai_next)
        {
            conn->addr_cur = conn->addr_cur->ai_next;
            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;
        int         thisport;
        int         ret;
        char        portstr[MAXPGPATH];

        if (conn->whichhost + 1 >= conn->nconnhost)
        {
            /*
             * Oops, no more hosts.  An appropriate error message is already
             * set up, so just set the right status.
             */
            goto error_return;
        }
        conn->whichhost++;

        /* 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;
        conn->addrlist_family = 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 (!parse_int_param(ch->port, &thisport, conn, "port"))
                goto error_return;

            if (thisport < 1 || thisport > 65535)
            {
                appendPQExpBuffer(&conn->errorMessage,
                                  libpq_gettext("invalid port number: \"%s\"\n"),
                                  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,
                                         &conn->addrlist);
                if (ret || !conn->addrlist)
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("could not translate host name \"%s\" to address: %s\n"),
                                      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,
                                         &conn->addrlist);
                if (ret || !conn->addrlist)
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("could not parse network address \"%s\": %s\n"),
                                      ch->hostaddr, gai_strerror(ret));
                    goto keep_going;
                }
                break;

            case CHT_UNIX_SOCKET:
#ifdef HAVE_UNIX_SOCKETS
                conn->addrlist_family = hint.ai_family = AF_UNIX;
                UNIXSOCK_PATH(portstr, thisport, ch->host);
                if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("Unix-domain socket path \"%s\" is too long (maximum %d bytes)\n"),
                                      portstr,
                                      (int) (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,
                                         &conn->addrlist);
                if (ret || !conn->addrlist)
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("could not translate Unix-domain socket path \"%s\" to address: %s\n"),
                                      portstr, gai_strerror(ret));
                    goto keep_going;
                }
#else
                Assert(false);
#endif
                break;
        }

        /* OK, scan this addrlist for a working server address */
        conn->addr_cur = conn->addrlist;
        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 = PG_PROTOCOL(3, 0);
        conn->send_appname = true;
#ifdef USE_SSL
        /* initialize these values based on SSL mode */
        conn->allow_ssl_try = (conn->sslmode[0] != 'd');    /* "disable" */
        conn->wait_ssl_try = (conn->sslmode[0] == 'a'); /* "allow" */
#endif

        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;
        pqClearAsyncResult(conn);

        /* Reset conn->status to put the state machine in the right state */
        conn->status = CONNECTION_NEEDED;

        need_new_connection = false;
    }

    /* 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->addr_cur 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.
                 */
                {
                    struct addrinfo *addr_cur = conn->addr_cur;
                    char        host_addr[NI_MAXHOST];

                    /*
                     * Advance to next possible host, if we've tried all of
                     * the addresses for the current host.
                     */
                    if (addr_cur == NULL)
                    {
                        conn->try_next_host = true;
                        goto keep_going;
                    }

                    /* Remember current address for possible error msg */
                    memcpy(&conn->raddr.addr, addr_cur->ai_addr,
                           addr_cur->ai_addrlen);
                    conn->raddr.salen = addr_cur->ai_addrlen;

                    /* set connip */
                    if (conn->connip != NULL)
                    {
                        free(conn->connip);
                        conn->connip = NULL;
                    }

                    getHostaddr(conn, host_addr, NI_MAXHOST);
                    if (strlen(host_addr) > 0)
                        conn->connip = strdup(host_addr);

                    /*
                     * purposely ignore strdup failure; not a big problem if
                     * it fails anyway.
                     */

                    conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
                    if (conn->sock == PGINVALID_SOCKET)
                    {
                        /*
                         * 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 (addr_cur->ai_next != NULL ||
                            conn->whichhost + 1 < conn->nconnhost)
                        {
                            conn->try_next_addr = true;
                            goto keep_going;
                        }
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("could not create socket: %s\n"),
                                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        goto error_return;
                    }

                    /*
                     * 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 (!IS_AF_UNIX(addr_cur->ai_family))
                    {
                        if (!connectNoDelay(conn))
                        {
                            /* error message already created */
                            conn->try_next_addr = true;
                            goto keep_going;
                        }
                    }
                    if (!pg_set_noblock(conn->sock))
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("could not set socket to nonblocking mode: %s\n"),
                                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        conn->try_next_addr = true;
                        goto keep_going;
                    }

#ifdef F_SETFD
                    if (fcntl(conn->sock, F_SETFD, FD_CLOEXEC) == -1)
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("could not set socket to close-on-exec mode: %s\n"),
                                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        conn->try_next_addr = true;
                        goto keep_going;
                    }
#endif                          /* F_SETFD */

                    if (!IS_AF_UNIX(addr_cur->ai_family))
                    {
#ifndef WIN32
                        int         on = 1;
#endif
                        int         usekeepalives = useKeepalives(conn);
                        int         err = 0;

                        if (usekeepalives < 0)
                        {
                            appendPQExpBufferStr(&conn->errorMessage,
                                                 libpq_gettext("keepalives parameter must be an integer\n"));
                            err = 1;
                        }
                        else if (usekeepalives == 0)
                        {
                            /* Do nothing */
                        }
#ifndef WIN32
                        else if (setsockopt(conn->sock,
                                            SOL_SOCKET, SO_KEEPALIVE,
                                            (char *) &on, sizeof(on)) < 0)
                        {
                            appendPQExpBuffer(&conn->errorMessage,
                                              libpq_gettext("setsockopt(%s) failed: %s\n"),
                                              "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 (!setKeepalivesWin32(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, addr_cur->ai_addr,
                                addr_cur->ai_addrlen) < 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:
            {
                ACCEPT_TYPE_ARG3 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)
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("could not get socket error status: %s\n"),
                                      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)
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("could not get client address from socket: %s\n"),
                                      SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                    goto error_return;
                }

                /*
                 * 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 HAVE_UNIX_SOCKETS

                /*
                 * Implement requirepeer check, if requested and it's a
                 * Unix-domain socket.
                 */
                if (conn->requirepeer && conn->requirepeer[0] &&
                    IS_AF_UNIX(conn->raddr.addr.ss_family))
                {
                    char        pwdbuf[BUFSIZ];
                    struct passwd pass_buf;
                    struct passwd *pass;
                    int         passerr;
                    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)
                            appendPQExpBufferStr(&conn->errorMessage,
                                                 libpq_gettext("requirepeer parameter is not supported on this platform\n"));
                        else
                            appendPQExpBuffer(&conn->errorMessage,
                                              libpq_gettext("could not get peer credentials: %s\n"),
                                              strerror_r(errno, sebuf, sizeof(sebuf)));
                        goto error_return;
                    }

                    passerr = pqGetpwuid(uid, &pass_buf, pwdbuf, sizeof(pwdbuf), &pass);
                    if (pass == NULL)
                    {
                        if (passerr != 0)
                            appendPQExpBuffer(&conn->errorMessage,
                                              libpq_gettext("could not look up local user ID %d: %s\n"),
                                              (int) uid,
                                              strerror_r(passerr, sebuf, sizeof(sebuf)));
                        else
                            appendPQExpBuffer(&conn->errorMessage,
                                              libpq_gettext("local user with ID %d does not exist\n"),
                                              (int) uid);
                        goto error_return;
                    }

                    if (strcmp(pass->pw_name, conn->requirepeer) != 0)
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("requirepeer specifies \"%s\", but actual peer user name is \"%s\"\n"),
                                          conn->requirepeer, pass->pw_name);
                        goto error_return;
                    }
                }
#endif                          /* HAVE_UNIX_SOCKETS */

                if (IS_AF_UNIX(conn->raddr.addr.ss_family))
                {
                    /* Don't request SSL or GSSAPI over Unix sockets */
#ifdef USE_SSL
                    conn->allow_ssl_try = false;
#endif
#ifdef ENABLE_GSS
                    conn->try_gss = false;
#endif
                }

#ifdef ENABLE_GSS

                /*
                 * If GSSAPI is enabled and we have a credential cache, try to
                 * set it up before sending startup messages.  If it's already
                 * operating, don't try SSL and instead just build the startup
                 * packet.
                 */
                if (conn->try_gss && !conn->gctx)
                    conn->try_gss = pg_GSS_have_cred_cache(&conn->gcred);
                if (conn->try_gss && !conn->gctx)
                {
                    ProtocolVersion pv = pg_hton32(NEGOTIATE_GSS_CODE);

                    if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("could not send GSSAPI negotiation packet: %s\n"),
                                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        goto error_return;
                    }

                    /* Ok, wait for response */
                    conn->status = CONNECTION_GSS_STARTUP;
                    return PGRES_POLLING_READING;
                }
                else if (!conn->gctx && conn->gssencmode[0] == 'r')
                {
                    appendPQExpBufferStr(&conn->errorMessage,
                                         libpq_gettext("GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)\n"));
                    goto error_return;
                }
#endif

#ifdef USE_SSL

                /*
                 * If SSL is enabled and we haven't already got it running,
                 * request it instead of sending the startup message.
                 */
                if (conn->allow_ssl_try && !conn->wait_ssl_try &&
                    !conn->ssl_in_use)
                {
                    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)
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("could not send SSL negotiation packet: %s\n"),
                                          SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
                        goto error_return;
                    }
                    /* Ok, wait for response */
                    conn->status = CONNECTION_SSL_STARTUP;
                    return PGRES_POLLING_READING;
                }
#endif                          /* USE_SSL */

                /*
                 * Build the startup packet.
                 */
                if (PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
                    startpacket = pqBuildStartupPacket3(conn, &packetlen,
                                                        EnvironmentOptions);
                else
                    startpacket = pqBuildStartupPacket2(conn, &packetlen,
                                                        EnvironmentOptions);
                if (!startpacket)
                {
                    /*
                     * will not appendbuffer here, since it's likely to also
                     * run out of memory
                     */
                    printfPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("out of memory\n"));
                    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)
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("could not send startup packet: %s\n"),
                                      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, get the postmaster's response to our
                 * SSL negotiation packet.
                 */
                if (!conn->ssl_in_use)
                {
                    /*
                     * 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')
                    {
                        /* mark byte consumed */
                        conn->inStart = conn->inCursor;
                        /* Set up global SSL state if required */
                        if (pqsecure_initialize(conn) != 0)
                            goto error_return;
                    }
                    else if (SSLok == 'N')
                    {
                        /* mark byte consumed */
                        conn->inStart = conn->inCursor;
                        /* OK to do without SSL? */
                        if (conn->sslmode[0] == 'r' ||  /* "require" */
                            conn->sslmode[0] == 'v')    /* "verify-ca" or
                                                         * "verify-full" */
                        {
                            /* Require SSL, but server does not want it */
                            appendPQExpBufferStr(&conn->errorMessage,
                                                 libpq_gettext("server does not support SSL, but SSL was required\n"));
                            goto error_return;
                        }
                        /* Otherwise, proceed with normal startup */
                        conn->allow_ssl_try = false;
                        conn->status = CONNECTION_MADE;
                        return PGRES_POLLING_WRITING;
                    }
                    else if (SSLok == 'E')
                    {
                        /*
                         * Server failure of some sort, such as failure to
                         * fork a backend process.  We need to process and
                         * report the error message, which might be formatted
                         * according to either protocol 2 or protocol 3.
                         * Rather than duplicate the code for that, we flip
                         * into AWAITING_RESPONSE state and let the code there
                         * deal with it.  Note we have *not* consumed the "E"
                         * byte here.
                         */
                        conn->status = CONNECTION_AWAITING_RESPONSE;
                        goto keep_going;
                    }
                    else
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("received invalid response to SSL negotiation: %c\n"),
                                          SSLok);
                        goto error_return;
                    }
                }

                /*
                 * Begin or continue the SSL negotiation process.
                 */
                pollres = pqsecure_open_client(conn);
                if (pollres == PGRES_POLLING_OK)
                {
                    /* SSL handshake done, ready to send startup packet */
                    conn->status = CONNECTION_MADE;
                    return PGRES_POLLING_WRITING;
                }
                if (pollres == PGRES_POLLING_FAILED)
                {
                    /*
                     * Failed ... if sslmode is "prefer" then do a non-SSL
                     * retry
                     */
                    if (conn->sslmode[0] == 'p' /* "prefer" */
                        && conn->allow_ssl_try  /* redundant? */
                        && !conn->wait_ssl_try) /* redundant? */
                    {
                        /* only retry once */
                        conn->allow_ssl_try = false;
                        need_new_connection = true;
                        goto keep_going;
                    }
                    /* Else it's a hard failure */
                    goto error_return;
                }
                /* 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->try_gss && !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.  Assume it's a
                         * protocol version support failure, and let's see if
                         * we can't recover (if it's not, we'll get a better
                         * error message on retry).  Server gets fussy if we
                         * don't hang up the socket, though.
                         */
                        conn->try_gss = false;
                        pqDropConnection(conn, true);
                        conn->status = CONNECTION_NEEDED;
                        goto keep_going;
                    }

                    /* mark byte consumed */
                    conn->inStart = conn->inCursor;

                    if (gss_ok == 'N')
                    {
                        /* Server doesn't want GSSAPI; fall back if we can */
                        if (conn->gssencmode[0] == 'r')
                        {
                            appendPQExpBufferStr(&conn->errorMessage,
                                                 libpq_gettext("server doesn't support GSSAPI encryption, but it was required\n"));
                            goto error_return;
                        }

                        conn->try_gss = false;
                        conn->status = CONNECTION_MADE;
                        return PGRES_POLLING_WRITING;
                    }
                    else if (gss_ok != 'G')
                    {
                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("received invalid response to GSSAPI negotiation: %c\n"),
                                          gss_ok);
                        goto error_return;
                    }
                }

                /* Begin or continue GSSAPI negotiation */
                pollres = pqsecure_open_gss(conn);
                if (pollres == PGRES_POLLING_OK)
                {
                    /* All set for startup packet */
                    conn->status = CONNECTION_MADE;
                    return PGRES_POLLING_WRITING;
                }
                else if (pollres == PGRES_POLLING_FAILED &&
                         conn->gssencmode[0] == 'p')
                {
                    /*
                     * We failed, but we can retry on "prefer".  Have to drop
                     * the current connection to do so, though.
                     */
                    conn->try_gss = false;
                    pqDropConnection(conn, true);
                    conn->status = CONNECTION_NEEDED;
                    goto keep_going;
                }
                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;

                /*
                 * 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 or an error here.  Anything else probably means
                 * it's not Postgres on the other end at all.
                 */
                if (!(beresp == 'R' || beresp == 'E'))
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext(
                                                    "expected authentication request from "
                                                    "server, but received %c\n"),
                                      beresp);
                    goto error_return;
                }

                if (PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
                {
                    /* Read message length word */
                    if (pqGetInt(&msgLength, 4, conn))
                    {
                        /* We'll come back when there is more data */
                        return PGRES_POLLING_READING;
                    }
                }
                else
                {
                    /* Set phony message length to disable checks below */
                    msgLength = 8;
                }

                /*
                 * Try to validate message length before using it.
                 * Authentication requests can't be very large, although GSS
                 * auth requests may not be that small.  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.
                 */
                if (beresp == 'R' && (msgLength < 8 || msgLength > 2000))
                {
                    appendPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext(
                                                    "expected authentication request from "
                                                    "server, but received %c\n"),
                                      beresp);
                    goto error_return;
                }

                if (beresp == 'E' && (msgLength < 8 || msgLength > 30000))
                {
                    /* Handle error from a pre-3.0 server */
                    conn->inCursor = conn->inStart + 1; /* reread data */
                    if (pqGets_append(&conn->errorMessage, conn))
                    {
                        /* We'll come back when there is more data */
                        return PGRES_POLLING_READING;
                    }
                    /* OK, we read the message; mark data consumed */
                    conn->inStart = conn->inCursor;

                    /*
                     * The postmaster typically won't end its message with a
                     * newline, so add one to conform to libpq conventions.
                     */
                    appendPQExpBufferChar(&conn->errorMessage, '\n');

                    /*
                     * If we tried to open the connection in 3.0 protocol,
                     * fall back to 2.0 protocol.
                     */
                    if (PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
                    {
                        conn->pversion = PG_PROTOCOL(2, 0);
                        need_new_connection = true;
                        goto keep_going;
                    }

                    goto error_return;
                }

                /*
                 * Can't process if message body isn't all here yet.
                 *
                 * (In protocol 2.0 case, we are assuming messages carry at
                 * least 4 bytes of data.)
                 */
                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 == 'E')
                {
                    if (PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
                    {
                        if (pqGetErrorNotice3(conn, true))
                        {
                            /* We'll come back when there is more data */
                            return PGRES_POLLING_READING;
                        }
                    }
                    else
                    {
                        if (pqGets_append(&conn->errorMessage, conn))
                        {
                            /* We'll come back when there is more data */
                            return PGRES_POLLING_READING;
                        }
                    }
                    /* OK, we read the message; mark data consumed */
                    conn->inStart = conn->inCursor;

                    /* Check to see if we should mention pgpassfile */
                    pgpassfileWarning(conn);

#ifdef ENABLE_GSS

                    /*
                     * If gssencmode is "prefer" and we're using GSSAPI, retry
                     * without it.
                     */
                    if (conn->gssenc && conn->gssencmode[0] == 'p')
                    {
                        OM_uint32   minor;

                        /* postmaster expects us to drop the connection */
                        conn->try_gss = false;
                        conn->gssenc = false;
                        gss_delete_sec_context(&minor, &conn->gctx, NULL);
                        pqDropConnection(conn, true);
                        conn->status = CONNECTION_NEEDED;
                        goto keep_going;
                    }
#endif

#ifdef USE_SSL

                    /*
                     * if sslmode is "allow" and we haven't tried an SSL
                     * connection already, then retry with an SSL connection
                     */
                    if (conn->sslmode[0] == 'a' /* "allow" */
                        && !conn->ssl_in_use
                        && conn->allow_ssl_try
                        && conn->wait_ssl_try)
                    {
                        /* only retry once */
                        conn->wait_ssl_try = false;
                        need_new_connection = true;
                        goto keep_going;
                    }

                    /*
                     * if sslmode is "prefer" and we're in an SSL connection,
                     * then do a non-SSL retry
                     */
                    if (conn->sslmode[0] == 'p' /* "prefer" */
                        && conn->ssl_in_use
                        && conn->allow_ssl_try  /* redundant? */
                        && !conn->wait_ssl_try) /* redundant? */
                    {
                        /* only retry once */
                        conn->allow_ssl_try = false;
                        need_new_connection = true;
                        goto keep_going;
                    }
#endif

                    goto error_return;
                }

                /* It is an authentication request. */
                conn->auth_req_received = true;

                /* Get the type of request. */
                if (pqGetInt((int *) &areq, 4, conn))
                {
                    /* We'll come back when there are more data */
                    return PGRES_POLLING_READING;
                }
                msgLength -= 4;

                /*
                 * Ensure the password salt is in the input buffer, if it's an
                 * MD5 request.  All the other authentication methods that
                 * contain extra data in the authentication request are only
                 * supported in protocol version 3, in which case we already
                 * read the whole message above.
                 */
                if (areq == AUTH_REQ_MD5 && PG_PROTOCOL_MAJOR(conn->pversion) < 3)
                {
                    msgLength += 4;

                    avail = conn->inEnd - conn->inCursor;
                    if (avail < 4)
                    {
                        /*
                         * 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) 4,
                                                 conn))
                            goto error_return;
                        /* We'll come back when there is more data */
                        return PGRES_POLLING_READING;
                    }
                }

                /*
                 * 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);
                conn->errorMessage.len = strlen(conn->errorMessage.data);

                /* OK, we have processed the message; mark data consumed */
                conn->inStart = conn->inCursor;

                if (res != STATUS_OK)
                    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_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)
                        appendPQExpBufferStr(&conn->errorMessage,
                                             libpq_gettext("unexpected message from server during startup\n"));
                    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;
                }

                /* Fire up post-connection housekeeping if needed */
                if (PG_PROTOCOL_MAJOR(conn->pversion) < 3)
                {
                    conn->status = CONNECTION_SETENV;
                    conn->setenv_state = SETENV_STATE_CLIENT_ENCODING_SEND;
                    conn->next_eo = EnvironmentOptions;
                    return PGRES_POLLING_WRITING;
                }

                /* Almost there now ... */
                conn->status = CONNECTION_CHECK_TARGET;
                goto keep_going;
            }

        case CONNECTION_CHECK_TARGET:
            {
                /*
                 * If a read-write connection is required, see if we have one.
                 *
                 * Servers before 7.4 lack the transaction_read_only GUC, but
                 * by the same token they don't have any read-only mode, so we
                 * may just skip the test in that case.
                 */
                if (conn->sversion >= 70400 &&
                    conn->target_session_attrs != NULL &&
                    strcmp(conn->target_session_attrs, "read-write") == 0)
                {
                    /*
                     * Save existing error messages across the PQsendQuery
                     * attempt.  This is necessary because PQsendQuery is
                     * going to reset conn->errorMessage, so we would lose
                     * error messages related to previous hosts we have tried
                     * and failed to connect to.
                     */
                    if (!saveErrorMessage(conn, &savedMessage))
                        goto error_return;

                    conn->status = CONNECTION_OK;
                    if (!PQsendQuery(conn,
                                     "SHOW transaction_read_only"))
                    {
                        restoreErrorMessage(conn, &savedMessage);
                        goto error_return;
                    }
                    conn->status = CONNECTION_CHECK_WRITABLE;
                    restoreErrorMessage(conn, &savedMessage);
                    return PGRES_POLLING_READING;
                }

                /* We can release the address list now. */
                release_conn_addrinfo(conn);

                /* We are open for business! */
                conn->status = CONNECTION_OK;
                return PGRES_POLLING_OK;
            }

        case CONNECTION_SETENV:
            {
                /*
                 * Do post-connection housekeeping (only needed in protocol
                 * 2.0).
                 *
                 * We pretend that the connection is OK for the duration of
                 * these queries.
                 */
                conn->status = CONNECTION_OK;

                switch (pqSetenvPoll(conn))
                {
                    case PGRES_POLLING_OK:  /* Success */
                        break;

                    case PGRES_POLLING_READING: /* Still going */
                        conn->status = CONNECTION_SETENV;
                        return PGRES_POLLING_READING;

                    case PGRES_POLLING_WRITING: /* Still going */
                        conn->status = CONNECTION_SETENV;
                        return PGRES_POLLING_WRITING;

                    default:
                        goto error_return;
                }

                /* Almost there now ... */
                conn->status = CONNECTION_CHECK_TARGET;
                goto keep_going;
            }

        case CONNECTION_CONSUME:
            {
                conn->status = CONNECTION_OK;
                if (!PQconsumeInput(conn))
                    goto error_return;

                if (PQisBusy(conn))
                {
                    conn->status = CONNECTION_CONSUME;
                    return PGRES_POLLING_READING;
                }

                /*
                 * Call PQgetResult() again to consume NULL result.
                 */
                res = PQgetResult(conn);
                if (res != NULL)
                {
                    PQclear(res);
                    conn->status = CONNECTION_CONSUME;
                    goto keep_going;
                }

                /* We can release the address list now. */
                release_conn_addrinfo(conn);

                /* We are open for business! */
                conn->status = CONNECTION_OK;
                return PGRES_POLLING_OK;
            }
        case CONNECTION_CHECK_WRITABLE:
            {
                const char *displayed_host;
                const char *displayed_port;

                if (!saveErrorMessage(conn, &savedMessage))
                    goto error_return;

                conn->status = CONNECTION_OK;
                if (!PQconsumeInput(conn))
                {
                    restoreErrorMessage(conn, &savedMessage);
                    goto error_return;
                }

                if (PQisBusy(conn))
                {
                    conn->status = CONNECTION_CHECK_WRITABLE;
                    restoreErrorMessage(conn, &savedMessage);
                    return PGRES_POLLING_READING;
                }

                res = PQgetResult(conn);
                if (res && (PQresultStatus(res) == PGRES_TUPLES_OK) &&
                    PQntuples(res) == 1)
                {
                    char       *val;

                    val = PQgetvalue(res, 0, 0);
                    if (strncmp(val, "on", 2) == 0)
                    {
                        /* Not writable; fail this connection. */
                        PQclear(res);
                        restoreErrorMessage(conn, &savedMessage);

                        /* Append error report to conn->errorMessage. */
                        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;

                        appendPQExpBuffer(&conn->errorMessage,
                                          libpq_gettext("could not make a writable "
                                                        "connection to server "
                                                        "\"%s:%s\"\n"),
                                          displayed_host, displayed_port);

                        /* 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;
                    }

                    /* Session is read-write, so we're good. */
                    PQclear(res);
                    termPQExpBuffer(&savedMessage);

                    /*
                     * Finish reading any remaining messages before being
                     * considered as ready.
                     */
                    conn->status = CONNECTION_CONSUME;
                    goto keep_going;
                }

                /*
                 * Something went wrong with "SHOW transaction_read_only". We
                 * should try next addresses.
                 */
                if (res)
                    PQclear(res);
                restoreErrorMessage(conn, &savedMessage);

                /* Append error report to conn->errorMessage. */
                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;
                appendPQExpBuffer(&conn->errorMessage,
                                  libpq_gettext("test \"SHOW transaction_read_only\" failed "
                                                "on server \"%s:%s\"\n"),
                                  displayed_host, displayed_port);

                /* Close connection politely. */
                conn->status = CONNECTION_OK;
                sendTerminateConn(conn);

                /* Try next address */
                conn->try_next_addr = true;
                goto keep_going;
            }

        default:
            appendPQExpBuffer(&conn->errorMessage,
                              libpq_gettext("invalid connection state %d, "
                                            "probably indicative of memory corruption\n"),
                              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;
}


/*
 * 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) connectDBComplete(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. (We
     * distinguish this case mainly for the convenience of pg_ctl.)
     */
    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;
}


/*
 * makeEmptyPGconn
 *   - create a PGconn data structure with (as yet) no interesting data
 */
static PGconn *
makeEmptyPGconn(void)
{
    PGconn     *conn;

#ifdef WIN32

    /*
     * Make sure socket support is up and running.
     */
    WSADATA     wsaData;

    if (WSAStartup(MAKEWORD(1, 1), &wsaData))
        return NULL;
    WSASetLastError(0);
#endif

    conn = (PGconn *) malloc(sizeof(PGconn));
    if (conn == NULL)
    {
#ifdef WIN32
        WSACleanup();
#endif
        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->xactStatus = PQTRANS_IDLE;
    conn->options_valid = false;
    conn->nonblocking = false;
    conn->setenv_state = SETENV_STATE_IDLE;
    conn->client_encoding = PG_SQL_ASCII;
    conn->std_strings = false;  /* unless server says differently */
    conn->verbosity = PQERRORS_DEFAULT;
    conn->show_context = PQSHOW_CONTEXT_ERRORS;
    conn->sock = PGINVALID_SOCKET;
#ifdef ENABLE_GSS
    conn->try_gss = true;
#endif

    /*
     * 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 closePGconn().
 * 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)
{
    int         i;

    /* let any event procs clean up their state data */
    for (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);
    }

    /* clean up pg_conn_host structures */
    if (conn->connhost != NULL)
    {
        for (i = 0; i < conn->nconnhost; ++i)
        {
            if (conn->connhost[i].host != NULL)
                free(conn->connhost[i].host);
            if (conn->connhost[i].hostaddr != NULL)
                free(conn->connhost[i].hostaddr);
            if (conn->connhost[i].port != NULL)
                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);
    }

    if (conn->client_encoding_initial)
        free(conn->client_encoding_initial);
    if (conn->events)
        free(conn->events);
    if (conn->pghost)
        free(conn->pghost);
    if (conn->pghostaddr)
        free(conn->pghostaddr);
    if (conn->pgport)
        free(conn->pgport);
    if (conn->pgtty)
        free(conn->pgtty);
    if (conn->connect_timeout)
        free(conn->connect_timeout);
    if (conn->pgtcp_user_timeout)
        free(conn->pgtcp_user_timeout);
    if (conn->pgoptions)
        free(conn->pgoptions);
    if (conn->appname)
        free(conn->appname);
    if (conn->fbappname)
        free(conn->fbappname);
    if (conn->dbName)
        free(conn->dbName);
    if (conn->replication)
        free(conn->replication);
    if (conn->pguser)
        free(conn->pguser);
    if (conn->pgpass)
    {
        explicit_bzero(conn->pgpass, strlen(conn->pgpass));
        free(conn->pgpass);
    }
    if (conn->pgpassfile)
        free(conn->pgpassfile);
    if (conn->channel_binding)
        free(conn->channel_binding);
    if (conn->keepalives)
        free(conn->keepalives);
    if (conn->keepalives_idle)
        free(conn->keepalives_idle);
    if (conn->keepalives_interval)
        free(conn->keepalives_interval);
    if (conn->keepalives_count)
        free(conn->keepalives_count);
    if (conn->sslmode)
        free(conn->sslmode);
    if (conn->sslcert)
        free(conn->sslcert);
    if (conn->sslkey)
        free(conn->sslkey);
    if (conn->sslrootcert)
        free(conn->sslrootcert);
    if (conn->sslcrl)
        free(conn->sslcrl);
    if (conn->sslcompression)
        free(conn->sslcompression);
    if (conn->requirepeer)
        free(conn->requirepeer);
    if (conn->connip)
        free(conn->connip);
    if (conn->gssencmode)
        free(conn->gssencmode);
#if defined(ENABLE_GSS) || defined(ENABLE_SSPI)
    if (conn->krbsrvname)
        free(conn->krbsrvname);
#endif
#ifdef ENABLE_GSS
    if (conn->gcred != GSS_C_NO_CREDENTIAL)
    {
        OM_uint32   minor;

        gss_release_cred(&minor, &conn->gcred);
        conn->gcred = GSS_C_NO_CREDENTIAL;
    }
    if (conn->gctx)
    {
        OM_uint32   minor;

        gss_delete_sec_context(&minor, &conn->gctx, GSS_C_NO_BUFFER);
        conn->gctx = NULL;
    }
#endif
#if defined(ENABLE_GSS) && defined(ENABLE_SSPI)
    if (conn->gsslib)
        free(conn->gsslib);
#endif
    /* Note that conn->Pfdebug is not ours to close or free */
    if (conn->last_query)
        free(conn->last_query);
    if (conn->write_err_msg)
        free(conn->write_err_msg);
    if (conn->inBuffer)
        free(conn->inBuffer);
    if (conn->outBuffer)
        free(conn->outBuffer);
    if (conn->rowBuf)
        free(conn->rowBuf);
    if (conn->target_session_attrs)
        free(conn->target_session_attrs);
    termPQExpBuffer(&conn->errorMessage);
    termPQExpBuffer(&conn->workBuffer);

    free(conn);

#ifdef WIN32
    WSACleanup();
#endif
}

/*
 * release_conn_addrinfo
 *   - Free any addrinfo list in the PGconn.
 */
static void
release_conn_addrinfo(PGconn *conn)
{
    if (conn->addrlist)
    {
        pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
        conn->addrlist = NULL;
        conn->addr_cur = NULL;  /* for safety */
    }
}

/*
 * sendTerminateConn
 *   - Send a terminate message to backend.
 */
static void
sendTerminateConn(PGconn *conn)
{
    /*
     * 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('X', false, conn);
        pqPutMsgEnd(conn);
        (void) pqFlush(conn);
    }
}

/*
 * closePGconn
 *   - 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()).
 */
static void
closePGconn(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.
     */
    pqDropConnection(conn, true);
    conn->status = CONNECTION_BAD;  /* Well, not really _bad_ - just absent */
    conn->asyncStatus = PGASYNC_IDLE;
    conn->xactStatus = PQTRANS_IDLE;
    pqClearAsyncResult(conn);   /* deallocate result */
    resetPQExpBuffer(&conn->errorMessage);
    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)
    {
        closePGconn(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)
    {
        closePGconn(conn);

        if (connectDBStart(conn) && connectDBComplete(conn))
        {
            /*
             * Notify event procs of successful reset.  We treat an event proc
             * failure as disabling the connection ... good idea?
             */
            int         i;

            for (i = 0; i < conn->nEvents; i++)
            {
                PGEventConnReset evt;

                evt.conn = conn;
                if (!conn->events[i].proc(PGEVT_CONNRESET, &evt,
                                          conn->events[i].passThrough))
                {
                    conn->status = CONNECTION_BAD;
                    printfPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("PGEventProc \"%s\" failed during PGEVT_CONNRESET event\n"),
                                      conn->events[i].name);
                    break;
                }
            }
        }
    }
}


/*
 * 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)
    {
        closePGconn(conn);

        return connectDBStart(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.  We treat an event proc
             * failure as disabling the connection ... good idea?
             */
            int         i;

            for (i = 0; i < conn->nEvents; i++)
            {
                PGEventConnReset evt;

                evt.conn = conn;
                if (!conn->events[i].proc(PGEVT_CONNRESET, &evt,
                                          conn->events[i].passThrough))
                {
                    conn->status = CONNECTION_BAD;
                    printfPQExpBuffer(&conn->errorMessage,
                                      libpq_gettext("PGEventProc \"%s\" failed during PGEVT_CONNRESET event\n"),
                                      conn->events[i].name);
                    return PGRES_POLLING_FAILED;
                }
            }
        }

        return status;
    }

    return PGRES_POLLING_FAILED;
}

/*
 * PQgetCancel: get a PGcancel structure corresponding to a connection.
 *
 * A copy is needed to be able to cancel a running query from a different
 * thread. If the same structure is used all structure members would have
 * to be individually locked (if the entire structure was locked, it would
 * be impossible to cancel a synchronous query because the structure would
 * have to stay locked for the duration of the query).
 */
PGcancel *
PQgetCancel(PGconn *conn)
{
    PGcancel   *cancel;

    if (!conn)
        return NULL;

    if (conn->sock == PGINVALID_SOCKET)
        return NULL;

    cancel = malloc(sizeof(PGcancel));
    if (cancel == NULL)
        return NULL;

    memcpy(&cancel->raddr, &conn->raddr, sizeof(SockAddr));
    cancel->be_pid = conn->be_pid;
    cancel->be_key = conn->be_key;

    return cancel;
}

/* PQfreeCancel: free a cancel structure */
void
PQfreeCancel(PGcancel *cancel)
{
    if (cancel)
        free(cancel);
}


/*
 * PQcancel and PQrequestCancel: attempt to request cancellation of the
 * current operation.
 *
 * The return value is true if the cancel request was successfully
 * dispatched, false if not (in which case an error message is available).
 * Note: successful dispatch is no guarantee that there will be any effect at
 * the backend.  The application must read the operation result as usual.
 *
 * CAUTION: we want this routine to be safely callable from a signal handler
 * (for example, an application might want to call it in a SIGINT handler).
 * This means we cannot use any C library routine that might be non-reentrant.
 * malloc/free are often non-reentrant, and anything that might call them is
 * just as dangerous.  We avoid sprintf here for that reason.  Building up
 * error messages with strcpy/strcat is tedious but should be quite safe.
 * We also save/restore errno in case the signal handler support doesn't.
 *
 * internal_cancel() is an internal helper function to make code-sharing
 * between the two versions of the cancel function possible.
 */
static int
internal_cancel(SockAddr *raddr, int be_pid, int be_key,
                char *errbuf, int errbufsize)
{
    int         save_errno = SOCK_ERRNO;
    pgsocket    tmpsock = PGINVALID_SOCKET;
    char        sebuf[PG_STRERROR_R_BUFLEN];
    int         maxlen;
    struct
    {
        uint32      packetlen;
        CancelRequestPacket cp;
    }           crp;

    /*
     * We need to open a temporary connection to the postmaster. Do this with
     * only kernel calls.
     */
    if ((tmpsock = socket(raddr->addr.ss_family, SOCK_STREAM, 0)) == PGINVALID_SOCKET)
    {
        strlcpy(errbuf, "PQcancel() -- socket() failed: ", errbufsize);
        goto cancel_errReturn;
    }
retry3:
    if (connect(tmpsock, (struct sockaddr *) &raddr->addr,
                raddr->salen) < 0)
    {
        if (SOCK_ERRNO == EINTR)
            /* Interrupted system call - we'll just try again */
            goto retry3;
        strlcpy(errbuf, "PQcancel() -- connect() failed: ", errbufsize);
        goto cancel_errReturn;
    }

    /*
     * We needn't set nonblocking I/O or NODELAY options here.
     */

    /* Create and send the cancel request packet. */

    crp.packetlen = pg_hton32((uint32) sizeof(crp));
    crp.cp.cancelRequestCode = (MsgType) pg_hton32(CANCEL_REQUEST_CODE);
    crp.cp.backendPID = pg_hton32(be_pid);
    crp.cp.cancelAuthCode = pg_hton32(be_key);

retry4:
    if (send(tmpsock, (char *) &crp, sizeof(crp), 0) != (int) sizeof(crp))
    {
        if (SOCK_ERRNO == EINTR)
            /* Interrupted system call - we'll just try again */
            goto retry4;
        strlcpy(errbuf, "PQcancel() -- send() failed: ", errbufsize);
        goto cancel_errReturn;
    }

    /*
     * Wait for the postmaster to close the connection, which indicates that
     * it's processed the request.  Without this delay, we might issue another
     * command only to find that our cancel zaps that command instead of the
     * one we thought we were canceling.  Note we don't actually expect this
     * read to obtain any data, we are just waiting for EOF to be signaled.
     */
retry5:
    if (recv(tmpsock, (char *) &crp, 1, 0) < 0)
    {
        if (SOCK_ERRNO == EINTR)
            /* Interrupted system call - we'll just try again */
            goto retry5;
        /* we ignore other error conditions */
    }

    /* All done */
    closesocket(tmpsock);
    SOCK_ERRNO_SET(save_errno);
    return true;

cancel_errReturn:

    /*
     * Make sure we don't overflow the error buffer. Leave space for the \n at
     * the end, and for the terminating zero.
     */
    maxlen = errbufsize - strlen(errbuf) - 2;
    if (maxlen >= 0)
    {
        strncat(errbuf, SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)),
                maxlen);
        strcat(errbuf, "\n");
    }
    if (tmpsock != PGINVALID_SOCKET)
        closesocket(tmpsock);
    SOCK_ERRNO_SET(save_errno);
    return false;
}

/*
 * PQcancel: request query cancel
 *
 * Returns true if able to send the cancel request, false if not.
 *
 * On failure, an error message is stored in *errbuf, which must be of size
 * errbufsize (recommended size is 256 bytes).  *errbuf is not changed on
 * success return.
 */
int
PQcancel(PGcancel *cancel, char *errbuf, int errbufsize)
{
    if (!cancel)
    {
        strlcpy(errbuf, "PQcancel() -- no cancel object supplied", errbufsize);
        return false;
    }

    return internal_cancel(&cancel->raddr, cancel->be_pid, cancel->be_key,
                           errbuf, errbufsize);
}

/*
 * PQrequestCancel: old, not thread-safe function for requesting query cancel
 *
 * Returns true if able to send the cancel request, false if not.
 *
 * On failure, the error message is saved in conn->errorMessage; this means
 * that this can't be used when there might be other active operations on
 * the connection object.
 *
 * NOTE: error messages will be cut off at the current size of the
 * error message buffer, since we dare not try to expand conn->errorMessage!
 */
int
PQrequestCancel(PGconn *conn)
{
    int         r;

    /* Check we have an open connection */
    if (!conn)
        return false;

    if (conn->sock == PGINVALID_SOCKET)
    {
        strlcpy(conn->errorMessage.data,
                "PQrequestCancel() -- connection is not open\n",
                conn->errorMessage.maxlen);
        conn->errorMessage.len = strlen(conn->errorMessage.data);

        return false;
    }

    r = internal_cancel(&conn->raddr, conn->be_pid, conn->be_key,
                        conn->errorMessage.data, conn->errorMessage.maxlen);

    if (!r)
        conn->errorMessage.len = strlen(conn->errorMessage.data);

    return r;
}


/*
 * 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.
 *
 * Note: all messages sent with this routine have a length word, whether
 * it's protocol 2.0 or 3.0.
 */
int
pqPacketSend(PGconn *conn, char pack_type,
             const void *buf, size_t buf_len)
{
    /* Start the message. */
    if (pqPutMsgStart(pack_type, true, 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 returned in the third argument 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};

    if ((url = strdup(purl)) == NULL)
    {
        printfPQExpBuffer(errorMessage, libpq_gettext("out of memory\n"));
        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)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("invalid LDAP URL \"%s\": scheme must be ldap://\n"), 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) == '?')
    {
        printfPQExpBuffer(errorMessage, libpq_gettext(
                                                      "invalid LDAP URL \"%s\": missing distinguished name\n"), purl);
        free(url);
        return 3;
    }
    *p = '\0';                  /* terminate hostname */
    dn = p + 1;

    /* attribute */
    if ((p = strchr(dn, '?')) == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        printfPQExpBuffer(errorMessage, libpq_gettext(
                                                      "invalid LDAP URL \"%s\": must have exactly one attribute\n"), purl);
        free(url);
        return 3;
    }
    *p = '\0';
    attrs[0] = p + 1;

    /* scope */
    if ((p = strchr(attrs[0], '?')) == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        printfPQExpBuffer(errorMessage, libpq_gettext("invalid LDAP URL \"%s\": must have search scope (base/one/sub)\n"), purl);
        free(url);
        return 3;
    }
    *p = '\0';
    scopestr = p + 1;

    /* filter */
    if ((p = strchr(scopestr, '?')) == NULL || *(p + 1) == '\0' || *(p + 1) == '?')
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("invalid LDAP URL \"%s\": no filter\n"), 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)
        {
            printfPQExpBuffer(errorMessage, libpq_gettext(
                                                          "invalid LDAP URL \"%s\": invalid port number\n"), purl);
            free(url);
            return 3;
        }
        port = (int) lport;
    }

    /* Allow only one attribute */
    if (strchr(attrs[0], ',') != NULL)
    {
        printfPQExpBuffer(errorMessage, libpq_gettext(
                                                      "invalid LDAP URL \"%s\": must have exactly one attribute\n"), 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
    {
        printfPQExpBuffer(errorMessage, libpq_gettext("invalid LDAP URL \"%s\": must have search scope (base/one/sub)\n"), purl);
        free(url);
        return 3;
    }

    /* initialize LDAP structure */
    if ((ld = ldap_init(hostname, port)) == NULL)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("could not create LDAP structure\n"));
        free(url);
        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);
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("lookup on LDAP server failed: %s\n"),
                          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)
    {
        printfPQExpBuffer(errorMessage,
                          rc ? libpq_gettext("more than one entry found on LDAP lookup\n")
                          : libpq_gettext("no entry found on LDAP lookup\n"));
        ldap_msgfree(res);
        ldap_unbind(ld);
        free(url);
        return 1;
    }

    /* get entry */
    if ((entry = ldap_first_entry(ld, res)) == NULL)
    {
        /* should never happen */
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("no entry found on LDAP lookup\n"));
        ldap_msgfree(res);
        ldap_unbind(ld);
        free(url);
        return 1;
    }

    /* get values */
    if ((values = ldap_get_values_len(ld, entry, attrs[0])) == NULL)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("attribute has no values on LDAP lookup\n"));
        ldap_msgfree(res);
        ldap_unbind(ld);
        free(url);
        return 1;
    }

    ldap_msgfree(res);
    free(url);

    if (values[0] == NULL)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("attribute has no values on LDAP lookup\n"));
        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++)
        size += values[i]->bv_len + 1;
    if ((result = malloc(size)) == NULL)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("out of memory\n"));
        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))
                {
                    printfPQExpBuffer(errorMessage, libpq_gettext(
                                                                  "missing \"=\" after \"%s\" in connection info string\n"),
                                      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))
                {
                    printfPQExpBuffer(errorMessage, libpq_gettext(
                                                                  "missing \"=\" after \"%s\" in connection info string\n"),
                                      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)
                        {
                            printfPQExpBuffer(errorMessage,
                                              libpq_gettext("out of memory\n"));
                            free(result);
                            return 3;
                        }
                    }
                    found_keyword = true;
                    break;
                }
            }
            if (!found_keyword)
            {
                printfPQExpBuffer(errorMessage,
                                  libpq_gettext("invalid connection option \"%s\"\n"),
                                  optname);
                free(result);
                return 1;
            }
            optname = NULL;
            optval = NULL;
        }
        oldstate = state;
    }

    free(result);

    if (state == 5 || state == 6)
    {
        printfPQExpBuffer(errorMessage, libpq_gettext(
                                                      "unterminated quoted string in connection info string\n"));
        return 3;
    }

    return 0;
}

#endif                          /* USE_LDAP */

#define MAXBUFSIZE 256

/*
 * 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 printfPQExpBuffer does nothing when passed
 * a null PQExpBuffer pointer.)
 */
static int
parseServiceInfo(PQconninfoOption *options, PQExpBuffer errorMessage)
{
    const char *service = conninfo_getval(options, "service");
    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;

    /*
     * Try PGSERVICEFILE if specified, else try ~/.pg_service.conf (if that
     * exists).
     */
    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)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("definition of service \"%s\" not found\n"), service);
        return 3;
    }

    return 0;
}

static int
parseServiceFile(const char *serviceFile,
                 const char *service,
                 PQconninfoOption *options,
                 PQExpBuffer errorMessage,
                 bool *group_found)
{
    int         linenr = 0,
                i;
    FILE       *f;
    char        buf[MAXBUFSIZE],
               *line;

    f = fopen(serviceFile, "r");
    if (f == NULL)
    {
        printfPQExpBuffer(errorMessage, libpq_gettext("service file \"%s\" not found\n"),
                          serviceFile);
        return 1;
    }

    while ((line = fgets(buf, sizeof(buf), f)) != NULL)
    {
        int         len;

        linenr++;

        if (strlen(line) >= sizeof(buf) - 1)
        {
            fclose(f);
            printfPQExpBuffer(errorMessage,
                              libpq_gettext("line %d too long in service file \"%s\"\n"),
                              linenr,
                              serviceFile);
            return 2;
        }

        /* 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)
            {
                /* group info already read */
                fclose(f);
                return 0;
            }

            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:
                            fclose(f);
                            return 0;
                        case 1:
                        case 3:
                            fclose(f);
                            return 3;
                        case 2:
                            continue;
                    }
                }
#endif

                key = line;
                val = strchr(line, '=');
                if (val == NULL)
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("syntax error in service file \"%s\", line %d\n"),
                                      serviceFile,
                                      linenr);
                    fclose(f);
                    return 3;
                }
                *val++ = '\0';

                if (strcmp(key, "service") == 0)
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("nested service specifications not supported in service file \"%s\", line %d\n"),
                                      serviceFile,
                                      linenr);
                    fclose(f);
                    return 3;
                }

                /*
                 * 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)
                        {
                            printfPQExpBuffer(errorMessage,
                                              libpq_gettext("out of memory\n"));
                            fclose(f);
                            return 3;
                        }
                        found_keyword = true;
                        break;
                    }
                }

                if (!found_keyword)
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("syntax error in service file \"%s\", line %d\n"),
                                      serviceFile,
                                      linenr);
                    fclose(f);
                    return 3;
                }
            }
        }
    }

    fclose(f);

    return 0;
}


/*
 *      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)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("out of memory\n"));
        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 left in 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)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("out of memory\n"));
        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 != '=')
        {
            printfPQExpBuffer(errorMessage,
                              libpq_gettext("missing \"=\" after \"%s\" in connection info string\n"),
                              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')
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("unterminated quoted string in connection info string\n"));
                    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
 * left in 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)
            {
                printfPQExpBuffer(errorMessage,
                                  libpq_gettext("invalid connection option \"%s\"\n"),
                                  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)
                            {
                                if (options[k].val)
                                    free(options[k].val);
                                options[k].val = strdup(str_option->val);
                                if (!options[k].val)
                                {
                                    printfPQExpBuffer(errorMessage,
                                                      libpq_gettext("out of memory\n"));
                                    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
                 */
                if (option->val)
                    free(option->val);
                option->val = strdup(pvalue);
                if (!option->val)
                {
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("out of memory\n"));
                    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;
    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 (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)
                        printfPQExpBuffer(errorMessage,
                                          libpq_gettext("out of memory\n"));
                    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)
                        printfPQExpBuffer(errorMessage,
                                          libpq_gettext("out of memory\n"));
                    return false;
                }
                continue;
            }
        }

        /*
         * 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)
                    printfPQExpBuffer(errorMessage,
                                      libpq_gettext("out of memory\n"));
                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;
        }
    }

    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))
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("out of memory\n"));
        goto cleanup;
    }

    /* need a modifiable copy of the input URI */
    buf = strdup(uri);
    if (buf == NULL)
    {
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("out of memory\n"));
        goto cleanup;
    }
    start = buf;

    /* Skip the URI prefix */
    prefix_len = uri_prefix_length(uri);
    if (prefix_len == 0)
    {
        /* Should never happen */
        printfPQExpBuffer(errorMessage,
                          libpq_gettext("invalid URI propagated to internal parser routine: \"%s\"\n"),
                          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)
            {
                printfPQExpBuffer(errorMessage,
                                  libpq_gettext("end of string reached when looking for matching \"]\" in IPv6 host address in URI: \"%s\"\n"),
                                  uri);
                goto cleanup;
            }
            if (p == host)
            {
                printfPQExpBuffer(errorMessage,
                                  libpq_gettext("IPv6 host address may not be empty in URI: \"%s\"\n"),
                                  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 != ',')
            {
                printfPQExpBuffer(errorMessage,
                                  libpq_gettext("unexpected character \"%c\" at position %d in URI (expected \":\" or \"/\"): \"%s\"\n"),
                                  *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);
    if (buf)
        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;

        /*
         * Scan the params string for '=' and '&', marking the end of keyword
         * and value respectively.
         */
        for (;;)