pg_verifybackup.c

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/*-------------------------------------------------------------------------
 *
 * pg_verifybackup.c
 *    Verify a backup against a backup manifest.
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/bin/pg_verifybackup/pg_verifybackup.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres_fe.h"

#include <dirent.h>
#include <fcntl.h>
#include <sys/stat.h>

#include "common/hashfn.h"
#include "common/logging.h"
#include "fe_utils/simple_list.h"
#include "getopt_long.h"
#include "parse_manifest.h"

/*
 * For efficiency, we'd like our hash table containing information about the
 * manifest to start out with approximately the correct number of entries.
 * There's no way to know the exact number of entries without reading the whole
 * file, but we can get an estimate by dividing the file size by the estimated
 * number of bytes per line.
 *
 * This could be off by about a factor of two in either direction, because the
 * checksum algorithm has a big impact on the line lengths; e.g. a SHA512
 * checksum is 128 hex bytes, whereas a CRC-32C value is only 8, and there
 * might be no checksum at all.
 */
#define ESTIMATED_BYTES_PER_MANIFEST_LINE   100

/*
 * How many bytes should we try to read from a file at once?
 */
#define READ_CHUNK_SIZE             4096

/*
 * Each file described by the manifest file is parsed to produce an object
 * like this.
 */
typedef struct manifest_file
{
    uint32      status;         /* hash status */
    char       *pathname;
    size_t      size;
    pg_checksum_type checksum_type;
    int         checksum_length;
    uint8      *checksum_payload;
    bool        matched;
    bool        bad;
} manifest_file;

/*
 * Define a hash table which we can use to store information about the files
 * mentioned in the backup manifest.
 */
static uint32 hash_string_pointer(char *s);
#define SH_PREFIX       manifest_files
#define SH_ELEMENT_TYPE manifest_file
#define SH_KEY_TYPE     char *
#define SH_KEY          pathname
#define SH_HASH_KEY(tb, key)    hash_string_pointer(key)
#define SH_EQUAL(tb, a, b)      (strcmp(a, b) == 0)
#define SH_SCOPE        static inline
#define SH_RAW_ALLOCATOR    pg_malloc0
#define SH_DECLARE
#define SH_DEFINE
#include "lib/simplehash.h"

/*
 * Each WAL range described by the manifest file is parsed to produce an
 * object like this.
 */
typedef struct manifest_wal_range
{
    TimeLineID  tli;
    XLogRecPtr  start_lsn;
    XLogRecPtr  end_lsn;
    struct manifest_wal_range *next;
    struct manifest_wal_range *prev;
} manifest_wal_range;

/*
 * Details we need in callbacks that occur while parsing a backup manifest.
 */
typedef struct parser_context
{
    manifest_files_hash *ht;
    manifest_wal_range *first_wal_range;
    manifest_wal_range *last_wal_range;
} parser_context;

/*
 * All of the context information we need while checking a backup manifest.
 */
typedef struct verifier_context
{
    manifest_files_hash *ht;
    char       *backup_directory;
    SimpleStringList ignore_list;
    bool        exit_on_error;
    bool        saw_any_error;
} verifier_context;

static void parse_manifest_file(char *manifest_path,
                                manifest_files_hash **ht_p,
                                manifest_wal_range **first_wal_range_p);

static void record_manifest_details_for_file(JsonManifestParseContext *context,
                                             char *pathname, size_t size,
                                             pg_checksum_type checksum_type,
                                             int checksum_length,
                                             uint8 *checksum_payload);
static void record_manifest_details_for_wal_range(JsonManifestParseContext *context,
                                                  TimeLineID tli,
                                                  XLogRecPtr start_lsn,
                                                  XLogRecPtr end_lsn);
static void report_manifest_error(JsonManifestParseContext *context,
                                  const char *fmt,...)
            pg_attribute_printf(2, 3) pg_attribute_noreturn();

static void verify_backup_directory(verifier_context *context,
                                    char *relpath, char *fullpath);
static void verify_backup_file(verifier_context *context,
                               char *relpath, char *fullpath);
static void report_extra_backup_files(verifier_context *context);
static void verify_backup_checksums(verifier_context *context);
static void verify_file_checksum(verifier_context *context,
                                 manifest_file *m, char *pathname);
static void parse_required_wal(verifier_context *context,
                               char *pg_waldump_path,
                               char *wal_directory,
                               manifest_wal_range *first_wal_range);

static void report_backup_error(verifier_context *context,
                                const char *pg_restrict fmt,...)
            pg_attribute_printf(2, 3);
static void report_fatal_error(const char *pg_restrict fmt,...)
            pg_attribute_printf(1, 2) pg_attribute_noreturn();
static bool should_ignore_relpath(verifier_context *context, char *relpath);

static void usage(void);

static const char *progname;

/*
 * Main entry point.
 */
int
main(int argc, char **argv)
{
    static struct option long_options[] = {
        {"exit-on-error", no_argument, NULL, 'e'},
        {"ignore", required_argument, NULL, 'i'},
        {"manifest-path", required_argument, NULL, 'm'},
        {"no-parse-wal", no_argument, NULL, 'n'},
        {"quiet", no_argument, NULL, 'q'},
        {"skip-checksums", no_argument, NULL, 's'},
        {"wal-directory", required_argument, NULL, 'w'},
        {NULL, 0, NULL, 0}
    };

    int         c;
    verifier_context context;
    manifest_wal_range *first_wal_range;
    char       *manifest_path = NULL;
    bool        no_parse_wal = false;
    bool        quiet = false;
    bool        skip_checksums = false;
    char       *wal_directory = NULL;
    char       *pg_waldump_path = NULL;

    pg_logging_init(argv[0]);
    set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_verifybackup"));
    progname = get_progname(argv[0]);

    memset(&context, 0, sizeof(context));

    if (argc > 1)
    {
        if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-?") == 0)
        {
            usage();
            exit(0);
        }
        if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
        {
            puts("pg_verifybackup (PostgreSQL) " PG_VERSION);
            exit(0);
        }
    }

    /*
     * Skip certain files in the toplevel directory.
     *
     * Ignore the backup_manifest file, because it's not included in the
     * backup manifest.
     *
     * Ignore the pg_wal directory, because those files are not included in
     * the backup manifest either, since they are fetched separately from the
     * backup itself, and verified via a separate mechanism.
     *
     * Ignore postgresql.auto.conf, recovery.signal, and standby.signal,
     * because we expect that those files may sometimes be created or changed
     * as part of the backup process. For example, pg_basebackup -R will
     * modify postgresql.auto.conf and create standby.signal.
     */
    simple_string_list_append(&context.ignore_list, "backup_manifest");
    simple_string_list_append(&context.ignore_list, "pg_wal");
    simple_string_list_append(&context.ignore_list, "postgresql.auto.conf");
    simple_string_list_append(&context.ignore_list, "recovery.signal");
    simple_string_list_append(&context.ignore_list, "standby.signal");

    while ((c = getopt_long(argc, argv, "ei:m:nqsw:", long_options, NULL)) != -1)
    {
        switch (c)
        {
            case 'e':
                context.exit_on_error = true;
                break;
            case 'i':
                {
                    char       *arg = pstrdup(optarg);

                    canonicalize_path(arg);
                    simple_string_list_append(&context.ignore_list, arg);
                    break;
                }
            case 'm':
                manifest_path = pstrdup(optarg);
                canonicalize_path(manifest_path);
                break;
            case 'n':
                no_parse_wal = true;
                break;
            case 'q':
                quiet = true;
                break;
            case 's':
                skip_checksums = true;
                break;
            case 'w':
                wal_directory = pstrdup(optarg);
                canonicalize_path(wal_directory);
                break;
            default:
                fprintf(stderr, _("Try \"%s --help\" for more information.\n"),
                        progname);
                exit(1);
        }
    }

    /* Get backup directory name */
    if (optind >= argc)
    {
        pg_log_fatal("no backup directory specified");
        fprintf(stderr, _("Try \"%s --help\" for more information.\n"),
                progname);
        exit(1);
    }
    context.backup_directory = pstrdup(argv[optind++]);
    canonicalize_path(context.backup_directory);

    /* Complain if any arguments remain */
    if (optind < argc)
    {
        pg_log_fatal("too many command-line arguments (first is \"%s\")",
                     argv[optind]);
        fprintf(stderr, _("Try \"%s --help\" for more information.\n"),
                progname);
        exit(1);
    }

    /* Unless --no-parse-wal was specified, we will need pg_waldump. */
    if (!no_parse_wal)
    {
        int         ret;

        pg_waldump_path = pg_malloc(MAXPGPATH);
        ret = find_other_exec(argv[0], "pg_waldump",
                              "pg_waldump (PostgreSQL) " PG_VERSION "\n",
                              pg_waldump_path);
        if (ret < 0)
        {
            char        full_path[MAXPGPATH];

            if (find_my_exec(argv[0], full_path) < 0)
                strlcpy(full_path, progname, sizeof(full_path));
            if (ret == -1)
                pg_log_fatal("The program \"%s\" is needed by %s but was not found in the\n"
                             "same directory as \"%s\".\n"
                             "Check your installation.",
                             "pg_waldump", "pg_verifybackup", full_path);
            else
                pg_log_fatal("The program \"%s\" was found by \"%s\"\n"
                             "but was not the same version as %s.\n"
                             "Check your installation.",
                             "pg_waldump", full_path, "pg_verifybackup");
        }
    }

    /* By default, look for the manifest in the backup directory. */
    if (manifest_path == NULL)
        manifest_path = psprintf("%s/backup_manifest",
                                 context.backup_directory);

    /* By default, look for the WAL in the backup directory, too. */
    if (wal_directory == NULL)
        wal_directory = psprintf("%s/pg_wal", context.backup_directory);

    /*
     * Try to read the manifest. We treat any errors encountered while parsing
     * the manifest as fatal; there doesn't seem to be much point in trying to
     * verify the backup directory against a corrupted manifest.
     */
    parse_manifest_file(manifest_path, &context.ht, &first_wal_range);

    /*
     * Now scan the files in the backup directory. At this stage, we verify
     * that every file on disk is present in the manifest and that the sizes
     * match. We also set the "matched" flag on every manifest entry that
     * corresponds to a file on disk.
     */
    verify_backup_directory(&context, NULL, context.backup_directory);

    /*
     * The "matched" flag should now be set on every entry in the hash table.
     * Any entries for which the bit is not set are files mentioned in the
     * manifest that don't exist on disk.
     */
    report_extra_backup_files(&context);

    /*
     * Now do the expensive work of verifying file checksums, unless we were
     * told to skip it.
     */
    if (!skip_checksums)
        verify_backup_checksums(&context);

    /*
     * Try to parse the required ranges of WAL records, unless we were told
     * not to do so.
     */
    if (!no_parse_wal)
        parse_required_wal(&context, pg_waldump_path,
                           wal_directory, first_wal_range);

    /*
     * If everything looks OK, tell the user this, unless we were asked to
     * work quietly.
     */
    if (!context.saw_any_error && !quiet)
        printf(_("backup successfully verified\n"));

    return context.saw_any_error ? 1 : 0;
}

/*
 * Parse a manifest file. Construct a hash table with information about
 * all the files it mentions, and a linked list of all the WAL ranges it
 * mentions.
 */
static void
parse_manifest_file(char *manifest_path, manifest_files_hash **ht_p,
                    manifest_wal_range **first_wal_range_p)
{
    int         fd;
    struct stat statbuf;
    off_t       estimate;
    uint32      initial_size;
    manifest_files_hash *ht;
    char       *buffer;
    int         rc;
    parser_context private_context;
    JsonManifestParseContext context;

    /* Open the manifest file. */
    if ((fd = open(manifest_path, O_RDONLY | PG_BINARY, 0)) < 0)
        report_fatal_error("could not open file \"%s\": %m", manifest_path);

    /* Figure out how big the manifest is. */
    if (fstat(fd, &statbuf) != 0)
        report_fatal_error("could not stat file \"%s\": %m", manifest_path);

    /* Guess how large to make the hash table based on the manifest size. */
    estimate = statbuf.st_size / ESTIMATED_BYTES_PER_MANIFEST_LINE;
    initial_size = Min(PG_UINT32_MAX, Max(estimate, 256));

    /* Create the hash table. */
    ht = manifest_files_create(initial_size, NULL);

    /*
     * Slurp in the whole file.
     *
     * This is not ideal, but there's currently no easy way to get
     * pg_parse_json() to perform incremental parsing.
     */
    buffer = pg_malloc(statbuf.st_size);
    rc = read(fd, buffer, statbuf.st_size);
    if (rc != statbuf.st_size)
    {
        if (rc < 0)
            report_fatal_error("could not read file \"%s\": %m",
                               manifest_path);
        else
            report_fatal_error("could not read file \"%s\": read %d of %lld",
                               manifest_path, rc, (long long int) statbuf.st_size);
    }

    /* Close the manifest file. */
    close(fd);

    /* Parse the manifest. */
    private_context.ht = ht;
    private_context.first_wal_range = NULL;
    private_context.last_wal_range = NULL;
    context.private_data = &private_context;
    context.perfile_cb = record_manifest_details_for_file;
    context.perwalrange_cb = record_manifest_details_for_wal_range;
    context.error_cb = report_manifest_error;
    json_parse_manifest(&context, buffer, statbuf.st_size);

    /* Done with the buffer. */
    pfree(buffer);

    /* Return the file hash table and WAL range list we constructed. */
    *ht_p = ht;
    *first_wal_range_p = private_context.first_wal_range;
}

/*
 * Report an error while parsing the manifest.
 *
 * We consider all such errors to be fatal errors. The manifest parser
 * expects this function not to return.
 */
static void
report_manifest_error(JsonManifestParseContext *context, const char *fmt,...)
{
    va_list     ap;

    va_start(ap, fmt);
    pg_log_generic_v(PG_LOG_FATAL, gettext(fmt), ap);
    va_end(ap);

    exit(1);
}

/*
 * Record details extracted from the backup manifest for one file.
 */
static void
record_manifest_details_for_file(JsonManifestParseContext *context,
                                 char *pathname, size_t size,
                                 pg_checksum_type checksum_type,
                                 int checksum_length, uint8 *checksum_payload)
{
    parser_context *pcxt = context->private_data;
    manifest_files_hash *ht = pcxt->ht;
    manifest_file *m;
    bool        found;

    /* Make a new entry in the hash table for this file. */
    m = manifest_files_insert(ht, pathname, &found);
    if (found)
        report_fatal_error("duplicate path name in backup manifest: \"%s\"",
                           pathname);

    /* Initialize the entry. */
    m->size = size;
    m->checksum_type = checksum_type;
    m->checksum_length = checksum_length;
    m->checksum_payload = checksum_payload;
    m->matched = false;
    m->bad = false;
}

/*
 * Record details extracted from the backup manifest for one WAL range.
 */
static void
record_manifest_details_for_wal_range(JsonManifestParseContext *context,
                                      TimeLineID tli,
                                      XLogRecPtr start_lsn, XLogRecPtr end_lsn)
{
    parser_context *pcxt = context->private_data;
    manifest_wal_range *range;

    /* Allocate and initialize a struct describing this WAL range. */
    range = palloc(sizeof(manifest_wal_range));
    range->tli = tli;
    range->start_lsn = start_lsn;
    range->end_lsn = end_lsn;
    range->prev = pcxt->last_wal_range;
    range->next = NULL;

    /* Add it to the end of the list. */
    if (pcxt->first_wal_range == NULL)
        pcxt->first_wal_range = range;
    else
        pcxt->last_wal_range->next = range;
    pcxt->last_wal_range = range;
}

/*
 * Verify one directory.
 *
 * 'relpath' is NULL if we are to verify the top-level backup directory,
 * and otherwise the relative path to the directory that is to be verified.
 *
 * 'fullpath' is the backup directory with 'relpath' appended; i.e. the actual
 * filesystem path at which it can be found.
 */
static void
verify_backup_directory(verifier_context *context, char *relpath,
                        char *fullpath)
{
    DIR        *dir;
    struct dirent *dirent;

    dir = opendir(fullpath);
    if (dir == NULL)
    {
        /*
         * If even the toplevel backup directory cannot be found, treat this
         * as a fatal error.
         */
        if (relpath == NULL)
            report_fatal_error("could not open directory \"%s\": %m", fullpath);

        /*
         * Otherwise, treat this as a non-fatal error, but ignore any further
         * errors related to this path and anything beneath it.
         */
        report_backup_error(context,
                            "could not open directory \"%s\": %m", fullpath);
        simple_string_list_append(&context->ignore_list, relpath);

        return;
    }

    while (errno = 0, (dirent = readdir(dir)) != NULL)
    {
        char       *filename = dirent->d_name;
        char       *newfullpath = psprintf("%s/%s", fullpath, filename);
        char       *newrelpath;

        /* Skip "." and ".." */
        if (filename[0] == '.' && (filename[1] == '\0'
                                   || strcmp(filename, "..") == 0))
            continue;

        if (relpath == NULL)
            newrelpath = pstrdup(filename);
        else
            newrelpath = psprintf("%s/%s", relpath, filename);

        if (!should_ignore_relpath(context, newrelpath))
            verify_backup_file(context, newrelpath, newfullpath);

        pfree(newfullpath);
        pfree(newrelpath);
    }

    if (closedir(dir))
    {
        report_backup_error(context,
                            "could not close directory \"%s\": %m", fullpath);
        return;
    }
}

/*
 * Verify one file (which might actually be a directory or a symlink).
 *
 * The arguments to this function have the same meaning as the arguments to
 * verify_backup_directory.
 */
static void
verify_backup_file(verifier_context *context, char *relpath, char *fullpath)
{
    struct stat sb;
    manifest_file *m;

    if (stat(fullpath, &sb) != 0)
    {
        report_backup_error(context,
                            "could not stat file or directory \"%s\": %m",
                            relpath);

        /*
         * Suppress further errors related to this path name and, if it's a
         * directory, anything underneath it.
         */
        simple_string_list_append(&context->ignore_list, relpath);

        return;
    }

    /* If it's a directory, just recurse. */
    if (S_ISDIR(sb.st_mode))
    {
        verify_backup_directory(context, relpath, fullpath);
        return;
    }

    /* If it's not a directory, it should be a plain file. */
    if (!S_ISREG(sb.st_mode))
    {
        report_backup_error(context,
                            "\"%s\" is not a file or directory",
                            relpath);
        return;
    }

    /* Check whether there's an entry in the manifest hash. */
    m = manifest_files_lookup(context->ht, relpath);
    if (m == NULL)
    {
        report_backup_error(context,
                            "\"%s\" is present on disk but not in the manifest",
                            relpath);
        return;
    }

    /* Flag this entry as having been encountered in the filesystem. */
    m->matched = true;

    /* Check that the size matches. */
    if (m->size != sb.st_size)
    {
        report_backup_error(context,
                            "\"%s\" has size %lld on disk but size %zu in the manifest",
                            relpath, (long long int) sb.st_size, m->size);
        m->bad = true;
    }

    /*
     * We don't verify checksums at this stage. We first finish verifying that
     * we have the expected set of files with the expected sizes, and only
     * afterwards verify the checksums. That's because computing checksums may
     * take a while, and we'd like to report more obvious problems quickly.
     */
}

/*
 * Scan the hash table for entries where the 'matched' flag is not set; report
 * that such files are present in the manifest but not on disk.
 */
static void
report_extra_backup_files(verifier_context *context)
{
    manifest_files_iterator it;
    manifest_file *m;

    manifest_files_start_iterate(context->ht, &it);
    while ((m = manifest_files_iterate(context->ht, &it)) != NULL)
        if (!m->matched && !should_ignore_relpath(context, m->pathname))
            report_backup_error(context,
                                "\"%s\" is present in the manifest but not on disk",
                                m->pathname);
}

/*
 * Verify checksums for hash table entries that are otherwise unproblematic.
 * If we've already reported some problem related to a hash table entry, or
 * if it has no checksum, just skip it.
 */
static void
verify_backup_checksums(verifier_context *context)
{
    manifest_files_iterator it;
    manifest_file *m;

    manifest_files_start_iterate(context->ht, &it);
    while ((m = manifest_files_iterate(context->ht, &it)) != NULL)
    {
        if (m->matched && !m->bad && m->checksum_type != CHECKSUM_TYPE_NONE &&
            !should_ignore_relpath(context, m->pathname))
        {
            char       *fullpath;

            /* Compute the full pathname to the target file. */
            fullpath = psprintf("%s/%s", context->backup_directory,
                                m->pathname);

            /* Do the actual checksum verification. */
            verify_file_checksum(context, m, fullpath);

            /* Avoid leaking memory. */
            pfree(fullpath);
        }
    }
}

/*
 * Verify the checksum of a single file.
 */
static void
verify_file_checksum(verifier_context *context, manifest_file *m,
                     char *fullpath)
{
    pg_checksum_context checksum_ctx;
    char       *relpath = m->pathname;
    int         fd;
    int         rc;
    size_t      bytes_read = 0;
    uint8       buffer[READ_CHUNK_SIZE];
    uint8       checksumbuf[PG_CHECKSUM_MAX_LENGTH];
    int         checksumlen;

    /* Open the target file. */
    if ((fd = open(fullpath, O_RDONLY | PG_BINARY, 0)) < 0)
    {
        report_backup_error(context, "could not open file \"%s\": %m",
                            relpath);
        return;
    }

    /* Initialize checksum context. */
    if (pg_checksum_init(&checksum_ctx, m->checksum_type) < 0)
    {
        report_backup_error(context, "could not initialize checksum of file \"%s\"",
                            relpath);
        close(fd);
        return;
    }

    /* Read the file chunk by chunk, updating the checksum as we go. */
    while ((rc = read(fd, buffer, READ_CHUNK_SIZE)) > 0)
    {
        bytes_read += rc;
        if (pg_checksum_update(&checksum_ctx, buffer, rc) < 0)
        {
            report_backup_error(context, "could not update checksum of file \"%s\"",
                                relpath);
            close(fd);
            return;
        }


    }
    if (rc < 0)
        report_backup_error(context, "could not read file \"%s\": %m",
                            relpath);

    /* Close the file. */
    if (close(fd) != 0)
    {
        report_backup_error(context, "could not close file \"%s\": %m",
                            relpath);
        return;
    }

    /* If we didn't manage to read the whole file, bail out now. */
    if (rc < 0)
        return;

    /*
     * Double-check that we read the expected number of bytes from the file.
     * Normally, a file size mismatch would be caught in verify_backup_file
     * and this check would never be reached, but this provides additional
     * safety and clarity in the event of concurrent modifications or
     * filesystem misbehavior.
     */
    if (bytes_read != m->size)
    {
        report_backup_error(context,
                            "file \"%s\" should contain %zu bytes, but read %zu bytes",
                            relpath, m->size, bytes_read);
        return;
    }

    /* Get the final checksum. */
    checksumlen = pg_checksum_final(&checksum_ctx, checksumbuf);
    if (checksumlen < 0)
    {
        report_backup_error(context,
                            "could not finalize checksum of file \"%s\"",
                            relpath);
        return;
    }

    /* And check it against the manifest. */
    if (checksumlen != m->checksum_length)
        report_backup_error(context,
                            "file \"%s\" has checksum of length %d, but expected %d",
                            relpath, m->checksum_length, checksumlen);
    else if (memcmp(checksumbuf, m->checksum_payload, checksumlen) != 0)
        report_backup_error(context,
                            "checksum mismatch for file \"%s\"",
                            relpath);
}

/*
 * Attempt to parse the WAL files required to restore from backup using
 * pg_waldump.
 */
static void
parse_required_wal(verifier_context *context, char *pg_waldump_path,
                   char *wal_directory, manifest_wal_range *first_wal_range)
{
    manifest_wal_range *this_wal_range = first_wal_range;

    while (this_wal_range != NULL)
    {
        char       *pg_waldump_cmd;

        pg_waldump_cmd = psprintf("\"%s\" --quiet --path=\"%s\" --timeline=%u --start=%X/%X --end=%X/%X\n",
                                  pg_waldump_path, wal_directory, this_wal_range->tli,
                                  LSN_FORMAT_ARGS(this_wal_range->start_lsn),
                                  LSN_FORMAT_ARGS(this_wal_range->end_lsn));
        if (system(pg_waldump_cmd) != 0)
            report_backup_error(context,
                                "WAL parsing failed for timeline %u",
                                this_wal_range->tli);

        this_wal_range = this_wal_range->next;
    }
}

/*
 * Report a problem with the backup.
 *
 * Update the context to indicate that we saw an error, and exit if the
 * context says we should.
 */
static void
report_backup_error(verifier_context *context, const char *pg_restrict fmt,...)
{
    va_list     ap;

    va_start(ap, fmt);
    pg_log_generic_v(PG_LOG_ERROR, gettext(fmt), ap);
    va_end(ap);

    context->saw_any_error = true;
    if (context->exit_on_error)
        exit(1);
}

/*
 * Report a fatal error and exit
 */
static void
report_fatal_error(const char *pg_restrict fmt,...)
{
    va_list     ap;

    va_start(ap, fmt);
    pg_log_generic_v(PG_LOG_FATAL, gettext(fmt), ap);
    va_end(ap);

    exit(1);
}

/*
 * Is the specified relative path, or some prefix of it, listed in the set
 * of paths to ignore?
 *
 * Note that by "prefix" we mean a parent directory; for this purpose,
 * "aa/bb" is not a prefix of "aa/bbb", but it is a prefix of "aa/bb/cc".
 */
static bool
should_ignore_relpath(verifier_context *context, char *relpath)
{
    SimpleStringListCell *cell;

    for (cell = context->ignore_list.head; cell != NULL; cell = cell->next)
    {
        char       *r = relpath;
        char       *v = cell->val;

        while (*v != '\0' && *r == *v)
            ++r, ++v;

        if (*v == '\0' && (*r == '\0' || *r == '/'))
            return true;
    }

    return false;
}

/*
 * Helper function for manifest_files hash table.
 */
static uint32
hash_string_pointer(char *s)
{
    unsigned char *ss = (unsigned char *) s;

    return hash_bytes(ss, strlen(s));
}

/*
 * Print out usage information and exit.
 */
static void
usage(void)
{
    printf(_("%s verifies a backup against the backup manifest.\n\n"), progname);
    printf(_("Usage:\n  %s [OPTION]... BACKUPDIR\n\n"), progname);
    printf(_("Options:\n"));
    printf(_("  -e, --exit-on-error         exit immediately on error\n"));
    printf(_("  -i, --ignore=RELATIVE_PATH  ignore indicated path\n"));
    printf(_("  -m, --manifest-path=PATH    use specified path for manifest\n"));
    printf(_("  -n, --no-parse-wal          do not try to parse WAL files\n"));
    printf(_("  -q, --quiet                 do not print any output, except for errors\n"));
    printf(_("  -s, --skip-checksums        skip checksum verification\n"));
    printf(_("  -w, --wal-directory=PATH    use specified path for WAL files\n"));
    printf(_("  -V, --version               output version information, then exit\n"));
    printf(_("  -?, --help                  show this help, then exit\n"));
    printf(_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
    printf(_("%s home page: <%s>\n"), PACKAGE_NAME, PACKAGE_URL);
}