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Fix tar files emitted by pg_dump and pg_basebackup to be POSIX conformant.

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Both programs got the "magic" string wrong, causing standard-conforming tar
implementations to believe the output was just legacy tar format without
any POSIX extensions.  This doesn't actually matter that much, especially
since pg_dump failed to fill the POSIX fields anyway, but still there is
little point in emitting tar format if we can't be compliant with the
standard.  In addition, pg_dump failed to write the EOF marker correctly
(there should be 2 blocks of zeroes not just one), pg_basebackup put the
numeric group ID in the wrong place, and both programs had a pretty
brain-dead idea of how to compute the checksum.  Fix all that and improve
the comments a bit.

pg_restore is modified to accept either the correct POSIX-compliant "magic"
string or the previous value.  This part of the change will need to be
back-patched to avoid an unnecessary compatibility break when a previous
version tries to read tar-format output from 9.3 pg_dump.

Brian Weaver and Tom Lane
This commit is contained in:
Tom Lane
2012-09-28 15:19:15 -04:00
parent edc9109c42
commit 05b555d12b
4 changed files with 110 additions and 69 deletions
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63
src/backend/replication/basebackup.c
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@ -568,7 +568,7 @@ sendFileWithContent(const char *filename, const char *content)
/*
* Include all files from the given directory in the output tar stream. If
* 'sizeonly' is true, we just calculate a total length and return ig, without
* 'sizeonly' is true, we just calculate a total length and return it, without
* actually sending anything.
*/
static int64
@ -763,11 +763,16 @@ _tarChecksum(char *header)
int i,
sum;
sum = 0;
/*
* Per POSIX, the checksum is the simple sum of all bytes in the header,
* treating the bytes as unsigned, and treating the checksum field (at
* offset 148) as though it contained 8 spaces.
*/
sum = 8 * ' '; /* presumed value for checksum field */
for (i = 0; i < 512; i++)
if (i < 148 || i >= 156)
sum += 0xFF & header[i];
return sum + 256; /* Assume 8 blanks in checksum field */
return sum;
}
/* Given the member, write the TAR header & send the file */
@ -846,9 +851,13 @@ _tarWriteHeader(const char *filename, const char *linktarget,
struct stat * statbuf)
{
char h[512];
int lastSum = 0;
int sum;
/*
* Note: most of the fields in a tar header are not supposed to be
* null-terminated. We use sprintf, which will write a null after the
* required bytes; that null goes into the first byte of the next field.
* This is okay as long as we fill the fields in order.
*/
memset(h, 0, sizeof(h));
/* Name 100 */
@ -860,8 +869,11 @@ _tarWriteHeader(const char *filename, const char *linktarget,
* indicated in the tar format by adding a slash at the end of the
* name, the same as for regular directories.
*/
h[strlen(filename)] = '/';
h[strlen(filename) + 1] = '\0';
int flen = strlen(filename);
flen = Min(flen, 99);
h[flen] = '/';
h[flen + 1] = '\0';
}
/* Mode 8 */
@ -871,9 +883,9 @@ _tarWriteHeader(const char *filename, const char *linktarget,
sprintf(&h[108], "%07o ", statbuf->st_uid);
/* Group 8 */
sprintf(&h[117], "%07o ", statbuf->st_gid);
sprintf(&h[116], "%07o ", statbuf->st_gid);
/* File size 12 - 11 digits, 1 space, no NUL */
/* File size 12 - 11 digits, 1 space; use print_val for 64 bit support */
if (linktarget != NULL || S_ISDIR(statbuf->st_mode))
/* Symbolic link or directory has size zero */
print_val(&h[124], 0, 8, 11);
@ -884,13 +896,13 @@ _tarWriteHeader(const char *filename, const char *linktarget,
/* Mod Time 12 */
sprintf(&h[136], "%011o ", (int) statbuf->st_mtime);
/* Checksum 8 */
sprintf(&h[148], "%06o ", lastSum);
/* Checksum 8 cannot be calculated until we've filled all other fields */
if (linktarget != NULL)
{
/* Type - Symbolic link */
sprintf(&h[156], "2");
/* Link Name 100 */
sprintf(&h[157], "%.99s", linktarget);
}
else if (S_ISDIR(statbuf->st_mode))
@ -900,10 +912,11 @@ _tarWriteHeader(const char *filename, const char *linktarget,
/* Type - regular file */
sprintf(&h[156], "0");
/* Link tag 100 (NULL) */
/* Magic 6 */
sprintf(&h[257], "ustar");
/* Magic 6 + Version 2 */
sprintf(&h[257], "ustar00");
/* Version 2 */
sprintf(&h[263], "00");
/* User 32 */
/* XXX: Do we need to care about setting correct username? */
@ -913,17 +926,21 @@ _tarWriteHeader(const char *filename, const char *linktarget,
/* XXX: Do we need to care about setting correct group name? */
sprintf(&h[297], "%.31s", "postgres");
/* Maj Dev 8 */
sprintf(&h[329], "%6o ", 0);
/* Major Dev 8 */
sprintf(&h[329], "%07o ", 0);
/* Min Dev 8 */
sprintf(&h[337], "%6o ", 0);
/* Minor Dev 8 */
sprintf(&h[337], "%07o ", 0);
while ((sum = _tarChecksum(h)) != lastSum)
{
sprintf(&h[148], "%06o ", sum);
lastSum = sum;
}
/* Prefix 155 - not used, leave as nulls */
/*
* We mustn't overwrite the next field while inserting the checksum.
* Fortunately, the checksum can't exceed 6 octal digits, so we just write
* 6 digits, a space, and a null, which is legal per POSIX.
*/
sprintf(&h[148], "%06o ", _tarChecksum(h));
/* Now send the completed header. */
pq_putmessage('d', h, 512);
}