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feat(xattr): rsync-interoperable --fake-super stat; fix --devices error parity

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TapTap
2026-09-22 22:03:41 +02:00
parent d780a4625e
commit 80e8d7f450
11 changed files with 315 additions and 149 deletions
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src/shared/xattr.h
+28 -21
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@@ -31,11 +31,14 @@
*/
/* Reserved key used by --fake-super to park the source's privileged ownership
* / mode / mtime on the destination file as an unprivileged user.* xattr, so a
* later privileged restore could re-apply them. Exact documented format:
* uid:gid:mode:mtime_sec:mtime_nsec (decimal, decimal, octal, dec, dec)
* e.g. "1000:1000:644:1765238400:0". */
#define FAKESUPER_XATTR "user.fastsync.stat"
* / mode / rdev on the destination file as an unprivileged user.* xattr, so the
* tree is interoperable with rsync 3.4.1 and a later privileged restore can
* re-apply them. This is rsync's own key and value grammar exactly:
* <octal st_mode with S_IFMT> <rdev_major>,<rdev_minor> <uid>:<gid>
* e.g. "104711 0,0 1234:5678" for a setuid regular file owned by 1234:5678,
* or "20644 1,3 111:222" for a char device. mtime is deliberately NOT part of
* the record: exactly like rsync, the file's own timestamp carries it. */
#define FAKESUPER_XATTR "user.rsync.%stat"
/* --- bounds --- */
#define XATTR_NAME_MAX 255 /* xattr names are limited to 255 bytes */
@@ -91,24 +94,28 @@ FileXattrList* xattr_receive(int fd, int* ok, bool preserve_acls);
* true when apply was attempted (allowing callers to treat it as best-effort). */
bool xattr_apply_fd(int fd, const FileXattrList* list);
/* --fake-super: write the source uid/gid/mode/mtime record into the reserved
* FAKESUPER_XATTR on `fd`. Best-effort (logged, never fatal). Only meaningful
* when metadata was transmitted so the values exist. */
void fake_super_store_fd(int fd, uint32_t uid, uint32_t gid, uint32_t mode, int64_t mtime_sec,
int64_t mtime_nsec);
/* --fake-super: write the source uid/gid/mode/rdev record into the reserved
* FAKESUPER_XATTR on `fd`, using rsync 3.4.1's exact grammar (see the key
* comment above). `mode` is the full st_mode including its S_IFMT bits.
* Best-effort (logged, never fatal). Only meaningful when metadata was
* transmitted so the values exist. */
void fake_super_store_fd(int fd, uint32_t uid, uint32_t gid, uint32_t mode, uint32_t rdev_major,
uint32_t rdev_minor);
/* --fake-super replay: parse the FAKESUPER_XATTR record previously written on
* `fd` by fake_super_store_fd and re-apply mode/mtime fd-relative. The
* recorded uid/gid are deliberately NOT chowned for real: --fake-super only
* RECORDS ownership (the caller stores the resolved mapping via
* identity_resolve_storage_ids), it never performs a real chown. Best-effort:
* absence of the xattr or a malformed record is a silent no-op that never fails
* the transfer. The MODE leg is applied only when policy.perms||policy.
* executability and the MTIME leg only when policy.times, so the fake-super
* replay cannot bypass the per-attribute split; the mode follows the normal
* metadata path exactly (under --perms the source mode is copied verbatim,
* special and group/other write bits included).
* Returns true when the xattr was present and parsed. */
* `fd` by fake_super_store_fd and re-apply the recorded permission bits
* fd-relative. The recorded uid/gid are deliberately NOT chowned for real:
* --fake-super only RECORDS ownership (the caller stores the resolved mapping
* via identity_resolve_storage_ids), it never performs a real chown. The
* recorded rdev is retained for a later privileged restore but is not acted on
* here. Best-effort: absence of the xattr or a malformed record is a silent
* no-op that never fails the transfer. The MODE leg is applied only when
* policy.perms||policy.executability, and the recorded special bits
* (setuid/setgid/sticky) are NOT applied to the real file -- exactly like
* rsync's fake-super receiver, which stores the full mode in the xattr but
* strips the special bits on disk. mtime is not part of the record; the normal
* metadata path carries it (policy.times) exactly as rsync sets the file's own
* timestamp. Returns true when the xattr was present and parsed. */
bool fake_super_restore_fd(int fd, FileAttrPolicy policy);
#endif