diff options
Diffstat (limited to '')
| -rw-r--r-- | src/basic/xattr-util.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/src/basic/xattr-util.c b/src/basic/xattr-util.c new file mode 100644 index 0000000..0ee0979 --- /dev/null +++ b/src/basic/xattr-util.c @@ -0,0 +1,217 @@ +/* SPDX-License-Identifier: LGPL-2.1+ */ + +#include <errno.h> +#include <fcntl.h> +#include <stdint.h> +#include <stdlib.h> +#include <string.h> +#include <sys/time.h> +#include <sys/xattr.h> + +#include "alloc-util.h" +#include "fd-util.h" +#include "macro.h" +#include "missing.h" +#include "sparse-endian.h" +#include "stdio-util.h" +#include "string-util.h" +#include "time-util.h" +#include "xattr-util.h" + +int getxattr_malloc(const char *path, const char *name, char **value, bool allow_symlink) { + char *v; + size_t l; + ssize_t n; + + assert(path); + assert(name); + assert(value); + + for (l = 100; ; l = (size_t) n + 1) { + v = new0(char, l); + if (!v) + return -ENOMEM; + + if (allow_symlink) + n = lgetxattr(path, name, v, l); + else + n = getxattr(path, name, v, l); + + if (n >= 0 && (size_t) n < l) { + *value = v; + return n; + } + + free(v); + + if (n < 0 && errno != ERANGE) + return -errno; + + if (allow_symlink) + n = lgetxattr(path, name, NULL, 0); + else + n = getxattr(path, name, NULL, 0); + if (n < 0) + return -errno; + } +} + +int fgetxattr_malloc(int fd, const char *name, char **value) { + char *v; + size_t l; + ssize_t n; + + assert(fd >= 0); + assert(name); + assert(value); + + for (l = 100; ; l = (size_t) n + 1) { + v = new0(char, l); + if (!v) + return -ENOMEM; + + n = fgetxattr(fd, name, v, l); + + if (n >= 0 && (size_t) n < l) { + *value = v; + return n; + } + + free(v); + + if (n < 0 && errno != ERANGE) + return -errno; + + n = fgetxattr(fd, name, NULL, 0); + if (n < 0) + return -errno; + } +} + +int fgetxattrat_fake( + int dirfd, + const char *filename, + const char *attribute, + void *value, size_t size, + int flags, + size_t *ret_size) { + + char fn[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; + _cleanup_close_ int fd = -1; + ssize_t l; + + /* The kernel doesn't have a fgetxattrat() command, hence let's emulate one */ + + if (flags & ~(AT_SYMLINK_NOFOLLOW|AT_EMPTY_PATH)) + return -EINVAL; + + if (isempty(filename)) { + if (!(flags & AT_EMPTY_PATH)) + return -EINVAL; + + xsprintf(fn, "/proc/self/fd/%i", dirfd); + } else { + fd = openat(dirfd, filename, O_CLOEXEC|O_PATH|(flags & AT_SYMLINK_NOFOLLOW ? O_NOFOLLOW : 0)); + if (fd < 0) + return -errno; + + xsprintf(fn, "/proc/self/fd/%i", fd); + } + + l = getxattr(fn, attribute, value, size); + if (l < 0) + return -errno; + + *ret_size = l; + return 0; +} + +static int parse_crtime(le64_t le, usec_t *usec) { + uint64_t u; + + assert(usec); + + u = le64toh(le); + if (IN_SET(u, 0, (uint64_t) -1)) + return -EIO; + + *usec = (usec_t) u; + return 0; +} + +int fd_getcrtime_at(int dirfd, const char *name, usec_t *ret, int flags) { + struct_statx sx; + usec_t a, b; + le64_t le; + size_t n; + int r; + + assert(ret); + + if (flags & ~(AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW)) + return -EINVAL; + + /* So here's the deal: the creation/birth time (crtime/btime) of a file is a relatively newly supported concept + * on Linux (or more strictly speaking: a concept that only recently got supported in the API, it was + * implemented on various file systems on the lower level since a while, but never was accessible). However, we + * needed a concept like that for vaccuuming algorithms and such, hence we emulated it via a user xattr for a + * long time. Starting with Linux 4.11 there's statx() which exposes the timestamp to userspace for the first + * time, where it is available. Thius function will read it, but it tries to keep some compatibility with older + * systems: we try to read both the crtime/btime and the xattr, and then use whatever is older. After all the + * concept is useful for determining how "old" a file really is, and hence using the older of the two makes + * most sense. */ + + if (statx(dirfd, strempty(name), flags|AT_STATX_DONT_SYNC, STATX_BTIME, &sx) >= 0 && + (sx.stx_mask & STATX_BTIME) && + sx.stx_btime.tv_sec != 0) + a = (usec_t) sx.stx_btime.tv_sec * USEC_PER_SEC + + (usec_t) sx.stx_btime.tv_nsec / NSEC_PER_USEC; + else + a = USEC_INFINITY; + + r = fgetxattrat_fake(dirfd, name, "user.crtime_usec", &le, sizeof(le), flags, &n); + if (r >= 0) { + if (n != sizeof(le)) + r = -EIO; + else + r = parse_crtime(le, &b); + } + if (r < 0) { + if (a != USEC_INFINITY) { + *ret = a; + return 0; + } + + return r; + } + + if (a != USEC_INFINITY) + *ret = MIN(a, b); + else + *ret = b; + + return 0; +} + +int fd_getcrtime(int fd, usec_t *ret) { + return fd_getcrtime_at(fd, NULL, ret, AT_EMPTY_PATH); +} + +int path_getcrtime(const char *p, usec_t *ret) { + return fd_getcrtime_at(AT_FDCWD, p, ret, 0); +} + +int fd_setcrtime(int fd, usec_t usec) { + le64_t le; + + assert(fd >= 0); + + if (IN_SET(usec, 0, USEC_INFINITY)) + usec = now(CLOCK_REALTIME); + + le = htole64((uint64_t) usec); + if (fsetxattr(fd, "user.crtime_usec", &le, sizeof(le), 0) < 0) + return -errno; + + return 0; +} |