[v4,2/2] timezone: Replace Localtime file copy with symbolic link
Commit Message
Based on the `man 5 localtime` documentation the `/etc/localtime`
file is expected to be a symbolic link, not a standalone
regular file.
This change replaces `write_file` with `write_symlink`, avoiding
unnecessary file I/O and memory mapping. It ensures Localtime accurately
reflects the selected timezone without duplicating data. This also
fixes `__connman_timezone_lookup()`, which requires Localtime to be a
symlink to function correctly.
---
src/timezone.c | 50 +++++++++++---------------------------------------
1 file changed, 11 insertions(+), 39 deletions(-)
Comments
Hi Andrea,
On 6/5/25 3:03 AM, Andrea Ricchi wrote:
> Based on the `man 5 localtime` documentation the `/etc/localtime`
> file is expected to be a symbolic link, not a standalone
> regular file.
>
> This change replaces `write_file` with `write_symlink`, avoiding
> unnecessary file I/O and memory mapping. It ensures Localtime accurately
> reflects the selected timezone without duplicating data. This also
> fixes `__connman_timezone_lookup()`, which requires Localtime to be a
> symlink to function correctly.
> ---
> src/timezone.c | 50 +++++++++++---------------------------------------
> 1 file changed, 11 insertions(+), 39 deletions(-)
>
<snip>
> @@ -537,35 +527,17 @@ static int write_file(void *src_map, struct stat *src_st, const char *pathname)
> int __connman_timezone_change(const char *zone)
> {
> struct stat st;
> - char *map, pathname[PATH_MAX];
> - int fd, err;
> + g_autofree char *pathname = NULL;
> + int err;
Amended this commit to remove 'err' variable in order to fix the warning this
patch introduced:
[denkenz@archdev connman]$ make
make --no-print-directory all-am
CC src/tools_dnsproxy_standalone-timezone.o
src/timezone.c: In function ‘__connman_timezone_change’:
src/timezone.c:531:13: error: unused variable ‘err’ [-Werror=unused-variable]
531 | int err;
| ^~~
cc1: all warnings being treated as errors
>
> DBG("zone %s", zone);
>
> - snprintf(pathname, PATH_MAX, "%s/%s", USR_SHARE_ZONEINFO, zone);
> + pathname = g_strdup_printf("%s/%s", USR_SHARE_ZONEINFO, zone);
>
> - fd = open(pathname, O_RDONLY | O_CLOEXEC);
> - if (fd < 0)
> + if (stat(pathname, &st) < 0 || !S_ISREG(st.st_mode))
> return -EINVAL;
>
> - if (fstat(fd, &st) < 0) {
> - close(fd);
> - return -EIO;
> - }
> -
> - map = mmap(0, st.st_size, PROT_READ, MAP_SHARED, fd, 0);
> - if (!map || map == MAP_FAILED) {
> - close(fd);
> - return -EIO;
> - }
> -
> - err = write_file(map, &st, connman_setting_get_string("Localtime"));
> -
> - munmap(map, st.st_size);
> -
> - close(fd);
> -
> - return err;
> + return write_symlink(pathname, connman_setting_get_string("Localtime"));
> }
>
> static guint inotify_watch = 0;
Applied, thanks.
Regards,
-Denis
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@@ -507,28 +507,18 @@ done:
return zone;
}
-static int write_file(void *src_map, struct stat *src_st, const char *pathname)
+static int write_symlink(const char *target, const char *link)
{
struct stat st;
- int fd;
- ssize_t written;
- DBG("pathname %s", pathname);
+ DBG("pathname %s", link);
- if (lstat(pathname, &st) == 0) {
- if (S_ISLNK(st.st_mode))
- unlink(pathname);
+ if (lstat(link, &st) == 0) {
+ if (S_ISLNK(st.st_mode) || S_ISREG(st.st_mode))
+ unlink(link);
}
- fd = open(pathname, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0644);
- if (fd < 0)
- return -EIO;
-
- written = write(fd, src_map, src_st->st_size);
-
- close(fd);
-
- if (written < 0)
+ if (symlink(target, link) < 0)
return -EIO;
return 0;
@@ -537,35 +527,17 @@ static int write_file(void *src_map, struct stat *src_st, const char *pathname)
int __connman_timezone_change(const char *zone)
{
struct stat st;
- char *map, pathname[PATH_MAX];
- int fd, err;
+ g_autofree char *pathname = NULL;
+ int err;
DBG("zone %s", zone);
- snprintf(pathname, PATH_MAX, "%s/%s", USR_SHARE_ZONEINFO, zone);
+ pathname = g_strdup_printf("%s/%s", USR_SHARE_ZONEINFO, zone);
- fd = open(pathname, O_RDONLY | O_CLOEXEC);
- if (fd < 0)
+ if (stat(pathname, &st) < 0 || !S_ISREG(st.st_mode))
return -EINVAL;
- if (fstat(fd, &st) < 0) {
- close(fd);
- return -EIO;
- }
-
- map = mmap(0, st.st_size, PROT_READ, MAP_SHARED, fd, 0);
- if (!map || map == MAP_FAILED) {
- close(fd);
- return -EIO;
- }
-
- err = write_file(map, &st, connman_setting_get_string("Localtime"));
-
- munmap(map, st.st_size);
-
- close(fd);
-
- return err;
+ return write_symlink(pathname, connman_setting_get_string("Localtime"));
}
static guint inotify_watch = 0;