[systemd-devel] [PATCH v9000 2/3] timedated: gather timezone from /etc/localtime sym target

[Frederic Crozat]

Le dimanche 12 août 2012 à 22:36 -0700, Shawn Landden a écrit :
> /etc/localtime -> /usr/share/zoneinfo/...
> 
> or
> 
> /etc/localtime -> ../usr/share/zoneinfo/...
> 
> (note, ../usr is not the same if /etc is a symlink, as this isn't
> using canonicalize_file_name())
> 
> keep other method for now, consider dropping later.
> 
> Supporting relative links here are problematic as timezones in
> /usr/share/zoneinfo are often themselves symlinks (and symlinks to
> symlinks), so this implamentation only supports absolute symlinks
> "/usr/share/zoneinfo/" and relative symlinks starting with
> "../usr/share/zoneinfo/"
> 
> From TODO (kay sievers):
> * kill /etc/timezone handling entirely? What does it provide?
>   - /etc/localtime carries the same information already:
>       $ ls -l /etc/localtime; cat /etc/timezone
>       lrwxrwxrwx 1 root root 33 Jul 27 09:55 /etc/localtime -> /usr/share/zoneinfo/Europe/Berlin
>       Europe/Berlin
>   - systemd enforces /usr to be available at bootup, so we can
>     enforce the use of the symlink
> ---
>  src/timedate/timedated.c |   50 ++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 40 insertions(+), 10 deletions(-)
> 
> diff --git a/src/timedate/timedated.c b/src/timedate/timedated.c
> index 09fd808..c3067c8 100644
> --- a/src/timedate/timedated.c
> +++ b/src/timedate/timedated.c
> @@ -74,6 +74,9 @@
>          BUS_GENERIC_INTERFACES_LIST             \
>          "org.freedesktop.timedate1\0"
>  
> +/* Must start and end with '/' */
> +#define ZONEINFO_PATH "/usr/share/zoneinfo/"
> +
>  const char timedate_interface[] _introspect_("timedate1") = INTERFACE;
>  
>  typedef struct TZ {
> @@ -152,16 +155,14 @@ static void verify_timezone(void) {
>                  return;
>  
>          p = strappend("/usr/share/zoneinfo/", tz.zone);
> -        if (!p) {
> -                log_oom();
> -                return;
> -        }
> +        if (!p)
> +                return (void)log_oom();
>  
> -        j = read_full_file("/etc/localtime", &a, &l);
>          k = read_full_file(p, &b, &q);
> -
>          free(p);
>  
> +        j = read_full_file("/etc/localtime", &a, &l);
> +
>          if (j < 0 || k < 0 || l != q || memcmp(a, b, l)) {
>                  log_warning("/etc/localtime and /etc/timezone out of sync.");
>                  free(tz.zone);
> @@ -174,9 +175,34 @@ static void verify_timezone(void) {
>  
>  static int read_data(void) {
>          int r;
> +        char *t;
>  
>          free_data();
>  
> +        r = readlink_malloc("/etc/localtime", &t);
> +        if (r < 0) {
> +                if (r == -EINVAL)
> +                        log_warning("/etc/localtime should be a symbolic link to a timezone data file in %s", ZONEINFO_PATH);
> +                else
> +                        log_warning("Failed to get target of %s: %s", "/etc/localtime", strerror(-r));
> +        } else {
> +                /* we only support the trivial relative link of (/etc/)..$ABSOLUTE */
> +                int rel_link_offset = startswith(t, "..") ? strlen("..") : 0;
> +
> +                if (!startswith(t + rel_link_offset, ZONEINFO_PATH))
> +                        log_warning("/etc/localtime should be a symbolic link to a timezone data file in %s", ZONEINFO_PATH);
> +                else {
> +                        tz.zone = strdup(t + rel_link_offset + strlen(ZONEINFO_PATH));
> +                        free(t);
> +                        if (!tz.zone)
> +                                return log_oom();
> +
> +                        goto have_timezone;
> +                }
> +        }
> +
> +        free(t);

t might be not assigned if there was an error in readlink_malloc
(if /etc/localtime isn't a symlink). 

-- 
Frederic Crozat <fcrozat at suse.com>
SUSE