On Wed, 2013-02-27 at 22:49 -0300, Leonardo Chiquitto wrote:
> Hello,
>
> I've got a bug report describing a case where AutoFS fails to read new
> entries from /etc/auto.master after a SIGHUP. Although the problem
> was reported in an older version of automount, it is reproducible using
> the latest revision from git.
>
> How to reproduce:
>
> 1. Add at least two sources of AutoFS maps to /etc/nsswitch.conf. I've
> tested only with "files nis". You don't need to configure NIS/YP, just
> having it listed there in the configuration is enough.
>
> 2. Start the automounter with a simple /etc/auto.master:
>
> /nfs1 /etc/auto.test1
> +auto.master
>
> 3. Add another entry to /etc/auto.master:
>
> /nfs1 /etc/auto.test1
> /nfs2 /etc/auto.test2
> +auto.master
>
> and reload the daemon. Notice that although AutoFS reads /etc/auto.test2,
> /nfs2 is not created/mounted.
>
> 4. Try to stop the daemon cleanly (SIGTERM only). You'll notice that it won't
> quit. SIGKILL is necessary.
>
> I've debugged this problem and found that after a SIGHUP, the following
> sequence is executed:
>
> do_hup_signal()
> do_read_master() (new thread)
> master_read_master() with readall=1
> lookup_nss_read_master()
> foreach nss source:
> read_master_map()
> do_read_master() // not the same as the new thread function
> lookup->lookup_read_master() // from lookup_file
>
> At this point it attempts to read /etc/auto.master again and the recursion
> is detected (modules/lookup_file.c:400):
I'll check this out.
The way it's supposed to work is that when lookup->lookup_read_master()
(from lookup_file.c) is called it should call check_self_include() and
see that the + included map name is the same as its map name and skip
the files source and move onto the next one.
>
> lookup_read_master()
> (...)
> 400 if (master->recurse)
> 401 return NSS_STATUS_UNAVAIL;
>
> NSS_STATUS_UNAVAIL goes all way back to lookup_nss_read_master(),
> that registers the failure to read the source in read_fail:
>
> 259 if (result == NSS_STATUS_UNAVAIL)
> 260 master->read_fail = 1;
>
> and returns to master_read_master(), that tests this flag:
>
> 864 if (!master->read_fail) // false, read_fail = 1
> 865 master_mount_mounts(master, age, readall);
> 866 else {
> 867 master->read_fail = 0;
> 868 if (!readall) // false, readall = 1
> 869 master_mount_mounts(master, age, readall);
> 870 }
>
> So, master_mount_mounts() is not called to setup the new mount point
> and we have a problem.
>
> When AutoFS is started (not reloaded), master_read_master() is called
> with readall=0 and master_mount_mounts() end up being called in line
> 869 above. That's why the problem doesn't happen after regular start-up.
>
> How to workaround the problem: the easiest way is to explicitly specify
> the map types in /etc/auto.master, for example:
>
> /nfs1 file:/etc/auto.test1
> /nfs2 file:/etc/auto.test2
> +yp:auto.master
>
> A first proposal to fix the problem would be to return a distinct error code
> to handle the recursion (see patch below). This seems to work well here.
> What do you think?
>
> Thanks,
> Leonardo
>
> Index: autofs/daemon/lookup.c
> ===================================================================
> --- autofs.orig/daemon/lookup.c
> +++ autofs/daemon/lookup.c
> @@ -230,6 +230,11 @@ int lookup_nss_read_master(struct master
>
> result = read_master_map(master, this->source, age);
>
> + if (result == NSS_STATUS_RECURSE) {
> + debug(logopt, "recursion - continuing to next source");
> + continue;
> + }
> +
> /*
> * If the name of the master map hasn't been explicitly
> * configured and we're not reading an included master map
> Index: autofs/include/nsswitch.h
> ===================================================================
> --- autofs.orig/include/nsswitch.h
> +++ autofs/include/nsswitch.h
> @@ -32,6 +32,7 @@ enum nsswitch_status {
> NSS_STATUS_NOTFOUND,
> NSS_STATUS_UNAVAIL,
> NSS_STATUS_TRYAGAIN,
> + NSS_STATUS_RECURSE,
> NSS_STATUS_MAX
> };
>
> Index: autofs/modules/lookup_file.c
> ===================================================================
> --- autofs.orig/modules/lookup_file.c
> +++ autofs/modules/lookup_file.c
> @@ -398,7 +398,7 @@ int lookup_read_master(struct master *ma
> int entry, cur_state;
>
> if (master->recurse)
> - return NSS_STATUS_UNAVAIL;
> + return NSS_STATUS_RECURSE;
>
> if (master->depth > MAX_INCLUDE_DEPTH) {
> error(logopt, MODPREFIX
> --
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