pasta: Add fallback timer mechanism to check if namespace is gone

We don't know how frequently this happens, but hitting
fs.inotify.max_user_watches or similar sysctl limits is definitely
not out of question, and Paul mentioned that, for example, Podman's
CI environments hit similar issues in the past.

Introduce a fallback mechanism based on a timer file descriptor: we
grab the directory handle at startup, and we can then use openat(),
triggered periodically, to check if the (network) namespace directory
still exists. If openat() fails at some point, exit.

Link: https://github.com/containers/podman/pull/21563#issuecomment-1943505707
Reported-by: Paul Holzinger <pholzing@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/pasta.h b/pasta.h
index 5d20063..4b063d1 100644
--- a/pasta.h
+++ b/pasta.h
@@ -13,7 +13,8 @@ void pasta_start_ns(struct ctx *c, uid_t uid, gid_t gid,
 		    int argc, char *argv[]);
 void pasta_ns_conf(struct ctx *c);
 void pasta_child_handler(int signal);
-int pasta_netns_quit_init(const struct ctx *c);
-void pasta_netns_quit_handler(struct ctx *c, int inotify_fd);
+void pasta_netns_quit_init(const struct ctx *c);
+void pasta_netns_quit_inotify_handler(struct ctx *c, int inotify_fd);
+void pasta_netns_quit_timer_handler(struct ctx *c, union epoll_ref ref);
 
 #endif /* PASTA_H */