pasta: By default, quit if filesystem-bound net namespace goes away

This should be convenient for users managing filesystem-bound network
namespaces: monitor the base directory of the namespace and exit if
the namespace given as PATH or NAME target is deleted. We can't add
an inotify watch directly on the namespace directory, that won't work
with nsfs.

Add an option to disable this behaviour, --no-netns-quit.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/pasta.c b/pasta.c
index 972cbcf..e45cc92 100644
--- a/pasta.c
+++ b/pasta.c
@@ -24,6 +24,8 @@
 #include <stdint.h>
 #include <unistd.h>
 #include <syslog.h>
+#include <sys/epoll.h>
+#include <sys/inotify.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -219,3 +221,53 @@ void pasta_ns_conf(struct ctx *c)
 
 	proto_update_l2_buf(c->mac_guest, NULL, NULL);
 }
+
+/**
+ * pasta_netns_quit_init() - Watch network namespace to quit once it's gone
+ * @c:		Execution context
+ *
+ * Return: inotify file descriptor, -1 on failure or if not needed/applicable
+ */
+int pasta_netns_quit_init(struct ctx *c)
+{
+	struct epoll_event ev = { .events = EPOLLIN };
+	int inotify_fd;
+
+	if (c->mode != MODE_PASTA || c->no_netns_quit || !*c->netns_base)
+		return -1;
+
+	if ((inotify_fd = inotify_init1(O_NONBLOCK)) < 0) {
+		perror("inotify_init(): won't quit once netns is gone");
+		return -1;
+	}
+
+	if (inotify_add_watch(inotify_fd, c->netns_dir, IN_DELETE) < 0) {
+		perror("inotify_add_watch(): won't quit once netns is gone");
+		return -1;
+	}
+
+	ev.data.fd = inotify_fd;
+	epoll_ctl(c->epollfd, EPOLL_CTL_ADD, inotify_fd, &ev);
+
+	return inotify_fd;
+}
+
+/**
+ * pasta_netns_quit_handler() - Handle ns directory events, exit if ns is gone
+ * @c:		Execution context
+ * @inotify_fd:	inotify file descriptor with watch on namespace directory
+ */
+void pasta_netns_quit_handler(struct ctx *c, int inotify_fd)
+{
+	char buf[sizeof(struct inotify_event) + NAME_MAX + 1];
+	struct inotify_event *in_ev = (struct inotify_event *)buf;
+
+	if (read(inotify_fd, buf, sizeof(buf)) < (ssize_t)sizeof(*in_ev))
+		return;
+
+	if (strncmp(in_ev->name, c->netns_base, sizeof(c->netns_base)))
+		return;
+
+	info("Namespace %s is gone, exiting", c->netns_base);
+	exit(EXIT_SUCCESS);
+}