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, 33 insertions, 10 deletions

diff --git a/conf.c b/conf.c
index 21e9bc0..9851575 100644
--- a/conf.c
+++ b/conf.c
@@ -20,6 +20,7 @@
 #include <sched.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <libgen.h>
 #include <limits.h>
 #include <stdlib.h>
 #include <stdint.h>
@@ -414,20 +415,34 @@ static int conf_ns_opt(struct ctx *c,
 
 		nfd = open(netns, O_RDONLY);
 
-		if (nfd >= 0 && (ufd >= 0 || c->netns_only)) {
-			c->pasta_netns_fd = nfd;
-			c->pasta_userns_fd = ufd;
+		if (nfd == -1 || (ufd == -1 && !c->netns_only)) {
+			if (nfd >= 0)
+				close(nfd);
 
-			NS_CALL(conf_ns_check, c);
-			if (c->pasta_netns_fd >= 0)
-				return 0;
+			if (ufd >= 0)
+				close(ufd);
+
+			continue;
 		}
 
-		if (nfd >= 0)
-			close(nfd);
+		c->pasta_netns_fd = nfd;
+		c->pasta_userns_fd = ufd;
+
+		NS_CALL(conf_ns_check, c);
+
+		if (c->pasta_netns_fd >= 0) {
+			char buf[PATH_MAX];
+
+			if (try == 0 || c->no_netns_quit)
+				return 0;
+
+			strncpy(buf, netns, PATH_MAX);
+			strncpy(c->netns_base, basename(buf), PATH_MAX - 1);
+			strncpy(buf, netns, PATH_MAX);
+			strncpy(c->netns_dir, dirname(buf), PATH_MAX - 1);
 
-		if (ufd >= 0)
-			close(ufd);
+			return 0;
+		}
 	}
 
 	c->netns_only = netns_only_reset;
@@ -813,6 +828,7 @@ void conf(struct ctx *c, int argc, char **argv)
 		{"dhcp-search", no_argument,		NULL,		7 },
 		{"no-dhcp-search", no_argument,		NULL,		8 },
 		{"dns-forward",	required_argument,	NULL,		9 },
+		{"no-netns-quit", no_argument,		NULL,		10 },
 		{ 0 },
 	};
 	struct get_bound_ports_ns_arg ns_ports_arg = { .c = c };
@@ -937,6 +953,13 @@ void conf(struct ctx *c, int argc, char **argv)
 			err("Invalid DNS forwarding address: %s", optarg);
 			usage(argv[0]);
 			break;
+		case 10:
+			if (c->mode != MODE_PASTA) {
+				err("--no-netns-quit is for pasta mode only");
+				usage(argv[0]);
+			}
+			c->no_netns_quit = 1;
+			break;
 		case 'd':
 			if (c->debug) {
 				err("Multiple --debug options given");