selftests/bpf: Handle SIGINT when creating netns

It's necessary to delete netns during BPF selftests interrupt, otherwise
the next tests run will fail due to unable to create netns.

This patch adds a new SIGINT handle netns_sig_handler() in create_netns(),
and deletes NS_TEST in this handler.

For passing argument to signal handler, a trick mentioned in [1] is
used.

[1]
https://stackoverflow.com/questions/6970224/providing-passing-argument-to-signal-handler

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>

tools/testing/selftests/bpf/network_helpers.c

@@ -519,6 +519,16 @@ void cleanup_netns(struct nstoken *token)
 	close_netns(token);
 }
 
+static int netns_sig_handler(const int sig, void *ptr)
+{
+	struct nstoken *token = (struct nstoken *)ptr;
+
+	signal(sig, SIG_IGN);
+	if (sig == SIGINT)
+		cleanup_netns(token);
+	return 0;
+}
+
 struct nstoken *create_netns(const char *name)
 {
 	struct nstoken *token = NULL;
@@ -539,6 +549,8 @@ struct nstoken *create_netns(const char *name)
 		goto fail;
 	}
 
+	signal(SIGINT, (__sighandler_t)netns_sig_handler);
+	netns_sig_handler(SIGUSR1, (void *)token);
 	return token;
 
 fail: