osmo-bsc: Add configurable option to spawn + respawn osmo-bsc_mgcplaforge/mgcp-rework

If it is configured in the config file or on the VTY, osmo-bsc will
fork+exec osmo-bsc_mgcp.   Furthermore, if osmo-bsc_mgcp dies, osmo-bsc
will re-spawn it.

This also means that we can now send a SIGHUP to osmo-bsc_mgcp in the
event of a Msc (re)connect, causing it to send RSIP, which in turn is
required by certain call agents that forget to send a AUEP on startup to
determine the endpoint state of the media gateway[s].

1 files changed, 41 insertions, 3 deletions

diff --git a/openbsc/src/osmo-bsc/osmo_bsc_main.c b/openbsc/src/osmo-bsc/osmo_bsc_main.c
index 9a799c0c6..6997f3b28 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_main.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_main.c
@@ -138,15 +138,44 @@ static struct vty_app_info vty_info = {
 	.is_config_node	= bsc_vty_is_config_node,
 };
 
+static int spawn_mgcp(void)
+{
+	pid_t pid;
+	struct osmo_msc_data *data = bsc_gsmnet->msc_data;
+
+	if (!data->bsc_mgcp.path) {
+		LOGP(DMGCP, LOGL_NOTICE,
+		     "Config file instructs us to not start osmo-bsc_mgcp!\n");
+		return 0;
+	}
+
+	pid = fork();
+	if (pid == 0) {
+		execlp(data->bsc_mgcp.path, "osmo-bsc_mgcp", "-c",
+			data->bsc_mgcp.config_path, NULL);
+		/* only in case of error we ever end up here */
+		fprintf(stderr, "Unable to exec() mgcp `%s`: %s\n",
+			data->bsc_mgcp.path, strerror(errno));
+		exit(1);
+	} else {
+		data->bsc_mgcp.pid = pid;
+		return 0;
+	}
+}
+
 extern int bsc_shutdown_net(struct gsm_network *net);
-static void signal_handler(int signal)
+static void signal_handler(int signum)
 {
-	fprintf(stdout, "signal %u received\n", signal);
+	fprintf(stdout, "signal %u received\n", signum);
 
-	switch (signal) {
+	switch (signum) {
 	case SIGINT:
 		bsc_shutdown_net(bsc_gsmnet);
 		osmo_signal_dispatch(SS_L_GLOBAL, S_L_GLOBAL_SHUTDOWN, NULL);
+		if (bsc_gsmnet->msc_data && bsc_gsmnet->msc_data->bsc_mgcp.pid) {
+			signal(SIGCHLD, SIG_IGN);
+			kill(bsc_gsmnet->msc_data->bsc_mgcp.pid, SIGTERM);
+		}
 		sleep(3);
 		exit(0);
 		break;
@@ -166,6 +195,12 @@ static void signal_handler(int signal)
 			return;
 		bsc_msc_lost(bsc_gsmnet->msc_data->msc_con);
 		break;
+	case SIGCHLD:
+		/* bsc_mgcp seems to have died */
+		/* sleep for some time to avoid fork bomb */
+		sleep(1);
+		spawn_mgcp();
+		break;
 	default:
 		break;
 	}
@@ -459,8 +494,11 @@ int main(int argc, char **argv)
 	signal(SIGABRT, &signal_handler);
 	signal(SIGUSR1, &signal_handler);
 	signal(SIGUSR2, &signal_handler);
+	signal(SIGCHLD, &signal_handler);
 	osmo_init_ignore_signals();
 
+	spawn_mgcp();
+
 	if (daemonize) {
 		rc = osmo_daemonize();
 		if (rc < 0) {