ortp: disable SO_REUSEADDR + SO_REUSEPORT

ortp >= 0.24.0 doesn't differentiate between SO_REUSEADDR and
SO_REUSEPORT, and has both enabled by default.  The latter means that
we can end up with non-unique port bindings as we will not fail to
bind the same port twice.

This should have caused visible problems not only when operating multiple
osmo-bts on one machine (rare), but also with a single osmo-bts. Once the range
(default 16384-17407 ) wraps, there is a risk of new sockets (for new cals)
colliding with old ones. As two ports (RTP+RTCP) are used per call, this means
every 512 voice calls we expect the BTS to wrap. And from that point onwards
there's a risk of overlapping with previously allocated sockets.

Change-Id: I4fc9eee561c7958c70c63b4ffdc6cb700b795e28
Closes: OS#4444

src/trau/osmo_ortp.c

@@ -378,6 +378,12 @@ struct osmo_rtp_socket *osmo_rtp_socket_create(void *talloc_ctx, unsigned int fl
 	rtp_session_set_profile(rs->sess, osmo_pt_profile);
 	rtp_session_set_jitter_compensation(rs->sess, 100);
 
+	/* ortp >= 0.24.0 doesn't differentiate between SO_REUSEADDR and
+	 * SO_REUSEPORT, and has both enabled by default.  The latter means that
+	 * we can end up with non-unique port bindings as we will not fail to
+	 * bind the same port twice */
+	rtp_session_set_reuseaddr(rs->sess, false);
+
 	rtp_session_signal_connect(rs->sess, "ssrc_changed",
 				   (RtpCallback) ortp_sig_cb_ssrc,
 				   RTP_SIGNAL_PTR_CAST(rs));

tests/rtp_test/rtp_test.c

@@ -54,7 +54,7 @@ static void test_bind_fail(void)
 	else {
 		printf("FAILED - second bind to port %u worked\n", port[0]);
 		fflush(stdout);
-		//OSMO_ASSERT(0);
+		OSMO_ASSERT(0);
 	}
 
 	osmo_rtp_socket_free(rs[0]);

tests/rtp_test/rtp_test.ok

@@ -1,2 +1,2 @@
 First bind to any random local port...
-Now try to bind another socket to the same port: FAILED - second bind to port 16384 worked
+Now try to bind another socket to the same port: OK (EADDRINUSE)