From a24dcc61d799bb24574a90266ba47432485fcb20 Mon Sep 17 00:00:00 2001
From: Pau Espin Pedrol <pespin@sysmocom.de>
Date: Tue, 6 Jul 2021 17:48:47 +0200
Subject: [PATCH] mgcp_send_dummy: Check RTP destination is available before
 attempt tx

Several log messages showing "Failed to send dummy RTP packet." were
seen in a osmo-mgw on the field. Let's re-use the function to check and
provide more information on what's wrong to ease debugging.

Related: SYS#5498
Change-Id: Iee6ac1f4d24c131e3bf40c37e6fdc252e5208ec8
---
 src/libosmo-mgcp/mgcp_network.c | 6 ++++++
 tests/mgcp/mgcp_test.c          | 4 ++++
 tests/mgcp/mgcp_test.ok         | 7 -------
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/libosmo-mgcp/mgcp_network.c b/src/libosmo-mgcp/mgcp_network.c
index dfa952bea..5b3ea51c3 100644
--- a/src/libosmo-mgcp/mgcp_network.c
+++ b/src/libosmo-mgcp/mgcp_network.c
@@ -1037,6 +1037,12 @@ int mgcp_send_dummy(struct mgcp_endpoint *endp, struct mgcp_conn_rtp *conn)
 	LOGPCONN(conn->conn, DRTP, LOGL_DEBUG, "sending dummy packet... %s\n",
 		 mgcp_conn_dump(conn->conn));
 
+	/* Before we try to deliver the packet, we check if the destination
+	 * port and IP-Address make sense at all. If not, we will be unable
+	 * to deliver the packet. */
+	if (check_rtp_destin(conn) != 0)
+		goto failed;
+
 	rc = mgcp_udp_send(conn->end.rtp.fd, &conn->end.addr,
 			   conn->end.rtp_port, rtp_dummy_payload, sizeof(rtp_dummy_payload));
 
diff --git a/tests/mgcp/mgcp_test.c b/tests/mgcp/mgcp_test.c
index e6862e533..5bb7b2734 100644
--- a/tests/mgcp/mgcp_test.c
+++ b/tests/mgcp/mgcp_test.c
@@ -634,6 +634,10 @@ ssize_t sendto(int sockfd, const void *buf, size_t len, int flags,
 		dummy_packets += 1;
 	}
 
+	/* Make sure address+port are valid */
+	OSMO_ASSERT(dest_host);
+	OSMO_ASSERT(dest_port);
+
 	return len;
 }
 
diff --git a/tests/mgcp/mgcp_test.ok b/tests/mgcp/mgcp_test.ok
index 9c4814706..d3f8a26bd 100644
--- a/tests/mgcp/mgcp_test.ok
+++ b/tests/mgcp/mgcp_test.ok
@@ -118,7 +118,6 @@ checking response:
 using message with patched conn_id for comparison
 Response matches our expectations.
 (response contains a connection id)
-Dummy packets: 2
 
 ================================================
 Testing MDCX4_PT1
@@ -142,7 +141,6 @@ checking response:
 using message with patched conn_id for comparison
 Response matches our expectations.
 (response contains a connection id)
-Dummy packets: 2
 
 ================================================
 Testing MDCX4_PT2
@@ -166,7 +164,6 @@ checking response:
 using message with patched conn_id for comparison
 Response matches our expectations.
 (response contains a connection id)
-Dummy packets: 2
 
 ================================================
 Testing MDCX4_PT3
@@ -190,7 +187,6 @@ checking response:
 using message with patched conn_id for comparison
 Response matches our expectations.
 (response contains a connection id)
-Dummy packets: 2
 
 ================================================
 Testing MDCX4_PT4
@@ -214,7 +210,6 @@ checking response:
 using message with patched conn_id for comparison
 Response matches our expectations.
 (response contains a connection id)
-Dummy packets: 2
 
 ================================================
 Testing MDCX4_SO
@@ -253,7 +248,6 @@ checking response:
 using message with patched conn_id for comparison
 Response matches our expectations.
 (response contains a connection id)
-Dummy packets: 2
 
 ================================================
 Testing DLCX
@@ -441,7 +435,6 @@ checking response:
 using message with patched conn_id for comparison
 Response matches our expectations.
 (response contains a connection id)
-Dummy packets: 2
 
 ================================================
 Testing CRCX