mgcp: Do not detect the initial package as a wrap around

The Annex A code has a probation period but we don't have it. When
starting with seq_no==0 do not assume that the sequence numbers
have wrapped. Do it by moving the entire checking code into the
else.

4 files changed, 67 insertions, 20 deletions

diff --git a/openbsc/include/openbsc/mgcp_internal.h b/openbsc/include/openbsc/mgcp_internal.h
index 0ec18cd5b..434b46c1f 100644
--- a/openbsc/include/openbsc/mgcp_internal.h
+++ b/openbsc/include/openbsc/mgcp_internal.h
@@ -248,6 +248,11 @@ void mgcp_get_net_downlink_format_default(struct mgcp_endpoint *endp,
 					  const char**subtype_name,
 					  const char**fmtp_extra);
 
+/* internal RTP Annex A counting */
+void mgcp_rtp_annex_count(struct mgcp_endpoint *endp, struct mgcp_rtp_state *state,
+			const uint16_t seq, const int32_t transit,
+			const uint32_t ssrc);
+
 enum {
 	MGCP_DEST_NET = 0,
 	MGCP_DEST_BTS,
diff --git a/openbsc/src/libmgcp/mgcp_network.c b/openbsc/src/libmgcp/mgcp_network.c
index 888ec6eb7..9def94e41 100644
--- a/openbsc/src/libmgcp/mgcp_network.c
+++ b/openbsc/src/libmgcp/mgcp_network.c
@@ -336,7 +336,6 @@ void mgcp_rtp_annex_count(struct mgcp_endpoint *endp, struct mgcp_rtp_state *sta
 			const uint16_t seq, const int32_t transit,
 			const uint32_t ssrc)
 {
-	uint16_t udelta;
 	int32_t d;
 
 	/* initialize or re-initialize */
@@ -348,25 +347,27 @@ void mgcp_rtp_annex_count(struct mgcp_endpoint *endp, struct mgcp_rtp_state *sta
 		state->stats_jitter = 0;
 		state->stats_transit = transit;
 		state->stats_cycles = 0;
-	}
-
-	/*
-	 * The below takes the shape of the validation of
-	 * Appendix A. Check if there is something weird with
-	 * the sequence number, otherwise check for a wrap
-	 * around in the sequence number.
-	 * It can't wrap during the initialization so let's
-	 * skip it here. The Appendix A probably doesn't have
-	 * this issue because of the probation.
-	 */
-	udelta = seq - state->stats_max_seq;
-	if (udelta < RTP_MAX_DROPOUT) {
-		if (seq < state->stats_max_seq)
-			state->stats_cycles += RTP_SEQ_MOD;
-	} else if (udelta <= RTP_SEQ_MOD - RTP_MAX_MISORDER) {
-		LOGP(DMGCP, LOGL_NOTICE,
-			"RTP seqno made a very large jump on 0x%x delta: %u\n",
-			ENDPOINT_NUMBER(endp), udelta);
+	} else {
+		uint16_t udelta;
+
+		/*
+		 * The below takes the shape of the validation of
+		 * Appendix A. Check if there is something weird with
+		 * the sequence number, otherwise check for a wrap
+		 * around in the sequence number.
+		 * It can't wrap during the initialization so let's
+		 * skip it here. The Appendix A probably doesn't have
+		 * this issue because of the probation.
+		 */
+		udelta = seq - state->stats_max_seq;
+		if (udelta < RTP_MAX_DROPOUT) {
+			if (seq < state->stats_max_seq)
+				state->stats_cycles += RTP_SEQ_MOD;
+		} else if (udelta <= RTP_SEQ_MOD - RTP_MAX_MISORDER) {
+			LOGP(DMGCP, LOGL_NOTICE,
+				"RTP seqno made a very large jump on 0x%x delta: %u\n",
+				ENDPOINT_NUMBER(endp), udelta);
+		}
 	}
 
 	/*
diff --git a/openbsc/tests/mgcp/mgcp_test.c b/openbsc/tests/mgcp/mgcp_test.c
index e145c6ab9..db2f4b35f 100644
--- a/openbsc/tests/mgcp/mgcp_test.c
+++ b/openbsc/tests/mgcp/mgcp_test.c
@@ -998,6 +998,45 @@ static void test_multilple_codec(void)
 	talloc_free(cfg);
 }
 
+static void test_no_cycle(void)
+{
+	struct mgcp_config *cfg;
+	struct mgcp_endpoint *endp;
+
+	printf("Testing no sequence flow on initial packet\n");
+
+	cfg = mgcp_config_alloc();
+	cfg->trunk.number_endpoints = 64;
+	mgcp_endpoints_allocate(&cfg->trunk);
+
+	endp = &cfg->trunk.endpoints[1];
+	OSMO_ASSERT(endp->net_state.stats_initialized == 0);
+
+	mgcp_rtp_annex_count(endp, &endp->net_state, 0, 0, 2342);
+	OSMO_ASSERT(endp->net_state.stats_initialized == 1);
+	OSMO_ASSERT(endp->net_state.stats_cycles == 0);
+	OSMO_ASSERT(endp->net_state.stats_max_seq == 0);
+
+	mgcp_rtp_annex_count(endp, &endp->net_state, 1, 0, 2342);
+	OSMO_ASSERT(endp->net_state.stats_initialized == 1);
+	OSMO_ASSERT(endp->net_state.stats_cycles == 0);
+	OSMO_ASSERT(endp->net_state.stats_max_seq == 1);
+
+	/* now jump.. */
+	mgcp_rtp_annex_count(endp, &endp->net_state, UINT16_MAX, 0, 2342);
+	OSMO_ASSERT(endp->net_state.stats_initialized == 1);
+	OSMO_ASSERT(endp->net_state.stats_cycles == 0);
+	OSMO_ASSERT(endp->net_state.stats_max_seq == UINT16_MAX);
+
+	/* and wrap */
+	mgcp_rtp_annex_count(endp, &endp->net_state, 0, 0, 2342);
+	OSMO_ASSERT(endp->net_state.stats_initialized == 1);
+	OSMO_ASSERT(endp->net_state.stats_cycles == UINT16_MAX + 1);
+	OSMO_ASSERT(endp->net_state.stats_max_seq == 0);
+
+	talloc_free(cfg);
+}
+
 int main(int argc, char **argv)
 {
 	osmo_init_logging(&log_info);
@@ -1014,6 +1053,7 @@ int main(int argc, char **argv)
 	test_packet_error_detection(0, 1);
 	test_packet_error_detection(1, 1);
 	test_multilple_codec();
+	test_no_cycle();
 
 	printf("Done\n");
 	return EXIT_SUCCESS;
diff --git a/openbsc/tests/mgcp/mgcp_test.ok b/openbsc/tests/mgcp/mgcp_test.ok
index a25bed4d3..6ca82af2b 100644
--- a/openbsc/tests/mgcp/mgcp_test.ok
+++ b/openbsc/tests/mgcp/mgcp_test.ok
@@ -475,4 +475,5 @@ In TS: 160320, dTS: 160, Seq: 1002
 Out TS change: 160, dTS: 160, Seq change: 1, TS Err change: in +0, out +0
 Stats: Jitter = 6810, Transit = -144000
 Testing multiple payload types
+Testing no sequence flow on initial packet
 Done