rtptwcc: fixed parsing of old sequence number

Co-authored-by: Havard Graff <havard.graff@gmail.com>
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/927>

2 files changed, 61 insertions, 2 deletions

diff --git a/gst/rtpmanager/rtptwcc.c b/gst/rtpmanager/rtptwcc.c
index eab88fc51..3bb054063 100644
--- a/gst/rtpmanager/rtptwcc.c
+++ b/gst/rtpmanager/rtptwcc.c
@@ -794,7 +794,7 @@ _check_for_lost_packets (RTPTWCCManager * twcc, GArray * twcc_packets,
   /* we have gone backwards, don't reset the expectations,
      but process the packet nonetheless */
   if (fb_pkt_count_diff < 0) {
-    GST_WARNING ("feedback packet count going backwards (%u < %u)",
+    GST_DEBUG ("feedback packet count going backwards (%u < %u)",
         fb_pkt_count, twcc->expected_parsed_fb_pkt_count);
     return;
   }
@@ -802,11 +802,17 @@ _check_for_lost_packets (RTPTWCCManager * twcc, GArray * twcc_packets,
   /* we have jumped forwards, reset expectations, but don't trigger
      lost packets in case the missing fb-packet(s) arrive later */
   if (fb_pkt_count_diff > 0) {
-    GST_WARNING ("feedback packet count jumped ahead (%u > %u)",
+    GST_DEBUG ("feedback packet count jumped ahead (%u > %u)",
         fb_pkt_count, twcc->expected_parsed_fb_pkt_count);
     goto done;
   }
 
+  if (base_seqnum < twcc->expected_parsed_seqnum) {
+    GST_DEBUG ("twcc seqnum is older than expected  (%u < %u)", base_seqnum,
+        twcc->expected_parsed_seqnum);
+    return;
+  }
+
   packets_lost = base_seqnum - twcc->expected_parsed_seqnum;
   for (i = 0; i < packets_lost; i++) {
     _add_twcc_packet (twcc_packets, twcc->expected_parsed_seqnum + i,
diff --git a/tests/check/elements/rtpsession.c b/tests/check/elements/rtpsession.c
index a11ed278c..451ae2d29 100644
--- a/tests/check/elements/rtpsession.c
+++ b/tests/check/elements/rtpsession.c
@@ -3780,6 +3780,58 @@ GST_START_TEST (test_twcc_feedback_count_wrap)
 
 GST_END_TEST;
 
+GST_START_TEST (test_twcc_feedback_old_seqnum)
+{
+  SessionHarness *h = session_harness_new ();
+  guint i;
+  GstBuffer *buf;
+  GstEvent *event;
+  GValueArray *packets_array;
+
+  guint8 fci1[] = {
+    0x05, 0xfd,                 /* base sequence number: 1533 */
+    0x00, 0x00,                 /* packet status count: 0 */
+    0x00, 0x00, 0x00,           /* reference time: 0 */
+    0x00,                       /* feedback packet count: 255 */
+    0x00, 0x00,                 /* packet chunk: run-length, 0 */
+    0x00,                       /* 0 recv-delta */
+  };
+
+  guint8 fci2[] = {
+    0x05, 0xdc,                 /* base sequence number: 1500 */
+    0x00, 0x00,                 /* packet status count: 0 */
+    0x00, 0x00, 0x00,           /* reference time: 0 */
+    0x01,                       /* feedback packet count: 1 */
+    0x00, 0x00,                 /* packet chunk: run-length, 0 */
+    0x00,                       /* 0 recv-delta */
+  };
+
+  buf = generate_twcc_feedback_rtcp (fci1, sizeof (fci1));
+  session_harness_recv_rtcp (h, buf);
+
+  buf = generate_twcc_feedback_rtcp (fci2, sizeof (fci2));
+  session_harness_recv_rtcp (h, buf);
+
+  /* two reconfigure events */
+  for (i = 0; i < 2; i++)
+    gst_event_unref (gst_harness_pull_upstream_event (h->send_rtp_h));
+
+  for (i = 0; i < 2; i++) {
+    event = gst_harness_pull_upstream_event (h->send_rtp_h);
+    packets_array =
+        g_value_get_boxed (gst_structure_get_value (gst_event_get_structure
+            (event), "packets"));
+
+    /* we expect zero packets due to old sequence number */
+    fail_unless_equals_int (packets_array->n_values, 0);
+    gst_event_unref (event);
+  }
+
+  session_harness_free (h);
+}
+
+GST_END_TEST;
+
 
 static Suite *
 rtpsession_suite (void)
@@ -3848,6 +3900,7 @@ rtpsession_suite (void)
   tcase_add_loop_test (tc_chain, test_twcc_feedback_interval, 0,
       G_N_ELEMENTS (test_twcc_feedback_interval_ctx));
   tcase_add_test (tc_chain, test_twcc_feedback_count_wrap);
+  tcase_add_test (tc_chain, test_twcc_feedback_old_seqnum);
 
 
   return s;