MT#55283 Defuse loop detection for duplicate packets that arrive >1s apart

Fixes #2153
Closes #2155

Change-Id: I24cf69b45a5a6810a96285da41fb3c8b0416bcae

daemon/media_socket.c

@@ -2740,6 +2740,17 @@ static int media_loop_detect(struct packet_handler_ctx *phc) {
 			continue;
 
 		dbg_int("packet dupe");
+
+		/* not a loop if duplicates arrive more than 1s apart */
+		if (rtpe_now - phc->mp.stream->lp_buf[i].recv_us > 1000000LL) {
+			dbg_int("duplicate packet too old to indicate a loop, resetting count");
+			phc->mp.stream->lp_count = 0;
+			phc->mp.stream->lp_buf[i].recv_us = rtpe_now;
+			return 0;
+		}
+
+		phc->mp.stream->lp_buf[i].recv_us = rtpe_now;
+
 		if (phc->mp.stream->lp_count >= RTP_LOOP_MAX_COUNT) {
 			ilog(LOG_WARNING, "More than %d duplicate packets detected, dropping packet from %s%s%s"
 					"to avoid potential loop",
@@ -2756,6 +2767,7 @@ static int media_loop_detect(struct packet_handler_ctx *phc) {
 	phc->mp.stream->lp_count = 0;
 	phc->mp.stream->lp_buf[phc->mp.stream->lp_idx].len = phc->s.len;
 	memcpy(phc->mp.stream->lp_buf[phc->mp.stream->lp_idx].buf, phc->s.s, MIN(phc->s.len, RTP_LOOP_PROTECT));
+	phc->mp.stream->lp_buf[phc->mp.stream->lp_idx].recv_us = rtpe_now;
 	phc->mp.stream->lp_idx = (phc->mp.stream->lp_idx + 1) % RTP_LOOP_PACKETS;
 
 	return 0;

include/call.h

@@ -401,6 +401,7 @@ struct endpoint_map {
 struct loop_protector {
 	unsigned int		len;
 	unsigned char		buf[RTP_LOOP_PROTECT];
+	int64_t			recv_us;
 };
 
 

t/auto-daemon-tests.pl

@@ -29646,6 +29646,81 @@ ok(!grep {$_ eq 'loop check'} @{$resp->{tags}{ft()}{medias}[0]{flags}},
 
 
 
+# Scenario: duplicate packets arriving >1s apart should not trigger loop detection. With loop check
+# enabled, 32 rapid identical packets trigger a drop. After waiting >1s, the time-based reset allows
+# the same packet through again.
+
+($sock_a, $sock_b) = new_call([qw(198.51.100.1 6140)], [qw(198.51.100.3 6142)]);
+
+($port_a) = offer('loop detection time reset', { }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.14
+s=tester
+c=IN IP4 203.0.113.1
+t=0 0
+m=audio 30140 RTP/AVP 0
+a=sendrecv
+----------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.14
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+($port_b) = answer('loop detection time reset', { }, <<SDP);
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.14
+s=tester
+c=IN IP4 198.51.100.3
+t=0 0
+m=audio 6142 RTP/AVP 0
+a=sendrecv
+----------------------------
+v=0
+o=- 1545997027 1 IN IP4 198.51.100.14
+s=tester
+t=0 0
+m=audio PORT RTP/AVP 0
+c=IN IP4 203.0.113.1
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+my $dup_pkt = rtp(0, 1000, 3000, 0x1234, "\x00" x 160);
+my $dup_match = rtpm(0, 1000, 3000, 0x1234, "\x00" x 160);
+
+# establish the call with a different packet first
+snd($sock_a, $port_b, rtp(0, 999, 2000, 0x1234, "\x00" x 160));
+rcv($sock_b, $port_a, rtpm(0, 999, 2000, 0x1234, "\x00" x 160));
+
+# send 31 identical packets
+for (1..31) {
+	snd($sock_a, $port_b, $dup_pkt);
+	rcv($sock_b, $port_a, $dup_match);
+}
+
+# 32nd packet, dropped
+snd($sock_a, $port_b, $dup_pkt);
+rcv_no($sock_b, $port_a);
+
+# 32nd packet, dropped again
+snd($sock_a, $port_b, $dup_pkt);
+rcv_no($sock_b, $port_a);
+
+# after >1s, the 32nd packet passes through
+sleep(2);
+
+snd($sock_a, $port_b, $dup_pkt);
+rcv($sock_b, $port_a, $dup_match);
+
+
+
 
 #done_testing;NGCP::Rtpengine::AutoTest::terminate('f00');exit;
 done_testing();