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Defuse loop detection for duplicate packets that arrive >1s apart #2155

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Defuse loop detection for duplicate packets that arrive >1s apart #2155

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12 changes: 12 additions & 0 deletions daemon/media_socket.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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",
Expand All @@ -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;
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1 change: 1 addition & 0 deletions include/call.h
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Expand Up @@ -401,6 +401,7 @@ struct endpoint_map {
struct loop_protector {
unsigned int len;
unsigned char buf[RTP_LOOP_PROTECT];
int64_t recv_us;
};


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75 changes: 75 additions & 0 deletions t/auto-daemon-tests.pl
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Original file line number Diff line number Diff line change
Expand Up @@ -29646,6 +29646,81 @@



# 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();
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