[SR-Users] Kamailio ignores some ACK

[Efelin Novak]

Hi folks,

I have a strange problem when Kamailio ignores ACKs in a specific
scenario. The call flow is as follows:

A -> INVITE -> kamailio -> INVITE -> B
[omitting 100 and 180]
A <- 200 OK <- kamailio <- 200 OK <- B
A -> ACK -> kamailio

There are INVITE Xlogs, Reply ROUTE xlogs and media-proxy logs in the
syslog. However there is no information about these ACKs. No XLOGs are
printed even if there is one on the top of the main route.

"tcpdump -A -s0 -i any -n port 5060" receives this message correctly:

14:47:01.246153 IP 111.111.11.11.5060 > 80.80.80.80.60442: SIP, length: 915
SIP/2.0 200 OK
Via: SIP/2.0/UDP
111.111.11.11:5060;rport=60442;x-route-tag="tgrp:A";branch=z9hG4bK1634E6A88
Record-Route: <sip:111.111.11.11;lr;ftag=599248D4-260;vsf=AAAAAAAAAAAAAAAAAAAAW0FVT0ZWHF1aNy4xGzA-;nat=yes;did=3bb.327c47e6>
Contact: <sip:80.80.80.80:65002;transport=udp>
To: "test_account"<sip:bob at server.com>;tag=cb7dd641
From: <sip:alice at 111.111.11.50>;tag=599248D4-260
Call-ID: 9AFCFC51.11.50
CSeq: 101 INVITE
Allow: INVITE, ACK, CANCEL, BYE, NOTIFY, REFER, OPTIONS, INFO, SUBSCRIBE, UPDATE
Content-Type: application/sdp
Content-Length:263

v=0
o=- 492575093 492575093 IN IP4 111.111.11.60
s=test_device
i=(o=IN IP4 192.168.1.10)
c=IN IP4 111.111.11.71
t=0 0
m=audio 16416 RTP/AVP 18 101
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=ptime:20

14:47:01.254511 IP 111.111.11.50.60442 > 111.111.11.11.5060: SIP, length: 521
ACK sip:80.80.80.80:65002;transport=udp SIP/2.0
Via: SIP/2.0/UDP
111.111.11.50:5060;x-route-tag="tgrp:A";branch=z9hG4bK1634E7DE8
From: <sip:alice at 111.111.11.50>;tag=599248D4-260
To: "test_account"<sip:bob at server.com>;tag=cb7dd641
Call-ID: 9AFCFC51.11.50
Route: <sip:111.111.11.11;lr;ftag=599248D4-260;vsf=AAAAAAAAAAAAAAAAAAAAW0FVT0ZWHF1aNy4xGzA-;nat=yes;did=3bb.327c47e6>
Max-Forwards: 70
CSeq: 101 ACK
Content-Length: 0

My Kamailio version is kamailio 3.1.0 (i386/linux) 1e204f.
Does anybody knows where can be a problem?
How can I check whether Kamailio receives something?

...

Jan