Hi Guys,

running kamailio 4.1.4 and using uac_replace_from, I am seeing a strange issue with the proxying of an ACK message back from a carrier to freeswitch on the ingress path into a network.

So its just a normal call inbound, where on outbound leg we modify the From address, on the inbound leg all remains the same.

Now after the ingress side receives the 200ok, it sends an ACK as below;

ACK sip:+441624111111@192.168.24.8:5080;transport=udp SIP/2.0

Via: SIP/2.0/UDP 4.4.4.4:5060;branch=z9hG4bK+7f5c8c756ae3b26a956b33b88c77c29f1+sip+3+aa6d1466

Call-ID: 8791dbd3855eeafd484f397de6e2f76e@carrier.peering.telecom.im

From: "+44792498881474" <sip:+44792498881474@192.168.24.8:5080;user=phone>;tag=carrier.peering.telecom.im+3+863d20a3+1b9801d2

To: "+441624111111" <sip:+441624111111@8.8.8.8:5080;user=phone>;tag=6rrtgNFQDNrFF

CSeq: 1 ACK

Contact: <sip:4.4.4.4:5060>

Route: <sip:192.168.24.8;lr=on;ftag=carrier.peering.telecom.im+3+863d20a3+1b9801d2;vsf=AAAAAAAAAAYNBgAPAAgLAgZ3UTMACgBXFUsVFwwcDkAKTwMZGh0YAA8KDkEEQ1NYC0NDXgdOFRpSHg1vbmU->

Content-Length: 0

Max-Forwards: 68

However kamailio changes the From address;

ACK sip:+441624111111@192.168.24.8:5080;transport=udp SIP/2.0

Via: SIP/2.0/UDP 109.73.69.165:5060;branch=z9hG4bKc1ce.47974fc3da2b669a78f2dcc9a057a127.0

Via: SIP/2.0/UDP 4.4.4.4:5060;rport=5060;branch=z9hG4bK+7f5c8c756ae3b26a956b33b88c77c29f1+sip+3+aa6d1466

Call-ID: 8791dbd3855eeafd484f397de6e2f76e@carrier.peering.telecom.im

From: "+44792498881474" <sip:+441444680332@es132y$}-9>.8n?~9,*%(;zyk393;7e&C^NRone>;tag=carrier.peering.telecom.im+3+863d20a3+1b9801d2

To: "+441624111111" <sip:+441624111111@8.8.8.8:5080;user=phone>;tag=6rrtgNFQDNrFF

CSeq: 1 ACK

Contact: <sip:4.4.4.4:5060>

Content-Length: 0

Max-Forwards: 67

Causing FreeSWITCH to not recognise the request, and therefore not send an ACK.

There are no rules set against the ACK processing.

Has anyone seen this before? We dont know when it started happening which doesnt help, I will look to setup debug on test environment but just wondered if this is an issue thats been seen before?

Many thanks in advance.

Jon