[sr-dev] ACK sometimes routed incorrectly on latest git master

[Peter Dunkley]

Hello,

The configuration is:

Jitsi #1 registered with sip2sip.info
Jitsi #2 registered with my server(s) (Kamailio edge proxy and Kamailio 
registrar) on Amazon AWS running Kamailio from git master

I make a call from Jitsi #1 to Jitsi #2 (there are SRV records for my 
domain in Amazon Route 53 so that sip2sip.info can find my servers).  
The flow of the call is:

    Jitsi #1 -> sip2sip.info -> Kamailio edge proxy -> Kamailio
    registrar -> Kamailio edge proxy -> Jitsi #2


The calls do not get established properly because the ACK is not 
correctly routed.  Calls between two Jitsi instances registered on my 
servers works.  Calls from Jitsi #2 to Jitsi #1 (my servers to 
sip2sip.info) also work.  This problem occurs whatever the value of the 
"enable_double_rr" modparam.

The 200 OK (INVITE) sent from my servers back to sip2sip.info looks OK 
and has a valid looking route-set:

    SIP/2.0 200 OK
    To: <sip:...callee... at ...callee domain...>;tag=e5116094
    Via: SIP/2.0/UDP 81.23.228.129:5060;rport=5060;branch=z9hG4bKdb93.87290485.0;i=0efbc,SIP/2.0/TLS 192.168.0.135:52379;rport=52379;received=a.b.c.d;branch=z9hG4bK-363631-23ca624fe9c119f229080992ed4fc143
    Record-Route: <sip:Rlwj4KMCy9UUUAMK9JufE8VamABismk=@e.f.g.h:5061;transport=tls;r2=on;lr=on>,<sip:Rlwj4KMCy9UUUAMK9JufE8VamABismk=@10.244.155.159:5080;transport=tcp;r2=on;lr=on>,<sip:10.101.62.154;transport=tcp;lr=on>,<sip:10.244.155.159:5080;transport=tcp;r2=on;lr=on>,<sip:e.f.g.h;r2=on;lr=on>,<sip:81.23.228.129;r2=on;lr;ftag=2d246de3;did=989.4a20eb73>,<sip:81.23.228.129:5061;transport=tls;r2=on;lr;ftag=2d246de3;did=989.4a20eb73>
    CSeq: 2 INVITE
    Call-ID: 38135c0b82a8a7d571352350d207b943 at 0:0:0:0:0:0:0:0
    From: "Caller" <sip:...caller... at sip2sip.info>;tag=2d246de3
    Contact: "callee" <sip:...callee... at 10.6.201.224:60847;transport=tls;registering_acc=...callee domain...>
    User-Agent: Jitsi2.3.4622.9647Linux
    Content-Type: application/sdp
    Content-Length: 838

    ...lots of SDP...


The ACK from sip2sip.info to my servers looks OK too:

    ACK sip:...callee... at 174.129.184.181:5060;transport=tls;registering_acc=...callee domain... SIP/2.0
    Call-ID: 38135c0b82a8a7d571352350d207b943 at 0:0:0:0:0:0:0:0
    CSeq: 2 ACK
    Via: SIP/2.0/UDP 81.23.228.129:5060;branch=z9hG4bKdb93.87290485.2;i=0efbc
    Via: SIP/2.0/TLS 192.168.0.135:52379;rport=52379;received=a.b.c.d;branch=z9hG4bK-363631-212696616e66a14286e3165485387895
    From: "Caller" <sip:...caller... at sip2sip.info>;tag=2d246de3
    To: "callee" <sip:...callee... at ...callee domain...>;tag=e5116094
    Max-Forwards: 69
    Route: <sip:e.f.g.h;r2=on;lr=on>,<sip:10.244.155.159:5080;transport=tcp;r2=on;lr=on>,<sip:10.101.62.154;transport=tcp;lr=on>,<sip:Rlwj4KMCy9UUUAMK9JufE8VamABismk=@10.244.155.159:5080;transport=tcp;r2=on;lr=on>,<sip:Rlwj4KMCy9UUUAMK9JufE8VamABismk=@e.f.g.h:5061;transport=tls;r2=on;lr=on>
    Contact: "Caller" <sip:...caller... at 90.152.0.102:52379;transport=tls;registering_acc=sip2sip_info>
    User-Agent: Jitsi2.2.4603.9615Windows 7
    Content-Length: 0

But the ACK from from my edge proxy to my registrar looks very broken:

    ACK sip:Rlwj4KMCy9UUUAMK9JufE8VamABismk=@e.f.g.h:5061;transport=tls;r2=on;lr=on SIP/2.0
    Call-ID: 38135c0b82a8a7d571352350d207b943 at 0:0:0:0:0:0:0:0
    CSeq: 2 ACK
    Via: SIP/2.0/TCP e.f.g.h:5060;branch=z9hG4bKdb93.444f42f24139f6dc512d70f61ca64be4.0
    Via: SIP/2.0/UDP 81.23.228.129:5060;rport=5060;branch=z9hG4bKdb93.87290485.2;i=0efbc
    Via: SIP/2.0/TLS 192.168.0.135:52379;rport=52379;received=a.b.c.d;branch=z9hG4bK-363631-212696616e66a14286e3165485387895
    From: "Caller" <sip:...caller... at sip2sip.info>;tag=2d246de3
    To: "callee" <sip:...callee... at ...callee domain...>;tag=e5116094
    Max-Forwards: 16
    Route: <sip:10.244.155.159:5080;transport=tcp;r2=on;lr=on>,<sip:10.101.62.154;transport=tcp;lr=on>,<sip:Rlwj4KMCy9UUUAMK9JufE8VamABismk=@10.244.155.159:5080;transport=tcp;r2=on;lr=on>
    Contact: "Caller" <sip:...caller... at a.b.c.d:52379;transport=tls;registering_acc=sip2sip_info>
    User-Agent: Jitsi2.2.4603.9615Windows 7
    Content-Length: 0

With debug turned up on the edge proxy I see the output from lines 673 
and 723 indicating that the loose.c:after_strict() is run.

My edge proxy configuration is:

    request_route {
    	route(REQINIT);

    	route(OPTIONS);

    	sip_trace();
    	setflag(F_SIPTRACE);

             if (is_method("CANCEL")) {
    		if (t_check_trans()) {
    			route(RELAY);
    		}
    		exit;
    	}

    	route(WITHINDLG);
    	...


    route[WITHINDLG] {
    	if (has_totag()) {
    		if (!loose_route()) {
    			switch($rc) {
    			case -2:
    				send_reply("403", "Forbidden");
    				exit;
    			default:
    				if (is_method("ACK")) {
    					if ( t_check_trans() ) {
    						route(RELAY);
    						exit;
    					} else {
    						exit;
    					}
    				}
    				send_reply("404","Not Found");
    			}
    		} else {
    			if ($rc == 2) {
    				setflag(F_OB_DRIVEN);
    			}

    			if (is_method("NOTIFY")) {
    				record_route();
    			}
    			route(RELAY);
    		}
    		exit;
    	}
    }

Have I done something fundamentally stupid here, or is there some 
obscure bug in the loose/strict routing code?

Regards,

Peter
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