Bug#691261: Phone PBX rejects refresh registration because of incorrect "expires" field in Contact header

[Ramón García Fernández]

Package: libopal3.10.4
Version: 3.10.4~dfsg-3

Hello,

We are using t38modem from Debian testing for sending and receiving faxes. We found that our PBX rejects SIP REGISTER refreshes, it complains that the Expires field is too short. The reason is that the header has two contradictory Expires values. One in the Expires header that is correct, and another in the expires field in the Contact header.

Here is the SIP traffic. I am replacing the IP addresses. our_pbx_ip is the IP of the SIP PBX, and our_fax_sever_ip is the IP of the machine with Debian GNU Linux and t38modem.

REGISTER sip:our_pbx_ip SIP/2.0
Route: <sip: :our_pbx_ip:5060;lr>
CSeq: 3 REGISTER
Via: SIP/2.0/UDP our_fax_server_ip:5060;branch=z9hG4bK92bf38f5-8e17-e211-9b43-001a4bc9fa1e;rport
User-Agent: T38Modem/2.0.0
From: <sip:34915854997@:our_pbx_ip >;tag=ea874e9c-8e17-e211-9b43-001a4bc9fa1e
Call-ID: c07a4e9c-8e17-e211-9b43-001a4bc9fa1e at elhuyar1
Organization: Vyacheslav Frolov
To: <sip:34915854997@:our_pbx_ip >
Contact: <sip:34915854997 at our_fax_server_ip:5060>;audio;expires=298
Allow: INVITE,ACK,OPTIONS,BYE,CANCEL,SUBSCRIBE,NOTIFY,REFER,MESSAGE,INFO,PING,PRACK
Expires: 300
Content-Length: 0
Max-Forwards: 70

SIP/2.0 423 Interval Too Brief
CSeq: 3 REGISTER
Via: SIP/2.0/UDP our_fax_server_ip:5060;branch=z9hG4bK92bf38f5-8e17-e211-9b43-001a4bc9fa1e;rport
From: <sip:34915854997 at our_pbx_ip>;tag=ea874e9c-8e17-e211-9b43-001a4bc9fa1e
Call-ID: c07a4e9c-8e17-e211-9b43-001a4bc9fa1e at elhuyar1
Min-Expires: 300
To: <sip:34915854997 at our_pbx_ip>
Warning: 399 our_pbx_ip "Registration received contact header with Expire value that less than allowed value = 300."
Content-Length: 0

Note the request has a contraction in the SIP request: expires=298 in the Contact header in Expires: 300

The patch bellow fixes the problem for us. The change that it makes is, when a SIP request contains Contact headers that contain expire values, and those values are less than the values of Expires: header, the former are fixed. I think that it is a conservative patch. Please forward it to the upstream maintainers. I think that opal 3.10.8 still has the same issue.

Best regards.




--- opal-3.10.4~dfsg.orig/src/sip/handlers.cxx
+++ opal-3.10.4~dfsg/src/sip/handlers.cxx
@@ -699,8 +699,17 @@ SIPTransaction * SIPRegisterHandler::Cre
           }
         }
       }
-      else
+      else {
+        for (SIPURLList::iterator contact = m_contactAddresses.begin(); contact != m_contactAddresses.end(); ++contact) {
+         if (contact->GetFieldParameters().Has("expires")) {
+           int stored_expire = contact->GetFieldParameters().GetInteger("expires", 0);
+           if (stored_expire < GetExpire()) {
+             contact->GetFieldParameters().SetInteger("expires", GetExpire());
+           }
+         }
+       }
         params.m_contactAddress = m_contactAddresses.ToString();
+      }
     }
   }



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