Status: New
Owner: ----
Labels: Type-Defect Priority-Medium Component-Sip-Servlets MSS-3.0.0.FINAL
Roadmap-Fix
New issue 244 by [email protected]: If an INVITE is forwarded in B2BUA
mode, the call is forked by some proxy, and the UAS that answers the call
is not the UAS that sent the first provisional response, then forwarding
the 200 OK to the UAC fails
http://code.google.com/p/sipservlets/issues/detail?id=244
What steps will reproduce the problem?
1. Send an INVITE to a servlet that forwards it using
B2buaHelper.createRequest()
2. Have some downstream proxy fork the call to UAS1 and UAS2
3. Have UAS1 send a provisional responses with a To tag
4. Have the servlet forward both provisional responses using
B2buaHelper.createResponseToOriginalRequest()
4. Answer the call with UAS2
5. Have the servlet forward the 200 OK response with
B2buaHelper.createResponseToOriginalRequest()
I tested this by routing to an instance of the reSIProcate proxy where two
phones had registered using the same account details.
What is the expected output? What do you see instead?
The expected behaviour is that the 200 OK from UAS2 is forwarded, with the
To tag being different to the To tag of the forwarded provisional response
from UAS1 (but the same as the To tag in any provisional responses
forwarded from UAS2). Instead, a SipException occurs:
org.mobicents.servlet.sip.core.DispatcherException: Unexpected exception
while processing response
at
org.mobicents.servlet.sip.core.dispatchers.ResponseDispatcher$1.dispatch(ResponseDispatcher.java:493)
at
org.mobicents.servlet.sip.core.dispatchers.DispatchTask.dispatchAndHandleExceptions(DispatchTask.java:61)
at
org.mobicents.servlet.sip.core.dispatchers.ResponseDispatcher.dispatchMessage(ResponseDispatcher.java:514)
at
org.mobicents.servlet.sip.core.SipApplicationDispatcherImpl.processResponse(SipApplicationDispatcherImpl.java:1002)
at
gov.nist.javax.sip.EventScanner.deliverEvent(EventScanner.java:296)
at
gov.nist.javax.sip.SipProviderImpl.handleEvent(SipProviderImpl.java:185)
at
gov.nist.javax.sip.DialogFilter.processResponse(DialogFilter.java:1498)
at
gov.nist.javax.sip.stack.SIPClientTransaction.inviteClientTransaction(SIPClientTransaction.java:906)
at
gov.nist.javax.sip.stack.SIPClientTransaction.processResponse(SIPClientTransaction.java:548)
at
gov.nist.javax.sip.stack.SIPClientTransaction.processResponse(SIPClientTransaction.java:1582)
at
gov.nist.javax.sip.stack.UDPMessageChannel.processMessage(UDPMessageChannel.java:602)
at
gov.nist.javax.sip.stack.UDPMessageChannel.processIncomingDataPacket(UDPMessageChannel.java:511)
at
gov.nist.javax.sip.stack.UDPMessageChannel.run(UDPMessageChannel.java:316)
at java.lang.Thread.run(Thread.java:679)
Caused by: java.lang.IllegalStateException: an exception occured when
sending the response SIP/2.0 200 OK
at
org.mobicents.servlet.sip.message.SipServletResponseImpl.send(SipServletResponseImpl.java:656)
at
org.mobicents.servlet.sip.message.SipServletResponseImpl.send(SipServletResponseImpl.java:458)
... (internal com.telsis calls removed)
at com.telsis.tasp.OceanServlet.doSuccessResponse()
at javax.servlet.sip.SipServlet.doResponse(SipServlet.java:274)
at javax.servlet.sip.SipServlet.service(SipServlet.java:334)
at
org.mobicents.servlet.sip.core.dispatchers.MessageDispatcher.callServlet(MessageDispatcher.java:457)
at
org.mobicents.servlet.sip.core.dispatchers.ResponseDispatcher$1.dispatch(ResponseDispatcher.java:481)
... 13 more
Caused by: javax.sip.SipException: Tag mismatch dialogTag is
42363132_09ba9498_60e91531-46a6-4bc3-98c1-dd4ed264574a responseTag is
58801370_09ba9498_60e91531-46a6-4bc3-98c1-dd4ed264574a
at
gov.nist.javax.sip.stack.SIPServerTransaction.sendResponse(SIPServerTransaction.java:1487)
at
org.mobicents.servlet.sip.message.SipServletResponseImpl.send(SipServletResponseImpl.java:637)
... 23 more
42363132_09ba9498_60e91531-46a6-4bc3-98c1-dd4ed264574a is the To tag on the
forwarded response from UAS1 (i.e. the response that Mobicents sent to the
UAC), while 58801370_09ba9498_60e91531-46a6-4bc3-98c1-dd4ed264574a is the
To tag on the forwarded response from UAS2.
What version of the product are you using? On what operating system?
MSS-2.0.0.Final on Tomcat7 on CentOS 5.10
Please provide any additional information below.
I think this is caused by the NIST SIPServerTransaction. It appears to
create a SIPDialog object when it first receives a provisional response
with a To tag (which is correct - the presence of a To tag in a provisional
response establishes an early dialog). When a successful response is sent
the stack "make[s] sure that the response being sent makes sense" and
checks that the To tag in its saved SIPDialog matches that of the response.
If they don't match then it refuses to send the response. It's this check
that is wrong, as there's no requirement in RFC3261 that the To tag in a
final response matches the To tag from *any* provisional responses (while
section 8.2.6.2 says "The same tag MUST be used for all responses to that
request", this can't be relied on for forked calls as multiple UAS
instances are involved).
Note that this bug could occur even for calls that aren't forked by a proxy
if the UAS uses fake forking (one real-world UAS does this to provide
different SDP answers in provisional and final responses).
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