opensipstack-devel

[OpenSIPStack] Response routing in OpenSBC

[Andrew P. <and...@po...>]

Hi,

I am trying to understand how the responses are routed in OpenSBC.
B2BUserAgent::ProcessEvent checks if there is a SIPMessage event, 
differentiates between different types of requests, then if event is not 
a request, event dispatcher checks if it already has a session for this 
response. Once session has been found, it calls 
B2BUAEndPoint::ProcessStackEvent. The latter does the following magic to 
handle the responses:
if( !msg.IsRequest() )
       {
         OString meth = msg.GetCSeqMethod();
         if( meth == "SUBSCRIBE" ||
             meth == "NOTIFY" ||
             meth == "PUBLISH" )
         {
           ///this is a response
           SIPSession::GCRef ref = proxy->FindGCRefByCallId( 
msg.GetCallId() );
           if( ref != NULL )
           {
             proxy->ProcessStackEvent( ref, event );
             return;
           }
         }
       }

So far so good. The switch loop inside the 
SIPSessionManager::ProcessStackEvent function calls OnIncomingSIPMessage:

       case SIPStackEvent::Message:
         LOG_CONTEXT( LogDetail(), eventObject->GetCallId(),
         "Event"
         << ": " << "---> Inbound - "
         << 
((SIPMessageArrival&)*eventObject).GetMessage().GetStartLine() );

         OnIncomingSIPMessage( (SIPMessageArrival&)*eventObject, session );
         break;

OnIncomingSIPMessage to dispatch a valid response calls 
SIPSession::OnIncomingSIPMessage. It does the following thing:
   if( messageEvent.GetMessage().IsRequest() )
   {
     if( !messageEvent.GetMessage().IsAck() )
     {
       PWaitAndSignal lock( m_CurrentUASRequestMutex );
       m_CurrentUASRequest = messageEvent.GetMessage();
     }
   }

I have kind of reached a deadlock here. What I want to know is how the 
response if actually delivered to the local transaction layer or remote 
proxy. We've seen a scenario where OpenBSC is serving as a frontend to 
PortaSIP and from it we know that responses are a subject to a check of 
Request-URI and To-URI to distinguish between local handling and relay. 
I just do not see where these checks are done. Thanks,

-- 
Sincerely,
Andrew Pogrebennyk

Re: [OpenSIPStack] Response routing in OpenSBC

[<jo...@op...>]

Responses are not routed.  They just get matched to corresponding 
CORE.   In the scenario you have pasted below, the response was given to 
the Proxy Core.   This means that the request that created the 
transaction was bound to a remote destination.


Andrew Pogrebennyk wrote:
> Hi,
>
> I am trying to understand how the responses are routed in OpenSBC.
> B2BUserAgent::ProcessEvent checks if there is a SIPMessage event, 
> differentiates between different types of requests, then if event is not 
> a request, event dispatcher checks if it already has a session for this 
> response. Once session has been found, it calls 
> B2BUAEndPoint::ProcessStackEvent. The latter does the following magic to 
> handle the responses:
> if( !msg.IsRequest() )
>        {
>          OString meth = msg.GetCSeqMethod();
>          if( meth == "SUBSCRIBE" ||
>              meth == "NOTIFY" ||
>              meth == "PUBLISH" )
>          {
>            ///this is a response
>            SIPSession::GCRef ref = proxy->FindGCRefByCallId( 
> msg.GetCallId() );
>            if( ref != NULL )
>            {
>              proxy->ProcessStackEvent( ref, event );
>              return;
>            }
>          }
>        }
>
> So far so good. The switch loop inside the 
> SIPSessionManager::ProcessStackEvent function calls OnIncomingSIPMessage:
>
>        case SIPStackEvent::Message:
>          LOG_CONTEXT( LogDetail(), eventObject->GetCallId(),
>          "Event"
>          << ": " << "---> Inbound - "
>          << 
> ((SIPMessageArrival&)*eventObject).GetMessage().GetStartLine() );
>
>          OnIncomingSIPMessage( (SIPMessageArrival&)*eventObject, session );
>          break;
>
> OnIncomingSIPMessage to dispatch a valid response calls 
> SIPSession::OnIncomingSIPMessage. It does the following thing:
>    if( messageEvent.GetMessage().IsRequest() )
>    {
>      if( !messageEvent.GetMessage().IsAck() )
>      {
>        PWaitAndSignal lock( m_CurrentUASRequestMutex );
>        m_CurrentUASRequest = messageEvent.GetMessage();
>      }
>    }
>
> I have kind of reached a deadlock here. What I want to know is how the 
> response if actually delivered to the local transaction layer or remote 
> proxy. We've seen a scenario where OpenBSC is serving as a frontend to 
> PortaSIP and from it we know that responses are a subject to a check of 
> Request-URI and To-URI to distinguish between local handling and relay. 
> I just do not see where these checks are done. Thanks,
>
>