[OpenSER-Devel] [ openser-Bugs-1983901 ] Retransmissions of 408 are not using received/rport from Via

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Bugs item #1983901, was opened at 2008-06-03 20:52
Message generated for change (Comment added) made by henningw
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Category: core
Group: ver 1.3.x
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Anatoly Pidruchny (apidruchny)
>Assigned to: Henning Westerholt (henningw)
Summary: Retransmissions of 408 are not using received/rport from Via

Initial Comment:
When fr_timer/fr_inv_timer expires for an INVITE transaction, OpenSER generates 408 Request Timeout reply. The first time the 408 reply is sent to the host/port that was saved in the received/rport parameters in Via header. But if the UAC does not send ACK and OpenSER starts retransmissions of the 408 reply, it is sent to the host/port in the Via header value, received/rport are not used any more.

I will try to provide the SIP message flow. Let's say OpenSER received and later relayed the following message:

INVITE sip:5105042000 at hostA.com SIP/2.0
Via: SIP/2.0/UDP hostA.com:5060;branch=z9hG4bK0000167000167^M
From: 167 <sip:5105041000 at hostA.com>;tag=167^M
To: Receiver <sip:5105042000 at hostA.com>^M
Call-ID: 167 at hostA.com^M
CSeq: 1 INVITE^M
Content-Length: 0^M
^M

Yes, UAC put the domain name of the OpenSER machine into the Via header. This is part of some SIP security test suite and so it was done on purpose. OpenSER added received/rport parameters into the Via header:

Via: SIP/2.0/UDP hostA.com:5060;branch=z9hG4bK0000167000167;rport=5060;received=10.104.49.186^M

When fr_timer or fr_inv_timer expires for this message, OpenSER sends the following reply to the UAC on host 10.104.49.186, port 5060:

SIP/2.0 408 Request Timeout^M
Via: SIP/2.0/UDP hostA.com:5060;branch=z9hG4bK0000167000167;rport=5060;received=10.104.49.186^M
From: 167 <sip:5105041000 at hostA.com>;tag=167^M
To: Receiver <sip:5105042000 at hostA.com>;tag=2d7a0ab08b3494791197ebc7134d5742-0de7^M
Call-ID: 167 at hostA.com^M
CSeq: 1 INVITE^M
Content-Length: 0^M
^M

But UAC did not answer with ACK, so then OpenSER started retransmitting the 408 reply. But the retransmissions did not go to host 10.104.49.186, port 5060. They were sent back to OpenSER's machine hostA.com that was in the value of the Via header. The first retransmission looked like this:

SIP/2.0 408 Request Timeout^M
Via: SIP/2.0/UDP xxx.xxx.xxx.xxx;branch=z9hG4bKe568.6c360a02.0^M
Via: SIP/2.0/UDP hostA.com:5060;rport=5060;received=10.104.49.186;branch=z9hG4bK0000167000167^M
From: 167 <sip:5105041000 at hostA.com>;tag=167^M
To: Receiver <sip:5105042000 at hostA.com>;tag=2d7a0ab08b3494791197ebc7134d5742-4615^M
Call-ID: 167 at hostA.com^M
CSeq: 1 INVITE^M
Content-Length: 0^M
^M

Subsequent retransmissions kept adding the Via header:
Via: SIP/2.0/UDP xxx.xxx.xxx.xxx;branch=z9hG4bKe568.xxxxxxxx.0^M


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>Comment By: Henning Westerholt (henningw)
Date: 2008-07-03 12:28

Message:
Logged In: YES 
user_id=337916
Originator: NO

Hi Anatoly

this UAC behaviour is not valid according to the RFC:

8.1.1.7 Via
The Via header field indicates the transport used for the transaction
and identifies the location where the response is to be sent.

I've tried to reproduce this anyway, and my openser loops subsequent
messages (1XX, 408) as expected. Can you give more details why do you think
this is a bug?

Henning

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