[OpenSIPS-Users] B2B bye method handling

[Alex Balashov]

Ross,

Could you provide a libpcap-formatted capture of this scenario, either 
on-list or privately?

-- Alex

On 02/09/2016 04:35 PM, Ross wrote:

> (I'm new to opensips, so bare with me if I'm off track).
>
> I setup a very simple configuration using b2bua for a quick top hiding
> setup/proxy, and it works correctly, except for handling BYE messages
> coming from the upstream connection. Note, db_mode is set to 0 for both
> b2b_logic + entities.
>
> setup: source client (aka invite initiator) -> os/b2b -> upstream
>
> Quick Issue description:
>
> Call sessions is established, and works fine, and when the client
> disconnects (initiates the bye message), the call disconnects cleanly
> with all parties as expected. (this is good/normal)
>
> But when the server side disconnects first (sends the initial bye
> message), opensips improperly handles the bye message by believing it to
> be from the client side. Therefore doesn't properly send the
> corresponding responses to the remote parties.
>
> In more detail:
>
> Delving into the code, and looking at some packet sniffs/debugs, I've
> come to the idea that the b2b code (notably starting dlg.c:706) doesn't
> take into account that the new BYE message will have the To/From Fields
> reversed when from the server as it's not technically a response.
> Because of this, the b2b_parse_key on 708 fails as it's only looking at
> the "to" field tag for it's index key.
>
> Then the request falls through and is then incorrectly parsed as a
> client sourced packet, as that lookup uses a different index key
> (callid), which is correct for the session.
>
> I've tested this using metaswitch and asterisk in both the client and
> server positions and they both return the same data (to/from), but would
> like anyone else's thoughts on this.  Apologies, while I can read code,
> I'm not a proper programmer to make a real patch.
>
> Thanks,
>    Ross.
>
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-- 
Alex Balashov | Principal | Evariste Systems LLC
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