[SR-Users] Rewrite contact address on 200 OK?

[Alex Balashov]

Hi,

I may be mistaken, but my reading of 3261 is that a final dialog-forming response may update the remote target (Contact) previously sent by an early dialog-forming provisional reply.

That having been said, apart from using nathelper techniques (add_contact_alias() and handle_ruri_alias()), I can’t see a good way to deal with this problem. In general, SIP doesn’t really contemplate situations where the network and transport-layer reachability information of an endpoint changes mid-dialog except as part of a target refresh request (UPDATE, re-INVITE).

—
Sent from mobile, with due apologies for brevity and errors.

> On Oct 25, 2019, at 10:37 AM, Oded Arbel <odeda at cloudonix.io> wrote:
> 
> 
> Hi, we are having a problem with a network change use case. It goes on something like this:
> 
> 1. Kamailio receives INVITE from caller.
> 2. Kamailio sends INVITE to callee MUA.
> 3. MUA response with 100, then 183.
> 4. MUA then loses network connectivity and re-establishes access with another IP address.
> 5. MUA sends 200 OK from the new IP address, but with `Contact` still set as the old address (which I think it should, because you aren't allowed to change contact in the middle of dialog?)
> 6. Kamailio forwards 200 OK to caller and receives ACK.
> 7. Kamailio sends ACK to old IP address of MUA.
> 
> The last step is obviously a problem as the MUA will not be able to see the ACK.
> 
> I'm trying to see how to resolve this issue. I can capture the "$si" and "$sp" of the new address in the reply route (I also tried to get the MUA to send OPTIONS immediately after reestablishing connectivity, and capture "$si"/"$sp" there, which also works), but I can't figure out how to update the destination of the ACK. I've tried running `fix_nated_contact()` as well as trying to write into various pseudo variables - in either the OPTIONS request handler or the 200 reply handler - which either errors or does nothing.
> 
> Any suggestions?
> -- 
> Oded Arbel
> 
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