Re: TOPOH masking not applied after 408 serial forking from failure_route in Kamailio 5.5

Hello David,

I can not offer a specific advice to your scenario, but I would recommend to a supported release, e.g. at least 5.8.x. There are several extensions and also bug fixes in the topos and topoh modules done in the later versions.

Cheers,

Henning

-- 
Kamailio & VoIP services - https://gilawa.com

> -----Original Message-----
> From: David Escartin Almudevar via sr-users <[email protected]>
> Sent: Mittwoch, 13. Mai 2026 07:52
> To: [email protected]
> Cc: [email protected]
> Subject: [SR-Users] TOPOH masking not applied after 408 serial forking from
> failure_route in Kamailio 5.5
> 
> Hi,
> 
> I would like to ask about a possible issue, or maybe a missing configuration on my
> side, when using the `topoh` module in Kamailio 5.5.
> 
> I am using `topoh` to mask SIP headers, and I enable/disable the masking logic
> through `event_route[topoh:msg-outgoing]`.
> 
> My current route is very simple:
> 
> ```kamailio
> event_route[topoh:msg-outgoing] {
>     if (!is_gflag(G_TOPOH)) {
>         drop;
>     }
> }
> ```
> 
> So basically, I only skip TOPOH masking when the global flag `G_TOPOH` is not
> enabled.
> 
> The issue I am seeing happens in a serial forking scenario handled from
> `failure_route`.
> 
> The initial INVITE is sent to the first provider and TOPOH masking is applied
> correctly. If that provider does not reply at all, the transaction times out with
> `408 Request Timeout`.
> 
> Then, from `failure_route`, I reroute the call to the next provider. The next
> destination is taken from an AVP stack, and I update `$rd` with the new
> destination before relaying the call again.
> 
> In that second outgoing branch, it looks like TOPOH masking is not applied to the
> headers anymore. The call is sent out, but some headers appear unmasked, as if
> `event_route[topoh:msg-outgoing]` was not being applied again during the serial
> forking / failure route processing after the 408.
> 
> Is this a known limitation or bug in `topoh` with serial forking after a timeout,
> specifically in Kamailio 5.5?
> 
> Is there any additional configuration required to make sure TOPOH masking is
> applied again on the new outgoing branch created from `failure_route` after a
> `408`?
> 
> Could the fact that I only update `$rd` from `failure_route`, instead of building a
> completely new `$du` / branch destination, affect how TOPOH processes the
> second outgoing INVITE?
> 
> Has anyone seen this behavior before, or is there anything special that needs to
> be done when using `topoh` together with serial forking / `failure_route`
> rerouting?
> 
> Thanks in advance.
> david escartin
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