[SR-Users] subst_hf to rewrite a contact header

[Federico Cabiddu]

Hi,
first of all you definitely do not want to put the contact received in the
INVITE in the 200 OK, since you will, in the best case generate a loop of
the UAC sending the ACK to itself.
About having to call msg_apply_changes this comes probably by the fact that
you've already manipulated the header with  fix_nated_contact(). Due to
kamailio's internals you cannot change the headers twice in a row without
invoking msg_apply_changes().
For your main problem with the ACK, I'd rather look at the Record-Route. I
see in the 200 OK that Record-Route has a private IP. Unless the caller is
on the same network or on a network that can communicate with your server,
you need to have there a public address (or a double Record-Route if your
server is running on two interfaces).
Have a look at "advertise" parameter of listen directive and to
http://www.kamailio.org/docs/modules/devel/modules/rr.html#rr.p.enable_double_rr
.

Best regards,

Federico

On Tue, Sep 25, 2018 at 12:24 AM Ben Hood <ben at relops.com> wrote:

>
> > On 24 Sep 2018, at 23:04, Alex Balashov <abalashov at evaristesys.com>
> wrote:
> >
> > On Mon, Sep 24, 2018 at 10:46:44PM +0100, Ben Hood wrote:
> >
> >> I was trying (as a temporary hack) to mangle this to become
> >>
> >> Contact: <sip:2018092417381900003 at 81.x.x.x
> <sip:2018092417381900003 at 81.x.x.x>>
> >
> > But that's not grammatically valid…
>
> You are absolutely correct, but I don’t think that is what I wrote (might
> be a typo from me?). I was trying to produce:
>
> Contact: <sip:2018092423082500003 at 81.x.x.x>
>
> Which I have now achieved by adding
>
> msg_apply_changes();
>
> after the invocation of subst_hf().
>
> Seems that the SIP buffer needs to be explicitly finalised before
> transport.
>
> However, my theory about patching the Contact header to make the remote
> system happy is wrong - the 200 OK is still not ACK’ed. So I need to look
> into the NAT’ing a bit more to see what might be going on - but this is a
> different question to how to use subst_hf().
>
> Many thanks for helping me out with this, very much appreciated.
>
>
>
>
>
>
>
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