Hi,
I have a similar issue with kamailio 4.3.4. I want to append a header to external 486 or 603 reply. If I got it right I should call append_hf, not append_to_reply which is for locally generated replies.

I've added append_hf() and in the end of failure route call exit but for some reason that header does not appear on the wire.
So I have added msg_apply_changes() in failure route to see if it changes something for me.
1st surprise is that kamailio actually started with this config. 2nd surprise is that is still doesn't work and throws an error which I didn't see before:

Dec 22 16:01:34 sp1 (local7.info) proxy[23957]: INFO: <script>: >>>>>>>> append reply_sock='udp:10.15.20.143:5060' in REPLY_ROUTE_NAT - ID=O4Oh8J6hm5ESJag-hlhXQIcBf6HSuZ2g UA='<null>'
Dec 22 16:01:34 sp1 (local7.err) proxy[23957]: ERROR: tm [t_reply.c:289]: update_totag_set(): ERROR: update_totag_set: to not parsed

Is that an expected behavior or why can't I append any header in failure route?

Regards,
Andrew

On 12/18/2015 03:55 PM, smititelu wrote:
Hello,

I don't understand why msg_apply changes() can be called from REQUEST_ROUTE only. Can someone explain? Can this be extended to FAILURE_ROUTES also?

Basically I need to call this from FAILURE_ROUTES in order to avoid double SDP for rtpengine offers. Searching in the mailing list I could see that there could be other means of handling this like keeping and reading the SDP from an avp(write/read_sdp_pv), but I find the above method pretty straightforward.

Thanks,
Stefan