I can put for example OpenSIPS before FS and manipulate the header there, but it's kind of strange actually that in SIP softswitch there's no way access to arbitrary SIP header.
Another idea is to make a dirty hack in mod_sofia and otherwrite some existing SIP channel variable, which I don't use :)
There is a way... It's called using the well-known practice of using X-headers which is properly name-spaced and reserved for custom headers. When people make comments like this it actually annoys me... "Well your free software and open community are sort of cool but really, if it was worth a damn at all, it would certainly be able to make me toast....." You are the one with the non-standard requirement that you "can't change" so there is a saying here in open source land ... "Patches Welcome!" -- Anthony Minessale II FreeSWITCH http://www.freeswitch.org/ ClueCon http://www.cluecon.com/ Twitter: http://twitter.com/FreeSWITCH_wire AIM: anthm MSN:anthony_minessale@hotmail.com GTALK/JABBER/PAYPAL:anthony.minessale@gmail.com IRC: irc.freenode.net #freeswitch FreeSWITCH Developer Conference sip:888@conference.freeswitch.org googletalk:conf+888@conference.freeswitch.org pstn:+19193869900