[asterisk-users] How to append custom option to Contact: header on outgoing SIP INVITE msgs?

[Bob Beers]

Hi list,

My need is to append a site specific parameter to the
 Contact: header on all INVITEs exiting * via a SIP trunk.
I'd like it to look something like this:

Contact: <bob:3125551212 at 10.10.10.10;SITE-ID=us.here>

where SITE-ID=us.here is set in a config file that * parses on
 startup.  Or in a Dial() command option? Or I don't care exactly
 how. :-)

It is possible to affect the Contact: header via a line in sip.conf:
 register =>  toronto:welcome at 192.168.1.101/contact
but I can't get it to also accept any ;X=Y params for the
contact.

I can add a custom Contact header in the dialplan with SipAddHeader,
 but then I have two.  SipRemoveHeader only removes headers
 previously added by SipAddHeader, so no luck there.

I have googled, and searched the asterisk-users mailing list archives
 and not yet found a solution.  I did see some work back in 2004
 (issues 732 and 777) which mentioned not stripping contact header
 parameters from arriving requests/registrations, but nothing about
 creating any such parameters.

Thanks for any help/hints,

-- 
-Bob Beers