I know that it is an untypical way and that a B2BUA would be the best solution - that is absolutely clear. But because of a missing framework and time I decided to try it with Kamailio that I've used in many other projects, too.
Textops is still used and working fine for any headers (except request line). But UAC (as you´ve recommended) didn't satisfy me. I missed a possibility for setting dialog-specific settings á la Call-ID, from-tag, to-tag and CSeq. When I´ve tried setting the CSeq header with the function
$uac_req(hdrs)="CSeq: 123 INVITEr\n";
it has only added a second CSeq header to the outgoing message, but didn't replace the original CSeq header that was created by the UAC module. Is there a way to influence the listed id´s, too?
Klaus
At the risk of sounding unhelpful, if you are having to modify the request/status line, there's probably something more deeply wrong here, and you should probably endeavour to fix the problem in a somewhat more realistic manner.
Furthermore, it must be said that proxies do not make a particularly good "protocol adaptor"; in contrast to "thicker" back-to-back user agents (B2BUAs), which build out two logically independent call legs and bridge signaling events between them selectively, as they see fit, proxies are more or less obligated, in principle, to pass on what they receive, in unadulterated form. Kamailio does offer some hacks around that, in the form of textops and so on, but it doesn't really mean that it is the right tool for the job.
That said, if you are dead-set on doing this, your best for regenerating a reply into a request is the 'uac' module and uac_req_send() functionality:
http://kamailio.org/docs/modules/3.3.x/modules_k/uac.html#id2494432
-- Alex