[OpenSIPS-Users] set_advertised_protocol ....

[John Quick]

When OpenSIPS is acting as a protocol translator, I have sometimes done
tricks like this:
  subst_uri('/transport=tls/transport=udp/i');
but for that to work, you need the local interfaces to support both
protocols.

You can manually insert your own version of a Record-Route header - or a
double RR - using record_route_preset(), but even if you did fix the
'transport' parameter value in the RR header so it was right for the load
balancer, it would then be wrong for OpenSIPS. This would probably break the
loose route handling. It would be a can of worms.
I don't think you can selectively alter the Via header, except through use
of advertised_address and advertised_port.

For your load balancer to truly provide "a transparent TCP/TLS interface",
it would have to inspect and fix the contents of packets at the application
layer (SIP).
Somewhat like wanting to use the Application Layer Gateway (ALG) option
available on a firewall. Even if the option were available, would you really
trust it?

John Quick
Smartvox Limited
Web: www.smartvox.co.uk