[MediaProxy] Add support for ICE

Hi,

The attached patch adds support for using ICE (http://tools.ietf.org/html/draft-ietf-mmusic-ice-19) in scenarios involving OpenSIPS and MediaProxy.

Currently NAT is usually fixed by mangling the SDP in OpenSIPS and directing RTP to a media relay server. This SDP mangling makes ICE not to work, because ICE needs to have a candidate for the IP present in the c line of the SDP, and as the proxy changed it, ICE negotiation breaks.

With the attached patch, OpenSIPS will add the necessary candidates to the SDP so that the ICE negotiation doesn't break and we can have p2p audio on LAN environments for example. :)

Please consder it for inclusion in some later relase,

Kind regards,

PS: The design on how the issue has been solved can be seen here: http://mediaproxy.ag-projects.com/wiki/ICE
PS2: This patch needs this other patch to be applied previously: https://sourceforge.net/tracker/?func=detail&aid=2949743&group_id=232389&atid=1086412

--
Saúl Ibarra Corretgé
AG Projects