asterisk users - Jul 2014 - Getting source ip adress of incoming INVITE

I'm interested in finding out what the source ip is of an invite in the
dialplan (Asterisk 11). As far as I can see this information isn't
accessible. The only solution I can think of is parsing either
Record-Route or Via headers. This is for recognizing "guests" in the
default context for sip.

> I'm interested in finding out what the source ip is of an invite in the
> dialplan (Asterisk 11).
${CHANNEL(recvip)}