Siproxd is a proxy/masquerading daemon for the SIP protocol.  It
handles registrations of SIP clients on a private IP network and
performs rewriting of the SIP message bodies to make SIP connections
work via an masquerading firewall (NAT).  It allows SIP software
clients (like kphone, linphone) or SIP hardware clients (Voice over
IP phones which are SIP-compatible, such as those from Cisco,
Grandstream or Snom) to work behind an IP masquerading firewall or
NAT router.