Free rfc3261 software for linux

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).
Siproxd project 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.
SIP (Session Initiation Protocol, RFC3261) is the protocol of choice for most VoIP (Voice over IP) phones to initiate communication. By itself, SIP does not work via masquerading firewalls as the transfered data contains IP addresses and port numbers.
There do exist other solutions to traverse NAT existing (like STUN, or SIP aware NAT routers), but such a solutions has its disadvantages or may not be applied to a given situation. Siproxd does not aim to be a replacement for these solutions, however in some situations siproxd may bring advantages.
HOW TO GET STARTED
make sure libosip2 is installed
If your libposip2 libraries are installed in /usr/local/lib, be sure to include this library path to /etc/ld.so.conf
$ ./configure
$ make
$ make install
edit /usr/etc/siproxd.conf according to your situation.
At least configure if_inbound and if_outbound. They must represent the interface names (e.g. on Linux: ppp0, eth1) for the inbound and outbound interface.
edit /usr/etc/siproxd_passwd.cfg if you enable client authentication in siproxd.conf
start siproxd (siproxd does not require root privileges)
$ siproxd
Enhancements:
- Several issues related to 64 bit architectures have been fixed and several minor bugfixes.

SIP Express Router (ser) is a high-performance, configurable, free SIP ( RFC3261 ) server .
SER features an application-server interface, presence support, SMS gateway, SIMPLE2Jabber gateway, RADIUS/syslog accounting and authorization, server status monitoring, FCP security, etc. Web-based user provisioning, serweb, available.
Its performance allows it to deal with operational burdens, such as broken network components, attacks, power-up reboots and rapidly growing user population.
SERs configuration ability meets needs of a whole range of scenarios including small-office use, enterprise PBX replacements and carrier services.
Main features:
- accounting
- digest authentication
- CPL scripts
- ENUM support
- instant messaging
- MySQL support
- PostgreSQL support
- a presence agent
- Radius authentication and accounting
- Diameter authentication
- record routing
- SMS gateway
- Jabber gateway
- NAT traversal support transaction module
- registrar
- user location
SER has been extensively and successfuly tested with many SIP products from other vendors (Microsoft, Cisco, Mitel, snom, Pingtel, Siemens, and many others). It has been powering our SIP services continuously for more than two years.

sipsak is a small comand line tool for developers and administrators of Session Initiation Protocol (SIP) applications. sipsak can be used for some simple tests on SIP applications and devices.
Main features:
- sending OPTIONS request
- sending text files (which should contain SIP requests)
- traceroute (see section 11 in RFC3261)
- user location test
- flooding test
- random character trashed test
- interpret and react on response
- authentication with qop supported
- short notation supported for receiving (not for sending)
- string replacement in files
- can simulate calls in usrloc mode
- uses symmetric signaling and thus should work behind NAT
- can upload any given contact to a registrar
- send messages to any SIP destination
- Nagios compliant return codes
- search for strings in reply with regluar expression
- use multiple processes to create more server load
- read SIP message from STDIN (e.g. from a pipe |)
- supports DNS SRV through libruli
Version restrictions:
- The hostname is used in the Via line, which is not correct in all cases (e.g. if the loopback interface is used, or if the host has several interfaces). The rport parameter should fix problmes with the incorrect hostname, but for backward compatibility whith implementations which do not support rport this should be fixed.
- The DNS responses are not parsed compeltly which can result in strange output during hostname detection.
- TCP is not supported as transport protocol.
- IPv6 is not supported as transport protocol.
- Missing support for the Record-Route and Route header.
- Not fully RFC3261 compatible.
- Some smaller problems are listed in the TODO file.
Enhancements:
- A new option allows to add any header to the outgoing requests.
- The variable replacement option now accepts any number of attribute value pairs.
- Besides MD5 now SHA1 is support as digest authentication algorithm.
- The password for authentication can be read from stdin to prevent password disclosure in the process list.
- Fixed problems when executed as user root and compiles fine again under cygwin.