Be warned, this (and all the other) documentation is far from
complete. This is still considered an alpha release.


OVERVIEW
========
Siproxd is a proxy/masquerading daemon for SIP (Session Initiation
Protocol), which is used in IP telephony.
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 a 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.

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.


PREREQUISITES
=============
- OS of either:
  * Linux (preferred kernel 2.2.x or 2.4.x)
  * FreeBSD
  * NetBSD
  * OpenBSD
  * SunOS
  * Mac OS X
  
- libosip2 package (https://www.fsf.org/software/osip/)



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
  For Flifl: see doc/FLI4L_HOWTO.txt

- make

- make install

- edit /usr/etc/siproxd.conf according to your situation
  At least configure  'if_inbound' and 'if_outbound'. The 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



PROBLEM REPORTING
=================
If you encounter problems/crashes and ask for support, please include
as much information as possible. Very helpful is a debug log that
has been recorded at the time of the misbehavior.
Also include the exact versions of the siproxd package and libosip2
that you are using. You should also include your siproxd.conf.
 

The easiest way to generate a debug log is:
  1) make sure siproxd is not started as daemon.
     -> 'daemonize = 0' in the config file.
  2) start siproxd:
     $ ./siproxd -d -1 2>debug.log
  3) reproduce the error
  4) include the file debug.log in your error report.

Since Version 0.5.10 there also exists the possibility to obtain
the debug log remote via TCP (useful if running siproxd on an embedded
system). To enable this feature, edit the configuration file and
set 'debug_port' to a free TCP port number (e.g. 5050). Then (after
starting siproxd) you can connect from any remote client to this
TCP port (e.g. using netcat) and all the debug output will be sent
via network:
  1) edit configuration file:
     -> 'daemonize = 1' have siproxd started as daemon
     -> 'silence_log' should be set to 1
     -> 'debug_level = -1'
     -> 'debug_port = 5050' (or any other TCP port you like)
  2) have siproxd started the usual way
  3) connect from a remote machine and write into a file:
     $ netcat <IP_of_siproxd> <port> > debug.log
  4) reproduce the error
  5) include the file debug.log in your error report.


If siproxd crashes, a stack backtrace usually is helpful to me:
  1) start siproxd in the debugger (daemonize set to 0):
     $ gdb ./src/siproxd
     (gdb) set args -c /path/to/siproxd.conf
     (gdb) run
  2) reproduce the crash
  3) use gdb to print the stack backtrace:
   (gdb) info thread
   ...
   (gdb) bt
   #0  0x400ec9ee in __select ()
   #1  0xbffff6f8 in ?? ()
   #2  0x804a5c2 in main (argc=3, argv=0xbffffc54) at siproxd.c:186
   #3  0x4005bcb3 in __libc_start_main (main=0x804a30c <main>, argc=3, 
       argv=0xbffffc54, init=0x8049a08 <_init>, fini=0x804edac <_fini>, 
       rtld_fini=0x4000a350 <_dl_fini>, stack_end=0xbffffc4c)
       at ../sysdeps/generic/libc-start.c:78
   (gdb) 
  4) copy-paste all the output and include it in your error report.



SENDING A PATCH
===============
If you send a patch, please make the diff using "diff -Naur" and
include the version of siproxd you used to patch. This makes it a lot
easier for me to merge it.


WHAT SIPROXD DOES
=================
Siproxd's purpose is to act as an SIP proxy for SIP softphones/hardphones
located behind an masquerading router (NAT). It will rewrite SIP messages
to allow a SIP phone to communicate to a counterpart that is located in
the Internet. Check the scenarios drawn below.



Scenario 1
----------

 private IP address range             :          Internet
 10.0.0.x                             :          (public IP address range)
                                      :
                                      :         foo.bar.org
 +-------------+	       +--------------+
 !             !.10	    .1 ! masquerading ! publicIP
 ! IntHost     !---------------! Firewall     !------------>>  
 !             !               !              !   
 +-------------+	       +--------------+
                           eth0       :        ppp0

 - The Firewall does IP masquerading (NAT) and is running siproxd

 - IntHost is running an SIP phone (like linphone, kphone)

 - The SIP address used by the SIP phone is sip:[email protected]

 - The SIP phone is configured to register itself at siproxd
   running on the firewall host (10.0.0.1) as sip:[email protected]

 - foo.bar.org is the domain name corresponding to the public IP address
   of the firewall (e.g. use some dynamic DNS service [1])


Scenario 2
----------

 private IP address range             :          Internet
 10.0.0.x                             :          (public IP address range)
                                      :
                                      :     foo.bar.org
 +-------------+	       +--------------+              +--------------+
 !             !.10	    .1 ! masquerading ! publicIP     ! external SIP !
 ! IntHost     !---------------! Firewall     !------------>>! Registrar    !
 !             !               !              !              !              !
 +-------------+	       +--------------+              +--------------+
                           eth0       :        ppp0

 - The Firewall does IP masquerading (NAT) and is running siproxd

 - IntHost is running an SIP phone (like linphone, kphone)

 - The SIP address used by the SIP phone is sip:[email protected]

 - The SIP phone is configured to register itself at the external<BR>
   registrar as sip:[email protected]

 - foo.bar.org is the domain name corresponding to the public IP address
   of the firewall (e.g. use some dynamic DNS service [1])


IPCHAINS:
 Firewall rules for incoming traffic:
 # ipchains -A input --proto udp --dport 5060 --log  -j ACCEPT
 # ipchains -A input --proto udp --dport 7070:7080   -j ACCEPT

IPTABLES:
 Firewall rules for incoming traffic:
 # iptables -A INPUT -i ppp0 -p udp -m udp --dport 5060      -j ACCEPT 
 # iptables -A INPUT -i ppp0 -p udp -m udp --dport 7070:7080 -j ACCEPT 

 The first line will allow incoming SIP traffic (UDP port 5060). The second
 line will allow incoming RTP traffic on the ports 7070-7080 (the default port
 range used by siproxd for incoming RTP traffic).<P>


REFERENCES
==========
[1] dynamic DNS service https://www.dyndns.org



LIMITATIONS
===========
- currently, the SIP part only supports UDP
- very likely it does not follow the SIP spec (RFC3261) in all details
- check the TODO file for more things that we-cannot-do-but-would-like-to


IMPORTANT NOTICE
================
The gethostbyname() function leaks memory in glibc 2.1.1 (-> RedHat 6.0).
The quick fix is to delete the nisplus service from hosts entry in
/etc/nsswitch.conf.
In my tests, memory usage remained stable after I made the mentioned change.

(source: https://www.squid-cache.org/Doc/FAQ/FAQ-14.html)


CONTACTS
========
Please feel free to contact the author to:
   - provide feedback, report bugs,
   - request for additional features
   - report interoperability with various phones
   - ...
and visit the website at https://siproxd.sourceforge.net/

A siproxd mailing list is available on sourceforge.

IRC: Libera.Chat #siproxd


GnuPG: pub  4096R/9D777F7D2AC27400 2017-07-11 <[email protected]>
-      Fingerprint = 6560 75BE 4D4D 6C4D 8005 D4B4 9D77 7F7D 2AC2 7400
-      PubKey via keys.openpgp.org


CREDITS
=======

Thanks to sourceforge.net for providing the distribution platform and
infrastructure.

Also credits to the maintainers of linphone from where I have taken some
code parts for MD5 proxy authentication.