[Serusers] reuse of existing tcp connection

[Andrei Pelinescu-Onciul]

On Oct 16, 2003 at 19:54, Juha Heinanen <jh at tutpro.com> wrote:
> Andrei Pelinescu-Onciul writes:
> 
>  > In this case if we don't care so much about security and you are
>  > interested only in the port number, we can add a compilation or runtime
>  > option to accept aliases only for ports and without any security checks
>  > (this means someone from the same host can hijack your connection).
> 
> that would be acceptable, since sip UAs seldomly run on multiuser
> hosts.


tcp port alias code is right now on unstable (HEAD) cvs.

Here are the relevant NEWS parts:

script vars:
   tcp_accept_aliases= yes|no
       if a message received over a tcp connection has "alias" in its via
       a new tcp alias port will be created for the connection the message
       came from (the alias port will be set to the via one).
       Based on draft-ietf-sip-connect-reuse-00.txt, but using only the port
       (host aliases are too dangerous IMHO, involve extra DNS
       lookups and the need for them is questionable)
       See force_tcp_alias for more details.
script commands:
   force_tcp_alias()
   force_tcp_alias(port)
       adds a tcp port alias for the current connection (if tcp).
       Usefull if you want to send all the trafic to port_alias through
       the same connection this request came from [it could help
       for firewall or nat traversal].
       With no parameters adds the port from the message via as the alias.
       When the "aliased" connection is closed (e.g. it's idle for too
       much time), all the port aliases are removed.
       Note: by default ser closes idle connection after 3 minutes (stable)
       or 1 minute (unstable) so to take full advantage of tcp aliases for
       things like firewall and nat traversal, redefine TCP_CON_*TIMEOUT
       in tcp_conn.h and recompile. Also right now there can be maximum
       3 port aliases to a connection (you shouldn't need more than one).
       To change this redefine TCP_CON_MAX_ALIASES in the same file
       (set it to you desired value + 1; 1 is needed for the real port).

WARNING: all this stuff involved major changes in some parts of the tcp code.
It was very little tested, might be unstable.


Andrei