Re: [PATCH] OpenBSD Networking-related randomization port

[Stephen Hemminger <shemminger@osdl.org>]

On Wed, 02 Feb 2005 18:38:37 +0100
Lorenzo Hernández García-Hierro <lorenzo@gnu.org> wrote:

> El mié, 02-02-2005 a las 17:17 +0000, linux@horizon.com escribió:
> > There *are* things in OpenBSD, like randomized port assignment (as opposed
> > to the linear scan in tcp_v4_get_port()) that would be worth emulating.
> > Maybe worry about that first?
> > 

Recent 2.6 does a more advanced form of port randomization already
using address hash at connect time.  tcp_v4_get_port is only used for the case
of applications that explicitly bind to port zero to find a free port.

So the sequence:
	socket(); connect(); 
will assign a random port in a manner similar to sequence number creation

The sequence:
	socket(); bind(); connect();
assigns a simple linear increasing port value.  It could be randomized, but
most applications don't bother binding, so the first case is sufficient.

-- 
Stephen Hemminger	<shemminger@osdl.org>