Ephemeral port range (patch)

[Robert Watson]

On Sat, 1 Mar 2008, Mike Silbersack wrote:

> On Sat, 1 Mar 2008, Fernando Gont wrote:
>
>> This patch changes the default ephemeral port range from 49152-65535 to 
>> 1024-65535. This makes it harder for an attacker to guess the ephemeral 
>> ports (as the port number space is larger). Also, it makes the chances of 
>> port number collisions smaller. 
>> (http://www.ietf.org/internet-drafts/draft-ietf-tsvwg-port-randomization-01.txt)
>
> There are a number of commonly used ports above 1000, such as nfs and x11. I 
> think OpenBSD uses 10000-65535, maybe that's a safer choice to go with.

In order to get acceptable open connection counts with 10gbps ethernet, I've 
needed to run with a significantly lower starting portrange.  In practice, the 
following seems to do the trick for me:

   sysctl net.inet.ip.portrange.first=10000

Of course, I only run into this if I also increase maxsockets:

   sysctl kern.ipc.maxsockets=30000

Lowering the lower end of the ephemeral range to 10,000 would do the trick for 
me, anyway.

Robert N M Watson
Computer Laboratory
University of Cambridge