Re: [PATCH] tcp: efficient port randomisation (revised)

["David S. Miller" <davem@xxxxxxxxxxxxx>]

On Wed, 17 Nov 2004 15:30:25 -0800
Stephen Hemminger <shemminger@xxxxxxxx> wrote:

> Here is a more conservative version of earlier patch vthat keeps the
> same port rover locking and global port rover. This randomizes TCP
> ephemeral ports of incoming connections using variation of existing
> sequence number hash.
> 
> Thanks to original author Michael Larsen. 
> http://www.ietf.org/internet-drafts/draft-larsen-tsvwg-port-randomisation-00.txt
> 
> It behaves correctly if someone is perverse and sets low > high
> and it separates the outgoing port rover (tcp_port_rover) from the
> incoming port rover (start_rover).

I'm fine with this patch semantically.  What do the
before/after microbenchmarks look like?  We're adding
a MD4 transform plus a modulus for every local port
select operation.