netdev - Re: [PATCH] tcp: Generalized TTL Security Mechanism

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Date:	Thu, 14 Jan 2010 12:22:16 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	David Miller <davem@...emloft.net>
Cc:	andi@...stfloor.org, shemminger@...tta.com, netdev@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH] tcp: Generalized TTL Security Mechanism

On Thu, Jan 14, 2010 at 03:04:54AM -0800, David Miller wrote:
> From: Andi Kleen <andi@...stfloor.org>
> Date: Thu, 14 Jan 2010 11:58:13 +0100
> 
> > Stephen Hemminger <shemminger@...tta.com> writes:
> >>
> >> Only TCP is supported, but could also be added to UDP, DCCP, SCTP
> >> if desired.
> > 
> > Perhaps I'm blind, but where is the default set if the socket
> > option is not used? 
> 
> Socket allocation memset()'s it to zero.

Yes, but there's no special case for zero in the check path?

It's just

+       if (iph->ttl < inet_sk(sk)->min_ttl)
+               goto discard_and_relse;

I'm probably missing something, but naively I would expect all 
packets with ttl > 0 to be discarded then when min_ttl is zero.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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