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

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Message-ID: <20100318105939.57f8d377@nehalam>
Date:	Thu, 18 Mar 2010 10:59:39 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Pekka Savola <pekkas@...core.fi>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] tcp: Generalized TTL Security Mechanism

On Thu, 18 Mar 2010 08:36:48 +0200 (EET)
Pekka Savola <pekkas@...core.fi> wrote:

> Hi,
> 
> On Sun, 10 Jan 2010, Stephen Hemminger wrote:
> > This patch adds the kernel portions needed to implement
> > RFC 5082 Generalized TTL Security Mechanism (GTSM).
> > It is a lightweight security measure against forged
> > packets causing DoS attacks (for BGP).
> ...
> 
> It's nice to see this added.  However, I must add that a compliant RFC 
> 5082 implementation is required to have similar TTL treatment for ICMP 
> errors which relate to the protected session.  AFAIK this does not 
> support that.
> 
> The experimental, earlier spec (GTSH, RFC3682) did not have this 
> requirement.  Most if not all implementations support only GTSH mode. 
> So a backward-compatibility option may be desirable.

The ICMP receive error handling does need to be updated. 

But any application using GTSM should be setting IP_TTL socket option
to set send TTL. But, not sure if Linux TCP ever sends ICMP 
for existing sessions at all.
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