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

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Message-ID: <4B4F1044.8080500@gmail.com>
Date:	Thu, 14 Jan 2010 07:38:28 -0500
From:	William Allen Simpson <william.allen.simpson@...il.com>
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

David Miller wrote:
> The idea is that the min_ttl is set very high, so that
> you'll only accept packets from hosts that started with
> a ttl of 255 and are within a hop or two from you.  (therefore
> you'd set min_ttl to 254 or 253, something like that)
> 
That's not a particularly good idea:

http://www.iana.org/assignments/ip-parameters

IP TIME TO LIVE PARAMETER

The current recommended default time to live (TTL) for the Internet
Protocol (IP) is 64 [RFC791, RFC1122].

===

It always bugs me that things get incorrectly labeled "security", yet
cannot secure anything.

Security requires a secret.

Various folks tried all kinds of games with TTL for BGP, but the only
thing that _actually_ provided security was MD5 authentication.
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