netdev - Re: [PATCH] ipv4/ipv6: check hop limit field on input

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Message-ID: <20090601171340.GB29745@Chamillionaire.breakpoint.cc>
Date:	Mon, 1 Jun 2009 19:13:40 +0200
From:	Florian Westphal <fw@...len.de>
To:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:	Florian Westphal <fw@...len.de>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] ipv4/ipv6: check hop limit field on input

Nicolas Dichtel <nicolas.dichtel@...nd.com> wrote:
>> Whats wrong with the checks in ip(6)_forward?
> It's on forward, not on input. Router must not process it.
> For example, if you try to ping (with ttl set to 0) the router, you will 
> receive a reply.

Ah.  That makes more sense.
However, I'd argue that this is sane behaviour.

The datagram did reach its intended destination and the TTL did not
"exceed in transit" (if it had, the datagram would not have been
received).  Why discard an otherwise perfectly legal packet?
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