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

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Message-Id: <20090602.023751.68661975.davem@davemloft.net>
Date:	Tue, 02 Jun 2009 02:37:51 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	nicolas.dichtel@...nd.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] ipv4/ipv6: check hop limit field on input

From: Nicolas Dichtel <nicolas.dichtel@...nd.com>
Date: Tue, 02 Jun 2009 11:36:29 +0200

> David Miller wrote:
>> From: Nicolas Dichtel <nicolas.dichtel@....6wind.com>
>> Date: Mon, 01 Jun 2009 17:13:43 +0200
>> 
>>> RFC indicates that a router must drop the packet if this field is 0.
>> It only must do this when executing the forwarding function.  It's an
>> egress check, not an ingress one.
> In my understanding, it can be on input to:
> RFC4443 Section 3.3:
>    If a router receives a packet with a Hop Limit of zero, or if a
>    router decrements a packet's Hop Limit to zero, it MUST discard the
>    packet and originate an ICMPv6 Time Exceeded message with Code 0 to
>    the source of the packet.

I think this was unintentional.

Usage of zero TTL by multicast applications is very well established.

Running such an application on a router should work as well.
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