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

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Message-Id: <20090601.224330.267938162.davem@davemloft.net>
Date:	Mon, 01 Jun 2009 22:43:30 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	dada1@...mosbay.com
Cc:	nicolas.dichtel@....6wind.com, netdev@...r.kernel.org
Subject: Re: [PATCH] ipv4/ipv6: check hop limit field on input

From: Eric Dumazet <dada1@...mosbay.com>
Date: Tue, 02 Jun 2009 07:31:12 +0200

> David Miller a écrit :
>> 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.
>> 
>> I'm not applying this patch, it can even break some applications
>> out there that use a TTL of zero intentionally to keep traffic
>> only on a local subnet.
> 
> I wonder if we then should allow setting ttl to zero. I had to patch
> my kernel to allow ping to do this...
> 
> I'll check RFC when time permits.

Eric, notice how I mentioned in my other reply to this thread
"multicast" applications, which use mc_ttl which we allow to be set to
zero.
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