netdev - Re: [PATCH net-next 5/5] ipv6: Compute multipath hash for forwarded ICMP errors from offending packet

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Message-ID: <af3e302e-4fd0-e63c-4520-63a6e2341c22@stressinduktion.org>
Date:   Tue, 1 Nov 2016 17:25:07 +0100
From:   Hannes Frederic Sowa <hannes@...essinduktion.org>
To:     Tom Herbert <tom@...bertland.com>, Jakub Sitnicki <jkbs@...hat.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH net-next 5/5] ipv6: Compute multipath hash for forwarded
 ICMP errors from offending packet

On 31.10.2016 20:25, Tom Herbert wrote:
> The normal hash for TCP or UDP using ECMP is over <protocol, srcIP,
> dstIP, srcPort, dstPort>. For an ICMP packet ECMP would most likely be
> done over <protocol, srcIP, dstIP>. There really is no way to ensure
> that an ICMP packet will follow the same path as TCP or any other
> protocol. Fortunately, this is really isn't so terrible. The Internet
> has worked this way ever since routers started using ports as input to
> ECMP and that hasn't caused any major meltdown.

The normal hash for forwarding is without srcPort or dstPort, so the
same as ICMP and especially also because of fragmentation problematic I
don't think a lot of routers use L4 port information for ECMP either.

Bye,
Hannes