netdev - Re: [bpf-next PATCH] samples/bpf: xdp_redirect_cpu handle parsing of double VLAN tagged packets

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Message-ID: <ae876878-4ad1-430b-5b0d-198f51275a77@iogearbox.net>
Date:   Sat, 14 Jul 2018 01:13:51 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org
Cc:     florian.maury-cv@...li.eu,
        Daniel Borkmann <borkmann@...earbox.net>, marek@...udflare.com,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: Re: [bpf-next PATCH] samples/bpf: xdp_redirect_cpu handle parsing of
 double VLAN tagged packets

On 07/13/2018 04:35 PM, Jesper Dangaard Brouer wrote:
> People noticed that the code match on IEEE 802.1ad (ETH_P_8021AD) ethertype,
> and this implies Q-in-Q or double tagged VLANs.  Thus, we better parse
> the next VLAN header too.  It is even marked as a TODO.
> 
> This is relevant for real world use-cases, as XDP cpumap redirect can be
> used when the NIC RSS hashing is broken.  E.g. the ixgbe driver HW cannot
> handle double tagged VLAN packets, and places everything into a single
> RX queue.  Using cpumap redirect, users can redistribute traffic across
> CPUs to solve this, which is faster than the network stacks RPS solution.
> 
> It is left as an exerise how to distribute the packets across CPUs.  It
> would be convenient to use the RX hash, but that is not _yet_ exposed
> to XDP programs. For now, users can code their own hash, as I've demonstrated
> in the Suricata code (where Q-in-Q is handled correctly).
> 
> Reported-by: Florian Maury <florian.maury-cv@...li.eu>
> Reported-by: Marek Majkowski <marek@...udflare.com>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>

Applied to bpf-next, thanks Jesper!