netdev - Re: [PATCH net] udp6: fix jumbogram reception

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Date:   Mon, 31 Jul 2017 22:01:54 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     pabeni@...hat.com
Cc:     netdev@...r.kernel.org, lorenzo@...gle.com,
        dsa@...ulusnetworks.com, david.lebrun@...ouvain.be,
        hannes@...essinduktion.org
Subject: Re: [PATCH net] udp6: fix jumbogram reception

From: Paolo Abeni <pabeni@...hat.com>
Date: Mon, 31 Jul 2017 16:52:36 +0200

> Since commit 67a51780aebb ("ipv6: udp: leverage scratch area
> helpers") udp6_recvmsg() read the skb len from the scratch area,
> to avoid a cache miss.
> But the UDP6 rx path support RFC 2675 UDPv6 jumbograms, and their
> length exceeds the 16 bits available in the scratch area. As a side
> effect the length returned by recvmsg() is:
> <ingress datagram len> % (1<<16)
> 
> This commit addresses the issue allocating one more bit in the
> IP6CB flags field and setting it for incoming jumbograms.
> Such field is still in the first cacheline, so at recvmsg()
> time we can check it and fallback to access skb->len if
> required, without a measurable overhead.
> 
> Fixes: 67a51780aebb ("ipv6: udp: leverage scratch area helpers")
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Applied, thanks Paolo.