From: Stephen Hemminger <stephen@networkplumber.org>
To: Thomas Graf <tgraf@suug.ch>
Cc: netdev@vger.kernel.org
Subject: Re: [RFC] Should skb->csum include 8021Q header for CHECKSUM_COMPLETE && NETIF_F_HW_VLAN_CTAG_RX
Date: Fri, 29 Nov 2013 11:08:22 -0800 [thread overview]
Message-ID: <20131129110822.6e4cf256@nehalam.linuxnetplumber.net> (raw)
In-Reply-To: <20131129132819.GA9176@casper.infradead.org>
On Fri, 29 Nov 2013 13:28:19 +0000
Thomas Graf <tgraf@suug.ch> wrote:
> Hi
>
> Given CHECKSUM_COMPLETE, is skb->csum supposed to include the
> checksum of the VLAN header if the header was stripped by the
> NIC?
>
> The answer is clear for non accelerated VLAN: it covers all of
> the packet without ethernet CRC.
>
> For the accelerated path the answer is less clear after staring
> at drivers. The stack currently only fixes the csum for the
> software path.
>
> We are seeing hw csum failure warnings for drivers like enic if
> OVS pops a VLAN header that was previously stripped in hardware.
> Should we force CHECKSUM_NONE like VXLAN does or are all drivers
> guaranteed to include VLAN bits for CHECK_COMPLETE regardless of
> acceleration?
>
> Best,
> Thomas
> --
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Most hardware is smart enough that if it strips the VLAN header,
it does not include it in the checksum.
prev parent reply other threads:[~2013-11-29 19:08 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-29 13:28 [RFC] Should skb->csum include 8021Q header for CHECKSUM_COMPLETE && NETIF_F_HW_VLAN_CTAG_RX Thomas Graf
2013-11-29 19:08 ` Stephen Hemminger [this message]
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