netdev - [PATCH RFC net-next v3 0/7] improve CRC32c in the forwarding path

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Message-Id: <cover.1491562390.git.dcaratti@redhat.com>
Date:   Fri,  7 Apr 2017 16:16:03 +0200
From:   Davide Caratti <dcaratti@...hat.com>
To:     Tom Herbert <tom@...bertland.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        David Laight <David.Laight@...lab.com>,
        "David S . Miller" <davem@...emloft.net>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        linux-sctp@...r.kernel.org
Subject: [PATCH RFC net-next v3 0/7] improve CRC32c in the forwarding path

On Tue, 2017-03-07 at 10:06 -0800, Alexander Duyck wrote:
> You might even take this one step
> further.  You could convert crc32_csum into a 1 bit enum for now.
> Basically you would use 0 for 1's compliement csum, and 1 to represent
> a crc32c csum.  Then if we end up having to add another bit for
> something like FCoE in the future it would give us 4 possible checksum
> types instead of just giving us 1 with a bit mask.


On Sat, 2017-03-18 at 15:35 -0700, Tom Herbert wrote:
> Just create a non_ip_csum bit in skbuff.
> csum_bad can replaced with this I think. If the bit is set then more
> work can be done to differentiate between alternative checksums.

hello Alexander and Tom,

I refreshed the series including your suggestions.
Some followups are still possible:

* drivers that parse the packet header to correctly resolve CHECKSUM_PARTIAL
(e.g. ixgbe_tx_csum()) can benefit from skb->csum_algo savng some CPU cycles
(e.g. avoiding calling ip_hdr(skb)->protocol or ixgbe_ipv6_csum_is_sctp(skb)).

* drivers that call skb_checksum_help() to resolve CHECKSUM_PARTIAL can
call skb_crc32c_csum_help (or skb_csum_hwoffload_help(skb, 0)) to avoid
wrong CRC on SCTP packets.

thank you in advance for looking at this!
regards,
--
davide

v3:
 * review documentation
 * include a fix for corrupted SCTP packets in openvswitch datapath
 * skb->crc32c_csum renamed in skb->csum_algo and converted to enum
 * deprecate skb->csum_bad to free one bit in struct sk_buff
 * use 'CRC32c csum' terminology everywhere