netdev - Re: [PATCH 9/9 v2] net: Add sysctl to trust checksum

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Message-ID: <1398549526.16049.20.camel@deadeye.wl.decadent.org.uk>
Date:	Sat, 26 Apr 2014 22:58:46 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Tom Herbert <therbert@...gle.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH 9/9 v2] net: Add sysctl to trust checksum_complete

On Sat, 2014-04-26 at 14:26 -0700, Tom Herbert wrote:
> Currently if a device provides CHECKSUM_COMPLETE but the checksum
> is calculated to be invalid we recompute the checksum and try
> again in software. On the other hand, if device returns
> CHECKSUM_UNNECESSARY we implicitly trust it and don't verify what it
> did. This seems backwards!
> 
> Add a sysctl to trust the device and report an invalid checksum when
> CHECKSUM_COMPLETE shows it is incorrect. sysctl defaults to enabled.
[...]

I think the sysctl and variable names need an '_error' or '_err' on the
end, to distinguish this from the NETIF_F_RXCSUM feature flag.

The new sysctl also needs to be documented, again making that
distinction clear.

Finally, if we're going to start trusting device checksum errors,
perhaps there should be a way to indicate a checksum error from a device
that only reports a checksum good/bad flag.  I do understand that such
devices are more likely to have bugs in checksum validation, though.

Ben.

-- 
Ben Hutchings
The most exhausting thing in life is being insincere. - Anne Morrow Lindberg

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