Re: [PATCH 3.2 085/115] veth: donât modify ip_summed; doing so treats packets with bad checksums as good.

[Ben Hutchings]

On Thu, 2016-04-28 at 06:45 -0700, Ben Greear wrote:
> 
> On 04/28/2016 03:29 AM, Sabrina Dubroca wrote:
[...]
> > Your use case is invalid, it just happened to work because of a
> > bug.ÂÂIf you want the stack to fill checksums so that you want capture
> > and reinject packets, you have to disable checksum offloading (or
> > compute the checksum yourself in userspace).
> Disabling checksum offloading or computing in user-space (and then
> recomputing in veth to verify the checksum?) is a huge performance loss.
> 
> Maybe we could add a socket option to enable Cong's patch on a per-socket
> basis?ÂÂThat way my use-case can still work and you can have this new
> behaviour by default?

It does sound like a useful option to have. ÂIf there are other
applications that depend on veth's checksum-fixing behaviour and are
being distributed in binary form, then a per-device option might be
necessary so users can keep those applications working before they're
updated.

Ben.

-- 
Ben Hutchings
Tomorrow will be cancelled due to lack of interest.

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