[ofa-general] [PATCHv2] IB/ipoib: S/G and HW checksum support

[Michael S. Tsirkin]

> Quoting Jason Gunthorpe <jgunthorpe at obsidianresearch.com>:
> Subject: Re: [ofa-general] [PATCHv2] IB/ipoib: S/G and HW checksum support
> 
> On Tue, Sep 04, 2007 at 12:11:33PM +0300, Michael S. Tsirkin wrote:
> 
> > I know some people find this approach controversial,
> > but from my perspective, this is not worse than e.g.
> > SDP which does not have SW checksums pretty much by design.
> 
> This would be alot better in my mind of the option was negotiated as
> part of the CM setup process.

Unfortunately, HW_CSUM device->features flag is a per-netdevice one.
We could do an extra pass over the packet, but this would mean a
performance hit for such paths. Your suggestion also does
not address multicast addresses.

> Otherwise this becomes a network wide
> all or nothing kind of feature..

Yes.
It would be relatively easy to make it possible to disable
this feature from sysfs, then you could partition the network
and use the feature for some partitions only.


> What if the RXing Linux IB side is acting as a forwarder to ethernet?
> It will forward corrupt packets if this option is set, right?

No. The checksum will be calculated by the gateway before being sent on the
ethernet interface.

-- 
MST