> Quoting Jason Gunthorpe <[EMAIL PROTECTED]>: > Subject: Re: [ofa-general] [PATCHv2] IB/ipoib: S/G and HW checksum support > > On Tue, Sep 04, 2007 at 08:04:19PM +0300, Michael S. Tsirkin wrote: > > > > 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. > > Why is there a big difference in performance if the stack does the > csum update or if the netdevice does the csum update? > > Aren't you already summing all UD packets (inclusing multicast) in the > driver before sending? Though, to be honest, I don't see this in your > patch, so maybe not..
no > > > 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. > > I thought linux only recomputed the checksum on the forwarding path if > the skb was marked as needing checksum. Since you set the skb as > already summed, there should be cases where invalid packets will be > forwarded.. I don't set CHECKSUM_UNECESSARY, so linux will have to recompute the checksum. > I'd be surprised if a real, hardware, IPoIB to XX device recomputed > the checksum unconditionally. The typical approach is to do an > incremental update of the checksum if you are changing the packet > headers. This preserves the end-to-end-ness and also does not require > buffering the entire packet before updating it. Since skb is not marked with CHECKSUM_COMPLETE, linux will recompute the checksum IMO. -- MST _______________________________________________ general mailing list [email protected] http://lists.openfabrics.org/cgi-bin/mailman/listinfo/general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
