Re: [MirageOS-devel] TCP checksum offload with Xen

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

On 19 Aug 2014, at 05:08, Thomas Leonard <talex5@xxxxxxxxx> wrote:

> I see Xen allows guests to indicate that the packet checksum is blank
> (XEN_NETTXF_csum_blank). Then dom0 will either fill it in itself or
> get the NIC to do it. How can I use this with Mirage?
> 
> I tried using ~flags:3 (Checksum_blank + Data_validated) in
> mirage-net-xen's netif.ml, but I don't see any TCP packets at all this
> way, even when the checksum is actually still being set. DHCP still
> works, though.
> 
> Does anyone know how this is supposed to work?

Probably best to trace through what netback is doing here:
http://lxr.free-electrons.com/source/drivers/net/xen-netback/netback.c#L1580

Looks like XEN_NETTXF_data_validated may need to be set as well
(and local packets are treated differently from off-host ones, to
add an extra twist).

-anil


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