[ovs-dev] [PATCH] netdev-dpdk: vhost: disable unsupported offload features.

[Flavio Leitner]

On Thu, Feb 13, 2020 at 01:42:32PM +0100, Ilya Maximets wrote:
> On 2/13/20 12:30 PM, Flavio Leitner wrote:
> > On Thu, Feb 13, 2020 at 11:10:15AM +0100, Ilya Maximets wrote:
> >> On 2/13/20 12:44 AM, Flavio Leitner wrote:
> >>> On Wed, Feb 12, 2020 at 04:31:09PM -0300, Flavio Leitner wrote:
> >>>> On Wed, Feb 12, 2020 at 04:26:46PM +0100, Ilya Maximets wrote:
> >>>>> On 2/10/20 8:18 PM, Flavio Leitner wrote:
> >>>>>> Disable ECN and UFO since this is not supported yet. Also, disable
> >>>>>> all other features when userspace_tso is not enabled.
> >>>>>
> >>>>> Disabling UFO saves us from receiving of a big unfragmented
> >>>>> UDP packets, but UDP packets will still have bad checksums
> >>>>> and will be dropped by the kernel on receive side.
> >>>>> So, this is only part of a fix.
> >>>>
> >>>> Yes, this patch is not intended to fix the UDP checksum problem.
> >>>> Unless you see a way to do that with changing the flags below.
> >>>
> >>> BTW, why do you think there is a problem with UDP checksum?
> >>> We set VIRTIO_NET_HDR_F_NEEDS_CSUM which should be all it is needed.
> >>
> >> At least we're sending UDP packets on a wire without
> >> requesting Tx UDP checksum offloading from HW NICs.
> > 
> > Packets from virtual machines relies on DPDK vhost library, and as
> > far as I can see, it does set PKT_TX_UDP_CKSUM properly.
> 
> vhost library will properly set flags, however, OVS doesn't care
> about this case, e.g.  we're not enabling DEV_TX_OFFLOAD_UDP_CKSUM
> while configuring physical devices.  Even though most of the DPDK
> drivers will enable UDP checksum offload support regardless of this
> flag, this is still a logical error and we can't rely on this
> behavior.

Ah, now I see what you're saying.

I think we can support UDP csum, so will post another separate patch
fixing it.

Thanks,
-- 
fbl