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

[Flavio Leitner]

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.

Now for packets coming from the kernel, then netdev_linux_parse_vnet_hdr()
will set that as well.

Packets from userspace to kernel are properly translated by
netdev_linux_prepend_vnet_hdr().

-- 
fbl