Re: [PATCH v6 1/2] virtio-net: define UDP tunnel segmentation offload feature

[Paolo Abeni <pabeni@redhat.com>]

On 7/31/24 20:21, Willem de Bruijn wrote:
> On Wed, Jul 31, 2024 at 1:32 PM Paolo Abeni <pabeni@redhat.com> wrote:
>> What about reserving an additional bit in gso_type to specify the inner
>> network header protocol?
> 
> Similar to VIRTIO_NET_HDR_GSO_ECN?
> 
> Is that preferable over VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IP4 and
> .._UDP_TUNNEL_IP6 variants?

Should be basically the same, as VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IP4 
VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IP6 will be 2 separate bits in gso_type, 
right?

> And to parsing just this one byte (or nibble) from packet data using
> inner_nh_offset?

I think one of the state goal is to avoid parsing. More importantly, 
accessing the inner network header content this early will cause 
possibly avoidable (or at least mitigable via prefetch) cache misses.

> If it's the best of those options, no objections from me. Definitely
> no need for a u16 if the only options are IPPROTO_IP and IPPROTO_IPV6.

Wrapping all the above I'll go for the additional bit for the inner 
network header type. If I misread something, please LMK:)

Thanks,

Paolo