linux-kernel - Re: [PATCH 2/4] virtio-net: add support of UDP segmentation (USO) on the host

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Message-ID: <CA+FuTSdfA6sT68AJNpa=VPBdwRFHvEY+=C-B_mS=y=WMpTyc=Q@mail.gmail.com>
Date:   Tue, 11 May 2021 13:47:26 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Yuri Benditovich <yuri.benditovich@...nix.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        Yan Vugenfirer <yan@...nix.com>
Subject: Re: [PATCH 2/4] virtio-net: add support of UDP segmentation (USO) on
 the host

On Tue, May 11, 2021 at 12:43 AM Yuri Benditovich
<yuri.benditovich@...nix.com> wrote:
>
> Large UDP packet provided by the guest with GSO type set to
> VIRTIO_NET_HDR_GSO_UDP_L4 will be divided to several UDP
> packets according to the gso_size field.
>
> Signed-off-by: Yuri Benditovich <yuri.benditovich@...nix.com>
> ---
>  include/linux/virtio_net.h | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index b465f8f3e554..4ecf9a1ca912 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -51,6 +51,11 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
>                         ip_proto = IPPROTO_UDP;
>                         thlen = sizeof(struct udphdr);
>                         break;
> +               case VIRTIO_NET_HDR_GSO_UDP_L4:
> +                       gso_type = SKB_GSO_UDP_L4;
> +                       ip_proto = IPPROTO_UDP;
> +                       thlen = sizeof(struct udphdr);
> +                       break;

If adding a new VIRTIO_NET_HDR type I suggest adding separate IPv4 and
IPv6 variants, analogous to VIRTIO_NET_HDR_GSO_TCPV[46]. To avoid
having to infer protocol again, as for UDP fragmentation offload (the
retry case below this code).