linux-kernel - Re: [RFC PATCH v2 0/5] TUN/VirtioNet USO features support.

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Date:   Tue, 17 May 2022 14:32:00 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Andrew Melnychenko <andrew@...nix.com>
Cc:     davem <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, mst <mst@...hat.com>,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        Yan Vugenfirer <yan@...nix.com>,
        Yuri Benditovich <yuri.benditovich@...nix.com>
Subject: Re: [RFC PATCH v2 0/5] TUN/VirtioNet USO features support.

On Thu, May 12, 2022 at 7:33 PM Andrew Melnychenko <andrew@...nix.com> wrote:
>
> Added new offloads for TUN devices TUN_F_USO4 and TUN_F_USO6.
> Technically they enable NETIF_F_GSO_UDP_L4
> (and only if USO4 & USO6 are set simultaneously).
> It allows to transmission of large UDP packets.
>
> Different features USO4 and USO6 are required for qemu where Windows guests can
> enable disable USO receives for IPv4 and IPv6 separately.
> On the other side, Linux can't really differentiate USO4 and USO6, for now.
> For now, to enable USO for TUN it requires enabling USO4 and USO6 together.
> In the future, there would be a mechanism to control UDP_L4 GSO separately.
>
> Test it WIP Qemu https://github.com/daynix/qemu/tree/Dev_USOv2
>
> New types for VirtioNet already on mailing:
> https://lists.oasis-open.org/archives/virtio-comment/202110/msg00010.html
>
> Also, there is a known issue with transmitting packages between two guests.

Could you explain this more? It looks like a bug. (Or any pointer to
the discussion)

Thanks

> Without hacks with skb's GSO - packages are still segmented on the host's postrouting.
>
> Andrew (5):
>   uapi/linux/if_tun.h: Added new offload types for USO4/6.
>   driver/net/tun: Added features for USO.
>   uapi/linux/virtio_net.h: Added USO types.
>   linux/virtio_net.h: Support USO offload in vnet header.
>   drivers/net/virtio_net.c: Added USO support.
>
>  drivers/net/tap.c               | 10 ++++++++--
>  drivers/net/tun.c               |  8 +++++++-
>  drivers/net/virtio_net.c        | 19 +++++++++++++++----
>  include/linux/virtio_net.h      |  9 +++++++++
>  include/uapi/linux/if_tun.h     |  2 ++
>  include/uapi/linux/virtio_net.h |  4 ++++
>  6 files changed, 45 insertions(+), 7 deletions(-)
>
> --
> 2.35.1
>