netdev - Re: [PATCH net-next v4 2/3] virtio_net: add optional flow dissection in virtio_net_hdr_to

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Message-ID: <2fd24801-bf77-02e3-03f5-b5e8fac595b6@redhat.com>
Date:   Thu, 10 Jun 2021 13:23:44 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Tanner Love <tannerlove.kernel@...il.com>,
        Network Development <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Petar Penkov <ppenkov@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Tanner Love <tannerlove@...gle.com>
Subject: Re: [PATCH net-next v4 2/3] virtio_net: add optional flow dissection
 in virtio_net_hdr_to_skb


在 2021/6/10 下午12:19, Alexei Starovoitov 写道:
> On Wed, Jun 9, 2021 at 9:13 PM Jason Wang <jasowang@...hat.com> wrote:
>> So I wonder why not simply use helpers to access the vnet header like
>> how tcp-bpf access the tcp header?
> Short answer - speed.
> tcp-bpf accesses all uapi and non-uapi structs directly.
>

Ok, this makes sense. But instead of coupling device specific stuffs 
like vnet header and neediness into general flow_keys as a context.

It would be better to introduce a vnet header context which contains

1) vnet header
2) flow keys
3) other contexts like endian and virtio-net features

So we preserve the performance and decouple the virtio-net stuffs from 
general structures like flow_keys or __sk_buff.

Thanks