netdev - Re: [PATCH bpf-next v6 1/2] Add skb_store_bytes() for BPF_PROG_TYPE_CGROUP

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Date:   Wed, 12 Jan 2022 16:43:44 -0800
From:   Song Liu <song@...nel.org>
To:     Tyler Wear <quic_twear@...cinc.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Maciej Żenczykowski <maze@...gle.com>,
        Yonghong Song <yhs@...com>, Martin KaFai Lau <kafai@...com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next v6 1/2] Add skb_store_bytes() for BPF_PROG_TYPE_CGROUP_SKB

On Wed, Jan 12, 2022 at 4:07 PM Tyler Wear <quic_twear@...cinc.com> wrote:
>
> Need to modify the ds field to support upcoming Wifi QoS Alliance spec.
> Instead of adding generic function for just modifying the ds field,
> add skb_store_bytes for BPF_PROG_TYPE_CGROUP_SKB.
> This allows other fields in the network and transport header to be
> modified in the future.
>
> Checksum API's also need to be added for completeness.
>
> It is not possible to use CGROUP_(SET|GET)SOCKOPT since
> the policy may change during runtime and would result
> in a large number of entries with wildcards.
>
> V4 patch fixes warnings and errors from checkpatch.

I don't think we need "V4 patch ..." part in the commit log.
To keep some history of patch, we can add these notes after
an "---" line, like:

Signed-off-by:
---
v4 patch ...
v3 patch ...
---
  net/core/filter.c | 12 ++++++++++++
...

With this format, git-am will remove the content between the
two "---" lines.

>
> The existing check for bpf_try_make_writable() should mean that
> skb_share_check() is not needed.
>
> Signed-off-by: Tyler Wear <quic_twear@...cinc.com>
> ---
>  net/core/filter.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 6102f093d59a..f30d939cb4cf 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -7299,6 +7299,18 @@ cg_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>                 return &bpf_sk_storage_delete_proto;
>         case BPF_FUNC_perf_event_output:
>                 return &bpf_skb_event_output_proto;
> +       case BPF_FUNC_skb_store_bytes:
> +               return &bpf_skb_store_bytes_proto;
> +       case BPF_FUNC_csum_update:
> +               return &bpf_csum_update_proto;
> +       case BPF_FUNC_csum_level:
> +               return &bpf_csum_level_proto;
> +       case BPF_FUNC_l3_csum_replace:
> +               return &bpf_l3_csum_replace_proto;
> +       case BPF_FUNC_l4_csum_replace:
> +               return &bpf_l4_csum_replace_proto;
> +       case BPF_FUNC_csum_diff:
> +               return &bpf_csum_diff_proto;
>  #ifdef CONFIG_SOCK_CGROUP_DATA
>         case BPF_FUNC_skb_cgroup_id:
>                 return &bpf_skb_cgroup_id_proto;
> --
> 2.25.1
>