netdev - Re: [PATCH bpf-next v6 6/6] bpf: Allow the new syncookie helpers to work with SKBs

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Date:   Tue, 26 Apr 2022 16:47:18 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Maxim Mikityanskiy <maximmi@...dia.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Networking <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...dia.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Petar Penkov <ppenkov@...gle.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Shuah Khan <shuah@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Joe Stringer <joe@...ium.io>,
        Florent Revest <revest@...omium.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Toke Høiland-Jørgensen <toke@...e.dk>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Florian Westphal <fw@...len.de>, pabeni@...hat.com
Subject: Re: [PATCH bpf-next v6 6/6] bpf: Allow the new syncookie helpers to
 work with SKBs

On Fri, Apr 22, 2022 at 10:25 AM Maxim Mikityanskiy <maximmi@...dia.com> wrote:
>
> This commits allows the new BPF helpers to work in SKB context (in TC
> BPF programs): bpf_tcp_raw_{gen,check}_syncookie_ipv{4,6}.
>
> The sample application and selftest are updated to support the TC mode.
> It's not the recommended mode of operation, because the SKB is already
> created at this point, and it's unlikely that the BPF program will
> provide any substantional speedup compared to regular SYN cookies or
> synproxy.
>
> Signed-off-by: Maxim Mikityanskiy <maximmi@...dia.com>
> Reviewed-by: Tariq Toukan <tariqt@...dia.com>
> ---
>  net/core/filter.c                             |  10 ++
>  .../selftests/bpf/prog_tests/xdp_synproxy.c   |  53 +++++--
>  .../selftests/bpf/progs/xdp_synproxy_kern.c   | 141 +++++++++++++-----
>  tools/testing/selftests/bpf/xdp_synproxy.c    |  94 +++++++++---
>  4 files changed, 230 insertions(+), 68 deletions(-)
>

[...]

>
> -       return hdr.tcp->syn ? syncookie_handle_syn(&hdr, ctx, data, data_end) :
> -                             syncookie_handle_ack(&hdr);
> +       return hdr->tcp->syn ? syncookie_handle_syn(hdr, ctx, data, data_end, xdp) :
> +                              syncookie_handle_ack(hdr);
> +}
> +
> +SEC("xdp/syncookie")

SEC("xdp")? libbpf will reject SEC("xdp/syncookie") in strict libbpf 1.0 mode

> +int syncookie_xdp(struct xdp_md *ctx)
> +{
> +       void *data_end = (void *)(long)ctx->data_end;
> +       void *data = (void *)(long)ctx->data;
> +       struct header_pointers hdr;
> +       int ret;
> +
> +       ret = syncookie_part1(ctx, data, data_end, &hdr, true);
> +       if (ret != XDP_TX)
> +               return ret;
> +
> +       data_end = (void *)(long)ctx->data_end;
> +       data = (void *)(long)ctx->data;
> +
> +       return syncookie_part2(ctx, data, data_end, &hdr, true);
> +}

[...]