netdev - Re: [PATCH bpf-next 10/10] bpf: Add sample for raw syncookie helpers

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Date:   Thu, 21 Oct 2021 20:19:15 +0300
From:   Maxim Mikityanskiy <maximmi@...dia.com>
To:     Joe Stringer <joe@...ium.io>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        "Jesper Dangaard Brouer" <hawk@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        "Nick Desaulniers" <ndesaulniers@...gle.com>,
        Brendan Jackman <jackmanb@...gle.com>,
        Florent Revest <revest@...omium.org>,
        Lorenz Bauer <lmb@...udflare.com>,
        Tariq Toukan <tariqt@...dia.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH bpf-next 10/10] bpf: Add sample for raw syncookie helpers

On 2021-10-20 21:01, Joe Stringer wrote:
> Hi,  just one comment related to the discussion on patch 7.
> 
> On Tue, Oct 19, 2021 at 7:49 AM Maxim Mikityanskiy <maximmi@...dia.com> wrote:
> 
> <snip>
> 
>> +
>> +       value = 0; // Flags.
>> +       ct = bpf_ct_lookup_tcp(ctx, &tup, tup_size, BPF_F_CURRENT_NETNS, &value);
>> +       if (ct) {
>> +               unsigned long status = ct->status;
>> +
>> +               bpf_ct_release(ct);
>> +               if (status & IPS_CONFIRMED_BIT)
>> +                       return XDP_PASS;
>> +       } else if (value != -ENOENT) {
>> +               return XDP_ABORTED;
>> +       }
> 
> Is this the only reason that you wish to expose conntrack lookup
> functions to the API?
> 
> You should be able to find out whether the TCP session is established
> by doing a TCP socket lookup and checking sk->state.

It's not possible to lookup a socket, because there is no socket. The 
traffic is forwarded through the firewall machine that runs synproxy and 
this XDP program.