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References: <20230613-so-reuseport-v2-3-b7c69a342613@isovalent.com> <20230613185647.64531-1-kuniyu@amazon.com>
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From:   Lorenz Bauer <lmb@isovalent.com>
Date:   Tue, 20 Jun 2023 15:26:05 +0100
Message-ID: <CAN+4W8ge-ZQjins-E1=GHDnsi9myFqt7pwNqMkUQHZOPHQhFvQ@mail.gmail.com>
Subject: Re: [PATCH bpf-next v2 3/6] net: remove duplicate reuseport_lookup functions
To:     Kuniyuki Iwashima <kuniyu@amazon.com>
Cc:     andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
        daniel@iogearbox.net, davem@davemloft.net, dsahern@kernel.org,
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        kpsingh@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, martin.lau@linux.dev,
        mykolal@fb.com, netdev@vger.kernel.org, pabeni@redhat.com,
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On Tue, Jun 13, 2023 at 7:57=E2=80=AFPM Kuniyuki Iwashima <kuniyu@amazon.co=
m> wrote:
>
> The assignment to result below is buggy.  Let's say SO_REUSEPROT group
> have TCP_CLOSE and TCP_ESTABLISHED sockets.
>
>   1. Find TCP_CLOSE sk and do SO_REUSEPORT lookup
>   2. result is not NULL, but the group has TCP_ESTABLISHED sk
>   3. result =3D result
>   4. Find TCP_ESTABLISHED sk, which has a higher score
>   5. result =3D result (TCP_CLOSE) <-- should be sk.
>
> Same for v6 function.

Thanks for your explanation, I think I get it now. I misunderstood
that you were worried about returning TCP_ESTABLISHED instead of
TCP_CLOSE, but it's exactly the other way around.

I have a follow up question regarding the existing code:

    result =3D lookup_reuseport(net, sk, skb,
                    saddr, sport, daddr, hnum);
    /* Fall back to scoring if group has connections */
    if (result && !reuseport_has_conns(sk))
        return result;

    result =3D result ? : sk;
    badness =3D score;

Assuming that result !=3D NULL but reuseport_has_conns() =3D=3D true, we us=
e
the reuseport socket as the result, but assign the score of sk to
badness. Shouldn't we use the score of the reuseport socket?

Thanks
Lorenz