netdev - Re: [PATCH net] net: ipv6: fix skb hash for some RST packets

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Message-ID: <CANn89i+5QO0a-unNjMRHWqCtp6-SsXs7ERTQXS5ybSFo+G2uUQ@mail.gmail.com>
Date:   Thu, 27 Apr 2023 15:23:56 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Antoine Tenart <atenart@...nel.org>
Cc:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net] net: ipv6: fix skb hash for some RST packets

On Thu, Apr 27, 2023 at 11:22 AM Antoine Tenart <atenart@...nel.org> wrote:
>
> The skb hash comes from sk->sk_txhash when using TCP, except for some
> IPv6 RST packets. This is because in tcp_v6_send_reset when not in
> TIME_WAIT the hash is taken from sk->sk_hash, while it should come from
> sk->sk_txhash as those two hashes are not computed the same way.
>
> Packetdrill script to test the above,
>
>    0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
>   +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
>   +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
>
>   +0 > (flowlabel 0x1) S 0:0(0) <...>
>
>   // Wrong ack seq, trigger a rst.
>   +0 < S. 0:0(0) ack 0 win 4000
>
>   // Check the flowlabel matches prior one from SYN.
>   +0 > (flowlabel 0x1) R 0:0(0) <...>
>
> Fixes: 9258b8b1be2e ("ipv6: tcp: send consistent autoflowlabel in RST packets")
> Signed-off-by: Antoine Tenart <atenart@...nel.org>
> ---

Good catch, thanks !

Reviewed-by: Eric Dumazet <edumazet@...gle.com>