linux-kernel - Re: [PATCH 7/7] net/tcp: Don't store TCP-AO maclen on reqsk

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Date:   Tue, 21 Nov 2023 09:13:42 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Dmitry Safonov <dima@...sta.com>
Cc:     David Ahern <dsahern@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Francesco Ruggeri <fruggeri05@...il.com>,
        Salam Noureddine <noureddine@...sta.com>,
        Simon Horman <horms@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH 7/7] net/tcp: Don't store TCP-AO maclen on reqsk

On Tue, Nov 21, 2023 at 3:01 AM Dmitry Safonov <dima@...sta.com> wrote:
>
> This extra check doesn't work for a handshake when SYN segment has
> (current_key.maclen != rnext_key.maclen). It could be amended to
> preserve rnext_key.maclen instead of current_key.maclen, but that
> requires a lookup on listen socket.
>
> Originally, this extra maclen check was introduced just because it was
> cheap. Drop it and convert tcp_request_sock::maclen into boolean
> tcp_request_sock::used_tcp_ao.
>
> Fixes: 06b22ef29591 ("net/tcp: Wire TCP-AO to request sockets")
> Signed-off-by: Dmitry Safonov <dima@...sta.com>
> ---
>  include/linux/tcp.h   | 10 ++++------
>  net/ipv4/tcp_ao.c     |  4 ++--
>  net/ipv4/tcp_input.c  |  5 +++--
>  net/ipv4/tcp_output.c |  9 +++------
>  4 files changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> index 68f3d315d2e1..3af897b00920 100644
> --- a/include/linux/tcp.h
> +++ b/include/linux/tcp.h
> @@ -155,6 +155,9 @@ struct tcp_request_sock {
>         bool                            req_usec_ts;
>  #if IS_ENABLED(CONFIG_MPTCP)
>         bool                            drop_req;
> +#endif
> +#ifdef CONFIG_TCP_AO
> +       bool                            used_tcp_ao;

Why adding another 8bit field here and creating a hole ?

>  #endif
>         u32                             txhash;
>         u32                             rcv_isn;
> @@ -169,7 +172,6 @@ struct tcp_request_sock {
>  #ifdef CONFIG_TCP_AO
>         u8                              ao_keyid;
>         u8                              ao_rcv_next;
> -       u8                              maclen;

Just rename maclen here to  used_tcp_ao ?

>  #endif
>  };
>