linux-kernel - Re: [PATCH v4 4/7] net/tcp: Allow removing current/rnext TCP-AO keys on TCP

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Date:   Wed, 29 Nov 2023 18:53:26 +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 v4 4/7] net/tcp: Allow removing current/rnext TCP-AO keys
 on TCP_LISTEN sockets

On Wed, Nov 29, 2023 at 5:57 PM Dmitry Safonov <dima@...sta.com> wrote:
>
> TCP_LISTEN sockets are not connected to any peer, so having
> current_key/rnext_key doesn't make sense.

I do not understand this patch.

This seems that the clearing should happen at disconnect time, from
tcp_disconnect() ?

Why forcing user to set a socket option to clear these fields ?

>
> The userspace may falter over this issue by setting current or rnext
> TCP-AO key before listen() syscall. setsockopt(TCP_AO_DEL_KEY) doesn't
> allow removing a key that is in use (in accordance to RFC 5925), so
> it might be inconvenient to have keys that can be destroyed only with
> listener socket.
>
> Fixes: 4954f17ddefc ("net/tcp: Introduce TCP_AO setsockopt()s")
> Signed-off-by: Dmitry Safonov <dima@...sta.com>
> ---
>  net/ipv4/tcp_ao.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
> index c8be1d526eac..bf41be6d4721 100644
> --- a/net/ipv4/tcp_ao.c
> +++ b/net/ipv4/tcp_ao.c
> @@ -1818,8 +1818,16 @@ static int tcp_ao_del_cmd(struct sock *sk, unsigned short int family,
>                 if (!new_rnext)
>                         return -ENOENT;
>         }
> -       if (cmd.del_async && sk->sk_state != TCP_LISTEN)
> -               return -EINVAL;
> +       if (sk->sk_state == TCP_LISTEN) {
> +               /* Cleaning up possible "stale" current/rnext keys state,
> +                * that may have preserved from TCP_CLOSE, before sys_listen()
> +                */
> +               ao_info->current_key = NULL;
> +               ao_info->rnext_key = NULL;
> +       } else {
> +               if (cmd.del_async)
> +                       return -EINVAL;
> +       }
>
>         if (family == AF_INET) {
>                 struct sockaddr_in *sin = (struct sockaddr_in *)&cmd.addr;
> --
> 2.43.0
>