netdev - Re: [PATCH net-next 4/6] tcp: set TCP

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Date: Fri, 4 Aug 2023 11:50:40 -0400
From: Soheil Hassas Yeganeh <soheil@...gle.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net-next 4/6] tcp: set TCP_KEEPCNT locklessly

On Fri, Aug 4, 2023 at 10:46 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> tp->keepalive_probes can be set locklessly, readers
> are already taking care of this field being potentially
> set by other threads.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>

> ---
>  net/ipv4/tcp.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 75d6359ee5750d8a867fb36ec2de960869d8c76a..e74a9593283c91aa23fe23fdd125d4ba680a542c 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -3358,10 +3358,8 @@ int tcp_sock_set_keepcnt(struct sock *sk, int val)
>         if (val < 1 || val > MAX_TCP_KEEPCNT)
>                 return -EINVAL;
>
> -       lock_sock(sk);
>         /* Paired with READ_ONCE() in keepalive_probes() */
>         WRITE_ONCE(tcp_sk(sk)->keepalive_probes, val);
> -       release_sock(sk);
>         return 0;
>  }
>  EXPORT_SYMBOL(tcp_sock_set_keepcnt);
> @@ -3471,6 +3469,8 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
>                 return tcp_sock_set_user_timeout(sk, val);
>         case TCP_KEEPINTVL:
>                 return tcp_sock_set_keepintvl(sk, val);
> +       case TCP_KEEPCNT:
> +               return tcp_sock_set_keepcnt(sk, val);
>         }
>
>         sockopt_lock_sock(sk);
> @@ -3568,12 +3568,6 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
>         case TCP_KEEPIDLE:
>                 err = tcp_sock_set_keepidle_locked(sk, val);
>                 break;
> -       case TCP_KEEPCNT:
> -               if (val < 1 || val > MAX_TCP_KEEPCNT)
> -                       err = -EINVAL;
> -               else
> -                       WRITE_ONCE(tp->keepalive_probes, val);
> -               break;
>         case TCP_SAVE_SYN:
>                 /* 0: disable, 1: enable, 2: start from ether_header */
>                 if (val < 0 || val > 2)
> --
> 2.41.0.640.ga95def55d0-goog
>