Subject: Re: [PATCH net-next v2 1/2] net: introduce and use custom sockopt socket flag

From: Kuniyuki Iwashima <[email-masked]>
Date: Thu, 20 Oct 2022 11:19:26 -0700

From:   Paolo Abeni <[email-masked]>
Date:   Thu, 20 Oct 2022 19:48:51 +0200
> We will soon introduce custom setsockopt for UDP sockets, too.
> Instead of doing even more complex arbitrary checks inside
> sock_use_custom_sol_socket(), add a new socket flag and set it
> for the relevant socket types (currently only MPTCP).
> 
> Reviewed-by: Matthieu Baerts <[email-masked]>
> Signed-off-by: Paolo Abeni <[email-masked]>

Acked-by: Kuniyuki Iwashima <[email-masked]>

> ---
>  include/linux/net.h  | 1 +
>  net/mptcp/protocol.c | 4 ++++
>  net/socket.c         | 8 +-------
>  3 files changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/net.h b/include/linux/net.h
> index 711c3593c3b8..59350fd85823 100644
> --- a/include/linux/net.h
> +++ b/include/linux/net.h
> @@ -41,6 +41,7 @@ struct net;
>  #define SOCK_NOSPACE		2
>  #define SOCK_PASSCRED		3
>  #define SOCK_PASSSEC		4
> +#define SOCK_CUSTOM_SOCKOPT	5
>  
>  #ifndef ARCH_HAS_SOCKET_TYPES
>  /**
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index f599ad44ed24..0448a5c3da3c 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -2708,6 +2708,8 @@ static int mptcp_init_sock(struct sock *sk)
>  	if (ret)
>  		return ret;
>  
> +	set_bit(SOCK_CUSTOM_SOCKOPT, &sk->sk_socket->flags);
> +
>  	/* fetch the ca name; do it outside __mptcp_init_sock(), so that clone will
>  	 * propagate the correct value
>  	 */
> @@ -3684,6 +3686,8 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
>  		struct mptcp_subflow_context *subflow;
>  		struct sock *newsk = newsock->sk;
>  
> +		set_bit(SOCK_CUSTOM_SOCKOPT, &newsock->flags);
> +
>  		lock_sock(newsk);
>  
>  		/* PM/worker can now acquire the first subflow socket
> diff --git a/net/socket.c b/net/socket.c
> index 00da9ce3dba0..55c5d536e5f6 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -2199,13 +2199,7 @@ SYSCALL_DEFINE4(recv, int, fd, void __user *, ubuf, size_t, size,
>  
>  static bool sock_use_custom_sol_socket(const struct socket *sock)
>  {
> -	const struct sock *sk = sock->sk;
> -
> -	/* Use sock->ops->setsockopt() for MPTCP */
> -	return IS_ENABLED(CONFIG_MPTCP) &&
> -	       sk->sk_protocol == IPPROTO_MPTCP &&
> -	       sk->sk_type == SOCK_STREAM &&
> -	       (sk->sk_family == AF_INET || sk->sk_family == AF_INET6);
> +	return test_bit(SOCK_CUSTOM_SOCKOPT, &sock->flags);
>  }
>  
>  /*
> -- 
> 2.37.3