Re: [PATCH mptcp-next v2 2/7] mptcp: take TCP_MAXSEG handling into __mptcp_setsockopt_set_val

[Geliang Tang <geliang@kernel.org>]

Hi Gang,

On Tue, 2026-07-21 at 10:40 +0800, Gang Yan wrote:
> From: Gang Yan <yangang@kylinos.cn>
> 
> mptcp_setsockopt_all_sf is only used in 'TCP_MAXSEG', and it can be
> replaced with __mptcp_setsockopt_set_val.
> 
> Signed-off-by: Gang Yan <yangang@kylinos.cn>
> ---
>  net/ipv4/tcp.c      |  1 +
>  net/mptcp/sockopt.c | 27 ++-------------------------
>  2 files changed, 3 insertions(+), 25 deletions(-)
> 
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index b427f924608c..5915d0e62f43 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -3830,6 +3830,7 @@ int tcp_sock_set_maxseg(struct sock *sk, int
> val)
>  	WRITE_ONCE(tcp_sk(sk)->rx_opt.user_mss, val);
>  	return 0;
>  }
> +EXPORT_SYMBOL(tcp_sock_set_maxseg);
>  
>  /*
>   *	Socket option code for TCP.
> diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
> index 9c4faa0d82ef..3e000436ab94 100644
> --- a/net/mptcp/sockopt.c
> +++ b/net/mptcp/sockopt.c
> @@ -808,28 +808,6 @@ static int mptcp_setsockopt_first_sf_only(struct
> mptcp_sock *msk, int level, int
>  	return ret;
>  }
>  
> -static int mptcp_setsockopt_all_sf(struct mptcp_sock *msk, int
> level,
> -				   int optname, sockptr_t optval,
> -				   unsigned int optlen)
> -{
> -	struct mptcp_subflow_context *subflow;
> -	int ret = 0;
> -
> -	mptcp_for_each_subflow(msk, subflow) {
> -		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
> -		int err;
> -
> -		err = tcp_setsockopt(ssk, level, optname, optval,
> optlen);
> -		if (err < 0 && ret == 0)
> -			ret = err;
> -	}
> -
> -	if (!ret)
> -		sockopt_seq_inc(msk);
> -
> -	return ret;
> -}

This helper will also be used when implementing IPV6_TCLASS [1], so
don't delete it for now. Let's wait until IPV6_TCLASS is merged before
posting this patch.

Thanks,
-Geliang

[1]
https://patchwork.kernel.org/project/mptcp/patch/2617b8684039574734b8622936ef126d6a7cd519.1754986785.git.tanggeliang@kylinos.cn/

> -
>  static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int
> optname,
>  				    sockptr_t optval, unsigned int
> optlen)
>  {
> @@ -889,9 +867,8 @@ static int mptcp_setsockopt_sol_tcp(struct
> mptcp_sock *msk, int optname,
>  						 val);
>  		break;
>  	case TCP_MAXSEG:
> -		msk->maxseg = val;
> -		ret = mptcp_setsockopt_all_sf(msk, SOL_TCP, optname,
> optval,
> -					      optlen);
> +		ret = __mptcp_setsockopt_set_val(msk,
> &tcp_sock_set_maxseg,
> +						 &msk->maxseg, val);
>  		break;
>  	default:
>  		ret = -ENOPROTOOPT;