Re: [PATCH mptcp-next 2/3] mptcp: implement .splice_eof

[Matthieu Baerts <matttbe@kernel.org>]

Hi Geliang,

Thank you for looking at that!

On 02/02/2026 10:21, Geliang Tang wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
> 
> This patch implements the .splice_eof interface for MPTCP, namely
> mptcp_splice_eof(), which sequentially calls do_tcp_splice_eof() for
> each subflow.

Can you please explain what this hook is supposed to do / used for please?
And also why the solution is to call do_tcp_splice_eof() on each subflow?

Also, I'm a bit confused: why is this needed? Does it fix something or
is it a new feature or an optimisation?

> Suggested-by: Matthieu Baerts <matttbe@kernel.org>
> Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
> ---
>  net/mptcp/protocol.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index c88882062c40..5635d196cb9f 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -4018,6 +4018,20 @@ static int mptcp_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
>  	return 0;
>  }
>  
> +static void mptcp_splice_eof(struct socket *sock)
> +{
> +	struct mptcp_subflow_context *subflow;
> +	struct sock *sk = sock->sk, *ssk;
> +
> +	lock_sock(sk);
> +	mptcp_for_each_subflow(mptcp_sk(sk), subflow) {
> +		ssk = mptcp_subflow_tcp_sock(subflow);
> +
> +		do_tcp_splice_eof(ssk);

Is it fine to call this on closed subflows? e.g. if the initial subflow
has been closed. (I didn't check, maybe that's OK)

> +	}
> +	release_sock(sk);
> +}
> +
>  static struct proto mptcp_prot = {
>  	.name		= "MPTCP",
>  	.owner		= THIS_MODULE,
> @@ -4049,6 +4063,7 @@ static struct proto mptcp_prot = {
>  	.obj_size	= sizeof(struct mptcp_sock),
>  	.slab_flags	= SLAB_TYPESAFE_BY_RCU,
>  	.no_autobind	= true,
> +	.splice_eof	= mptcp_splice_eof,
>  };
>  
>  static int mptcp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int addr_len)
> @@ -4540,6 +4555,7 @@ static const struct proto_ops mptcp_stream_ops = {
>  	.set_rcvlowat	   = mptcp_set_rcvlowat,
>  	.read_sock	   = mptcp_read_sock,
>  	.splice_read	   = mptcp_splice_read,
> +	.splice_eof	   = inet_splice_eof,

Is this line required? Will it not call inet_splice_eof() by default? (I
didn't check)

>  };
>  
>  static struct inet_protosw mptcp_protosw = {

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.