[PATCH net-next 0/6] mptcp: implement .read_sock and .splice_read

[PATCH net-next 0/6] mptcp: implement .read_sock and .splice_read

[Matthieu Baerts (NGI0)]

This series is a preparation work for future in-kernel MPTCP sockets
usage. Here, two interfaces are implemented: read_sock and splice_read.
As a result of this series, splice() with MPTCP sockets -- which was
already supported -- is now improved.

- Patches 1-2: .read_sock implementation

- Patches 3-4: .splice_read implementation

- Patches 5-6: validate splice() support with MPTCP sockets.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Geliang Tang (6):
      mptcp: add eat_recv_skb helper
      mptcp: implement .read_sock
      tcp: export tcp_splice_state
      mptcp: implement .splice_read
      selftests: mptcp: add splice io mode
      selftests: mptcp: connect: cover splice mode

 include/net/tcp.h                                  |  11 ++
 net/ipv4/tcp.c                                     |  13 +-
 net/mptcp/protocol.c                               | 215 ++++++++++++++++++++-
 tools/testing/selftests/net/mptcp/Makefile         |   1 +
 tools/testing/selftests/net/mptcp/mptcp_connect.c  |  63 +++++-
 .../selftests/net/mptcp/mptcp_connect_splice.sh    |   5 +
 6 files changed, 289 insertions(+), 19 deletions(-)
---
base-commit: e75e408dc524ba32b3bd66e89d2ba1e337877bfa
change-id: 20260129-net-next-mptcp-splice-62db4a1a9c52

Best regards,
-- 
Matthieu Baerts (NGI0) <matttbe@kernel.org>

[PATCH net-next 1/6] mptcp: add eat_recv_skb helper

[Matthieu Baerts (NGI0)]

From: Geliang Tang <tanggeliang@kylinos.cn>

This patch extracts the free skb related code in __mptcp_recvmsg_mskq()
into a new helper mptcp_eat_recv_skb().

This new helper will be used in the next patch.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index f505b780f713..80f37220ef0c 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1994,6 +1994,17 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
 static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied);
 
+static void mptcp_eat_recv_skb(struct sock *sk, struct sk_buff *skb)
+{
+	/* avoid the indirect call, we know the destructor is sock_rfree */
+	skb->destructor = NULL;
+	skb->sk = NULL;
+	atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
+	sk_mem_uncharge(sk, skb->truesize);
+	__skb_unlink(skb, &sk->sk_receive_queue);
+	skb_attempt_defer_free(skb);
+}
+
 static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg,
 				size_t len, int flags, int copied_total,
 				struct scm_timestamping_internal *tss,
@@ -2048,13 +2059,7 @@ static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg,
 				break;
 			}
 
-			/* avoid the indirect call, we know the destructor is sock_rfree */
-			skb->destructor = NULL;
-			skb->sk = NULL;
-			atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
-			sk_mem_uncharge(sk, skb->truesize);
-			__skb_unlink(skb, &sk->sk_receive_queue);
-			skb_attempt_defer_free(skb);
+			mptcp_eat_recv_skb(sk, skb);
 		}
 
 		if (copied >= len)

-- 
2.51.0

[PATCH net-next 2/6] mptcp: implement .read_sock

[Matthieu Baerts (NGI0)]

From: Geliang Tang <tanggeliang@kylinos.cn>

Current in-kernel TCP sockets -- i.e. from nvme_tcp_try_recv() -- need
to call .read_sock interface of struct proto_ops, but it's not
implemented in MPTCP.

This patch implements it with reference to __tcp_read_sock() and
__mptcp_recvmsg_mskq().

Corresponding to tcp_recv_skb(), a new helper for MPTCP named
mptcp_recv_skb() is added to peek a skb from sk->sk_receive_queue.

Compared with __mptcp_recvmsg_mskq(), mptcp_read_sock() uses
sk->sk_rcvbuf as the max read length. The LISTEN status is checked
before the while loop, and mptcp_recv_skb() and mptcp_cleanup_rbuf()
are invoked after the loop. In the loop, all flags checks for
__mptcp_recvmsg_mskq() are removed.

Reviewed-by: Hannes Reinecke <hare@kernel.org>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 80f37220ef0c..c58e306ec3ef 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -4316,6 +4316,86 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock,
 	return mask;
 }
 
+static struct sk_buff *mptcp_recv_skb(struct sock *sk, u32 *off)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sk_buff *skb;
+	u32 offset;
+
+	if (!list_empty(&msk->backlog_list))
+		mptcp_move_skbs(sk);
+
+	while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
+		offset = MPTCP_SKB_CB(skb)->offset;
+		if (offset < skb->len) {
+			*off = offset;
+			return skb;
+		}
+		mptcp_eat_recv_skb(sk, skb);
+	}
+	return NULL;
+}
+
+/*
+ * Note:
+ *	- It is assumed that the socket was locked by the caller.
+ */
+static int __mptcp_read_sock(struct sock *sk, read_descriptor_t *desc,
+			     sk_read_actor_t recv_actor, bool noack)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sk_buff *skb;
+	int copied = 0;
+	u32 offset;
+
+	msk_owned_by_me(msk);
+
+	if (sk->sk_state == TCP_LISTEN)
+		return -ENOTCONN;
+	while ((skb = mptcp_recv_skb(sk, &offset)) != NULL) {
+		u32 data_len = skb->len - offset;
+		int count;
+		u32 size;
+
+		size = min_t(size_t, data_len, INT_MAX);
+		count = recv_actor(desc, skb, offset, size);
+		if (count <= 0) {
+			if (!copied)
+				copied = count;
+			break;
+		}
+
+		copied += count;
+
+		msk->bytes_consumed += count;
+		if (count < data_len) {
+			MPTCP_SKB_CB(skb)->offset += count;
+			MPTCP_SKB_CB(skb)->map_seq += count;
+			break;
+		}
+
+		mptcp_eat_recv_skb(sk, skb);
+	}
+
+	if (noack)
+		goto out;
+
+	mptcp_rcv_space_adjust(msk, copied);
+
+	if (copied > 0) {
+		mptcp_recv_skb(sk, &offset);
+		mptcp_cleanup_rbuf(msk, copied);
+	}
+out:
+	return copied;
+}
+
+static int mptcp_read_sock(struct sock *sk, read_descriptor_t *desc,
+			   sk_read_actor_t recv_actor)
+{
+	return __mptcp_read_sock(sk, desc, recv_actor, false);
+}
+
 static const struct proto_ops mptcp_stream_ops = {
 	.family		   = PF_INET,
 	.owner		   = THIS_MODULE,
@@ -4336,6 +4416,7 @@ static const struct proto_ops mptcp_stream_ops = {
 	.recvmsg	   = inet_recvmsg,
 	.mmap		   = sock_no_mmap,
 	.set_rcvlowat	   = mptcp_set_rcvlowat,
+	.read_sock	   = mptcp_read_sock,
 };
 
 static struct inet_protosw mptcp_protosw = {
@@ -4440,6 +4521,7 @@ static const struct proto_ops mptcp_v6_stream_ops = {
 	.compat_ioctl	   = inet6_compat_ioctl,
 #endif
 	.set_rcvlowat	   = mptcp_set_rcvlowat,
+	.read_sock	   = mptcp_read_sock,
 };
 
 static struct proto mptcp_v6_prot;

-- 
2.51.0

[PATCH net-next 3/6] tcp: export tcp_splice_state

[Matthieu Baerts (NGI0)]

From: Geliang Tang <tanggeliang@kylinos.cn>

Export struct tcp_splice_state and tcp_splice_data_recv() in net/tcp.h
so that they can be used by MPTCP in the next patch.

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Acked-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 include/net/tcp.h | 11 +++++++++++
 net/ipv4/tcp.c    | 13 ++-----------
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index f1cf9e6730c8..cecec1a92d5e 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -347,6 +347,15 @@ extern struct proto tcp_prot;
 #define TCP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
 #define TCP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
 
+/*
+ * TCP splice context
+ */
+struct tcp_splice_state {
+	struct pipe_inode_info *pipe;
+	size_t len;
+	unsigned int flags;
+};
+
 void tcp_tsq_work_init(void);
 
 int tcp_v4_err(struct sk_buff *skb, u32);
@@ -378,6 +387,8 @@ void tcp_rcv_space_adjust(struct sock *sk);
 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
 void tcp_twsk_destructor(struct sock *sk);
 void tcp_twsk_purge(struct list_head *net_exit_list);
+int tcp_splice_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
+			 unsigned int offset, size_t len);
 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
 			struct pipe_inode_info *pipe, size_t len,
 			unsigned int flags);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e4009158b908..6e94c5859f4b 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -318,15 +318,6 @@ EXPORT_SYMBOL(tcp_have_smc);
 struct percpu_counter tcp_sockets_allocated ____cacheline_aligned_in_smp;
 EXPORT_IPV6_MOD(tcp_sockets_allocated);
 
-/*
- * TCP splice context
- */
-struct tcp_splice_state {
-	struct pipe_inode_info *pipe;
-	size_t len;
-	unsigned int flags;
-};
-
 /*
  * Pressure flag: try to collapse.
  * Technical note: it is used by multiple contexts non atomically.
@@ -791,8 +782,8 @@ void tcp_push(struct sock *sk, int flags, int mss_now,
 	__tcp_push_pending_frames(sk, mss_now, nonagle);
 }
 
-static int tcp_splice_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
-				unsigned int offset, size_t len)
+int tcp_splice_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
+			 unsigned int offset, size_t len)
 {
 	struct tcp_splice_state *tss = rd_desc->arg.data;
 	int ret;

-- 
2.51.0

[PATCH net-next 4/6] mptcp: implement .splice_read

[Matthieu Baerts (NGI0)]

From: Geliang Tang <tanggeliang@kylinos.cn>

This patch implements .splice_read interface of mptcp struct proto_ops
as mptcp_splice_read() with reference to tcp_splice_read().

Corresponding to __tcp_splice_read(), __mptcp_splice_read() is defined,
invoking mptcp_read_sock() instead of tcp_read_sock().

mptcp_splice_read() is almost the same as tcp_splice_read(), except for
sock_rps_record_flow().

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index c58e306ec3ef..3aee29f70954 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -4396,6 +4396,118 @@ static int mptcp_read_sock(struct sock *sk, read_descriptor_t *desc,
 	return __mptcp_read_sock(sk, desc, recv_actor, false);
 }
 
+static int __mptcp_splice_read(struct sock *sk, struct tcp_splice_state *tss)
+{
+	/* Store TCP splice context information in read_descriptor_t. */
+	read_descriptor_t rd_desc = {
+		.arg.data = tss,
+		.count	  = tss->len,
+	};
+
+	return mptcp_read_sock(sk, &rd_desc, tcp_splice_data_recv);
+}
+
+/**
+ *  mptcp_splice_read - splice data from MPTCP socket to a pipe
+ * @sock:	socket to splice from
+ * @ppos:	position (not valid)
+ * @pipe:	pipe to splice to
+ * @len:	number of bytes to splice
+ * @flags:	splice modifier flags
+ *
+ * Description:
+ *    Will read pages from given socket and fill them into a pipe.
+ *
+ **/
+static ssize_t mptcp_splice_read(struct socket *sock, loff_t *ppos,
+				 struct pipe_inode_info *pipe, size_t len,
+				 unsigned int flags)
+{
+	struct tcp_splice_state tss = {
+		.pipe	= pipe,
+		.len	= len,
+		.flags	= flags,
+	};
+	struct sock *sk = sock->sk;
+	ssize_t spliced = 0;
+	int ret = 0;
+	long timeo;
+
+	/*
+	 * We can't seek on a socket input
+	 */
+	if (unlikely(*ppos))
+		return -ESPIPE;
+
+	lock_sock(sk);
+
+	mptcp_rps_record_subflows(mptcp_sk(sk));
+
+	timeo = sock_rcvtimeo(sk, sock->file->f_flags & O_NONBLOCK);
+	while (tss.len) {
+		ret = __mptcp_splice_read(sk, &tss);
+		if (ret < 0) {
+			break;
+		} else if (!ret) {
+			if (spliced)
+				break;
+			if (sock_flag(sk, SOCK_DONE))
+				break;
+			if (sk->sk_err) {
+				ret = sock_error(sk);
+				break;
+			}
+			if (sk->sk_shutdown & RCV_SHUTDOWN)
+				break;
+			if (sk->sk_state == TCP_CLOSE) {
+				/*
+				 * This occurs when user tries to read
+				 * from never connected socket.
+				 */
+				ret = -ENOTCONN;
+				break;
+			}
+			if (!timeo) {
+				ret = -EAGAIN;
+				break;
+			}
+			/* if __mptcp_splice_read() got nothing while we have
+			 * an skb in receive queue, we do not want to loop.
+			 * This might happen with URG data.
+			 */
+			if (!skb_queue_empty(&sk->sk_receive_queue))
+				break;
+			ret = sk_wait_data(sk, &timeo, NULL);
+			if (ret < 0)
+				break;
+			if (signal_pending(current)) {
+				ret = sock_intr_errno(timeo);
+				break;
+			}
+			continue;
+		}
+		tss.len -= ret;
+		spliced += ret;
+
+		if (!tss.len || !timeo)
+			break;
+		release_sock(sk);
+		lock_sock(sk);
+
+		if (sk->sk_err || sk->sk_state == TCP_CLOSE ||
+		    (sk->sk_shutdown & RCV_SHUTDOWN) ||
+		    signal_pending(current))
+			break;
+	}
+
+	release_sock(sk);
+
+	if (spliced)
+		return spliced;
+
+	return ret;
+}
+
 static const struct proto_ops mptcp_stream_ops = {
 	.family		   = PF_INET,
 	.owner		   = THIS_MODULE,
@@ -4417,6 +4529,7 @@ static const struct proto_ops mptcp_stream_ops = {
 	.mmap		   = sock_no_mmap,
 	.set_rcvlowat	   = mptcp_set_rcvlowat,
 	.read_sock	   = mptcp_read_sock,
+	.splice_read	   = mptcp_splice_read,
 };
 
 static struct inet_protosw mptcp_protosw = {
@@ -4522,6 +4635,7 @@ static const struct proto_ops mptcp_v6_stream_ops = {
 #endif
 	.set_rcvlowat	   = mptcp_set_rcvlowat,
 	.read_sock	   = mptcp_read_sock,
+	.splice_read	   = mptcp_splice_read,
 };
 
 static struct proto mptcp_v6_prot;

-- 
2.51.0

Re: [PATCH net-next 4/6] mptcp: implement .splice_read

[Matthieu Baerts]

Hello,

On 29/01/2026 20:23, Matthieu Baerts (NGI0) wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
> 
> This patch implements .splice_read interface of mptcp struct proto_ops
> as mptcp_splice_read() with reference to tcp_splice_read().
> 
> Corresponding to __tcp_splice_read(), __mptcp_splice_read() is defined,
> invoking mptcp_read_sock() instead of tcp_read_sock().
> 
> mptcp_splice_read() is almost the same as tcp_splice_read(), except for
> sock_rps_record_flow().
> 
> Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
> Reviewed-by: Mat Martineau <martineau@kernel.org>
> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
> ---
>  net/mptcp/protocol.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 114 insertions(+)
> 
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index c58e306ec3ef..3aee29f70954 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -4396,6 +4396,118 @@ static int mptcp_read_sock(struct sock *sk, read_descriptor_t *desc,
>  	return __mptcp_read_sock(sk, desc, recv_actor, false);
>  }
>  
> +static int __mptcp_splice_read(struct sock *sk, struct tcp_splice_state *tss)
> +{
> +	/* Store TCP splice context information in read_descriptor_t. */
> +	read_descriptor_t rd_desc = {
> +		.arg.data = tss,
> +		.count	  = tss->len,
> +	};
> +
> +	return mptcp_read_sock(sk, &rd_desc, tcp_splice_data_recv);
> +}
> +
> +/**
> + *  mptcp_splice_read - splice data from MPTCP socket to a pipe
> + * @sock:	socket to splice from
> + * @ppos:	position (not valid)
> + * @pipe:	pipe to splice to
> + * @len:	number of bytes to splice
> + * @flags:	splice modifier flags
> + *
> + * Description:
> + *    Will read pages from given socket and fill them into a pipe.

This comment is a copy of tcp_splice_read() where only the first line
has been adapted, but this seems to cause a new kdoc warning:

  net/mptcp/protocol.c:4424 No description found for return value of
'mptcp_splice_read'


I guess something like that should be added in a v2:

  Return:
     Amount of bytes that have been spliced.

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

[PATCH net-next 5/6] selftests: mptcp: add splice io mode

[Matthieu Baerts (NGI0)]

From: Geliang Tang <tanggeliang@kylinos.cn>

This patch adds a new 'splice' io mode for mptcp_connect to test
the newly added read_sock() and splice_read() functions of MPTCP.

do_splice() efficiently transfers data directly between two file
descriptors (infd and outfd) without copying to userspace, using
Linux's splice() system call.

Usage:
	./mptcp_connect.sh -m splice

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 tools/testing/selftests/net/mptcp/mptcp_connect.c | 63 ++++++++++++++++++++++-
 1 file changed, 62 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
index 10f6f99cfd4e..1c4fe60089a2 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
@@ -52,6 +52,7 @@ enum cfg_mode {
 	CFG_MODE_POLL,
 	CFG_MODE_MMAP,
 	CFG_MODE_SENDFILE,
+	CFG_MODE_SPLICE,
 };
 
 enum cfg_peek {
@@ -124,7 +125,7 @@ static void die_usage(void)
 	fprintf(stderr, "\t-j     -- add additional sleep at connection start and tear down "
 		"-- for MPJ tests\n");
 	fprintf(stderr, "\t-l     -- listens mode, accepts incoming connection\n");
-	fprintf(stderr, "\t-m [poll|mmap|sendfile] -- use poll(default)/mmap+write/sendfile\n");
+	fprintf(stderr, "\t-m [poll|mmap|sendfile|splice] -- use poll(default)/mmap+write/sendfile/splice\n");
 	fprintf(stderr, "\t-M mark -- set socket packet mark\n");
 	fprintf(stderr, "\t-o option -- test sockopt <option>\n");
 	fprintf(stderr, "\t-p num -- use port num\n");
@@ -935,6 +936,55 @@ static int copyfd_io_sendfile(int infd, int peerfd, int outfd,
 	return err;
 }
 
+static int do_splice(const int infd, const int outfd, const size_t len,
+		     struct wstate *winfo)
+{
+	int pipefd[2];
+	ssize_t bytes;
+	int err;
+
+	err = pipe(pipefd);
+	if (err)
+		return err;
+
+	while ((bytes = splice(infd, NULL, pipefd[1], NULL,
+			       len - winfo->total_len,
+			       SPLICE_F_MOVE | SPLICE_F_MORE)) > 0) {
+		splice(pipefd[0], NULL, outfd, NULL, bytes,
+		       SPLICE_F_MOVE | SPLICE_F_MORE);
+	}
+
+	close(pipefd[0]);
+	close(pipefd[1]);
+
+	return 0;
+}
+
+static int copyfd_io_splice(int infd, int peerfd, int outfd, unsigned int size,
+			    bool *in_closed_after_out, struct wstate *winfo)
+{
+	int err;
+
+	if (listen_mode) {
+		err = do_splice(peerfd, outfd, size, winfo);
+		if (err)
+			return err;
+
+		err = do_splice(infd, peerfd, size, winfo);
+	} else {
+		err = do_splice(infd, peerfd, size, winfo);
+		if (err)
+			return err;
+
+		shut_wr(peerfd);
+
+		err = do_splice(peerfd, outfd, size, winfo);
+		*in_closed_after_out = true;
+	}
+
+	return err;
+}
+
 static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd, struct wstate *winfo)
 {
 	bool in_closed_after_out = false;
@@ -967,6 +1017,14 @@ static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd, struct
 					 &in_closed_after_out, winfo);
 		break;
 
+	case CFG_MODE_SPLICE:
+		file_size = get_infd_size(infd);
+		if (file_size < 0)
+			return file_size;
+		ret = copyfd_io_splice(infd, peerfd, outfd, file_size,
+				       &in_closed_after_out, winfo);
+		break;
+
 	default:
 		fprintf(stderr, "Invalid mode %d\n", cfg_mode);
 
@@ -1380,12 +1438,15 @@ int parse_mode(const char *mode)
 		return CFG_MODE_MMAP;
 	if (!strcasecmp(mode, "sendfile"))
 		return CFG_MODE_SENDFILE;
+	if (!strcasecmp(mode, "splice"))
+		return CFG_MODE_SPLICE;
 
 	fprintf(stderr, "Unknown test mode: %s\n", mode);
 	fprintf(stderr, "Supported modes are:\n");
 	fprintf(stderr, "\t\t\"poll\" - interleaved read/write using poll()\n");
 	fprintf(stderr, "\t\t\"mmap\" - send entire input file (mmap+write), then read response (-l will read input first)\n");
 	fprintf(stderr, "\t\t\"sendfile\" - send entire input file (sendfile), then read response (-l will read input first)\n");
+	fprintf(stderr, "\t\t\"splice\" - send entire input file (splice), then read response (-l will read input first)\n");
 
 	die_usage();
 

-- 
2.51.0

Re: [PATCH net-next 5/6] selftests: mptcp: add splice io mode

[Matthieu Baerts]

Hello,

On 29/01/2026 20:23, Matthieu Baerts (NGI0) wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
> 
> This patch adds a new 'splice' io mode for mptcp_connect to test
> the newly added read_sock() and splice_read() functions of MPTCP.
> 
> do_splice() efficiently transfers data directly between two file
> descriptors (infd and outfd) without copying to userspace, using
> Linux's splice() system call.
> 
> Usage:
> 	./mptcp_connect.sh -m splice

(...)

> diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
> index 10f6f99cfd4e..1c4fe60089a2 100644
> --- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
> +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c

(...)

> @@ -935,6 +936,55 @@ static int copyfd_io_sendfile(int infd, int peerfd, int outfd,
>  	return err;
>  }
>  
> +static int do_splice(const int infd, const int outfd, const size_t len,
> +		     struct wstate *winfo)
> +{
> +	int pipefd[2];
> +	ssize_t bytes;
> +	int err;
> +
> +	err = pipe(pipefd);
> +	if (err)
> +		return err;
> +
> +	while ((bytes = splice(infd, NULL, pipefd[1], NULL,
> +			       len - winfo->total_len,
> +			       SPLICE_F_MOVE | SPLICE_F_MORE)) > 0) {
> +		splice(pipefd[0], NULL, outfd, NULL, bytes,
> +		       SPLICE_F_MOVE | SPLICE_F_MORE);

The review assistant rightly spotted errors with splice() are simply...
ignored! Technically, the script launching this tool will check the
integrity of the transfer, but still, that's clearly not a good practice!

Sorry for the noise, I didn't spot that when sending these patches. I
will fix the issues and send a v2 later.

pw-bot: cr

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

[PATCH net-next 6/6] selftests: mptcp: connect: cover splice mode

[Matthieu Baerts (NGI0)]

From: Geliang Tang <tanggeliang@kylinos.cn>

The "splice" alternate mode for mptcp_connect.sh/.c is available now,
this patch adds mptcp_connect_splice.sh to test it in the MPTCP CI by
default.

Note that this mode is also supported by stable kernel versions, but
optimised in this patch series.

Suggested-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 tools/testing/selftests/net/mptcp/Makefile                | 1 +
 tools/testing/selftests/net/mptcp/mptcp_connect_splice.sh | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/tools/testing/selftests/net/mptcp/Makefile b/tools/testing/selftests/net/mptcp/Makefile
index 4dd6278cd3dd..22ba0da2adb8 100644
--- a/tools/testing/selftests/net/mptcp/Makefile
+++ b/tools/testing/selftests/net/mptcp/Makefile
@@ -11,6 +11,7 @@ TEST_PROGS := \
 	mptcp_connect_checksum.sh \
 	mptcp_connect_mmap.sh \
 	mptcp_connect_sendfile.sh \
+	mptcp_connect_splice.sh \
 	mptcp_join.sh \
 	mptcp_sockopt.sh \
 	pm_netlink.sh \
diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect_splice.sh b/tools/testing/selftests/net/mptcp/mptcp_connect_splice.sh
new file mode 100755
index 000000000000..241254a966c9
--- /dev/null
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect_splice.sh
@@ -0,0 +1,5 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+MPTCP_LIB_KSFT_TEST="$(basename "${0}" .sh)" \
+	"$(dirname "${0}")/mptcp_connect.sh" -m splice "${@}"

-- 
2.51.0