[PATCH net-next 0/5] mptcp: support MSG_EOR and small cleanups

[PATCH net-next 0/5] mptcp: support MSG_EOR and small cleanups

[Matthieu Baerts (NGI0)]

This series contains various unrelated patches:

- Patches 1 & 2: support MSG_EOR instead of ignoring it.

- Patch 3: avoid duplicated code in TCP and MPTCP by using a new helper.

- Patch 4: remove duplicated condition.

- Patch 5: adapt test to reproduce bug and increase code coverage.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Gang Yan (2):
      mptcp: reduce 'overhead' from u16 to u8
      mptcp: preserve MSG_EOR semantics in sendmsg path

Geliang Tang (1):
      tcp: add recv_should_stop helper

Matthieu Baerts (NGI0) (2):
      mptcp: pm: in-kernel: remove mptcp_pm_has_addr_attr_id
      selftests: mptcp: join: recreate signal endp with same ID

 include/net/tcp.h                               |  8 +++++
 net/ipv4/tcp.c                                  |  9 ++----
 net/mptcp/pm_kernel.c                           | 24 +++------------
 net/mptcp/protocol.c                            | 41 ++++++++++++++++++-------
 net/mptcp/protocol.h                            |  3 +-
 tools/testing/selftests/net/mptcp/mptcp_join.sh |  4 +--
 6 files changed, 49 insertions(+), 40 deletions(-)
---
base-commit: 8b0e64d6c9e7feec5ba5643b4fa8b7fd54464778
change-id: 20260403-net-next-mptcp-msg_eor-misc-6b4567dd37dc

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

[PATCH net-next 1/5] mptcp: reduce 'overhead' from u16 to u8

[Matthieu Baerts (NGI0)]

From: Gang Yan <yangang@kylinos.cn>

The 'overhead' in struct mptcp_data_frag can safely use u8, as it
represents 'alignment + sizeof(mptcp_data_frag)'. With a maximum
alignment of 7('ALIGN(1, sizeof(long)) - 1'), the overhead is at most
47, well below U8_MAX and validated with BUILD_BUG_ON().

This patch also adds a field named 'unused' for further extensions.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 6 ++++++
 net/mptcp/protocol.h | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 239fb9e75c7c..79315e575d07 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -4616,6 +4616,12 @@ void __init mptcp_proto_init(void)
 	inet_register_protosw(&mptcp_protosw);
 
 	BUILD_BUG_ON(sizeof(struct mptcp_skb_cb) > sizeof_field(struct sk_buff, cb));
+
+	/* struct mptcp_data_frag: 'overhead' corresponds to the alignment
+	 * (ALIGN(1, sizeof(long)) - 1, so 8-1) + the struct's size
+	 */
+	BUILD_BUG_ON(ALIGN(1, sizeof(long)) - 1 + sizeof(struct mptcp_data_frag)
+		     > U8_MAX);
 }
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 0bd1ee860316..02031007100b 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -263,7 +263,8 @@ struct mptcp_data_frag {
 	u64 data_seq;
 	u16 data_len;
 	u16 offset;
-	u16 overhead;
+	u8 overhead;
+	u8 __unused;
 	u16 already_sent;
 	struct page *page;
 };

-- 
2.53.0

[PATCH net-next 2/5] mptcp: preserve MSG_EOR semantics in sendmsg path

[Matthieu Baerts (NGI0)]

From: Gang Yan <yangang@kylinos.cn>

Extend MPTCP's sendmsg handling to recognize and honor the MSG_EOR flag,
which marks the end of a record for application-level message boundaries.

Data fragments tagged with MSG_EOR are explicitly marked in the
mptcp_data_frag structure and skb context to prevent unintended
coalescing with subsequent data chunks. This ensures the intent of
applications using MSG_EOR is preserved across MPTCP subflows,
maintaining consistent message segmentation behavior.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 24 +++++++++++++++++++++---
 net/mptcp/protocol.h |  2 +-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 79315e575d07..e21e416cd19a 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1005,7 +1005,8 @@ static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
 				       const struct page_frag *pfrag,
 				       const struct mptcp_data_frag *df)
 {
-	return df && pfrag->page == df->page &&
+	return df && !df->eor &&
+		pfrag->page == df->page &&
 		pfrag->size - pfrag->offset > 0 &&
 		pfrag->offset == (df->offset + df->data_len) &&
 		df->data_seq + df->data_len == msk->write_seq;
@@ -1147,6 +1148,7 @@ mptcp_carve_data_frag(const struct mptcp_sock *msk, struct page_frag *pfrag,
 	dfrag->offset = offset + sizeof(struct mptcp_data_frag);
 	dfrag->already_sent = 0;
 	dfrag->page = pfrag->page;
+	dfrag->eor = 0;
 
 	return dfrag;
 }
@@ -1408,6 +1410,13 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 		mptcp_update_infinite_map(msk, ssk, mpext);
 	trace_mptcp_sendmsg_frag(mpext);
 	mptcp_subflow_ctx(ssk)->rel_write_seq += copy;
+
+	/* if this is the last chunk of a dfrag with MSG_EOR set,
+	 * mark the skb to prevent coalescing with subsequent data.
+	 */
+	if (dfrag->eor && info->sent + copy >= dfrag->data_len)
+		TCP_SKB_CB(skb)->eor = 1;
+
 	return copy;
 }
 
@@ -1868,7 +1877,8 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	long timeo;
 
 	/* silently ignore everything else */
-	msg->msg_flags &= MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL | MSG_FASTOPEN;
+	msg->msg_flags &= MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL |
+			  MSG_FASTOPEN | MSG_EOR;
 
 	lock_sock(sk);
 
@@ -1975,8 +1985,16 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 			goto do_error;
 	}
 
-	if (copied)
+	if (copied) {
+		/* mark the last dfrag with EOR if MSG_EOR was set */
+		if (msg->msg_flags & MSG_EOR) {
+			struct mptcp_data_frag *dfrag = mptcp_pending_tail(sk);
+
+			if (dfrag)
+				dfrag->eor = 1;
+		}
 		__mptcp_push_pending(sk, msg->msg_flags);
+	}
 
 out:
 	release_sock(sk);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 02031007100b..1208f317ac33 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -264,7 +264,7 @@ struct mptcp_data_frag {
 	u16 data_len;
 	u16 offset;
 	u8 overhead;
-	u8 __unused;
+	u8 eor;			/* currently using 1 bit */
 	u16 already_sent;
 	struct page *page;
 };

-- 
2.53.0

[PATCH net-next 3/5] tcp: add recv_should_stop helper

[Matthieu Baerts (NGI0)]

From: Geliang Tang <tanggeliang@kylinos.cn>

Factor out a new helper tcp_recv_should_stop() from tcp_recvmsg_locked()
and tcp_splice_read() to check whether to stop receiving. And use this
helper in mptcp_recvmsg() and mptcp_splice_read() to reduce redundant code.

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Acked-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
To: Neal Cardwell <ncardwell@google.com>
To: Kuniyuki Iwashima <kuniyu@google.com>
To: David Ahern <dsahern@kernel.org>
---
 include/net/tcp.h    |  8 ++++++++
 net/ipv4/tcp.c       |  9 ++-------
 net/mptcp/protocol.c | 11 +++--------
 3 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 565943c34b7e..6156d1d068e1 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -3077,4 +3077,12 @@ enum skb_drop_reason tcp_inbound_hash(struct sock *sk,
 		const void *saddr, const void *daddr,
 		int family, int dif, int sdif);
 
+static inline int tcp_recv_should_stop(struct sock *sk)
+{
+	return sk->sk_err ||
+	       sk->sk_state == TCP_CLOSE ||
+	       (sk->sk_shutdown & RCV_SHUTDOWN) ||
+	       signal_pending(current);
+}
+
 #endif	/* _TCP_H */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index bd2c3c4587e1..e57eaffc007a 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -888,9 +888,7 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
 		release_sock(sk);
 		lock_sock(sk);
 
-		if (sk->sk_err || sk->sk_state == TCP_CLOSE ||
-		    (sk->sk_shutdown & RCV_SHUTDOWN) ||
-		    signal_pending(current))
+		if (tcp_recv_should_stop(sk))
 			break;
 	}
 
@@ -2755,10 +2753,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
 
 		if (copied) {
 			if (!timeo ||
-			    sk->sk_err ||
-			    sk->sk_state == TCP_CLOSE ||
-			    (sk->sk_shutdown & RCV_SHUTDOWN) ||
-			    signal_pending(current))
+			    tcp_recv_should_stop(sk))
 				break;
 		} else {
 			if (sock_flag(sk, SOCK_DONE))
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index e21e416cd19a..2f4776a4f06a 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2333,11 +2333,8 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 			break;
 
 		if (copied) {
-			if (sk->sk_err ||
-			    sk->sk_state == TCP_CLOSE ||
-			    (sk->sk_shutdown & RCV_SHUTDOWN) ||
-			    !timeo ||
-			    signal_pending(current))
+			if (tcp_recv_should_stop(sk) ||
+			    !timeo)
 				break;
 		} else {
 			if (sk->sk_err) {
@@ -4520,9 +4517,7 @@ static ssize_t mptcp_splice_read(struct socket *sock, loff_t *ppos,
 		release_sock(sk);
 		lock_sock(sk);
 
-		if (sk->sk_err || sk->sk_state == TCP_CLOSE ||
-		    (sk->sk_shutdown & RCV_SHUTDOWN) ||
-		    signal_pending(current))
+		if (tcp_recv_should_stop(sk))
 			break;
 	}
 

-- 
2.53.0

[PATCH net-next 4/5] mptcp: pm: in-kernel: remove mptcp_pm_has_addr_attr_id

[Matthieu Baerts (NGI0)]

There is no need to call this helper: it will check if the address ID
attribute is set, but this attribute has already been parsed previously.

Indeed, the value has been set in 'entry->addr.id' if it was set and
positive, which is what we were looking at. Then only looking at this
already parsed value is enough, not need to re-extract all Netlink
attributes again.

Reviewed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_kernel.c | 24 +++++-------------------
 1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c
index 82e59f9c6dd9..0ebf43be9939 100644
--- a/net/mptcp/pm_kernel.c
+++ b/net/mptcp/pm_kernel.c
@@ -720,7 +720,7 @@ static void __mptcp_pm_release_addr_entry(struct mptcp_pm_addr_entry *entry)
 
 static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,
 					     struct mptcp_pm_addr_entry *entry,
-					     bool needs_id, bool replace)
+					     bool replace)
 {
 	struct mptcp_pm_addr_entry *cur, *del_entry = NULL;
 	int ret = -EINVAL;
@@ -779,7 +779,7 @@ static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,
 		}
 	}
 
-	if (!entry->addr.id && needs_id) {
+	if (!entry->addr.id) {
 find_next:
 		entry->addr.id = find_next_zero_bit(pernet->id_bitmap,
 						    MPTCP_PM_MAX_ADDR_ID + 1,
@@ -790,7 +790,7 @@ static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,
 		}
 	}
 
-	if (!entry->addr.id && needs_id)
+	if (!entry->addr.id)
 		goto out;
 
 	__set_bit(entry->addr.id, pernet->id_bitmap);
@@ -923,7 +923,7 @@ int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk,
 		return -ENOMEM;
 
 	entry->addr.port = 0;
-	ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, true, false);
+	ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, false);
 	if (ret < 0)
 		kfree(entry);
 
@@ -977,18 +977,6 @@ static int mptcp_nl_add_subflow_or_signal_addr(struct net *net,
 	return 0;
 }
 
-static bool mptcp_pm_has_addr_attr_id(const struct nlattr *attr,
-				      struct genl_info *info)
-{
-	struct nlattr *tb[MPTCP_PM_ADDR_ATTR_MAX + 1];
-
-	if (!nla_parse_nested_deprecated(tb, MPTCP_PM_ADDR_ATTR_MAX, attr,
-					 mptcp_pm_address_nl_policy, info->extack) &&
-	    tb[MPTCP_PM_ADDR_ATTR_ID])
-		return true;
-	return false;
-}
-
 /* Add an MPTCP endpoint */
 int mptcp_pm_nl_add_addr_doit(struct sk_buff *skb, struct genl_info *info)
 {
@@ -1037,9 +1025,7 @@ int mptcp_pm_nl_add_addr_doit(struct sk_buff *skb, struct genl_info *info)
 			goto out_free;
 		}
 	}
-	ret = mptcp_pm_nl_append_new_local_addr(pernet, entry,
-						!mptcp_pm_has_addr_attr_id(attr, info),
-						true);
+	ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, true);
 	if (ret < 0) {
 		GENL_SET_ERR_MSG_FMT(info, "too many addresses or duplicate one: %d", ret);
 		goto out_free;

-- 
2.53.0

Re: [PATCH net-next 4/5] mptcp: pm: in-kernel: remove mptcp_pm_has_addr_attr_id

[Matthieu Baerts]

[-- Attachment #1: Type: text/plain, Size: 1279 bytes --]

Hello,

On 03/04/2026 13:29, Matthieu Baerts (NGI0) wrote:
> There is no need to call this helper: it will check if the address ID
> attribute is set, but this attribute has already been parsed previously.
> 
> Indeed, the value has been set in 'entry->addr.id' if it was set and
> positive, which is what we were looking at. Then only looking at this
> already parsed value is enough, not need to re-extract all Netlink
> attributes again.

Sashiko [1] is complaining that endpoints with an ID 0 are now no longer
supported. But they were never supposed to: "ip mptcp endpoint add id 0"
reports an error.

In fact, this patch is for 'net': from what I see, this patch reverts
commit 584f38942626 ("mptcp: add needs_id for netlink appending addr"),
which should not have been introduced. Other tools could happily add
endpoints with an unexpected ID 0.

If that's OK with the net maintainers, I suggest dropping only this
patch: the rest of the series is OK and not related to it. I will send
this exact same patch for 'net' after having adapted the commit message
and added a "Fixes" tag.

[1]
https://sashiko.dev/#/patchset/20260403-net-next-mptcp-msg_eor-misc-v1-0-b0b33bea3fed%40kernel.org

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

[PATCH net-next 5/5] selftests: mptcp: join: recreate signal endp with same ID

[Matthieu Baerts (NGI0)]

In this "delete re-add signal" MPTCP Join subtest, the endpoint linked
to the initial subflow is removed, but readded once with different ID.

It appears that there was an issue when reusing the same ID, recently
fixed by commit d191101dee25 ("mptcp: pm: in-kernel: always set ID as
avail when rm endp"). The test then now reuses the same ID the first
time, but continue to use another one (88) the second time.

This should then cover more cases.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/615
Reviewed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
To: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index a3144d7298a5..beec41f6662a 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -4343,13 +4343,13 @@ endpoint_tests()
 		chk_mptcp_info add_addr_signal 2 add_addr_accepted 2
 		[ ${ipt} = 1 ] && ip netns exec "${ns1}" ${iptables} -D OUTPUT 1
 
-		pm_nl_add_endpoint $ns1 10.0.1.1 id 99 flags signal
+		pm_nl_add_endpoint $ns1 10.0.1.1 id 42 flags signal
 		wait_mpj 4
 		chk_subflow_nr "after re-add ID 0" 3
 		chk_mptcp_info subflows 3 subflows 3
 		chk_mptcp_info add_addr_signal 3 add_addr_accepted 2
 
-		pm_nl_del_endpoint $ns1 99 10.0.1.1
+		pm_nl_del_endpoint $ns1 42 10.0.1.1
 		sleep 0.5
 		chk_subflow_nr "after re-delete ID 0" 2
 		chk_mptcp_info subflows 2 subflows 2

-- 
2.53.0

Re: [PATCH net-next 0/5] mptcp: support MSG_EOR and small cleanups

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 03 Apr 2026 13:29:26 +0200 you wrote:
> This series contains various unrelated patches:
> 
> - Patches 1 & 2: support MSG_EOR instead of ignoring it.
> 
> - Patch 3: avoid duplicated code in TCP and MPTCP by using a new helper.
> 
> - Patch 4: remove duplicated condition.
> 
> [...]

Here is the summary with links:
  - [net-next,1/5] mptcp: reduce 'overhead' from u16 to u8
    https://git.kernel.org/netdev/net-next/c/00d46be3c319
  - [net-next,2/5] mptcp: preserve MSG_EOR semantics in sendmsg path
    https://git.kernel.org/netdev/net-next/c/7fb2f5f96499
  - [net-next,3/5] tcp: add recv_should_stop helper
    https://git.kernel.org/netdev/net-next/c/eb477fdd6803
  - [net-next,4/5] mptcp: pm: in-kernel: remove mptcp_pm_has_addr_attr_id
    (no matching commit)
  - [net-next,5/5] selftests: mptcp: join: recreate signal endp with same ID
    https://git.kernel.org/netdev/net-next/c/c4a5cb2f00f9

You are awesome, thank you!
-- 
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