FAILED: patch "[PATCH] mptcp: fastclose msk when linger time is 0" failed to apply to 6.1-stable tree

FAILED: patch "[PATCH] mptcp: fastclose msk when linger time is 0" failed to apply to 6.1-stable tree

[gregkh]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x f14d6e9c3678a067f304abba561e0c5446c7e845
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026051200-skewed-easing-cc4c@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f14d6e9c3678a067f304abba561e0c5446c7e845 Mon Sep 17 00:00:00 2001
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Mon, 27 Apr 2026 21:54:35 +0200
Subject: [PATCH] mptcp: fastclose msk when linger time is 0

The SO_LINGER socket option has been supported for a while with MPTCP
sockets [1], but it didn't cause the equivalent of a TCP reset as
expected when enabled and its time was set to 0. This was causing some
behavioural differences with TCP where some connections were not
promptly stopped as expected.

To fix that, an extra condition is checked at close() time before
sending an MP_FASTCLOSE, the MPTCP equivalent of a TCP reset.

Note that backporting up to [1] will be difficult as more changes are
needed to be able to send MP_FASTCLOSE. It seems better to stop at [2],
which was supposed to already imitate TCP.

Validated with MPTCP packetdrill tests [3].

Fixes: 268b12387460 ("mptcp: setsockopt: support SO_LINGER") [1]
Fixes: d21f83485518 ("mptcp: use fastclose on more edge scenarios") [2]
Cc: stable@vger.kernel.org
Reported-by: Lance Tuller <lance@lance0.com>
Closes: https://github.com/lance0/xfr/pull/67
Link: https://github.com/multipath-tcp/packetdrill/pull/196 [3]
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260427-net-mptcp-misc-fixes-7-1-rc2-v1-3-7432b7f279fa@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 718e910ff23f..4546a8b09884 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3302,7 +3302,8 @@ bool __mptcp_close(struct sock *sk, long timeout)
 		goto cleanup;
 	}
 
-	if (mptcp_data_avail(msk) || timeout < 0) {
+	if (mptcp_data_avail(msk) || timeout < 0 ||
+	    (sock_flag(sk, SOCK_LINGER) && !sk->sk_lingertime)) {
 		/* If the msk has read data, or the caller explicitly ask it,
 		 * do the MPTCP equivalent of TCP reset, aka MPTCP fastclose
 		 */

[PATCH 6.1.y] mptcp: fastclose msk when linger time is 0

[Sasha Levin]

From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>

[ Upstream commit f14d6e9c3678a067f304abba561e0c5446c7e845 ]

The SO_LINGER socket option has been supported for a while with MPTCP
sockets [1], but it didn't cause the equivalent of a TCP reset as
expected when enabled and its time was set to 0. This was causing some
behavioural differences with TCP where some connections were not
promptly stopped as expected.

To fix that, an extra condition is checked at close() time before
sending an MP_FASTCLOSE, the MPTCP equivalent of a TCP reset.

Note that backporting up to [1] will be difficult as more changes are
needed to be able to send MP_FASTCLOSE. It seems better to stop at [2],
which was supposed to already imitate TCP.

Validated with MPTCP packetdrill tests [3].

Fixes: 268b12387460 ("mptcp: setsockopt: support SO_LINGER") [1]
Fixes: d21f83485518 ("mptcp: use fastclose on more edge scenarios") [2]
Cc: stable@vger.kernel.org
Reported-by: Lance Tuller <lance@lance0.com>
Closes: https://github.com/lance0/xfr/pull/67
Link: https://github.com/multipath-tcp/packetdrill/pull/196 [3]
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260427-net-mptcp-misc-fixes-7-1-rc2-v1-3-7432b7f279fa@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ kept `mptcp_check_readable()` name and explicit `inet_sk_state_store(sk, TCP_CLOSE)` ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/mptcp/protocol.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 965819ddc04c9..fec40ce165101 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3154,7 +3154,8 @@ bool __mptcp_close(struct sock *sk, long timeout)
 		goto cleanup;
 	}
 
-	if (mptcp_check_readable(msk)) {
+	if (mptcp_check_readable(msk) ||
+	    (sock_flag(sk, SOCK_LINGER) && !sk->sk_lingertime)) {
 		/* the msk has read data, do the MPTCP equivalent of TCP reset */
 		inet_sk_state_store(sk, TCP_CLOSE);
 		mptcp_do_fastclose(sk);
-- 
2.53.0