netdev - [PATCH net 5/8] mptcp: disable add_addr retransmission when timeout is 0

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Message-Id: <20250815-net-mptcp-misc-fixes-6-17-rc2-v1-5-521fe9957892@kernel.org>
Date: Fri, 15 Aug 2025 19:28:23 +0200
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>, 
 Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
 Jianguo Wu <wujianguo@...natelecom.cn>, Shuah Khan <shuah@...nel.org>, 
 Jonathan Corbet <corbet@....net>, zhenwei pi <pizhenwei@...edance.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org, 
 "Matthieu Baerts (NGI0)" <matttbe@...nel.org>, stable@...r.kernel.org, 
 Geliang Tang <geliang@...nel.org>
Subject: [PATCH net 5/8] mptcp: disable add_addr retransmission when
 timeout is 0

From: Geliang Tang <tanggeliang@...inos.cn>

When add_addr_timeout was set to 0, this caused the ADD_ADDR to be
retransmitted immediately, which looks like a buggy behaviour. Instead,
interpret 0 as "no retransmissions needed".

The documentation is updated to explicitly state that setting the timeout
to 0 disables retransmission.

Fixes: 93f323b9cccc ("mptcp: add a new sysctl add_addr_timeout")
Cc: stable@...r.kernel.org
Suggested-by: Matthieu Baerts <matttbe@...nel.org>
Signed-off-by: Geliang Tang <tanggeliang@...inos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
 Documentation/networking/mptcp-sysctl.rst |  2 ++
 net/mptcp/pm.c                            | 13 ++++++++++---
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/Documentation/networking/mptcp-sysctl.rst b/Documentation/networking/mptcp-sysctl.rst
index 5bfab01eff5a9db89e1484787953241c16e147cf..1683c139821e3ba6d9eaa3c59330a523d29f1164 100644
--- a/Documentation/networking/mptcp-sysctl.rst
+++ b/Documentation/networking/mptcp-sysctl.rst
@@ -12,6 +12,8 @@ add_addr_timeout - INTEGER (seconds)
 	resent to an MPTCP peer that has not acknowledged a previous
 	ADD_ADDR message.

+	Do not retransmit if set to 0.
+
 	The default value matches TCP_RTO_MAX. This is a per-namespace
 	sysctl.

diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index c5f6a53ce5f1e10dada52865e41b685d888a71fa..136a380602cae872b76560649c924330e5f42533 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -274,6 +274,7 @@ static void mptcp_pm_add_timer(struct timer_list *timer)
 							      add_timer);
 	struct mptcp_sock *msk = entry->sock;
 	struct sock *sk = (struct sock *)msk;
+	unsigned int timeout;

 	pr_debug("msk=%p\n", msk);

@@ -291,6 +292,10 @@ static void mptcp_pm_add_timer(struct timer_list *timer)
 		goto out;
 	}

+	timeout = mptcp_get_add_addr_timeout(sock_net(sk));
+	if (!timeout)
+		goto out;
+
 	spin_lock_bh(&msk->pm.lock);

 	if (!mptcp_pm_should_add_signal_addr(msk)) {
@@ -302,7 +307,7 @@ static void mptcp_pm_add_timer(struct timer_list *timer)

 	if (entry->retrans_times < ADD_ADDR_RETRANS_MAX)
 		sk_reset_timer(sk, timer,
-			       jiffies + mptcp_get_add_addr_timeout(sock_net(sk)));
+			       jiffies + timeout);

 	spin_unlock_bh(&msk->pm.lock);

@@ -344,6 +349,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk,
 	struct mptcp_pm_add_entry *add_entry = NULL;
 	struct sock *sk = (struct sock *)msk;
 	struct net *net = sock_net(sk);
+	unsigned int timeout;

 	lockdep_assert_held(&msk->pm.lock);

@@ -368,8 +374,9 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk,

 	timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0);
 reset_timer:
-	sk_reset_timer(sk, &add_entry->add_timer,
-		       jiffies + mptcp_get_add_addr_timeout(net));
+	timeout = mptcp_get_add_addr_timeout(net);
+	if (timeout)
+		sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout);

 	return true;
 }

-- 
2.50.0