The patch below does not apply to the 6.12-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-6.12.y git checkout FETCH_HEAD git cherry-pick -x f5ce0714623cffd00bf2a83e890d09c609b7f50a # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025082241-oxidant-avoid-0017@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From f5ce0714623cffd00bf2a83e890d09c609b7f50a Mon Sep 17 00:00:00 2001 From: Geliang Tang geliang@kernel.org Date: Fri, 15 Aug 2025 19:28:23 +0200 Subject: [PATCH] mptcp: disable add_addr retransmission when timeout is 0

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@vger.kernel.org Suggested-by: Matthieu Baerts matttbe@kernel.org Signed-off-by: Geliang Tang tanggeliang@kylinos.cn Reviewed-by: Matthieu Baerts (NGI0) matttbe@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org Link: https://patch.msgid.link/20250815-net-mptcp-misc-fixes-6-17-rc2-v1-5-521fe99... Signed-off-by: Jakub Kicinski kuba@kernel.org

diff --git a/Documentation/networking/mptcp-sysctl.rst b/Documentation/networking/mptcp-sysctl.rst index 5bfab01eff5a..1683c139821e 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 c5f6a53ce5f1..136a380602ca 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; }