* FAILED: patch "[PATCH] mptcp: do not reschedule the RTX timer for fallback sockets" failed to apply to 6.12-stable tree
@ 2026-09-16 16:29 gregkh
2026-09-17 3:35 ` [PATCH 6.12.y 1/2] tcp: introduce icsk->icsk_keepalive_timer Sasha Levin
0 siblings, 1 reply; 3+ messages in thread
From: gregkh @ 2026-09-16 16:29 UTC (permalink / raw)
To: pabeni, kuba, matttbe; +Cc: stable
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 e2ab913f68c7d11e2561b8a8ad0b87ffefcad667
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026091614-glory-fiftieth-da3b@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From e2ab913f68c7d11e2561b8a8ad0b87ffefcad667 Mon Sep 17 00:00:00 2001
From: Paolo Abeni <pabeni@redhat.com>
Date: Tue, 8 Sep 2026 16:07:06 +0200
Subject: [PATCH] mptcp: do not reschedule the RTX timer for fallback sockets
On fallback socket the retrans timer is a quite convoluted no-op, but
currently nothing prevents the MPTCP core to keep rescheduling it.
Additionally gate RTX timer reset to the msk not being fallen back to
TCP yet. To avoid adding multiple tests in fast-path, use a new flags
bit for such condition.
The RTX enable bit is clear at close time and set before the msk could
start retransmitting, with a couple of caveats:
- passive sockets inherit the bit from the listener msk; set the bit on
such socket to avoid flipping it in the fast-path, even if the
listener will obviously never retransmit.
- while fastopening (MPTFO), mptcp_sendmsg_fastopen still ends-up
calling mptcp_connect via tcp_sendmsg_fastopen ->
__inet_stream_connect(ssk->sk_socket), and the first subflow's
sk_socket points to the msk one.
Fixes: b51f9b80c032 ("mptcp: introduce MPTCP retransmission timer")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260908-net-mptcp-misc-fixes-7-3-rc1-v2-1-df1de70348b6@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index e1f08f71cdb1..be59651e708e 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -95,6 +95,7 @@ bool __mptcp_try_fallback(struct mptcp_sock *msk, int fb_mib)
msk->allow_subflows = false;
set_bit(MPTCP_FALLBACK_DONE, &msk->flags);
+ clear_bit(MPTCP_RTX_ENABLED, &msk->flags);
__MPTCP_INC_STATS(net, fb_mib);
spin_unlock_bh(&msk->fallback_lock);
return true;
@@ -1084,13 +1085,14 @@ static bool mptcp_rtx_timer_pending(struct sock *sk)
static void mptcp_reset_rtx_timer(struct sock *sk)
{
+ struct mptcp_sock *msk = mptcp_sk(sk);
unsigned long tout;
- /* prevent rescheduling on close */
- if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE))
+ /* Prevent rescheduling on close and in case of fallback. */
+ if (!test_bit(MPTCP_RTX_ENABLED, &msk->flags))
return;
- tout = mptcp_sk(sk)->timer_ival;
+ tout = msk->timer_ival;
sk_reset_timer(sk, &sk->mptcp_retransmit_timer, jiffies + tout);
}
@@ -3323,6 +3325,9 @@ void mptcp_set_state(struct sock *sk, int state)
* transition from TCP_SYN_RECV to TCP_CLOSE_WAIT.
*/
break;
+ case TCP_CLOSE:
+ clear_bit(MPTCP_RTX_ENABLED, &mptcp_sk(sk)->flags);
+ fallthrough;
default:
if (oldstate == TCP_ESTABLISHED || oldstate == TCP_CLOSE_WAIT)
MPTCP_DEC_STATS(sock_net(sk), MPTCP_MIB_CURRESTAB);
@@ -4141,6 +4146,7 @@ static int mptcp_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
if (IS_ERR(ssk))
return PTR_ERR(ssk);
+ set_bit(MPTCP_RTX_ENABLED, &msk->flags);
mptcp_set_state(sk, TCP_SYN_SENT);
subflow = mptcp_subflow_ctx(ssk);
#ifdef CONFIG_TCP_MD5SIG
@@ -4288,6 +4294,7 @@ static int mptcp_listen(struct socket *sock, int backlog)
goto unlock;
}
+ set_bit(MPTCP_RTX_ENABLED, &msk->flags);
mptcp_set_state(sk, TCP_LISTEN);
sock_set_flag(sk, SOCK_RCU_FREE);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 87ccb84e9927..2b4c27426477 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -116,6 +116,7 @@
#define MPTCP_WORK_RTX 1
#define MPTCP_FALLBACK_DONE 2
#define MPTCP_WORK_CLOSE_SUBFLOW 3
+#define MPTCP_RTX_ENABLED 4
/* MPTCP socket release cb flags */
#define MPTCP_PUSH_PENDING 1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH 6.12.y 1/2] tcp: introduce icsk->icsk_keepalive_timer
2026-09-16 16:29 FAILED: patch "[PATCH] mptcp: do not reschedule the RTX timer for fallback sockets" failed to apply to 6.12-stable tree gregkh
@ 2026-09-17 3:35 ` Sasha Levin
2026-09-17 3:35 ` [PATCH 6.12.y 2/2] mptcp: do not reschedule the RTX timer for fallback sockets Sasha Levin
0 siblings, 1 reply; 3+ messages in thread
From: Sasha Levin @ 2026-09-17 3:35 UTC (permalink / raw)
To: stable; +Cc: Eric Dumazet, Kuniyuki Iwashima, Jakub Kicinski, Sasha Levin
From: Eric Dumazet <edumazet@google.com>
[ Upstream commit 08dfe370239e53494453cee1e2ded2cdaa1efd12 ]
sk->sk_timer has been used for TCP keepalives.
Keepalive timers are not in fast path, we want to use sk->sk_timer
storage for retransmit timers, for better cache locality.
Create icsk->icsk_keepalive_timer and change keepalive
code to no longer use sk->sk_timer.
Added space is reclaimed in the following patch.
This includes changes to MPTCP, which was also using sk_timer.
Alias icsk->mptcp_tout_timer and icsk->icsk_keepalive_timer
for inet_sk_diag_fill() sake.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20251124175013.1473655-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable dependency adaptation for e2ab913f68c7d11e2561b8a8ad0b87ffefcad667:
Retain the 6.12 from_timer() API, icsk_timeout fields, documentation
format and existing inet_csk_{reset,delete}_keepalive_timer() helpers.
Convert the DCCP keepalive callback as well, since DCCP still shares the
inet_csk timer initialization on this branch. Do not add TCP-only timer
helper functions from newer kernels.
Include the MPTCP portion of 9a5e5334adc03: alias sk_timer storage as
mptcp_retransmit_timer and migrate every MPTCP retransmit timer user.
TCP and DCCP retain their existing icsk_retransmit_timer storage.
Adapt the fallback accounting preparation from c65c2e3bae69, authored by
Paolo Abeni. Move the existing __mptcp_try_fallback() from protocol.h to
protocol.c, pass its fallback MIB through the existing callers, and add
the matching counters. Preserve the mptcp_subflow_early_fallback() name
and use the stable simultaneous-connect and blackhole fallback paths.
This supplies the fallback-helper context expected by the target.
No new functions are introduced. The target's RTX enable-bit fix remains
in the target commit; this dependency only prepares its application.
Stable-dep-of: e2ab913f68c7 ("mptcp: do not reschedule the RTX timer for fallback sockets")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../net_cachelines/inet_connection_sock.rst | 1 +
include/net/inet_connection_sock.h | 11 ++-
include/net/sock.h | 6 +-
net/dccp/timer.c | 4 +-
net/ipv4/inet_connection_sock.c | 10 +--
net/ipv4/inet_diag.c | 4 +-
net/ipv4/tcp_ipv4.c | 4 +-
net/ipv4/tcp_timer.c | 5 +-
net/ipv6/tcp_ipv6.c | 4 +-
net/mptcp/ctrl.c | 4 +-
net/mptcp/mib.c | 5 ++
net/mptcp/mib.h | 5 ++
net/mptcp/options.c | 6 +-
net/mptcp/protocol.c | 70 +++++++++++--------
net/mptcp/protocol.h | 31 +++-----
net/mptcp/subflow.c | 10 +--
.../selftests/bpf/progs/bpf_iter_tcp4.c | 4 +-
.../selftests/bpf/progs/bpf_iter_tcp6.c | 4 +-
18 files changed, 107 insertions(+), 81 deletions(-)
diff --git a/Documentation/networking/net_cachelines/inet_connection_sock.rst b/Documentation/networking/net_cachelines/inet_connection_sock.rst
index 7a911dc95652e..ffae3c419649e 100644
--- a/Documentation/networking/net_cachelines/inet_connection_sock.rst
+++ b/Documentation/networking/net_cachelines/inet_connection_sock.rst
@@ -14,6 +14,7 @@ struct_inet_bind2_bucket icsk_bind2_hash read_mostly -
unsigned_long icsk_timeout read_mostly - inet_csk_reset_xmit_timer,tcp_connect
struct_timer_list icsk_retransmit_timer read_mostly - inet_csk_reset_xmit_timer,tcp_connect
struct_timer_list icsk_delack_timer read_mostly - inet_csk_reset_xmit_timer,tcp_connect
+struct_timer_list icsk_keepalive_timer - -
u32 icsk_rto read_write - tcp_cwnd_validate,tcp_schedule_loss_probe,tcp_connect_init,tcp_connect,tcp_write_xmit,tcp_push_one
u32 icsk_rto_min - -
u32 icsk_delack_max - -
diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index 41354036b0c87..e8ee9164ec5ac 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -62,6 +62,9 @@ struct inet_connection_sock_af_ops {
* @icsk_bind2_hash: Bind node in the bhash2 table
* @icsk_timeout: Timeout
* @icsk_retransmit_timer: Resend (no ack)
+ * @icsk_delack_timer: Delayed ACK timer
+ * @icsk_keepalive_timer: Keepalive timer
+ * @mptcp_tout_timer: MPTCP timeout timer
* @icsk_rto: Retransmit timeout
* @icsk_pmtu_cookie Last pmtu seen by socket
* @icsk_ca_ops Pluggable congestion control hook
@@ -88,8 +91,12 @@ struct inet_connection_sock {
struct inet_bind_bucket *icsk_bind_hash;
struct inet_bind2_bucket *icsk_bind2_hash;
unsigned long icsk_timeout;
- struct timer_list icsk_retransmit_timer;
- struct timer_list icsk_delack_timer;
+ struct timer_list icsk_retransmit_timer;
+ struct timer_list icsk_delack_timer;
+ union {
+ struct timer_list icsk_keepalive_timer;
+ struct timer_list mptcp_tout_timer;
+ };
__u32 icsk_rto;
__u32 icsk_rto_min;
__u32 icsk_delack_max;
diff --git a/include/net/sock.h b/include/net/sock.h
index dffbaaa7fe493..416d96f443246 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -300,6 +300,7 @@ struct sk_filter;
* @sk_txrehash: enable TX hash rethink
* @sk_filter: socket filtering instructions
* @sk_timer: sock cleanup timer
+ * @mptcp_retransmit_timer: MPTCP retransmit timer
* @sk_stamp: time stamp of last packet received
* @sk_stamp_seq: lock for accessing sk_stamp on 32 bit architectures only
* @sk_tsflags: SO_TIMESTAMPING flags
@@ -465,7 +466,10 @@ struct sock {
u32 sk_dst_pending_confirm;
u32 sk_pacing_status; /* see enum sk_pacing */
struct page_frag sk_frag;
- struct timer_list sk_timer;
+ union {
+ struct timer_list sk_timer;
+ struct timer_list mptcp_retransmit_timer;
+ };
unsigned long sk_pacing_rate; /* bytes per second */
atomic_t sk_zckey;
diff --git a/net/dccp/timer.c b/net/dccp/timer.c
index a4cfb47b60e52..fc1d88d6bc3fb 100644
--- a/net/dccp/timer.c
+++ b/net/dccp/timer.c
@@ -160,7 +160,9 @@ static void dccp_write_timer(struct timer_list *t)
static void dccp_keepalive_timer(struct timer_list *t)
{
- struct sock *sk = from_timer(sk, t, sk_timer);
+ struct inet_connection_sock *icsk =
+ from_timer(icsk, t, icsk_keepalive_timer);
+ struct sock *sk = &icsk->icsk_inet.sk;
pr_err("dccp should not use a keepalive timer !\n");
sock_put(sk);
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 117a424d1fee3..18e95dd367843 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -750,7 +750,7 @@ void inet_csk_init_xmit_timers(struct sock *sk,
timer_setup(&icsk->icsk_retransmit_timer, retransmit_handler, 0);
timer_setup(&icsk->icsk_delack_timer, delack_handler, 0);
- timer_setup(&sk->sk_timer, keepalive_handler, 0);
+ timer_setup(&icsk->icsk_keepalive_timer, keepalive_handler, 0);
icsk->icsk_pending = icsk->icsk_ack.pending = 0;
}
EXPORT_SYMBOL(inet_csk_init_xmit_timers);
@@ -763,7 +763,7 @@ void inet_csk_clear_xmit_timers(struct sock *sk)
sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
sk_stop_timer(sk, &icsk->icsk_delack_timer);
- sk_stop_timer(sk, &sk->sk_timer);
+ sk_stop_timer(sk, &icsk->icsk_keepalive_timer);
}
EXPORT_SYMBOL(inet_csk_clear_xmit_timers);
@@ -778,18 +778,18 @@ void inet_csk_clear_xmit_timers_sync(struct sock *sk)
sk_stop_timer_sync(sk, &icsk->icsk_retransmit_timer);
sk_stop_timer_sync(sk, &icsk->icsk_delack_timer);
- sk_stop_timer_sync(sk, &sk->sk_timer);
+ sk_stop_timer_sync(sk, &icsk->icsk_keepalive_timer);
}
void inet_csk_delete_keepalive_timer(struct sock *sk)
{
- sk_stop_timer(sk, &sk->sk_timer);
+ sk_stop_timer(sk, &inet_csk(sk)->icsk_keepalive_timer);
}
EXPORT_SYMBOL(inet_csk_delete_keepalive_timer);
void inet_csk_reset_keepalive_timer(struct sock *sk, unsigned long len)
{
- sk_reset_timer(sk, &sk->sk_timer, jiffies + len);
+ sk_reset_timer(sk, &inet_csk(sk)->icsk_keepalive_timer, jiffies + len);
}
EXPORT_SYMBOL(inet_csk_reset_keepalive_timer);
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index f2de2f2962595..01b6b50ae11d4 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -319,11 +319,11 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk,
r->idiag_retrans = icsk->icsk_probes_out;
r->idiag_expires =
jiffies_delta_to_msecs(icsk->icsk_timeout - jiffies);
- } else if (timer_pending(&sk->sk_timer)) {
+ } else if (timer_pending(&icsk->icsk_keepalive_timer)) {
r->idiag_timer = 2;
r->idiag_retrans = icsk->icsk_probes_out;
r->idiag_expires =
- jiffies_delta_to_msecs(sk->sk_timer.expires - jiffies);
+ jiffies_delta_to_msecs(icsk->icsk_keepalive_timer.expires - jiffies);
}
if ((ext & (1 << (INET_DIAG_INFO - 1))) && handler->idiag_info_size) {
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 2b7c580e37281..36862681731f2 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2919,9 +2919,9 @@ static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i)
} else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
timer_active = 4;
timer_expires = icsk->icsk_timeout;
- } else if (timer_pending(&sk->sk_timer)) {
+ } else if (timer_pending(&icsk->icsk_keepalive_timer)) {
timer_active = 2;
- timer_expires = sk->sk_timer.expires;
+ timer_expires = icsk->icsk_keepalive_timer.expires;
} else {
timer_active = 0;
timer_expires = jiffies;
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index a58094b0acd4f..566e4bf1b5eff 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -755,8 +755,9 @@ EXPORT_IPV6_MOD_GPL(tcp_set_keepalive);
static void tcp_keepalive_timer (struct timer_list *t)
{
- struct sock *sk = from_timer(sk, t, sk_timer);
- struct inet_connection_sock *icsk = inet_csk(sk);
+ struct inet_connection_sock *icsk =
+ from_timer(icsk, t, icsk_keepalive_timer);
+ struct sock *sk = &icsk->icsk_inet.sk;
struct tcp_sock *tp = tcp_sk(sk);
u32 elapsed;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 84efaf846f07f..c8c6b7625e6d4 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -2177,9 +2177,9 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
} else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
timer_active = 4;
timer_expires = icsk->icsk_timeout;
- } else if (timer_pending(&sp->sk_timer)) {
+ } else if (timer_pending(&icsk->icsk_keepalive_timer)) {
timer_active = 2;
- timer_expires = sp->sk_timer.expires;
+ timer_expires = icsk->icsk_keepalive_timer.expires;
} else {
timer_active = 0;
timer_expires = jiffies;
diff --git a/net/mptcp/ctrl.c b/net/mptcp/ctrl.c
index 0d60556cfefab..34169b1cb924a 100644
--- a/net/mptcp/ctrl.c
+++ b/net/mptcp/ctrl.c
@@ -407,9 +407,9 @@ void mptcp_active_detect_blackhole(struct sock *ssk, bool expired)
if (subflow->request_mptcp && ssk->sk_state == TCP_SYN_SENT) {
if (timeouts == 2 || (timeouts < 2 && expired)) {
- MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPCAPABLEACTIVEDROP);
subflow->mpc_drop = 1;
- mptcp_subflow_early_fallback(mptcp_sk(subflow->conn), subflow);
+ mptcp_subflow_early_fallback(mptcp_sk(subflow->conn), subflow,
+ MPTCP_MIB_MPCAPABLEACTIVEDROP);
}
} else if (ssk->sk_state == TCP_SYN_SENT) {
subflow->mpc_drop = 0;
diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c
index 19eb9292bd609..7d65c507427dc 100644
--- a/net/mptcp/mib.c
+++ b/net/mptcp/mib.c
@@ -79,6 +79,11 @@ static const struct snmp_mib mptcp_snmp_list[] = {
SNMP_MIB_ITEM("RcvWndConflict", MPTCP_MIB_RCVWNDCONFLICT),
SNMP_MIB_ITEM("MPCurrEstab", MPTCP_MIB_CURRESTAB),
SNMP_MIB_ITEM("Blackhole", MPTCP_MIB_BLACKHOLE),
+ SNMP_MIB_ITEM("MPCapableDataFallback", MPTCP_MIB_MPCAPABLEDATAFALLBACK),
+ SNMP_MIB_ITEM("MD5SigFallback", MPTCP_MIB_MD5SIGFALLBACK),
+ SNMP_MIB_ITEM("DssFallback", MPTCP_MIB_DSSFALLBACK),
+ SNMP_MIB_ITEM("SimultConnectFallback", MPTCP_MIB_SIMULTCONNFALLBACK),
+ SNMP_MIB_ITEM("FallbackFailed", MPTCP_MIB_FALLBACKFAILED),
SNMP_MIB_SENTINEL
};
diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h
index 128282982843a..8776cfc77b975 100644
--- a/net/mptcp/mib.h
+++ b/net/mptcp/mib.h
@@ -80,6 +80,11 @@ enum linux_mptcp_mib_field {
MPTCP_MIB_RCVWNDCONFLICT, /* Conflict with while updating msk rcv wnd */
MPTCP_MIB_CURRESTAB, /* Current established MPTCP connections */
MPTCP_MIB_BLACKHOLE, /* A blackhole has been detected */
+ MPTCP_MIB_MPCAPABLEDATAFALLBACK, /* No DSS/MPC+data on first established packet */
+ MPTCP_MIB_MD5SIGFALLBACK, /* Conflicting TCP option enabled */
+ MPTCP_MIB_DSSFALLBACK, /* Bad or missing DSS */
+ MPTCP_MIB_SIMULTCONNFALLBACK, /* Simultaneous connect */
+ MPTCP_MIB_FALLBACKFAILED, /* Can't fallback due to msk status */
__MPTCP_MIB_MAX
};
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 41aa6c9442586..5555b550855bf 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -472,7 +472,7 @@ bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
if (subflow->request_mptcp) {
if (unlikely(subflow_simultaneous_connect(sk))) {
- WARN_ON_ONCE(!mptcp_try_fallback(sk));
+ WARN_ON_ONCE(!mptcp_try_fallback(sk, MPTCP_MIB_SIMULTCONNFALLBACK));
/* Ensure mptcp_finish_connect() will not process the
* MPC handshake.
@@ -1042,8 +1042,10 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
if (subflow->mp_join)
goto reset;
subflow->mp_capable = 0;
- if (!mptcp_try_fallback(ssk))
+ if (!mptcp_try_fallback(ssk, MPTCP_MIB_MPCAPABLEDATAFALLBACK)) {
+ MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_FALLBACKFAILED);
goto reset;
+ }
pr_fallback(msk);
return false;
}
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 8b61fe656ec66..fa77eb4ad201b 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -67,6 +67,26 @@ static const struct proto_ops *mptcp_fallback_tcp_ops(const struct sock *sk)
return &inet_stream_ops;
}
+bool __mptcp_try_fallback(struct mptcp_sock *msk, int fb_mib)
+{
+ struct net *net = sock_net((struct sock *)msk);
+
+ if (__mptcp_check_fallback(msk))
+ return true;
+
+ spin_lock_bh(&msk->fallback_lock);
+ if (!msk->allow_infinite_fallback) {
+ spin_unlock_bh(&msk->fallback_lock);
+ return false;
+ }
+
+ msk->allow_subflows = false;
+ set_bit(MPTCP_FALLBACK_DONE, &msk->flags);
+ __MPTCP_INC_STATS(net, fb_mib);
+ spin_unlock_bh(&msk->fallback_lock);
+ return true;
+}
+
static int __mptcp_socket_create(struct mptcp_sock *msk)
{
struct mptcp_subflow_context *subflow;
@@ -414,9 +434,7 @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb)
static void mptcp_stop_rtx_timer(struct sock *sk)
{
- struct inet_connection_sock *icsk = inet_csk(sk);
-
- sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
+ sk_stop_timer(sk, &sk->mptcp_retransmit_timer);
mptcp_sk(sk)->timer_ival = 0;
}
@@ -659,10 +677,7 @@ static bool mptcp_check_data_fin(struct sock *sk)
static void mptcp_dss_corruption(struct mptcp_sock *msk, struct sock *ssk)
{
- if (mptcp_try_fallback(ssk)) {
- MPTCP_INC_STATS(sock_net(ssk),
- MPTCP_MIB_DSSCORRUPTIONFALLBACK);
- } else {
+ if (!mptcp_try_fallback(ssk, MPTCP_MIB_DSSCORRUPTIONFALLBACK)) {
MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSCORRUPTIONRESET);
mptcp_subflow_reset(ssk);
}
@@ -973,12 +988,11 @@ static void __mptcp_flush_join_list(struct sock *sk, struct list_head *join_list
static bool mptcp_rtx_timer_pending(struct sock *sk)
{
- return timer_pending(&inet_csk(sk)->icsk_retransmit_timer);
+ return timer_pending(&sk->mptcp_retransmit_timer);
}
static void mptcp_reset_rtx_timer(struct sock *sk)
{
- struct inet_connection_sock *icsk = inet_csk(sk);
unsigned long tout;
/* prevent rescheduling on close */
@@ -986,7 +1000,7 @@ static void mptcp_reset_rtx_timer(struct sock *sk)
return;
tout = mptcp_sk(sk)->timer_ival;
- sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + tout);
+ sk_reset_timer(sk, &sk->mptcp_retransmit_timer, jiffies + tout);
}
bool mptcp_schedule_work(struct sock *sk)
@@ -1293,12 +1307,12 @@ static void mptcp_update_infinite_map(struct mptcp_sock *msk,
mpext->infinite_map = 1;
mpext->data_len = 0;
- if (!mptcp_try_fallback(ssk)) {
+ if (!mptcp_try_fallback(ssk, MPTCP_MIB_INFINITEMAPTX)) {
+ MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_FALLBACKFAILED);
mptcp_subflow_reset(ssk);
return;
}
- MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPTX);
mptcp_subflow_ctx(ssk)->send_infinite_map = 0;
pr_fallback(msk);
}
@@ -2390,9 +2404,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
static void mptcp_retransmit_timer(struct timer_list *t)
{
- struct inet_connection_sock *icsk = from_timer(icsk, t,
- icsk_retransmit_timer);
- struct sock *sk = &icsk->icsk_inet.sk;
+ struct sock *sk = from_timer(sk, t, mptcp_retransmit_timer);
struct mptcp_sock *msk = mptcp_sk(sk);
bh_lock_sock(sk);
@@ -2410,7 +2422,9 @@ static void mptcp_retransmit_timer(struct timer_list *t)
static void mptcp_tout_timer(struct timer_list *t)
{
- struct sock *sk = from_timer(sk, t, sk_timer);
+ struct inet_connection_sock *icsk =
+ from_timer(icsk, t, mptcp_tout_timer);
+ struct sock *sk = &icsk->icsk_inet.sk;
mptcp_schedule_work(sk);
sock_put(sk);
@@ -2853,7 +2867,7 @@ void mptcp_reset_tout_timer(struct mptcp_sock *msk, unsigned long fail_tout)
*/
timeout = inet_csk(sk)->icsk_mtup.probe_timestamp ? close_timeout : fail_tout;
- sk_reset_timer(sk, &sk->sk_timer, timeout);
+ sk_reset_timer(sk, &inet_csk(sk)->mptcp_tout_timer, timeout);
}
static void mptcp_mp_fail_no_response(struct mptcp_sock *msk)
@@ -2986,9 +3000,8 @@ static void __mptcp_init_sock(struct sock *sk)
mptcp_pm_data_init(msk);
spin_lock_init(&msk->fallback_lock);
- /* re-use the csk retrans timer for MPTCP-level retrans */
- timer_setup(&msk->sk.icsk_retransmit_timer, mptcp_retransmit_timer, 0);
- timer_setup(&sk->sk_timer, mptcp_tout_timer, 0);
+ timer_setup(&sk->mptcp_retransmit_timer, mptcp_retransmit_timer, 0);
+ timer_setup(&msk->sk.mptcp_tout_timer, mptcp_tout_timer, 0);
}
static void mptcp_ca_reset(struct sock *sk)
@@ -3190,7 +3203,7 @@ static void __mptcp_destroy_sock(struct sock *sk)
might_sleep();
mptcp_stop_rtx_timer(sk);
- sk_stop_timer(sk, &sk->sk_timer);
+ sk_stop_timer(sk, &inet_csk(sk)->mptcp_tout_timer);
msk->pm.status = 0;
mptcp_release_sched(msk);
@@ -3936,16 +3949,15 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
* TCP option space.
*/
if (rcu_access_pointer(tcp_sk(ssk)->md5sig_info))
- mptcp_subflow_early_fallback(msk, subflow);
+ mptcp_subflow_early_fallback(msk, subflow, MPTCP_MIB_MD5SIGFALLBACK);
#endif
if (subflow->request_mptcp) {
- if (mptcp_active_should_disable(sk)) {
- MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPCAPABLEACTIVEDISABLED);
- mptcp_subflow_early_fallback(msk, subflow);
- } else if (mptcp_token_new_connect(ssk) < 0) {
- MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_TOKENFALLBACKINIT);
- mptcp_subflow_early_fallback(msk, subflow);
- }
+ if (mptcp_active_should_disable(sk))
+ mptcp_subflow_early_fallback(msk, subflow,
+ MPTCP_MIB_MPCAPABLEACTIVEDISABLED);
+ else if (mptcp_token_new_connect(ssk) < 0)
+ mptcp_subflow_early_fallback(msk, subflow,
+ MPTCP_MIB_TOKENFALLBACKINIT);
}
WRITE_ONCE(msk->write_seq, subflow->idsn);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 36f3f5b34a5d6..defb5563d176c 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -844,7 +844,7 @@ static inline void mptcp_stop_tout_timer(struct sock *sk)
if (!inet_csk(sk)->icsk_mtup.probe_timestamp)
return;
- sk_stop_timer(sk, &sk->sk_timer);
+ sk_stop_timer(sk, &inet_csk(sk)->mptcp_tout_timer);
inet_csk(sk)->icsk_mtup.probe_timestamp = 0;
}
@@ -1215,24 +1215,6 @@ static inline bool mptcp_check_fallback(const struct sock *sk)
return __mptcp_check_fallback(msk);
}
-static inline bool __mptcp_try_fallback(struct mptcp_sock *msk)
-{
- if (__mptcp_check_fallback(msk)) {
- pr_debug("TCP fallback already done (msk=%p)\n", msk);
- return true;
- }
- spin_lock_bh(&msk->fallback_lock);
- if (!msk->allow_infinite_fallback) {
- spin_unlock_bh(&msk->fallback_lock);
- return false;
- }
-
- msk->allow_subflows = false;
- set_bit(MPTCP_FALLBACK_DONE, &msk->flags);
- spin_unlock_bh(&msk->fallback_lock);
- return true;
-}
-
static inline bool __mptcp_has_initial_subflow(const struct mptcp_sock *msk)
{
struct sock *ssk = READ_ONCE(msk->first);
@@ -1242,14 +1224,16 @@ static inline bool __mptcp_has_initial_subflow(const struct mptcp_sock *msk)
TCPF_SYN_RECV | TCPF_LISTEN));
}
-static inline bool mptcp_try_fallback(struct sock *ssk)
+bool __mptcp_try_fallback(struct mptcp_sock *msk, int fb_mib);
+
+static inline bool mptcp_try_fallback(struct sock *ssk, int fb_mib)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
struct sock *sk = subflow->conn;
struct mptcp_sock *msk;
msk = mptcp_sk(sk);
- if (!__mptcp_try_fallback(msk))
+ if (!__mptcp_try_fallback(msk, fb_mib))
return false;
if (READ_ONCE(msk->snd_data_fin_enable) && !(ssk->sk_shutdown & SEND_SHUTDOWN)) {
gfp_t saved_allocation = ssk->sk_allocation;
@@ -1268,11 +1252,12 @@ static inline bool mptcp_try_fallback(struct sock *ssk)
#define pr_fallback(a) pr_debug("%s:fallback to TCP (msk=%p)\n", __func__, a)
static inline void mptcp_subflow_early_fallback(struct mptcp_sock *msk,
- struct mptcp_subflow_context *subflow)
+ struct mptcp_subflow_context *subflow,
+ int fb_mib)
{
pr_fallback(msk);
subflow->request_mptcp = 0;
- WARN_ON_ONCE(!__mptcp_try_fallback(msk));
+ WARN_ON_ONCE(!__mptcp_try_fallback(msk, fb_mib));
}
static inline bool mptcp_check_infinite_map(struct sk_buff *skb)
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 4fc9a5a788761..30d054a6ac917 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -546,11 +546,13 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
mptcp_get_options(skb, &mp_opt);
if (subflow->request_mptcp) {
if (!(mp_opt.suboptions & OPTION_MPTCP_MPC_SYNACK)) {
- if (!mptcp_try_fallback(sk))
+ if (!mptcp_try_fallback(sk,
+ MPTCP_MIB_MPCAPABLEACTIVEFALLBACK)) {
+ MPTCP_INC_STATS(sock_net(sk),
+ MPTCP_MIB_FALLBACKFAILED);
goto do_reset;
+ }
- MPTCP_INC_STATS(sock_net(sk),
- MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
pr_fallback(msk);
goto fallback;
}
@@ -1400,7 +1402,7 @@ static bool subflow_check_data_avail(struct sock *ssk)
return true;
}
- if (!mptcp_try_fallback(ssk)) {
+ if (!mptcp_try_fallback(ssk, MPTCP_MIB_DSSFALLBACK)) {
/* fatal protocol error, close the socket.
* subflow_error_report() will introduce the appropriate barriers
*/
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_tcp4.c b/tools/testing/selftests/bpf/progs/bpf_iter_tcp4.c
index 92267abb462fc..be540970fcc1f 100644
--- a/tools/testing/selftests/bpf/progs/bpf_iter_tcp4.c
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_tcp4.c
@@ -103,9 +103,9 @@ static int dump_tcp_sock(struct seq_file *seq, struct tcp_sock *tp,
} else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
timer_active = 4;
timer_expires = icsk->icsk_timeout;
- } else if (timer_pending(&sp->sk_timer)) {
+ } else if (timer_pending(&icsk->icsk_keepalive_timer)) {
timer_active = 2;
- timer_expires = sp->sk_timer.expires;
+ timer_expires = icsk->icsk_keepalive_timer.expires;
} else {
timer_active = 0;
timer_expires = bpf_jiffies64();
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_tcp6.c b/tools/testing/selftests/bpf/progs/bpf_iter_tcp6.c
index 943f7bba180e7..9f72398fc3cc3 100644
--- a/tools/testing/selftests/bpf/progs/bpf_iter_tcp6.c
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_tcp6.c
@@ -103,9 +103,9 @@ static int dump_tcp6_sock(struct seq_file *seq, struct tcp6_sock *tp,
} else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
timer_active = 4;
timer_expires = icsk->icsk_timeout;
- } else if (timer_pending(&sp->sk_timer)) {
+ } else if (timer_pending(&icsk->icsk_keepalive_timer)) {
timer_active = 2;
- timer_expires = sp->sk_timer.expires;
+ timer_expires = icsk->icsk_keepalive_timer.expires;
} else {
timer_active = 0;
timer_expires = bpf_jiffies64();
--
2.53.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH 6.12.y 2/2] mptcp: do not reschedule the RTX timer for fallback sockets
2026-09-17 3:35 ` [PATCH 6.12.y 1/2] tcp: introduce icsk->icsk_keepalive_timer Sasha Levin
@ 2026-09-17 3:35 ` Sasha Levin
0 siblings, 0 replies; 3+ messages in thread
From: Sasha Levin @ 2026-09-17 3:35 UTC (permalink / raw)
To: stable; +Cc: Paolo Abeni, Matthieu Baerts (NGI0), Jakub Kicinski, Sasha Levin
From: Paolo Abeni <pabeni@redhat.com>
[ Upstream commit e2ab913f68c7d11e2561b8a8ad0b87ffefcad667 ]
On fallback socket the retrans timer is a quite convoluted no-op, but
currently nothing prevents the MPTCP core to keep rescheduling it.
Additionally gate RTX timer reset to the msk not being fallen back to
TCP yet. To avoid adding multiple tests in fast-path, use a new flags
bit for such condition.
The RTX enable bit is clear at close time and set before the msk could
start retransmitting, with a couple of caveats:
- passive sockets inherit the bit from the listener msk; set the bit on
such socket to avoid flipping it in the fast-path, even if the
listener will obviously never retransmit.
- while fastopening (MPTFO), mptcp_sendmsg_fastopen still ends-up
calling mptcp_connect via tcp_sendmsg_fastopen ->
__inet_stream_connect(ssk->sk_socket), and the first subflow's
sk_socket points to the msk one.
Fixes: b51f9b80c032 ("mptcp: introduce MPTCP retransmission timer")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260908-net-mptcp-misc-fixes-7-3-rc1-v2-1-df1de70348b6@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/mptcp/protocol.c | 13 ++++++++++---
net/mptcp/protocol.h | 1 +
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index fa77eb4ad201b..d86696807020e 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -82,6 +82,7 @@ bool __mptcp_try_fallback(struct mptcp_sock *msk, int fb_mib)
msk->allow_subflows = false;
set_bit(MPTCP_FALLBACK_DONE, &msk->flags);
+ clear_bit(MPTCP_RTX_ENABLED, &msk->flags);
__MPTCP_INC_STATS(net, fb_mib);
spin_unlock_bh(&msk->fallback_lock);
return true;
@@ -993,13 +994,14 @@ static bool mptcp_rtx_timer_pending(struct sock *sk)
static void mptcp_reset_rtx_timer(struct sock *sk)
{
+ struct mptcp_sock *msk = mptcp_sk(sk);
unsigned long tout;
- /* prevent rescheduling on close */
- if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE))
+ /* Prevent rescheduling on close and in case of fallback. */
+ if (!test_bit(MPTCP_RTX_ENABLED, &msk->flags))
return;
- tout = mptcp_sk(sk)->timer_ival;
+ tout = msk->timer_ival;
sk_reset_timer(sk, &sk->mptcp_retransmit_timer, jiffies + tout);
}
@@ -3119,6 +3121,9 @@ void mptcp_set_state(struct sock *sk, int state)
* transition from TCP_SYN_RECV to TCP_CLOSE_WAIT.
*/
break;
+ case TCP_CLOSE:
+ clear_bit(MPTCP_RTX_ENABLED, &mptcp_sk(sk)->flags);
+ fallthrough;
default:
if (oldstate == TCP_ESTABLISHED || oldstate == TCP_CLOSE_WAIT)
MPTCP_DEC_STATS(sock_net(sk), MPTCP_MIB_CURRESTAB);
@@ -3942,6 +3947,7 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
if (IS_ERR(ssk))
return PTR_ERR(ssk);
+ set_bit(MPTCP_RTX_ENABLED, &msk->flags);
mptcp_set_state(sk, TCP_SYN_SENT);
subflow = mptcp_subflow_ctx(ssk);
#ifdef CONFIG_TCP_MD5SIG
@@ -4090,6 +4096,7 @@ static int mptcp_listen(struct socket *sock, int backlog)
goto unlock;
}
+ set_bit(MPTCP_RTX_ENABLED, &msk->flags);
mptcp_set_state(sk, TCP_LISTEN);
sock_set_flag(sk, SOCK_RCU_FREE);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index defb5563d176c..d85eb3982a3ab 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -116,6 +116,7 @@
#define MPTCP_WORK_RTX 1
#define MPTCP_FALLBACK_DONE 2
#define MPTCP_WORK_CLOSE_SUBFLOW 3
+#define MPTCP_RTX_ENABLED 4
/* MPTCP socket release cb flags */
#define MPTCP_PUSH_PENDING 1
--
2.53.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-09-17 3:35 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2026-09-16 16:29 FAILED: patch "[PATCH] mptcp: do not reschedule the RTX timer for fallback sockets" failed to apply to 6.12-stable tree gregkh
2026-09-17 3:35 ` [PATCH 6.12.y 1/2] tcp: introduce icsk->icsk_keepalive_timer Sasha Levin
2026-09-17 3:35 ` [PATCH 6.12.y 2/2] mptcp: do not reschedule the RTX timer for fallback sockets Sasha Levin
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