Merge branch 'mptcp-misc-fixes-for-v6-18-rc7'

Matthieu Baerts says:

====================
mptcp: misc fixes for v6.18-rc7

Here are various unrelated fixes:

- Patch 1: Fix window space computation for fallback connections which
  can affect ACK generation. A fix for v5.11.

- Patch 2: Avoid unneeded subflow-level drops due to unsynced received
  window. A fix for v5.11.

- Patch 3: Avoid premature close for fallback connections with PREEMPT
  kernels. A fix for v5.12.

- Patch 4: Reset instead of fallback in case of data in the MPTCP
  out-of-order queue. A fix for v5.7.

- Patches 5-7: Avoid also sending "plain" TCP reset when closing with an
  MP_FASTCLOSE. A fix for v6.1.

- Patches 8-9: Longer timeout for background connections in MPTCP Join
  selftests. An additional fix for recent patches for v5.13/v6.1.

- Patches 10-11: Fix typo in a check introduce in a recent refactoring.
  A fix for v6.15.
====================

Link: https://patch.msgid.link/20251118-net-mptcp-misc-fixes-6-18-rc6-v1-0-806d3781c95f@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/mptcp/options.c

@@ -838,8 +838,11 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 
 	opts->suboptions = 0;
 
+	/* Force later mptcp_write_options(), but do not use any actual
+	 * option space.
+	 */
 	if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb)))
-		return false;
+		return true;
 
 	if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 		if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
@@ -1041,6 +1044,31 @@ static void __mptcp_snd_una_update(struct mptcp_sock *msk, u64 new_snd_una)
 	WRITE_ONCE(msk->snd_una, new_snd_una);
 }
 
+static void rwin_update(struct mptcp_sock *msk, struct sock *ssk,
+			struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct tcp_sock *tp = tcp_sk(ssk);
+	u64 mptcp_rcv_wnd;
+
+	/* Avoid touching extra cachelines if TCP is going to accept this
+	 * skb without filling the TCP-level window even with a possibly
+	 * outdated mptcp-level rwin.
+	 */
+	if (!skb->len || skb->len < tcp_receive_window(tp))
+		return;
+
+	mptcp_rcv_wnd = atomic64_read(&msk->rcv_wnd_sent);
+	if (!after64(mptcp_rcv_wnd, subflow->rcv_wnd_sent))
+		return;
+
+	/* Some other subflow grew the mptcp-level rwin since rcv_wup,
+	 * resync.
+	 */
+	tp->rcv_wnd += mptcp_rcv_wnd - subflow->rcv_wnd_sent;
+	subflow->rcv_wnd_sent = mptcp_rcv_wnd;
+}
+
 static void ack_update_msk(struct mptcp_sock *msk,
 			   struct sock *ssk,
 			   struct mptcp_options_received *mp_opt)
@@ -1208,6 +1236,7 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 	 */
 	if (mp_opt.use_ack)
 		ack_update_msk(msk, sk, &mp_opt);
+	rwin_update(msk, sk, skb);
 
 	/* Zero-data-length packets are dropped by the caller and not
 	 * propagated to the MPTCP layer, so the skb extension does not
@@ -1294,6 +1323,10 @@ static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
 
 	if (rcv_wnd_new != rcv_wnd_old) {
 raise_win:
+		/* The msk-level rcv wnd is after the tcp level one,
+		 * sync the latter.
+		 */
+		rcv_wnd_new = rcv_wnd_old;
 		win = rcv_wnd_old - ack_seq;
 		tp->rcv_wnd = min_t(u64, win, U32_MAX);
 		new_win = tp->rcv_wnd;
@@ -1317,6 +1350,21 @@ static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
 
 update_wspace:
 	WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);
+	subflow->rcv_wnd_sent = rcv_wnd_new;
+}
+
+static void mptcp_track_rwin(struct tcp_sock *tp)
+{
+	const struct sock *ssk = (const struct sock *)tp;
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk;
+
+	if (!ssk)
+		return;
+
+	subflow = mptcp_subflow_ctx(ssk);
+	msk = mptcp_sk(subflow->conn);
+	WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);
 }
 
 __sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
@@ -1611,6 +1659,10 @@ void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
 				      opts->reset_transient,
 				      opts->reset_reason);
 		return;
+	} else if (unlikely(!opts->suboptions)) {
+		/* Fallback to TCP */
+		mptcp_track_rwin(tp);
+		return;
 	}
 
 	if (OPTION_MPTCP_PRIO & opts->suboptions) {

net/mptcp/pm_kernel.c

@@ -672,7 +672,7 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
 
 void mptcp_pm_nl_rm_addr(struct mptcp_sock *msk, u8 rm_id)
 {
-	if (rm_id && WARN_ON_ONCE(msk->pm.add_addr_accepted == 0)) {
+	if (rm_id && !WARN_ON_ONCE(msk->pm.add_addr_accepted == 0)) {
 		u8 limit_add_addr_accepted =
 			mptcp_pm_get_limit_add_addr_accepted(msk);
 

net/mptcp/protocol.c

@@ -76,6 +76,13 @@ bool __mptcp_try_fallback(struct mptcp_sock *msk, int fb_mib)
 	if (__mptcp_check_fallback(msk))
 		return true;
 
+	/* The caller possibly is not holding the msk socket lock, but
+	 * in the fallback case only the current subflow is touching
+	 * the OoO queue.
+	 */
+	if (!RB_EMPTY_ROOT(&msk->out_of_order_queue))
+		return false;
+
 	spin_lock_bh(&msk->fallback_lock);
 	if (!msk->allow_infinite_fallback) {
 		spin_unlock_bh(&msk->fallback_lock);
@@ -2402,7 +2409,6 @@ bool __mptcp_retransmit_pending_data(struct sock *sk)
 
 /* flags for __mptcp_close_ssk() */
 #define MPTCP_CF_PUSH		BIT(1)
-#define MPTCP_CF_FASTCLOSE	BIT(2)
 
 /* be sure to send a reset only if the caller asked for it, also
  * clean completely the subflow status when the subflow reaches
@@ -2413,7 +2419,7 @@ static void __mptcp_subflow_disconnect(struct sock *ssk,
 				       unsigned int flags)
 {
 	if (((1 << ssk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
-	    (flags & MPTCP_CF_FASTCLOSE)) {
+	    subflow->send_fastclose) {
 		/* The MPTCP code never wait on the subflow sockets, TCP-level
 		 * disconnect should never fail
 		 */
@@ -2460,14 +2466,8 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 
 	lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);
 
-	if ((flags & MPTCP_CF_FASTCLOSE) && !__mptcp_check_fallback(msk)) {
-		/* be sure to force the tcp_close path
-		 * to generate the egress reset
-		 */
-		ssk->sk_lingertime = 0;
-		sock_set_flag(ssk, SOCK_LINGER);
-		subflow->send_fastclose = 1;
-	}
+	if (subflow->send_fastclose && ssk->sk_state != TCP_CLOSE)
+		tcp_set_state(ssk, TCP_CLOSE);
 
 	need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk);
 	if (!dispose_it) {
@@ -2563,7 +2563,8 @@ static void __mptcp_close_subflow(struct sock *sk)
 
 		if (ssk_state != TCP_CLOSE &&
 		    (ssk_state != TCP_CLOSE_WAIT ||
-		     inet_sk_state_load(sk) != TCP_ESTABLISHED))
+		     inet_sk_state_load(sk) != TCP_ESTABLISHED ||
+		     __mptcp_check_fallback(msk)))
 			continue;
 
 		/* 'subflow_data_ready' will re-sched once rx queue is empty */
@@ -2771,9 +2772,26 @@ static void mptcp_do_fastclose(struct sock *sk)
 	struct mptcp_sock *msk = mptcp_sk(sk);
 
 	mptcp_set_state(sk, TCP_CLOSE);
-	mptcp_for_each_subflow_safe(msk, subflow, tmp)
-		__mptcp_close_ssk(sk, mptcp_subflow_tcp_sock(subflow),
-				  subflow, MPTCP_CF_FASTCLOSE);
+
+	/* Explicitly send the fastclose reset as need */
+	if (__mptcp_check_fallback(msk))
+		return;
+
+	mptcp_for_each_subflow_safe(msk, subflow, tmp) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		lock_sock(ssk);
+
+		/* Some subflow socket states don't allow/need a reset.*/
+		if ((1 << ssk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE))
+			goto unlock;
+
+		subflow->send_fastclose = 1;
+		tcp_send_active_reset(ssk, ssk->sk_allocation,
+				      SK_RST_REASON_TCP_ABORT_ON_CLOSE);
+unlock:
+		release_sock(ssk);
+	}
 }
 
 static void mptcp_worker(struct work_struct *work)
@@ -2800,7 +2818,11 @@ static void mptcp_worker(struct work_struct *work)
 		__mptcp_close_subflow(sk);
 
 	if (mptcp_close_tout_expired(sk)) {
+		struct mptcp_subflow_context *subflow, *tmp;
+
 		mptcp_do_fastclose(sk);
+		mptcp_for_each_subflow_safe(msk, subflow, tmp)
+			__mptcp_close_ssk(sk, subflow->tcp_sock, subflow, 0);
 		mptcp_close_wake_up(sk);
 	}
 
@@ -3225,7 +3247,8 @@ static int mptcp_disconnect(struct sock *sk, int flags)
 	/* msk->subflow is still intact, the following will not free the first
 	 * subflow
 	 */
-	mptcp_destroy_common(msk, MPTCP_CF_FASTCLOSE);
+	mptcp_do_fastclose(sk);
+	mptcp_destroy_common(msk);
 
 	/* The first subflow is already in TCP_CLOSE status, the following
 	 * can't overlap with a fallback anymore
@@ -3404,7 +3427,7 @@ void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk)
 		msk->rcvq_space.space = TCP_INIT_CWND * TCP_MSS_DEFAULT;
 }
 
-void mptcp_destroy_common(struct mptcp_sock *msk, unsigned int flags)
+void mptcp_destroy_common(struct mptcp_sock *msk)
 {
 	struct mptcp_subflow_context *subflow, *tmp;
 	struct sock *sk = (struct sock *)msk;
@@ -3413,7 +3436,7 @@ void mptcp_destroy_common(struct mptcp_sock *msk, unsigned int flags)
 
 	/* join list will be eventually flushed (with rst) at sock lock release time */
 	mptcp_for_each_subflow_safe(msk, subflow, tmp)
-		__mptcp_close_ssk(sk, mptcp_subflow_tcp_sock(subflow), subflow, flags);
+		__mptcp_close_ssk(sk, mptcp_subflow_tcp_sock(subflow), subflow, 0);
 
 	__skb_queue_purge(&sk->sk_receive_queue);
 	skb_rbtree_purge(&msk->out_of_order_queue);
@@ -3431,7 +3454,7 @@ static void mptcp_destroy(struct sock *sk)
 
 	/* allow the following to close even the initial subflow */
 	msk->free_first = 1;
-	mptcp_destroy_common(msk, 0);
+	mptcp_destroy_common(msk);
 	sk_sockets_allocated_dec(sk);
 }
 

net/mptcp/protocol.h

@@ -509,6 +509,7 @@ struct mptcp_subflow_context {
 	u64	remote_key;
 	u64	idsn;
 	u64	map_seq;
+	u64	rcv_wnd_sent;
 	u32	snd_isn;
 	u32	token;
 	u32	rel_write_seq;
@@ -976,7 +977,7 @@ static inline void mptcp_propagate_sndbuf(struct sock *sk, struct sock *ssk)
 	local_bh_enable();
 }
 
-void mptcp_destroy_common(struct mptcp_sock *msk, unsigned int flags);
+void mptcp_destroy_common(struct mptcp_sock *msk);
 
 #define MPTCP_TOKEN_MAX_RETRIES	4