Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4099 insertions, 0 deletions

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
new file mode 100644
index 000000000..76539d100
--- /dev/null
+++ b/net/mptcp/protocol.c
@@ -0,0 +1,4099 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2017 - 2019, Intel Corporation.
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/sched/signal.h>
+#include <linux/atomic.h>
+#include <net/sock.h>
+#include <net/inet_common.h>
+#include <net/inet_hashtables.h>
+#include <net/protocol.h>
+#include <net/tcp.h>
+#include <net/tcp_states.h>
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+#include <net/transp_v6.h>
+#endif
+#include <net/mptcp.h>
+#include <net/xfrm.h>
+#include <asm/ioctls.h>
+#include "protocol.h"
+#include "mib.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/mptcp.h>
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+struct mptcp6_sock {
+	struct mptcp_sock msk;
+	struct ipv6_pinfo np;
+};
+#endif
+
+struct mptcp_skb_cb {
+	u64 map_seq;
+	u64 end_seq;
+	u32 offset;
+	u8  has_rxtstamp:1;
+};
+
+#define MPTCP_SKB_CB(__skb)	((struct mptcp_skb_cb *)&((__skb)->cb[0]))
+
+enum {
+	MPTCP_CMSG_TS = BIT(0),
+	MPTCP_CMSG_INQ = BIT(1),
+};
+
+static struct percpu_counter mptcp_sockets_allocated ____cacheline_aligned_in_smp;
+
+static void __mptcp_destroy_sock(struct sock *sk);
+static void mptcp_check_send_data_fin(struct sock *sk);
+
+DEFINE_PER_CPU(struct mptcp_delegated_action, mptcp_delegated_actions);
+static struct net_device mptcp_napi_dev;
+
+/* If msk has an initial subflow socket, and the MP_CAPABLE handshake has not
+ * completed yet or has failed, return the subflow socket.
+ * Otherwise return NULL.
+ */
+struct socket *__mptcp_nmpc_socket(const struct mptcp_sock *msk)
+{
+	if (!msk->subflow || READ_ONCE(msk->can_ack))
+		return NULL;
+
+	return msk->subflow;
+}
+
+/* Returns end sequence number of the receiver's advertised window */
+static u64 mptcp_wnd_end(const struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->wnd_end);
+}
+
+static bool mptcp_is_tcpsk(struct sock *sk)
+{
+	struct socket *sock = sk->sk_socket;
+
+	if (unlikely(sk->sk_prot == &tcp_prot)) {
+		/* we are being invoked after mptcp_accept() has
+		 * accepted a non-mp-capable flow: sk is a tcp_sk,
+		 * not an mptcp one.
+		 *
+		 * Hand the socket over to tcp so all further socket ops
+		 * bypass mptcp.
+		 */
+		sock->ops = &inet_stream_ops;
+		return true;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	} else if (unlikely(sk->sk_prot == &tcpv6_prot)) {
+		sock->ops = &inet6_stream_ops;
+		return true;
+#endif
+	}
+
+	return false;
+}
+
+static int __mptcp_socket_create(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	struct socket *ssock;
+	int err;
+
+	err = mptcp_subflow_create_socket(sk, sk->sk_family, &ssock);
+	if (err)
+		return err;
+
+	WRITE_ONCE(msk->first, ssock->sk);
+	WRITE_ONCE(msk->subflow, ssock);
+	subflow = mptcp_subflow_ctx(ssock->sk);
+	list_add(&subflow->node, &msk->conn_list);
+	sock_hold(ssock->sk);
+	subflow->request_mptcp = 1;
+
+	/* This is the first subflow, always with id 0 */
+	subflow->local_id_valid = 1;
+	mptcp_sock_graft(msk->first, sk->sk_socket);
+
+	return 0;
+}
+
+static void mptcp_drop(struct sock *sk, struct sk_buff *skb)
+{
+	sk_drops_add(sk, skb);
+	__kfree_skb(skb);
+}
+
+static void mptcp_rmem_fwd_alloc_add(struct sock *sk, int size)
+{
+	WRITE_ONCE(mptcp_sk(sk)->rmem_fwd_alloc,
+		   mptcp_sk(sk)->rmem_fwd_alloc + size);
+}
+
+static void mptcp_rmem_charge(struct sock *sk, int size)
+{
+	mptcp_rmem_fwd_alloc_add(sk, -size);
+}
+
+static bool mptcp_try_coalesce(struct sock *sk, struct sk_buff *to,
+			       struct sk_buff *from)
+{
+	bool fragstolen;
+	int delta;
+
+	if (MPTCP_SKB_CB(from)->offset ||
+	    !skb_try_coalesce(to, from, &fragstolen, &delta))
+		return false;
+
+	pr_debug("colesced seq %llx into %llx new len %d new end seq %llx",
+		 MPTCP_SKB_CB(from)->map_seq, MPTCP_SKB_CB(to)->map_seq,
+		 to->len, MPTCP_SKB_CB(from)->end_seq);
+	MPTCP_SKB_CB(to)->end_seq = MPTCP_SKB_CB(from)->end_seq;
+
+	/* note the fwd memory can reach a negative value after accounting
+	 * for the delta, but the later skb free will restore a non
+	 * negative one
+	 */
+	atomic_add(delta, &sk->sk_rmem_alloc);
+	mptcp_rmem_charge(sk, delta);
+	kfree_skb_partial(from, fragstolen);
+
+	return true;
+}
+
+static bool mptcp_ooo_try_coalesce(struct mptcp_sock *msk, struct sk_buff *to,
+				   struct sk_buff *from)
+{
+	if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq)
+		return false;
+
+	return mptcp_try_coalesce((struct sock *)msk, to, from);
+}
+
+static void __mptcp_rmem_reclaim(struct sock *sk, int amount)
+{
+	amount >>= PAGE_SHIFT;
+	mptcp_rmem_charge(sk, amount << PAGE_SHIFT);
+	__sk_mem_reduce_allocated(sk, amount);
+}
+
+static void mptcp_rmem_uncharge(struct sock *sk, int size)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	int reclaimable;
+
+	mptcp_rmem_fwd_alloc_add(sk, size);
+	reclaimable = msk->rmem_fwd_alloc - sk_unused_reserved_mem(sk);
+
+	/* see sk_mem_uncharge() for the rationale behind the following schema */
+	if (unlikely(reclaimable >= PAGE_SIZE))
+		__mptcp_rmem_reclaim(sk, reclaimable);
+}
+
+static void mptcp_rfree(struct sk_buff *skb)
+{
+	unsigned int len = skb->truesize;
+	struct sock *sk = skb->sk;
+
+	atomic_sub(len, &sk->sk_rmem_alloc);
+	mptcp_rmem_uncharge(sk, len);
+}
+
+static void mptcp_set_owner_r(struct sk_buff *skb, struct sock *sk)
+{
+	skb_orphan(skb);
+	skb->sk = sk;
+	skb->destructor = mptcp_rfree;
+	atomic_add(skb->truesize, &sk->sk_rmem_alloc);
+	mptcp_rmem_charge(sk, skb->truesize);
+}
+
+/* "inspired" by tcp_data_queue_ofo(), main differences:
+ * - use mptcp seqs
+ * - don't cope with sacks
+ */
+static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct rb_node **p, *parent;
+	u64 seq, end_seq, max_seq;
+	struct sk_buff *skb1;
+
+	seq = MPTCP_SKB_CB(skb)->map_seq;
+	end_seq = MPTCP_SKB_CB(skb)->end_seq;
+	max_seq = atomic64_read(&msk->rcv_wnd_sent);
+
+	pr_debug("msk=%p seq=%llx limit=%llx empty=%d", msk, seq, max_seq,
+		 RB_EMPTY_ROOT(&msk->out_of_order_queue));
+	if (after64(end_seq, max_seq)) {
+		/* out of window */
+		mptcp_drop(sk, skb);
+		pr_debug("oow by %lld, rcv_wnd_sent %llu\n",
+			 (unsigned long long)end_seq - (unsigned long)max_seq,
+			 (unsigned long long)atomic64_read(&msk->rcv_wnd_sent));
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_NODSSWINDOW);
+		return;
+	}
+
+	p = &msk->out_of_order_queue.rb_node;
+	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUE);
+	if (RB_EMPTY_ROOT(&msk->out_of_order_queue)) {
+		rb_link_node(&skb->rbnode, NULL, p);
+		rb_insert_color(&skb->rbnode, &msk->out_of_order_queue);
+		msk->ooo_last_skb = skb;
+		goto end;
+	}
+
+	/* with 2 subflows, adding at end of ooo queue is quite likely
+	 * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
+	 */
+	if (mptcp_ooo_try_coalesce(msk, msk->ooo_last_skb, skb)) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE);
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL);
+		return;
+	}
+
+	/* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
+	if (!before64(seq, MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq)) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL);
+		parent = &msk->ooo_last_skb->rbnode;
+		p = &parent->rb_right;
+		goto insert;
+	}
+
+	/* Find place to insert this segment. Handle overlaps on the way. */
+	parent = NULL;
+	while (*p) {
+		parent = *p;
+		skb1 = rb_to_skb(parent);
+		if (before64(seq, MPTCP_SKB_CB(skb1)->map_seq)) {
+			p = &parent->rb_left;
+			continue;
+		}
+		if (before64(seq, MPTCP_SKB_CB(skb1)->end_seq)) {
+			if (!after64(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) {
+				/* All the bits are present. Drop. */
+				mptcp_drop(sk, skb);
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+				return;
+			}
+			if (after64(seq, MPTCP_SKB_CB(skb1)->map_seq)) {
+				/* partial overlap:
+				 *     |     skb      |
+				 *  |     skb1    |
+				 * continue traversing
+				 */
+			} else {
+				/* skb's seq == skb1's seq and skb covers skb1.
+				 * Replace skb1 with skb.
+				 */
+				rb_replace_node(&skb1->rbnode, &skb->rbnode,
+						&msk->out_of_order_queue);
+				mptcp_drop(sk, skb1);
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+				goto merge_right;
+			}
+		} else if (mptcp_ooo_try_coalesce(msk, skb1, skb)) {
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE);
+			return;
+		}
+		p = &parent->rb_right;
+	}
+
+insert:
+	/* Insert segment into RB tree. */
+	rb_link_node(&skb->rbnode, parent, p);
+	rb_insert_color(&skb->rbnode, &msk->out_of_order_queue);
+
+merge_right:
+	/* Remove other segments covered by skb. */
+	while ((skb1 = skb_rb_next(skb)) != NULL) {
+		if (before64(end_seq, MPTCP_SKB_CB(skb1)->end_seq))
+			break;
+		rb_erase(&skb1->rbnode, &msk->out_of_order_queue);
+		mptcp_drop(sk, skb1);
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+	}
+	/* If there is no skb after us, we are the last_skb ! */
+	if (!skb1)
+		msk->ooo_last_skb = skb;
+
+end:
+	skb_condense(skb);
+	mptcp_set_owner_r(skb, sk);
+}
+
+static bool mptcp_rmem_schedule(struct sock *sk, struct sock *ssk, int size)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	int amt, amount;
+
+	if (size <= msk->rmem_fwd_alloc)
+		return true;
+
+	size -= msk->rmem_fwd_alloc;
+	amt = sk_mem_pages(size);
+	amount = amt << PAGE_SHIFT;
+	if (!__sk_mem_raise_allocated(sk, size, amt, SK_MEM_RECV))
+		return false;
+
+	mptcp_rmem_fwd_alloc_add(sk, amount);
+	return true;
+}
+
+static bool __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
+			     struct sk_buff *skb, unsigned int offset,
+			     size_t copy_len)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct sock *sk = (struct sock *)msk;
+	struct sk_buff *tail;
+	bool has_rxtstamp;
+
+	__skb_unlink(skb, &ssk->sk_receive_queue);
+
+	skb_ext_reset(skb);
+	skb_orphan(skb);
+
+	/* try to fetch required memory from subflow */
+	if (!mptcp_rmem_schedule(sk, ssk, skb->truesize))
+		goto drop;
+
+	has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp;
+
+	/* the skb map_seq accounts for the skb offset:
+	 * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq
+	 * value
+	 */
+	MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow);
+	MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + copy_len;
+	MPTCP_SKB_CB(skb)->offset = offset;
+	MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp;
+
+	if (MPTCP_SKB_CB(skb)->map_seq == msk->ack_seq) {
+		/* in sequence */
+		WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len);
+		tail = skb_peek_tail(&sk->sk_receive_queue);
+		if (tail && mptcp_try_coalesce(sk, tail, skb))
+			return true;
+
+		mptcp_set_owner_r(skb, sk);
+		__skb_queue_tail(&sk->sk_receive_queue, skb);
+		return true;
+	} else if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) {
+		mptcp_data_queue_ofo(msk, skb);
+		return false;
+	}
+
+	/* old data, keep it simple and drop the whole pkt, sender
+	 * will retransmit as needed, if needed.
+	 */
+	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+drop:
+	mptcp_drop(sk, skb);
+	return false;
+}
+
+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);
+	mptcp_sk(sk)->timer_ival = 0;
+}
+
+static void mptcp_close_wake_up(struct sock *sk)
+{
+	if (sock_flag(sk, SOCK_DEAD))
+		return;
+
+	sk->sk_state_change(sk);
+	if (sk->sk_shutdown == SHUTDOWN_MASK ||
+	    sk->sk_state == TCP_CLOSE)
+		sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
+	else
+		sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
+}
+
+static bool mptcp_pending_data_fin_ack(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	return ((1 << sk->sk_state) &
+		(TCPF_FIN_WAIT1 | TCPF_CLOSING | TCPF_LAST_ACK)) &&
+	       msk->write_seq == READ_ONCE(msk->snd_una);
+}
+
+static void mptcp_check_data_fin_ack(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	/* Look for an acknowledged DATA_FIN */
+	if (mptcp_pending_data_fin_ack(sk)) {
+		WRITE_ONCE(msk->snd_data_fin_enable, 0);
+
+		switch (sk->sk_state) {
+		case TCP_FIN_WAIT1:
+			inet_sk_state_store(sk, TCP_FIN_WAIT2);
+			break;
+		case TCP_CLOSING:
+		case TCP_LAST_ACK:
+			inet_sk_state_store(sk, TCP_CLOSE);
+			break;
+		}
+
+		mptcp_close_wake_up(sk);
+	}
+}
+
+static bool mptcp_pending_data_fin(struct sock *sk, u64 *seq)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (READ_ONCE(msk->rcv_data_fin) &&
+	    ((1 << sk->sk_state) &
+	     (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2))) {
+		u64 rcv_data_fin_seq = READ_ONCE(msk->rcv_data_fin_seq);
+
+		if (msk->ack_seq == rcv_data_fin_seq) {
+			if (seq)
+				*seq = rcv_data_fin_seq;
+
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static void mptcp_set_datafin_timeout(const struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	u32 retransmits;
+
+	retransmits = min_t(u32, icsk->icsk_retransmits,
+			    ilog2(TCP_RTO_MAX / TCP_RTO_MIN));
+
+	mptcp_sk(sk)->timer_ival = TCP_RTO_MIN << retransmits;
+}
+
+static void __mptcp_set_timeout(struct sock *sk, long tout)
+{
+	mptcp_sk(sk)->timer_ival = tout > 0 ? tout : TCP_RTO_MIN;
+}
+
+static long mptcp_timeout_from_subflow(const struct mptcp_subflow_context *subflow)
+{
+	const struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+	return inet_csk(ssk)->icsk_pending && !subflow->stale_count ?
+	       inet_csk(ssk)->icsk_timeout - jiffies : 0;
+}
+
+static void mptcp_set_timeout(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow;
+	long tout = 0;
+
+	mptcp_for_each_subflow(mptcp_sk(sk), subflow)
+		tout = max(tout, mptcp_timeout_from_subflow(subflow));
+	__mptcp_set_timeout(sk, tout);
+}
+
+static inline bool tcp_can_send_ack(const struct sock *ssk)
+{
+	return !((1 << inet_sk_state_load(ssk)) &
+	       (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_TIME_WAIT | TCPF_CLOSE | TCPF_LISTEN));
+}
+
+void __mptcp_subflow_send_ack(struct sock *ssk)
+{
+	if (tcp_can_send_ack(ssk))
+		tcp_send_ack(ssk);
+}
+
+static void mptcp_subflow_send_ack(struct sock *ssk)
+{
+	bool slow;
+
+	slow = lock_sock_fast(ssk);
+	__mptcp_subflow_send_ack(ssk);
+	unlock_sock_fast(ssk, slow);
+}
+
+static void mptcp_send_ack(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+
+	mptcp_for_each_subflow(msk, subflow)
+		mptcp_subflow_send_ack(mptcp_subflow_tcp_sock(subflow));
+}
+
+static void mptcp_subflow_cleanup_rbuf(struct sock *ssk)
+{
+	bool slow;
+
+	slow = lock_sock_fast(ssk);
+	if (tcp_can_send_ack(ssk))
+		tcp_cleanup_rbuf(ssk, 1);
+	unlock_sock_fast(ssk, slow);
+}
+
+static bool mptcp_subflow_could_cleanup(const struct sock *ssk, bool rx_empty)
+{
+	const struct inet_connection_sock *icsk = inet_csk(ssk);
+	u8 ack_pending = READ_ONCE(icsk->icsk_ack.pending);
+	const struct tcp_sock *tp = tcp_sk(ssk);
+
+	return (ack_pending & ICSK_ACK_SCHED) &&
+		((READ_ONCE(tp->rcv_nxt) - READ_ONCE(tp->rcv_wup) >
+		  READ_ONCE(icsk->icsk_ack.rcv_mss)) ||
+		 (rx_empty && ack_pending &
+			      (ICSK_ACK_PUSHED2 | ICSK_ACK_PUSHED)));
+}
+
+static void mptcp_cleanup_rbuf(struct mptcp_sock *msk)
+{
+	int old_space = READ_ONCE(msk->old_wspace);
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	int space =  __mptcp_space(sk);
+	bool cleanup, rx_empty;
+
+	cleanup = (space > 0) && (space >= (old_space << 1));
+	rx_empty = !__mptcp_rmem(sk);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if (cleanup || mptcp_subflow_could_cleanup(ssk, rx_empty))
+			mptcp_subflow_cleanup_rbuf(ssk);
+	}
+}
+
+static bool mptcp_check_data_fin(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	u64 rcv_data_fin_seq;
+	bool ret = false;
+
+	/* Need to ack a DATA_FIN received from a peer while this side
+	 * of the connection is in ESTABLISHED, FIN_WAIT1, or FIN_WAIT2.
+	 * msk->rcv_data_fin was set when parsing the incoming options
+	 * at the subflow level and the msk lock was not held, so this
+	 * is the first opportunity to act on the DATA_FIN and change
+	 * the msk state.
+	 *
+	 * If we are caught up to the sequence number of the incoming
+	 * DATA_FIN, send the DATA_ACK now and do state transition.  If
+	 * not caught up, do nothing and let the recv code send DATA_ACK
+	 * when catching up.
+	 */
+
+	if (mptcp_pending_data_fin(sk, &rcv_data_fin_seq)) {
+		WRITE_ONCE(msk->ack_seq, msk->ack_seq + 1);
+		WRITE_ONCE(msk->rcv_data_fin, 0);
+
+		WRITE_ONCE(sk->sk_shutdown, sk->sk_shutdown | RCV_SHUTDOWN);
+		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
+
+		switch (sk->sk_state) {
+		case TCP_ESTABLISHED:
+			inet_sk_state_store(sk, TCP_CLOSE_WAIT);
+			break;
+		case TCP_FIN_WAIT1:
+			inet_sk_state_store(sk, TCP_CLOSING);
+			break;
+		case TCP_FIN_WAIT2:
+			inet_sk_state_store(sk, TCP_CLOSE);
+			break;
+		default:
+			/* Other states not expected */
+			WARN_ON_ONCE(1);
+			break;
+		}
+
+		ret = true;
+		if (!__mptcp_check_fallback(msk))
+			mptcp_send_ack(msk);
+		mptcp_close_wake_up(sk);
+	}
+	return ret;
+}
+
+static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
+					   struct sock *ssk,
+					   unsigned int *bytes)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct sock *sk = (struct sock *)msk;
+	unsigned int moved = 0;
+	bool more_data_avail;
+	struct tcp_sock *tp;
+	bool done = false;
+	int sk_rbuf;
+
+	sk_rbuf = READ_ONCE(sk->sk_rcvbuf);
+
+	if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
+		int ssk_rbuf = READ_ONCE(ssk->sk_rcvbuf);
+
+		if (unlikely(ssk_rbuf > sk_rbuf)) {
+			WRITE_ONCE(sk->sk_rcvbuf, ssk_rbuf);
+			sk_rbuf = ssk_rbuf;
+		}
+	}
+
+	pr_debug("msk=%p ssk=%p", msk, ssk);
+	tp = tcp_sk(ssk);
+	do {
+		u32 map_remaining, offset;
+		u32 seq = tp->copied_seq;
+		struct sk_buff *skb;
+		bool fin;
+
+		/* try to move as much data as available */
+		map_remaining = subflow->map_data_len -
+				mptcp_subflow_get_map_offset(subflow);
+
+		skb = skb_peek(&ssk->sk_receive_queue);
+		if (!skb) {
+			/* With racing move_skbs_to_msk() and __mptcp_move_skbs(),
+			 * a different CPU can have already processed the pending
+			 * data, stop here or we can enter an infinite loop
+			 */
+			if (!moved)
+				done = true;
+			break;
+		}
+
+		if (__mptcp_check_fallback(msk)) {
+			/* Under fallback skbs have no MPTCP extension and TCP could
+			 * collapse them between the dummy map creation and the
+			 * current dequeue. Be sure to adjust the map size.
+			 */
+			map_remaining = skb->len;
+			subflow->map_data_len = skb->len;
+		}
+
+		offset = seq - TCP_SKB_CB(skb)->seq;
+		fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
+		if (fin) {
+			done = true;
+			seq++;
+		}
+
+		if (offset < skb->len) {
+			size_t len = skb->len - offset;
+
+			if (tp->urg_data)
+				done = true;
+
+			if (__mptcp_move_skb(msk, ssk, skb, offset, len))
+				moved += len;
+			seq += len;
+
+			if (WARN_ON_ONCE(map_remaining < len))
+				break;
+		} else {
+			WARN_ON_ONCE(!fin);
+			sk_eat_skb(ssk, skb);
+			done = true;
+		}
+
+		WRITE_ONCE(tp->copied_seq, seq);
+		more_data_avail = mptcp_subflow_data_available(ssk);
+
+		if (atomic_read(&sk->sk_rmem_alloc) > sk_rbuf) {
+			done = true;
+			break;
+		}
+	} while (more_data_avail);
+
+	*bytes += moved;
+	return done;
+}
+
+static bool __mptcp_ofo_queue(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct sk_buff *skb, *tail;
+	bool moved = false;
+	struct rb_node *p;
+	u64 end_seq;
+
+	p = rb_first(&msk->out_of_order_queue);
+	pr_debug("msk=%p empty=%d", msk, RB_EMPTY_ROOT(&msk->out_of_order_queue));
+	while (p) {
+		skb = rb_to_skb(p);
+		if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq))
+			break;
+
+		p = rb_next(p);
+		rb_erase(&skb->rbnode, &msk->out_of_order_queue);
+
+		if (unlikely(!after64(MPTCP_SKB_CB(skb)->end_seq,
+				      msk->ack_seq))) {
+			mptcp_drop(sk, skb);
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+			continue;
+		}
+
+		end_seq = MPTCP_SKB_CB(skb)->end_seq;
+		tail = skb_peek_tail(&sk->sk_receive_queue);
+		if (!tail || !mptcp_ooo_try_coalesce(msk, tail, skb)) {
+			int delta = msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq;
+
+			/* skip overlapping data, if any */
+			pr_debug("uncoalesced seq=%llx ack seq=%llx delta=%d",
+				 MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq,
+				 delta);
+			MPTCP_SKB_CB(skb)->offset += delta;
+			MPTCP_SKB_CB(skb)->map_seq += delta;
+			__skb_queue_tail(&sk->sk_receive_queue, skb);
+		}
+		msk->ack_seq = end_seq;
+		moved = true;
+	}
+	return moved;
+}
+
+static bool __mptcp_subflow_error_report(struct sock *sk, struct sock *ssk)
+{
+	int err = sock_error(ssk);
+	int ssk_state;
+
+	if (!err)
+		return false;
+
+	/* only propagate errors on fallen-back sockets or
+	 * on MPC connect
+	 */
+	if (sk->sk_state != TCP_SYN_SENT && !__mptcp_check_fallback(mptcp_sk(sk)))
+		return false;
+
+	/* We need to propagate only transition to CLOSE state.
+	 * Orphaned socket will see such state change via
+	 * subflow_sched_work_if_closed() and that path will properly
+	 * destroy the msk as needed.
+	 */
+	ssk_state = inet_sk_state_load(ssk);
+	if (ssk_state == TCP_CLOSE && !sock_flag(sk, SOCK_DEAD))
+		inet_sk_state_store(sk, ssk_state);
+	WRITE_ONCE(sk->sk_err, -err);
+
+	/* This barrier is coupled with smp_rmb() in mptcp_poll() */
+	smp_wmb();
+	sk_error_report(sk);
+	return true;
+}
+
+void __mptcp_error_report(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	mptcp_for_each_subflow(msk, subflow)
+		if (__mptcp_subflow_error_report(sk, mptcp_subflow_tcp_sock(subflow)))
+			break;
+}
+
+/* In most cases we will be able to lock the mptcp socket.  If its already
+ * owned, we need to defer to the work queue to avoid ABBA deadlock.
+ */
+static bool move_skbs_to_msk(struct mptcp_sock *msk, struct sock *ssk)
+{
+	struct sock *sk = (struct sock *)msk;
+	unsigned int moved = 0;
+
+	__mptcp_move_skbs_from_subflow(msk, ssk, &moved);
+	__mptcp_ofo_queue(msk);
+	if (unlikely(ssk->sk_err)) {
+		if (!sock_owned_by_user(sk))
+			__mptcp_error_report(sk);
+		else
+			__set_bit(MPTCP_ERROR_REPORT,  &msk->cb_flags);
+	}
+
+	/* If the moves have caught up with the DATA_FIN sequence number
+	 * it's time to ack the DATA_FIN and change socket state, but
+	 * this is not a good place to change state. Let the workqueue
+	 * do it.
+	 */
+	if (mptcp_pending_data_fin(sk, NULL))
+		mptcp_schedule_work(sk);
+	return moved > 0;
+}
+
+void mptcp_data_ready(struct sock *sk, struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	int sk_rbuf, ssk_rbuf;
+
+	/* The peer can send data while we are shutting down this
+	 * subflow at msk destruction time, but we must avoid enqueuing
+	 * more data to the msk receive queue
+	 */
+	if (unlikely(subflow->disposable))
+		return;
+
+	ssk_rbuf = READ_ONCE(ssk->sk_rcvbuf);
+	sk_rbuf = READ_ONCE(sk->sk_rcvbuf);
+	if (unlikely(ssk_rbuf > sk_rbuf))
+		sk_rbuf = ssk_rbuf;
+
+	/* over limit? can't append more skbs to msk, Also, no need to wake-up*/
+	if (__mptcp_rmem(sk) > sk_rbuf) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED);
+		return;
+	}
+
+	/* Wake-up the reader only for in-sequence data */
+	mptcp_data_lock(sk);
+	if (move_skbs_to_msk(msk, ssk))
+		sk->sk_data_ready(sk);
+
+	mptcp_data_unlock(sk);
+}
+
+static void mptcp_subflow_joined(struct mptcp_sock *msk, struct sock *ssk)
+{
+	mptcp_subflow_ctx(ssk)->map_seq = READ_ONCE(msk->ack_seq);
+	WRITE_ONCE(msk->allow_infinite_fallback, false);
+	mptcp_event(MPTCP_EVENT_SUB_ESTABLISHED, msk, ssk, GFP_ATOMIC);
+}
+
+static bool __mptcp_finish_join(struct mptcp_sock *msk, struct sock *ssk)
+{
+	struct sock *sk = (struct sock *)msk;
+
+	if (sk->sk_state != TCP_ESTABLISHED)
+		return false;
+
+	/* attach to msk socket only after we are sure we will deal with it
+	 * at close time
+	 */
+	if (sk->sk_socket && !ssk->sk_socket)
+		mptcp_sock_graft(ssk, sk->sk_socket);
+
+	mptcp_sockopt_sync_locked(msk, ssk);
+	mptcp_subflow_joined(msk, ssk);
+	mptcp_stop_tout_timer(sk);
+	return true;
+}
+
+static void __mptcp_flush_join_list(struct sock *sk, struct list_head *join_list)
+{
+	struct mptcp_subflow_context *tmp, *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	list_for_each_entry_safe(subflow, tmp, join_list, node) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow = lock_sock_fast(ssk);
+
+		list_move_tail(&subflow->node, &msk->conn_list);
+		if (!__mptcp_finish_join(msk, ssk))
+			mptcp_subflow_reset(ssk);
+		unlock_sock_fast(ssk, slow);
+	}
+}
+
+static bool mptcp_rtx_timer_pending(struct sock *sk)
+{
+	return timer_pending(&inet_csk(sk)->icsk_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 */
+	if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE))
+		return;
+
+	tout = mptcp_sk(sk)->timer_ival;
+	sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + tout);
+}
+
+bool mptcp_schedule_work(struct sock *sk)
+{
+	if (inet_sk_state_load(sk) != TCP_CLOSE &&
+	    schedule_work(&mptcp_sk(sk)->work)) {
+		/* each subflow already holds a reference to the sk, and the
+		 * workqueue is invoked by a subflow, so sk can't go away here.
+		 */
+		sock_hold(sk);
+		return true;
+	}
+	return false;
+}
+
+void mptcp_subflow_eof(struct sock *sk)
+{
+	if (!test_and_set_bit(MPTCP_WORK_EOF, &mptcp_sk(sk)->flags))
+		mptcp_schedule_work(sk);
+}
+
+static void mptcp_check_for_eof(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	int receivers = 0;
+
+	mptcp_for_each_subflow(msk, subflow)
+		receivers += !subflow->rx_eof;
+	if (receivers)
+		return;
+
+	if (!(sk->sk_shutdown & RCV_SHUTDOWN)) {
+		/* hopefully temporary hack: propagate shutdown status
+		 * to msk, when all subflows agree on it
+		 */
+		WRITE_ONCE(sk->sk_shutdown, sk->sk_shutdown | RCV_SHUTDOWN);
+
+		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
+		sk->sk_data_ready(sk);
+	}
+
+	switch (sk->sk_state) {
+	case TCP_ESTABLISHED:
+		inet_sk_state_store(sk, TCP_CLOSE_WAIT);
+		break;
+	case TCP_FIN_WAIT1:
+		inet_sk_state_store(sk, TCP_CLOSING);
+		break;
+	case TCP_FIN_WAIT2:
+		inet_sk_state_store(sk, TCP_CLOSE);
+		break;
+	default:
+		return;
+	}
+	mptcp_close_wake_up(sk);
+}
+
+static struct sock *mptcp_subflow_recv_lookup(const struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+
+	sock_owned_by_me(sk);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->data_avail))
+			return mptcp_subflow_tcp_sock(subflow);
+	}
+
+	return NULL;
+}
+
+static bool mptcp_skb_can_collapse_to(u64 write_seq,
+				      const struct sk_buff *skb,
+				      const struct mptcp_ext *mpext)
+{
+	if (!tcp_skb_can_collapse_to(skb))
+		return false;
+
+	/* can collapse only if MPTCP level sequence is in order and this
+	 * mapping has not been xmitted yet
+	 */
+	return mpext && mpext->data_seq + mpext->data_len == write_seq &&
+	       !mpext->frozen;
+}
+
+/* we can append data to the given data frag if:
+ * - there is space available in the backing page_frag
+ * - the data frag tail matches the current page_frag free offset
+ * - the data frag end sequence number matches the current write seq
+ */
+static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
+				       const struct page_frag *pfrag,
+				       const struct mptcp_data_frag *df)
+{
+	return df && pfrag->page == df->page &&
+		pfrag->size - pfrag->offset > 0 &&
+		pfrag->offset == (df->offset + df->data_len) &&
+		df->data_seq + df->data_len == msk->write_seq;
+}
+
+static void dfrag_uncharge(struct sock *sk, int len)
+{
+	sk_mem_uncharge(sk, len);
+	sk_wmem_queued_add(sk, -len);
+}
+
+static void dfrag_clear(struct sock *sk, struct mptcp_data_frag *dfrag)
+{
+	int len = dfrag->data_len + dfrag->overhead;
+
+	list_del(&dfrag->list);
+	dfrag_uncharge(sk, len);
+	put_page(dfrag->page);
+}
+
+static void __mptcp_clean_una(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_data_frag *dtmp, *dfrag;
+	u64 snd_una;
+
+	/* on fallback we just need to ignore snd_una, as this is really
+	 * plain TCP
+	 */
+	if (__mptcp_check_fallback(msk))
+		msk->snd_una = READ_ONCE(msk->snd_nxt);
+
+	snd_una = msk->snd_una;
+	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list) {
+		if (after64(dfrag->data_seq + dfrag->data_len, snd_una))
+			break;
+
+		if (unlikely(dfrag == msk->first_pending)) {
+			/* in recovery mode can see ack after the current snd head */
+			if (WARN_ON_ONCE(!msk->recovery))
+				break;
+
+			WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
+		}
+
+		dfrag_clear(sk, dfrag);
+	}
+
+	dfrag = mptcp_rtx_head(sk);
+	if (dfrag && after64(snd_una, dfrag->data_seq)) {
+		u64 delta = snd_una - dfrag->data_seq;
+
+		/* prevent wrap around in recovery mode */
+		if (unlikely(delta > dfrag->already_sent)) {
+			if (WARN_ON_ONCE(!msk->recovery))
+				goto out;
+			if (WARN_ON_ONCE(delta > dfrag->data_len))
+				goto out;
+			dfrag->already_sent += delta - dfrag->already_sent;
+		}
+
+		dfrag->data_seq += delta;
+		dfrag->offset += delta;
+		dfrag->data_len -= delta;
+		dfrag->already_sent -= delta;
+
+		dfrag_uncharge(sk, delta);
+	}
+
+	/* all retransmitted data acked, recovery completed */
+	if (unlikely(msk->recovery) && after64(msk->snd_una, msk->recovery_snd_nxt))
+		msk->recovery = false;
+
+out:
+	if (snd_una == READ_ONCE(msk->snd_nxt) &&
+	    snd_una == READ_ONCE(msk->write_seq)) {
+		if (mptcp_rtx_timer_pending(sk) && !mptcp_data_fin_enabled(msk))
+			mptcp_stop_rtx_timer(sk);
+	} else {
+		mptcp_reset_rtx_timer(sk);
+	}
+}
+
+static void __mptcp_clean_una_wakeup(struct sock *sk)
+{
+	lockdep_assert_held_once(&sk->sk_lock.slock);
+
+	__mptcp_clean_una(sk);
+	mptcp_write_space(sk);
+}
+
+static void mptcp_clean_una_wakeup(struct sock *sk)
+{
+	mptcp_data_lock(sk);
+	__mptcp_clean_una_wakeup(sk);
+	mptcp_data_unlock(sk);
+}
+
+static void mptcp_enter_memory_pressure(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool first = true;
+
+	sk_stream_moderate_sndbuf(sk);
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if (first)
+			tcp_enter_memory_pressure(ssk);
+		sk_stream_moderate_sndbuf(ssk);
+		first = false;
+	}
+}
+
+/* ensure we get enough memory for the frag hdr, beyond some minimal amount of
+ * data
+ */
+static bool mptcp_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
+{
+	if (likely(skb_page_frag_refill(32U + sizeof(struct mptcp_data_frag),
+					pfrag, sk->sk_allocation)))
+		return true;
+
+	mptcp_enter_memory_pressure(sk);
+	return false;
+}
+
+static struct mptcp_data_frag *
+mptcp_carve_data_frag(const struct mptcp_sock *msk, struct page_frag *pfrag,
+		      int orig_offset)
+{
+	int offset = ALIGN(orig_offset, sizeof(long));
+	struct mptcp_data_frag *dfrag;
+
+	dfrag = (struct mptcp_data_frag *)(page_to_virt(pfrag->page) + offset);
+	dfrag->data_len = 0;
+	dfrag->data_seq = msk->write_seq;
+	dfrag->overhead = offset - orig_offset + sizeof(struct mptcp_data_frag);
+	dfrag->offset = offset + sizeof(struct mptcp_data_frag);
+	dfrag->already_sent = 0;
+	dfrag->page = pfrag->page;
+
+	return dfrag;
+}
+
+struct mptcp_sendmsg_info {
+	int mss_now;
+	int size_goal;
+	u16 limit;
+	u16 sent;
+	unsigned int flags;
+	bool data_lock_held;
+};
+
+static int mptcp_check_allowed_size(const struct mptcp_sock *msk, struct sock *ssk,
+				    u64 data_seq, int avail_size)
+{
+	u64 window_end = mptcp_wnd_end(msk);
+	u64 mptcp_snd_wnd;
+
+	if (__mptcp_check_fallback(msk))
+		return avail_size;
+
+	mptcp_snd_wnd = window_end - data_seq;
+	avail_size = min_t(unsigned int, mptcp_snd_wnd, avail_size);
+
+	if (unlikely(tcp_sk(ssk)->snd_wnd < mptcp_snd_wnd)) {
+		tcp_sk(ssk)->snd_wnd = min_t(u64, U32_MAX, mptcp_snd_wnd);
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_SNDWNDSHARED);
+	}
+
+	return avail_size;
+}
+
+static bool __mptcp_add_ext(struct sk_buff *skb, gfp_t gfp)
+{
+	struct skb_ext *mpext = __skb_ext_alloc(gfp);
+
+	if (!mpext)
+		return false;
+	__skb_ext_set(skb, SKB_EXT_MPTCP, mpext);
+	return true;
+}
+
+static struct sk_buff *__mptcp_do_alloc_tx_skb(struct sock *sk, gfp_t gfp)
+{
+	struct sk_buff *skb;
+
+	skb = alloc_skb_fclone(MAX_TCP_HEADER, gfp);
+	if (likely(skb)) {
+		if (likely(__mptcp_add_ext(skb, gfp))) {
+			skb_reserve(skb, MAX_TCP_HEADER);
+			skb->ip_summed = CHECKSUM_PARTIAL;
+			INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
+			return skb;
+		}
+		__kfree_skb(skb);
+	} else {
+		mptcp_enter_memory_pressure(sk);
+	}
+	return NULL;
+}
+
+static struct sk_buff *__mptcp_alloc_tx_skb(struct sock *sk, struct sock *ssk, gfp_t gfp)
+{
+	struct sk_buff *skb;
+
+	skb = __mptcp_do_alloc_tx_skb(sk, gfp);
+	if (!skb)
+		return NULL;
+
+	if (likely(sk_wmem_schedule(ssk, skb->truesize))) {
+		tcp_skb_entail(ssk, skb);
+		return skb;
+	}
+	tcp_skb_tsorted_anchor_cleanup(skb);
+	kfree_skb(skb);
+	return NULL;
+}
+
+static struct sk_buff *mptcp_alloc_tx_skb(struct sock *sk, struct sock *ssk, bool data_lock_held)
+{
+	gfp_t gfp = data_lock_held ? GFP_ATOMIC : sk->sk_allocation;
+
+	return __mptcp_alloc_tx_skb(sk, ssk, gfp);
+}
+
+/* note: this always recompute the csum on the whole skb, even
+ * if we just appended a single frag. More status info needed
+ */
+static void mptcp_update_data_checksum(struct sk_buff *skb, int added)
+{
+	struct mptcp_ext *mpext = mptcp_get_ext(skb);
+	__wsum csum = ~csum_unfold(mpext->csum);
+	int offset = skb->len - added;
+
+	mpext->csum = csum_fold(csum_block_add(csum, skb_checksum(skb, offset, added, 0), offset));
+}
+
+static void mptcp_update_infinite_map(struct mptcp_sock *msk,
+				      struct sock *ssk,
+				      struct mptcp_ext *mpext)
+{
+	if (!mpext)
+		return;
+
+	mpext->infinite_map = 1;
+	mpext->data_len = 0;
+
+	MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPTX);
+	mptcp_subflow_ctx(ssk)->send_infinite_map = 0;
+	pr_fallback(msk);
+	mptcp_do_fallback(ssk);
+}
+
+#define MPTCP_MAX_GSO_SIZE (GSO_LEGACY_MAX_SIZE - (MAX_TCP_HEADER + 1))
+
+static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
+			      struct mptcp_data_frag *dfrag,
+			      struct mptcp_sendmsg_info *info)
+{
+	u64 data_seq = dfrag->data_seq + info->sent;
+	int offset = dfrag->offset + info->sent;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool zero_window_probe = false;
+	struct mptcp_ext *mpext = NULL;
+	bool can_coalesce = false;
+	bool reuse_skb = true;
+	struct sk_buff *skb;
+	size_t copy;
+	int i;
+
+	pr_debug("msk=%p ssk=%p sending dfrag at seq=%llu len=%u already sent=%u",
+		 msk, ssk, dfrag->data_seq, dfrag->data_len, info->sent);
+
+	if (WARN_ON_ONCE(info->sent > info->limit ||
+			 info->limit > dfrag->data_len))
+		return 0;
+
+	if (unlikely(!__tcp_can_send(ssk)))
+		return -EAGAIN;
+
+	/* compute send limit */
+	if (unlikely(ssk->sk_gso_max_size > MPTCP_MAX_GSO_SIZE))
+		ssk->sk_gso_max_size = MPTCP_MAX_GSO_SIZE;
+	info->mss_now = tcp_send_mss(ssk, &info->size_goal, info->flags);
+	copy = info->size_goal;
+
+	skb = tcp_write_queue_tail(ssk);
+	if (skb && copy > skb->len) {
+		/* Limit the write to the size available in the
+		 * current skb, if any, so that we create at most a new skb.
+		 * Explicitly tells TCP internals to avoid collapsing on later
+		 * queue management operation, to avoid breaking the ext <->
+		 * SSN association set here
+		 */
+		mpext = skb_ext_find(skb, SKB_EXT_MPTCP);
+		if (!mptcp_skb_can_collapse_to(data_seq, skb, mpext)) {
+			TCP_SKB_CB(skb)->eor = 1;
+			goto alloc_skb;
+		}
+
+		i = skb_shinfo(skb)->nr_frags;
+		can_coalesce = skb_can_coalesce(skb, i, dfrag->page, offset);
+		if (!can_coalesce && i >= READ_ONCE(sysctl_max_skb_frags)) {
+			tcp_mark_push(tcp_sk(ssk), skb);
+			goto alloc_skb;
+		}
+
+		copy -= skb->len;
+	} else {
+alloc_skb:
+		skb = mptcp_alloc_tx_skb(sk, ssk, info->data_lock_held);
+		if (!skb)
+			return -ENOMEM;
+
+		i = skb_shinfo(skb)->nr_frags;
+		reuse_skb = false;
+		mpext = skb_ext_find(skb, SKB_EXT_MPTCP);
+	}
+
+	/* Zero window and all data acked? Probe. */
+	copy = mptcp_check_allowed_size(msk, ssk, data_seq, copy);
+	if (copy == 0) {
+		u64 snd_una = READ_ONCE(msk->snd_una);
+
+		if (snd_una != msk->snd_nxt || tcp_write_queue_tail(ssk)) {
+			tcp_remove_empty_skb(ssk);
+			return 0;
+		}
+
+		zero_window_probe = true;
+		data_seq = snd_una - 1;
+		copy = 1;
+	}
+
+	copy = min_t(size_t, copy, info->limit - info->sent);
+	if (!sk_wmem_schedule(ssk, copy)) {
+		tcp_remove_empty_skb(ssk);
+		return -ENOMEM;
+	}
+
+	if (can_coalesce) {
+		skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
+	} else {
+		get_page(dfrag->page);
+		skb_fill_page_desc(skb, i, dfrag->page, offset, copy);
+	}
+
+	skb->len += copy;
+	skb->data_len += copy;
+	skb->truesize += copy;
+	sk_wmem_queued_add(ssk, copy);
+	sk_mem_charge(ssk, copy);
+	WRITE_ONCE(tcp_sk(ssk)->write_seq, tcp_sk(ssk)->write_seq + copy);
+	TCP_SKB_CB(skb)->end_seq += copy;
+	tcp_skb_pcount_set(skb, 0);
+
+	/* on skb reuse we just need to update the DSS len */
+	if (reuse_skb) {
+		TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;
+		mpext->data_len += copy;
+		goto out;
+	}
+
+	memset(mpext, 0, sizeof(*mpext));
+	mpext->data_seq = data_seq;
+	mpext->subflow_seq = mptcp_subflow_ctx(ssk)->rel_write_seq;
+	mpext->data_len = copy;
+	mpext->use_map = 1;
+	mpext->dsn64 = 1;
+
+	pr_debug("data_seq=%llu subflow_seq=%u data_len=%u dsn64=%d",
+		 mpext->data_seq, mpext->subflow_seq, mpext->data_len,
+		 mpext->dsn64);
+
+	if (zero_window_probe) {
+		mptcp_subflow_ctx(ssk)->rel_write_seq += copy;
+		mpext->frozen = 1;
+		if (READ_ONCE(msk->csum_enabled))
+			mptcp_update_data_checksum(skb, copy);
+		tcp_push_pending_frames(ssk);
+		return 0;
+	}
+out:
+	if (READ_ONCE(msk->csum_enabled))
+		mptcp_update_data_checksum(skb, copy);
+	if (mptcp_subflow_ctx(ssk)->send_infinite_map)
+		mptcp_update_infinite_map(msk, ssk, mpext);
+	trace_mptcp_sendmsg_frag(mpext);
+	mptcp_subflow_ctx(ssk)->rel_write_seq += copy;
+	return copy;
+}
+
+#define MPTCP_SEND_BURST_SIZE		((1 << 16) - \
+					 sizeof(struct tcphdr) - \
+					 MAX_TCP_OPTION_SPACE - \
+					 sizeof(struct ipv6hdr) - \
+					 sizeof(struct frag_hdr))
+
+struct subflow_send_info {
+	struct sock *ssk;
+	u64 linger_time;
+};
+
+void mptcp_subflow_set_active(struct mptcp_subflow_context *subflow)
+{
+	if (!subflow->stale)
+		return;
+
+	subflow->stale = 0;
+	MPTCP_INC_STATS(sock_net(mptcp_subflow_tcp_sock(subflow)), MPTCP_MIB_SUBFLOWRECOVER);
+}
+
+bool mptcp_subflow_active(struct mptcp_subflow_context *subflow)
+{
+	if (unlikely(subflow->stale)) {
+		u32 rcv_tstamp = READ_ONCE(tcp_sk(mptcp_subflow_tcp_sock(subflow))->rcv_tstamp);
+
+		if (subflow->stale_rcv_tstamp == rcv_tstamp)
+			return false;
+
+		mptcp_subflow_set_active(subflow);
+	}
+	return __mptcp_subflow_active(subflow);
+}
+
+#define SSK_MODE_ACTIVE	0
+#define SSK_MODE_BACKUP	1
+#define SSK_MODE_MAX	2
+
+/* implement the mptcp packet scheduler;
+ * returns the subflow that will transmit the next DSS
+ * additionally updates the rtx timeout
+ */
+static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
+{
+	struct subflow_send_info send_info[SSK_MODE_MAX];
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	u32 pace, burst, wmem;
+	int i, nr_active = 0;
+	struct sock *ssk;
+	u64 linger_time;
+	long tout = 0;
+
+	sock_owned_by_me(sk);
+
+	if (__mptcp_check_fallback(msk)) {
+		if (!msk->first)
+			return NULL;
+		return __tcp_can_send(msk->first) &&
+		       sk_stream_memory_free(msk->first) ? msk->first : NULL;
+	}
+
+	/* re-use last subflow, if the burst allow that */
+	if (msk->last_snd && msk->snd_burst > 0 &&
+	    sk_stream_memory_free(msk->last_snd) &&
+	    mptcp_subflow_active(mptcp_subflow_ctx(msk->last_snd))) {
+		mptcp_set_timeout(sk);
+		return msk->last_snd;
+	}
+
+	/* pick the subflow with the lower wmem/wspace ratio */
+	for (i = 0; i < SSK_MODE_MAX; ++i) {
+		send_info[i].ssk = NULL;
+		send_info[i].linger_time = -1;
+	}
+
+	mptcp_for_each_subflow(msk, subflow) {
+		trace_mptcp_subflow_get_send(subflow);
+		ssk =  mptcp_subflow_tcp_sock(subflow);
+		if (!mptcp_subflow_active(subflow))
+			continue;
+
+		tout = max(tout, mptcp_timeout_from_subflow(subflow));
+		nr_active += !subflow->backup;
+		pace = subflow->avg_pacing_rate;
+		if (unlikely(!pace)) {
+			/* init pacing rate from socket */
+			subflow->avg_pacing_rate = READ_ONCE(ssk->sk_pacing_rate);
+			pace = subflow->avg_pacing_rate;
+			if (!pace)
+				continue;
+		}
+
+		linger_time = div_u64((u64)READ_ONCE(ssk->sk_wmem_queued) << 32, pace);
+		if (linger_time < send_info[subflow->backup].linger_time) {
+			send_info[subflow->backup].ssk = ssk;
+			send_info[subflow->backup].linger_time = linger_time;
+		}
+	}
+	__mptcp_set_timeout(sk, tout);
+
+	/* pick the best backup if no other subflow is active */
+	if (!nr_active)
+		send_info[SSK_MODE_ACTIVE].ssk = send_info[SSK_MODE_BACKUP].ssk;
+
+	/* According to the blest algorithm, to avoid HoL blocking for the
+	 * faster flow, we need to:
+	 * - estimate the faster flow linger time
+	 * - use the above to estimate the amount of byte transferred
+	 *   by the faster flow
+	 * - check that the amount of queued data is greter than the above,
+	 *   otherwise do not use the picked, slower, subflow
+	 * We select the subflow with the shorter estimated time to flush
+	 * the queued mem, which basically ensure the above. We just need
+	 * to check that subflow has a non empty cwin.
+	 */
+	ssk = send_info[SSK_MODE_ACTIVE].ssk;
+	if (!ssk || !sk_stream_memory_free(ssk))
+		return NULL;
+
+	burst = min_t(int, MPTCP_SEND_BURST_SIZE, mptcp_wnd_end(msk) - msk->snd_nxt);
+	wmem = READ_ONCE(ssk->sk_wmem_queued);
+	if (!burst) {
+		msk->last_snd = NULL;
+		return ssk;
+	}
+
+	subflow = mptcp_subflow_ctx(ssk);
+	subflow->avg_pacing_rate = div_u64((u64)subflow->avg_pacing_rate * wmem +
+					   READ_ONCE(ssk->sk_pacing_rate) * burst,
+					   burst + wmem);
+	msk->last_snd = ssk;
+	msk->snd_burst = burst;
+	return ssk;
+}
+
+static void mptcp_push_release(struct sock *ssk, struct mptcp_sendmsg_info *info)
+{
+	tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle, info->size_goal);
+	release_sock(ssk);
+}
+
+static void mptcp_update_post_push(struct mptcp_sock *msk,
+				   struct mptcp_data_frag *dfrag,
+				   u32 sent)
+{
+	u64 snd_nxt_new = dfrag->data_seq;
+
+	dfrag->already_sent += sent;
+
+	msk->snd_burst -= sent;
+
+	snd_nxt_new += dfrag->already_sent;
+
+	/* snd_nxt_new can be smaller than snd_nxt in case mptcp
+	 * is recovering after a failover. In that event, this re-sends
+	 * old segments.
+	 *
+	 * Thus compute snd_nxt_new candidate based on
+	 * the dfrag->data_seq that was sent and the data
+	 * that has been handed to the subflow for transmission
+	 * and skip update in case it was old dfrag.
+	 */
+	if (likely(after64(snd_nxt_new, msk->snd_nxt)))
+		msk->snd_nxt = snd_nxt_new;
+}
+
+void mptcp_check_and_set_pending(struct sock *sk)
+{
+	if (mptcp_send_head(sk))
+		mptcp_sk(sk)->push_pending |= BIT(MPTCP_PUSH_PENDING);
+}
+
+void __mptcp_push_pending(struct sock *sk, unsigned int flags)
+{
+	struct sock *prev_ssk = NULL, *ssk = NULL;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_sendmsg_info info = {
+				.flags = flags,
+	};
+	bool do_check_data_fin = false;
+	struct mptcp_data_frag *dfrag;
+	int len;
+
+	while ((dfrag = mptcp_send_head(sk))) {
+		info.sent = dfrag->already_sent;
+		info.limit = dfrag->data_len;
+		len = dfrag->data_len - dfrag->already_sent;
+		while (len > 0) {
+			int ret = 0;
+
+			prev_ssk = ssk;
+			ssk = mptcp_subflow_get_send(msk);
+
+			/* First check. If the ssk has changed since
+			 * the last round, release prev_ssk
+			 */
+			if (ssk != prev_ssk && prev_ssk)
+				mptcp_push_release(prev_ssk, &info);
+			if (!ssk)
+				goto out;
+
+			/* Need to lock the new subflow only if different
+			 * from the previous one, otherwise we are still
+			 * helding the relevant lock
+			 */
+			if (ssk != prev_ssk)
+				lock_sock(ssk);
+
+			ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
+			if (ret <= 0) {
+				if (ret == -EAGAIN)
+					continue;
+				mptcp_push_release(ssk, &info);
+				goto out;
+			}
+
+			do_check_data_fin = true;
+			info.sent += ret;
+			len -= ret;
+
+			mptcp_update_post_push(msk, dfrag, ret);
+		}
+		WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
+	}
+
+	/* at this point we held the socket lock for the last subflow we used */
+	if (ssk)
+		mptcp_push_release(ssk, &info);
+
+out:
+	/* ensure the rtx timer is running */
+	if (!mptcp_rtx_timer_pending(sk))
+		mptcp_reset_rtx_timer(sk);
+	if (do_check_data_fin)
+		mptcp_check_send_data_fin(sk);
+}
+
+static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_sendmsg_info info = {
+		.data_lock_held = true,
+	};
+	struct mptcp_data_frag *dfrag;
+	struct sock *xmit_ssk;
+	int len, copied = 0;
+	bool first = true;
+
+	info.flags = 0;
+	while ((dfrag = mptcp_send_head(sk))) {
+		info.sent = dfrag->already_sent;
+		info.limit = dfrag->data_len;
+		len = dfrag->data_len - dfrag->already_sent;
+		while (len > 0) {
+			int ret = 0;
+
+			/* the caller already invoked the packet scheduler,
+			 * check for a different subflow usage only after
+			 * spooling the first chunk of data
+			 */
+			xmit_ssk = first ? ssk : mptcp_subflow_get_send(mptcp_sk(sk));
+			if (!xmit_ssk)
+				goto out;
+			if (xmit_ssk != ssk) {
+				mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk),
+						       MPTCP_DELEGATE_SEND);
+				goto out;
+			}
+
+			ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
+			if (ret <= 0)
+				goto out;
+
+			info.sent += ret;
+			copied += ret;
+			len -= ret;
+			first = false;
+
+			mptcp_update_post_push(msk, dfrag, ret);
+		}
+		WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
+	}
+
+out:
+	/* __mptcp_alloc_tx_skb could have released some wmem and we are
+	 * not going to flush it via release_sock()
+	 */
+	if (copied) {
+		tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
+			 info.size_goal);
+		if (!mptcp_rtx_timer_pending(sk))
+			mptcp_reset_rtx_timer(sk);
+
+		if (msk->snd_data_fin_enable &&
+		    msk->snd_nxt + 1 == msk->write_seq)
+			mptcp_schedule_work(sk);
+	}
+}
+
+static void mptcp_set_nospace(struct sock *sk)
+{
+	/* enable autotune */
+	set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+
+	/* will be cleared on avail space */
+	set_bit(MPTCP_NOSPACE, &mptcp_sk(sk)->flags);
+}
+
+static int mptcp_disconnect(struct sock *sk, int flags);
+
+static int mptcp_sendmsg_fastopen(struct sock *sk, struct sock *ssk, struct msghdr *msg,
+				  size_t len, int *copied_syn)
+{
+	unsigned int saved_flags = msg->msg_flags;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	int ret;
+
+	lock_sock(ssk);
+	msg->msg_flags |= MSG_DONTWAIT;
+	msk->fastopening = 1;
+	ret = tcp_sendmsg_fastopen(ssk, msg, copied_syn, len, NULL);
+	msk->fastopening = 0;
+	msg->msg_flags = saved_flags;
+	release_sock(ssk);
+
+	/* do the blocking bits of inet_stream_connect outside the ssk socket lock */
+	if (ret == -EINPROGRESS && !(msg->msg_flags & MSG_DONTWAIT)) {
+		ret = __inet_stream_connect(sk->sk_socket, msg->msg_name,
+					    msg->msg_namelen, msg->msg_flags, 1);
+
+		/* Keep the same behaviour of plain TCP: zero the copied bytes in
+		 * case of any error, except timeout or signal
+		 */
+		if (ret && ret != -EINPROGRESS && ret != -ERESTARTSYS && ret != -EINTR)
+			*copied_syn = 0;
+	} else if (ret && ret != -EINPROGRESS) {
+		/* The disconnect() op called by tcp_sendmsg_fastopen()/
+		 * __inet_stream_connect() can fail, due to looking check,
+		 * see mptcp_disconnect().
+		 * Attempt it again outside the problematic scope.
+		 */
+		if (!mptcp_disconnect(sk, 0))
+			sk->sk_socket->state = SS_UNCONNECTED;
+	}
+
+	return ret;
+}
+
+static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct page_frag *pfrag;
+	struct socket *ssock;
+	size_t copied = 0;
+	int ret = 0;
+	long timeo;
+
+	/* we don't support FASTOPEN yet */
+	if (msg->msg_flags & MSG_FASTOPEN)
+		return -EOPNOTSUPP;
+
+	/* silently ignore everything else */
+	msg->msg_flags &= MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL;
+
+	lock_sock(sk);
+
+	ssock = __mptcp_nmpc_socket(msk);
+	if (unlikely(ssock && inet_sk(ssock->sk)->defer_connect)) {
+		int copied_syn = 0;
+
+		ret = mptcp_sendmsg_fastopen(sk, ssock->sk, msg, len, &copied_syn);
+		copied += copied_syn;
+		if (ret == -EINPROGRESS && copied_syn > 0)
+			goto out;
+		else if (ret)
+			goto do_error;
+	}
+
+	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
+
+	if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
+		ret = sk_stream_wait_connect(sk, &timeo);
+		if (ret)
+			goto do_error;
+	}
+
+	ret = -EPIPE;
+	if (unlikely(sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)))
+		goto do_error;
+
+	pfrag = sk_page_frag(sk);
+
+	while (msg_data_left(msg)) {
+		int total_ts, frag_truesize = 0;
+		struct mptcp_data_frag *dfrag;
+		bool dfrag_collapsed;
+		size_t psize, offset;
+
+		/* reuse tail pfrag, if possible, or carve a new one from the
+		 * page allocator
+		 */
+		dfrag = mptcp_pending_tail(sk);
+		dfrag_collapsed = mptcp_frag_can_collapse_to(msk, pfrag, dfrag);
+		if (!dfrag_collapsed) {
+			if (!sk_stream_memory_free(sk))
+				goto wait_for_memory;
+
+			if (!mptcp_page_frag_refill(sk, pfrag))
+				goto wait_for_memory;
+
+			dfrag = mptcp_carve_data_frag(msk, pfrag, pfrag->offset);
+			frag_truesize = dfrag->overhead;
+		}
+
+		/* we do not bound vs wspace, to allow a single packet.
+		 * memory accounting will prevent execessive memory usage
+		 * anyway
+		 */
+		offset = dfrag->offset + dfrag->data_len;
+		psize = pfrag->size - offset;
+		psize = min_t(size_t, psize, msg_data_left(msg));
+		total_ts = psize + frag_truesize;
+
+		if (!sk_wmem_schedule(sk, total_ts))
+			goto wait_for_memory;
+
+		if (copy_page_from_iter(dfrag->page, offset, psize,
+					&msg->msg_iter) != psize) {
+			ret = -EFAULT;
+			goto do_error;
+		}
+
+		/* data successfully copied into the write queue */
+		sk_forward_alloc_add(sk, -total_ts);
+		copied += psize;
+		dfrag->data_len += psize;
+		frag_truesize += psize;
+		pfrag->offset += frag_truesize;
+		WRITE_ONCE(msk->write_seq, msk->write_seq + psize);
+
+		/* charge data on mptcp pending queue to the msk socket
+		 * Note: we charge such data both to sk and ssk
+		 */
+		sk_wmem_queued_add(sk, frag_truesize);
+		if (!dfrag_collapsed) {
+			get_page(dfrag->page);
+			list_add_tail(&dfrag->list, &msk->rtx_queue);
+			if (!msk->first_pending)
+				WRITE_ONCE(msk->first_pending, dfrag);
+		}
+		pr_debug("msk=%p dfrag at seq=%llu len=%u sent=%u new=%d", msk,
+			 dfrag->data_seq, dfrag->data_len, dfrag->already_sent,
+			 !dfrag_collapsed);
+
+		continue;
+
+wait_for_memory:
+		mptcp_set_nospace(sk);
+		__mptcp_push_pending(sk, msg->msg_flags);
+		ret = sk_stream_wait_memory(sk, &timeo);
+		if (ret)
+			goto do_error;
+	}
+
+	if (copied)
+		__mptcp_push_pending(sk, msg->msg_flags);
+
+out:
+	release_sock(sk);
+	return copied;
+
+do_error:
+	if (copied)
+		goto out;
+
+	copied = sk_stream_error(sk, msg->msg_flags, ret);
+	goto out;
+}
+
+static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
+				struct msghdr *msg,
+				size_t len, int flags,
+				struct scm_timestamping_internal *tss,
+				int *cmsg_flags)
+{
+	struct sk_buff *skb, *tmp;
+	int copied = 0;
+
+	skb_queue_walk_safe(&msk->receive_queue, skb, tmp) {
+		u32 offset = MPTCP_SKB_CB(skb)->offset;
+		u32 data_len = skb->len - offset;
+		u32 count = min_t(size_t, len - copied, data_len);
+		int err;
+
+		if (!(flags & MSG_TRUNC)) {
+			err = skb_copy_datagram_msg(skb, offset, msg, count);
+			if (unlikely(err < 0)) {
+				if (!copied)
+					return err;
+				break;
+			}
+		}
+
+		if (MPTCP_SKB_CB(skb)->has_rxtstamp) {
+			tcp_update_recv_tstamps(skb, tss);
+			*cmsg_flags |= MPTCP_CMSG_TS;
+		}
+
+		copied += count;
+
+		if (count < data_len) {
+			if (!(flags & MSG_PEEK)) {
+				MPTCP_SKB_CB(skb)->offset += count;
+				MPTCP_SKB_CB(skb)->map_seq += count;
+			}
+			break;
+		}
+
+		if (!(flags & MSG_PEEK)) {
+			/* we will bulk release the skb memory later */
+			skb->destructor = NULL;
+			WRITE_ONCE(msk->rmem_released, msk->rmem_released + skb->truesize);
+			__skb_unlink(skb, &msk->receive_queue);
+			__kfree_skb(skb);
+		}
+
+		if (copied >= len)
+			break;
+	}
+
+	return copied;
+}
+
+/* receive buffer autotuning.  See tcp_rcv_space_adjust for more information.
+ *
+ * Only difference: Use highest rtt estimate of the subflows in use.
+ */
+static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	u32 time, advmss = 1;
+	u64 rtt_us, mstamp;
+
+	sock_owned_by_me(sk);
+
+	if (copied <= 0)
+		return;
+
+	msk->rcvq_space.copied += copied;
+
+	mstamp = div_u64(tcp_clock_ns(), NSEC_PER_USEC);
+	time = tcp_stamp_us_delta(mstamp, msk->rcvq_space.time);
+
+	rtt_us = msk->rcvq_space.rtt_us;
+	if (rtt_us && time < (rtt_us >> 3))
+		return;
+
+	rtt_us = 0;
+	mptcp_for_each_subflow(msk, subflow) {
+		const struct tcp_sock *tp;
+		u64 sf_rtt_us;
+		u32 sf_advmss;
+
+		tp = tcp_sk(mptcp_subflow_tcp_sock(subflow));
+
+		sf_rtt_us = READ_ONCE(tp->rcv_rtt_est.rtt_us);
+		sf_advmss = READ_ONCE(tp->advmss);
+
+		rtt_us = max(sf_rtt_us, rtt_us);
+		advmss = max(sf_advmss, advmss);
+	}
+
+	msk->rcvq_space.rtt_us = rtt_us;
+	if (time < (rtt_us >> 3) || rtt_us == 0)
+		return;
+
+	if (msk->rcvq_space.copied <= msk->rcvq_space.space)
+		goto new_measure;
+
+	if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_moderate_rcvbuf) &&
+	    !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
+		int rcvmem, rcvbuf;
+		u64 rcvwin, grow;
+
+		rcvwin = ((u64)msk->rcvq_space.copied << 1) + 16 * advmss;
+
+		grow = rcvwin * (msk->rcvq_space.copied - msk->rcvq_space.space);
+
+		do_div(grow, msk->rcvq_space.space);
+		rcvwin += (grow << 1);
+
+		rcvmem = SKB_TRUESIZE(advmss + MAX_TCP_HEADER);
+		while (tcp_win_from_space(sk, rcvmem) < advmss)
+			rcvmem += 128;
+
+		do_div(rcvwin, advmss);
+		rcvbuf = min_t(u64, rcvwin * rcvmem,
+			       READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2]));
+
+		if (rcvbuf > sk->sk_rcvbuf) {
+			u32 window_clamp;
+
+			window_clamp = tcp_win_from_space(sk, rcvbuf);
+			WRITE_ONCE(sk->sk_rcvbuf, rcvbuf);
+
+			/* Make subflows follow along.  If we do not do this, we
+			 * get drops at subflow level if skbs can't be moved to
+			 * the mptcp rx queue fast enough (announced rcv_win can
+			 * exceed ssk->sk_rcvbuf).
+			 */
+			mptcp_for_each_subflow(msk, subflow) {
+				struct sock *ssk;
+				bool slow;
+
+				ssk = mptcp_subflow_tcp_sock(subflow);
+				slow = lock_sock_fast(ssk);
+				WRITE_ONCE(ssk->sk_rcvbuf, rcvbuf);
+				tcp_sk(ssk)->window_clamp = window_clamp;
+				tcp_cleanup_rbuf(ssk, 1);
+				unlock_sock_fast(ssk, slow);
+			}
+		}
+	}
+
+	msk->rcvq_space.space = msk->rcvq_space.copied;
+new_measure:
+	msk->rcvq_space.copied = 0;
+	msk->rcvq_space.time = mstamp;
+}
+
+static void __mptcp_update_rmem(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (!msk->rmem_released)
+		return;
+
+	atomic_sub(msk->rmem_released, &sk->sk_rmem_alloc);
+	mptcp_rmem_uncharge(sk, msk->rmem_released);
+	WRITE_ONCE(msk->rmem_released, 0);
+}
+
+static void __mptcp_splice_receive_queue(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	skb_queue_splice_tail_init(&sk->sk_receive_queue, &msk->receive_queue);
+}
+
+static bool __mptcp_move_skbs(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+	unsigned int moved = 0;
+	bool ret, done;
+
+	do {
+		struct sock *ssk = mptcp_subflow_recv_lookup(msk);
+		bool slowpath;
+
+		/* we can have data pending in the subflows only if the msk
+		 * receive buffer was full at subflow_data_ready() time,
+		 * that is an unlikely slow path.
+		 */
+		if (likely(!ssk))
+			break;
+
+		slowpath = lock_sock_fast(ssk);
+		mptcp_data_lock(sk);
+		__mptcp_update_rmem(sk);
+		done = __mptcp_move_skbs_from_subflow(msk, ssk, &moved);
+		mptcp_data_unlock(sk);
+
+		if (unlikely(ssk->sk_err))
+			__mptcp_error_report(sk);
+		unlock_sock_fast(ssk, slowpath);
+	} while (!done);
+
+	/* acquire the data lock only if some input data is pending */
+	ret = moved > 0;
+	if (!RB_EMPTY_ROOT(&msk->out_of_order_queue) ||
+	    !skb_queue_empty_lockless(&sk->sk_receive_queue)) {
+		mptcp_data_lock(sk);
+		__mptcp_update_rmem(sk);
+		ret |= __mptcp_ofo_queue(msk);
+		__mptcp_splice_receive_queue(sk);
+		mptcp_data_unlock(sk);
+	}
+	if (ret)
+		mptcp_check_data_fin((struct sock *)msk);
+	return !skb_queue_empty(&msk->receive_queue);
+}
+
+static unsigned int mptcp_inq_hint(const struct sock *sk)
+{
+	const struct mptcp_sock *msk = mptcp_sk(sk);
+	const struct sk_buff *skb;
+
+	skb = skb_peek(&msk->receive_queue);
+	if (skb) {
+		u64 hint_val = msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq;
+
+		if (hint_val >= INT_MAX)
+			return INT_MAX;
+
+		return (unsigned int)hint_val;
+	}
+
+	if (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN))
+		return 1;
+
+	return 0;
+}
+
+static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
+			 int flags, int *addr_len)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct scm_timestamping_internal tss;
+	int copied = 0, cmsg_flags = 0;
+	int target;
+	long timeo;
+
+	/* MSG_ERRQUEUE is really a no-op till we support IP_RECVERR */
+	if (unlikely(flags & MSG_ERRQUEUE))
+		return inet_recv_error(sk, msg, len, addr_len);
+
+	lock_sock(sk);
+	if (unlikely(sk->sk_state == TCP_LISTEN)) {
+		copied = -ENOTCONN;
+		goto out_err;
+	}
+
+	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
+
+	len = min_t(size_t, len, INT_MAX);
+	target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
+
+	if (unlikely(msk->recvmsg_inq))
+		cmsg_flags = MPTCP_CMSG_INQ;
+
+	while (copied < len) {
+		int bytes_read;
+
+		bytes_read = __mptcp_recvmsg_mskq(msk, msg, len - copied, flags, &tss, &cmsg_flags);
+		if (unlikely(bytes_read < 0)) {
+			if (!copied)
+				copied = bytes_read;
+			goto out_err;
+		}
+
+		copied += bytes_read;
+
+		/* be sure to advertise window change */
+		mptcp_cleanup_rbuf(msk);
+
+		if (skb_queue_empty(&msk->receive_queue) && __mptcp_move_skbs(msk))
+			continue;
+
+		/* only the master socket status is relevant here. The exit
+		 * conditions mirror closely tcp_recvmsg()
+		 */
+		if (copied >= target)
+			break;
+
+		if (copied) {
+			if (sk->sk_err ||
+			    sk->sk_state == TCP_CLOSE ||
+			    (sk->sk_shutdown & RCV_SHUTDOWN) ||
+			    !timeo ||
+			    signal_pending(current))
+				break;
+		} else {
+			if (sk->sk_err) {
+				copied = sock_error(sk);
+				break;
+			}
+
+			if (test_and_clear_bit(MPTCP_WORK_EOF, &msk->flags))
+				mptcp_check_for_eof(msk);
+
+			if (sk->sk_shutdown & RCV_SHUTDOWN) {
+				/* race breaker: the shutdown could be after the
+				 * previous receive queue check
+				 */
+				if (__mptcp_move_skbs(msk))
+					continue;
+				break;
+			}
+
+			if (sk->sk_state == TCP_CLOSE) {
+				copied = -ENOTCONN;
+				break;
+			}
+
+			if (!timeo) {
+				copied = -EAGAIN;
+				break;
+			}
+
+			if (signal_pending(current)) {
+				copied = sock_intr_errno(timeo);
+				break;
+			}
+		}
+
+		pr_debug("block timeout %ld", timeo);
+		sk_wait_data(sk, &timeo, NULL);
+	}
+
+out_err:
+	if (cmsg_flags && copied >= 0) {
+		if (cmsg_flags & MPTCP_CMSG_TS)
+			tcp_recv_timestamp(msg, sk, &tss);
+
+		if (cmsg_flags & MPTCP_CMSG_INQ) {
+			unsigned int inq = mptcp_inq_hint(sk);
+
+			put_cmsg(msg, SOL_TCP, TCP_CM_INQ, sizeof(inq), &inq);
+		}
+	}
+
+	pr_debug("msk=%p rx queue empty=%d:%d copied=%d",
+		 msk, skb_queue_empty_lockless(&sk->sk_receive_queue),
+		 skb_queue_empty(&msk->receive_queue), copied);
+	if (!(flags & MSG_PEEK))
+		mptcp_rcv_space_adjust(msk, copied);
+
+	release_sock(sk);
+	return copied;
+}
+
+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 mptcp_sock *msk = mptcp_sk(sk);
+
+	bh_lock_sock(sk);
+	if (!sock_owned_by_user(sk)) {
+		/* we need a process context to retransmit */
+		if (!test_and_set_bit(MPTCP_WORK_RTX, &msk->flags))
+			mptcp_schedule_work(sk);
+	} else {
+		/* delegate our work to tcp_release_cb() */
+		__set_bit(MPTCP_RETRANSMIT, &msk->cb_flags);
+	}
+	bh_unlock_sock(sk);
+	sock_put(sk);
+}
+
+static void mptcp_tout_timer(struct timer_list *t)
+{
+	struct sock *sk = from_timer(sk, t, sk_timer);
+
+	mptcp_schedule_work(sk);
+	sock_put(sk);
+}
+
+/* Find an idle subflow.  Return NULL if there is unacked data at tcp
+ * level.
+ *
+ * A backup subflow is returned only if that is the only kind available.
+ */
+static struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
+{
+	struct sock *backup = NULL, *pick = NULL;
+	struct mptcp_subflow_context *subflow;
+	int min_stale_count = INT_MAX;
+
+	sock_owned_by_me((const struct sock *)msk);
+
+	if (__mptcp_check_fallback(msk))
+		return NULL;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if (!__mptcp_subflow_active(subflow))
+			continue;
+
+		/* still data outstanding at TCP level? skip this */
+		if (!tcp_rtx_and_write_queues_empty(ssk)) {
+			mptcp_pm_subflow_chk_stale(msk, ssk);
+			min_stale_count = min_t(int, min_stale_count, subflow->stale_count);
+			continue;
+		}
+
+		if (subflow->backup) {
+			if (!backup)
+				backup = ssk;
+			continue;
+		}
+
+		if (!pick)
+			pick = ssk;
+	}
+
+	if (pick)
+		return pick;
+
+	/* use backup only if there are no progresses anywhere */
+	return min_stale_count > 1 ? backup : NULL;
+}
+
+static void mptcp_dispose_initial_subflow(struct mptcp_sock *msk)
+{
+	if (msk->subflow) {
+		iput(SOCK_INODE(msk->subflow));
+		WRITE_ONCE(msk->subflow, NULL);
+	}
+}
+
+bool __mptcp_retransmit_pending_data(struct sock *sk)
+{
+	struct mptcp_data_frag *cur, *rtx_head;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (__mptcp_check_fallback(mptcp_sk(sk)))
+		return false;
+
+	if (tcp_rtx_and_write_queues_empty(sk))
+		return false;
+
+	/* the closing socket has some data untransmitted and/or unacked:
+	 * some data in the mptcp rtx queue has not really xmitted yet.
+	 * keep it simple and re-inject the whole mptcp level rtx queue
+	 */
+	mptcp_data_lock(sk);
+	__mptcp_clean_una_wakeup(sk);
+	rtx_head = mptcp_rtx_head(sk);
+	if (!rtx_head) {
+		mptcp_data_unlock(sk);
+		return false;
+	}
+
+	msk->recovery_snd_nxt = msk->snd_nxt;
+	msk->recovery = true;
+	mptcp_data_unlock(sk);
+
+	msk->first_pending = rtx_head;
+	msk->snd_burst = 0;
+
+	/* be sure to clear the "sent status" on all re-injected fragments */
+	list_for_each_entry(cur, &msk->rtx_queue, list) {
+		if (!cur->already_sent)
+			break;
+		cur->already_sent = 0;
+	}
+
+	return true;
+}
+
+/* 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
+ * TCP_CLOSE state
+ */
+static void __mptcp_subflow_disconnect(struct sock *ssk,
+				       struct mptcp_subflow_context *subflow,
+				       unsigned int flags)
+{
+	if (((1 << ssk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
+	    (flags & MPTCP_CF_FASTCLOSE)) {
+		/* The MPTCP code never wait on the subflow sockets, TCP-level
+		 * disconnect should never fail
+		 */
+		WARN_ON_ONCE(tcp_disconnect(ssk, 0));
+		mptcp_subflow_ctx_reset(subflow);
+	} else {
+		tcp_shutdown(ssk, SEND_SHUTDOWN);
+	}
+}
+
+/* subflow sockets can be either outgoing (connect) or incoming
+ * (accept).
+ *
+ * Outgoing subflows use in-kernel sockets.
+ * Incoming subflows do not have their own 'struct socket' allocated,
+ * so we need to use tcp_close() after detaching them from the mptcp
+ * parent socket.
+ */
+static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
+			      struct mptcp_subflow_context *subflow,
+			      unsigned int flags)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool dispose_it, need_push = false;
+
+	/* If the first subflow moved to a close state before accept, e.g. due
+	 * to an incoming reset or listener shutdown, the subflow socket is
+	 * already deleted by inet_child_forget() and the mptcp socket can't
+	 * survive too.
+	 */
+	if (msk->in_accept_queue && msk->first == ssk &&
+	    (sock_flag(sk, SOCK_DEAD) || sock_flag(ssk, SOCK_DEAD))) {
+		/* ensure later check in mptcp_worker() will dispose the msk */
+		mptcp_set_close_tout(sk, tcp_jiffies32 - (TCP_TIMEWAIT_LEN + 1));
+		sock_set_flag(sk, SOCK_DEAD);
+		lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);
+		mptcp_subflow_drop_ctx(ssk);
+		goto out_release;
+	}
+
+	dispose_it = !msk->subflow || ssk != msk->subflow->sk;
+	if (dispose_it)
+		list_del(&subflow->node);
+
+	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;
+	}
+
+	need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk);
+	if (!dispose_it) {
+		__mptcp_subflow_disconnect(ssk, subflow, flags);
+		msk->subflow->state = SS_UNCONNECTED;
+		release_sock(ssk);
+
+		goto out;
+	}
+
+	subflow->disposable = 1;
+
+	/* if ssk hit tcp_done(), tcp_cleanup_ulp() cleared the related ops
+	 * the ssk has been already destroyed, we just need to release the
+	 * reference owned by msk;
+	 */
+	if (!inet_csk(ssk)->icsk_ulp_ops) {
+		WARN_ON_ONCE(!sock_flag(ssk, SOCK_DEAD));
+		kfree_rcu(subflow, rcu);
+	} else {
+		/* otherwise tcp will dispose of the ssk and subflow ctx */
+		__tcp_close(ssk, 0);
+
+		/* close acquired an extra ref */
+		__sock_put(ssk);
+	}
+
+out_release:
+	__mptcp_subflow_error_report(sk, ssk);
+	release_sock(ssk);
+
+	sock_put(ssk);
+
+	if (ssk == msk->first)
+		WRITE_ONCE(msk->first, NULL);
+
+out:
+	if (ssk == msk->last_snd)
+		msk->last_snd = NULL;
+
+	if (need_push)
+		__mptcp_push_pending(sk, 0);
+
+	/* Catch every 'all subflows closed' scenario, including peers silently
+	 * closing them, e.g. due to timeout.
+	 * For established sockets, allow an additional timeout before closing,
+	 * as the protocol can still create more subflows.
+	 */
+	if (list_is_singular(&msk->conn_list) && msk->first &&
+	    inet_sk_state_load(msk->first) == TCP_CLOSE) {
+		if (sk->sk_state != TCP_ESTABLISHED ||
+		    msk->in_accept_queue || sock_flag(sk, SOCK_DEAD)) {
+			inet_sk_state_store(sk, TCP_CLOSE);
+			mptcp_close_wake_up(sk);
+		} else {
+			mptcp_start_tout_timer(sk);
+		}
+	}
+}
+
+void mptcp_close_ssk(struct sock *sk, struct sock *ssk,
+		     struct mptcp_subflow_context *subflow)
+{
+	if (sk->sk_state == TCP_ESTABLISHED)
+		mptcp_event(MPTCP_EVENT_SUB_CLOSED, mptcp_sk(sk), ssk, GFP_KERNEL);
+
+	/* subflow aborted before reaching the fully_established status
+	 * attempt the creation of the next subflow
+	 */
+	mptcp_pm_subflow_check_next(mptcp_sk(sk), ssk, subflow);
+
+	__mptcp_close_ssk(sk, ssk, subflow, MPTCP_CF_PUSH);
+}
+
+static unsigned int mptcp_sync_mss(struct sock *sk, u32 pmtu)
+{
+	return 0;
+}
+
+static void __mptcp_close_subflow(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow, *tmp;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	might_sleep();
+
+	mptcp_for_each_subflow_safe(msk, subflow, tmp) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if (inet_sk_state_load(ssk) != TCP_CLOSE)
+			continue;
+
+		/* 'subflow_data_ready' will re-sched once rx queue is empty */
+		if (!skb_queue_empty_lockless(&ssk->sk_receive_queue))
+			continue;
+
+		mptcp_close_ssk(sk, ssk, subflow);
+	}
+
+}
+
+static bool mptcp_close_tout_expired(const struct sock *sk)
+{
+	if (!inet_csk(sk)->icsk_mtup.probe_timestamp ||
+	    sk->sk_state == TCP_CLOSE)
+		return false;
+
+	return time_after32(tcp_jiffies32,
+		  inet_csk(sk)->icsk_mtup.probe_timestamp + TCP_TIMEWAIT_LEN);
+}
+
+static void mptcp_check_fastclose(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow, *tmp;
+	struct sock *sk = &msk->sk.icsk_inet.sk;
+
+	if (likely(!READ_ONCE(msk->rcv_fastclose)))
+		return;
+
+	mptcp_token_destroy(msk);
+
+	mptcp_for_each_subflow_safe(msk, subflow, tmp) {
+		struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
+		bool slow;
+
+		slow = lock_sock_fast(tcp_sk);
+		if (tcp_sk->sk_state != TCP_CLOSE) {
+			tcp_send_active_reset(tcp_sk, GFP_ATOMIC);
+			tcp_set_state(tcp_sk, TCP_CLOSE);
+		}
+		unlock_sock_fast(tcp_sk, slow);
+	}
+
+	/* Mirror the tcp_reset() error propagation */
+	switch (sk->sk_state) {
+	case TCP_SYN_SENT:
+		WRITE_ONCE(sk->sk_err, ECONNREFUSED);
+		break;
+	case TCP_CLOSE_WAIT:
+		WRITE_ONCE(sk->sk_err, EPIPE);
+		break;
+	case TCP_CLOSE:
+		return;
+	default:
+		WRITE_ONCE(sk->sk_err, ECONNRESET);
+	}
+
+	inet_sk_state_store(sk, TCP_CLOSE);
+	WRITE_ONCE(sk->sk_shutdown, SHUTDOWN_MASK);
+	smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
+	set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags);
+
+	/* the calling mptcp_worker will properly destroy the socket */
+	if (sock_flag(sk, SOCK_DEAD))
+		return;
+
+	sk->sk_state_change(sk);
+	sk_error_report(sk);
+}
+
+static void __mptcp_retrans(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_sendmsg_info info = {};
+	struct mptcp_data_frag *dfrag;
+	size_t copied = 0;
+	struct sock *ssk;
+	int ret;
+
+	mptcp_clean_una_wakeup(sk);
+
+	/* first check ssk: need to kick "stale" logic */
+	ssk = mptcp_subflow_get_retrans(msk);
+	dfrag = mptcp_rtx_head(sk);
+	if (!dfrag) {
+		if (mptcp_data_fin_enabled(msk)) {
+			struct inet_connection_sock *icsk = inet_csk(sk);
+
+			icsk->icsk_retransmits++;
+			mptcp_set_datafin_timeout(sk);
+			mptcp_send_ack(msk);
+
+			goto reset_timer;
+		}
+
+		if (!mptcp_send_head(sk))
+			return;
+
+		goto reset_timer;
+	}
+
+	if (!ssk)
+		goto reset_timer;
+
+	lock_sock(ssk);
+
+	/* limit retransmission to the bytes already sent on some subflows */
+	info.sent = 0;
+	info.limit = READ_ONCE(msk->csum_enabled) ? dfrag->data_len : dfrag->already_sent;
+	while (info.sent < info.limit) {
+		ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
+		if (ret <= 0)
+			break;
+
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RETRANSSEGS);
+		copied += ret;
+		info.sent += ret;
+	}
+	if (copied) {
+		dfrag->already_sent = max(dfrag->already_sent, info.sent);
+		tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
+			 info.size_goal);
+		WRITE_ONCE(msk->allow_infinite_fallback, false);
+	}
+
+	release_sock(ssk);
+
+reset_timer:
+	mptcp_check_and_set_pending(sk);
+
+	if (!mptcp_rtx_timer_pending(sk))
+		mptcp_reset_rtx_timer(sk);
+}
+
+/* schedule the timeout timer for the relevant event: either close timeout
+ * or mp_fail timeout. The close timeout takes precedence on the mp_fail one
+ */
+void mptcp_reset_tout_timer(struct mptcp_sock *msk, unsigned long fail_tout)
+{
+	struct sock *sk = (struct sock *)msk;
+	unsigned long timeout, close_timeout;
+
+	if (!fail_tout && !inet_csk(sk)->icsk_mtup.probe_timestamp)
+		return;
+
+	close_timeout = inet_csk(sk)->icsk_mtup.probe_timestamp - tcp_jiffies32 + jiffies +
+			TCP_TIMEWAIT_LEN;
+
+	/* the close timeout takes precedence on the fail one, and here at least one of
+	 * them is active
+	 */
+	timeout = inet_csk(sk)->icsk_mtup.probe_timestamp ? close_timeout : fail_tout;
+
+	sk_reset_timer(sk, &sk->sk_timer, timeout);
+}
+
+static void mptcp_mp_fail_no_response(struct mptcp_sock *msk)
+{
+	struct sock *ssk = msk->first;
+	bool slow;
+
+	if (!ssk)
+		return;
+
+	pr_debug("MP_FAIL doesn't respond, reset the subflow");
+
+	slow = lock_sock_fast(ssk);
+	mptcp_subflow_reset(ssk);
+	WRITE_ONCE(mptcp_subflow_ctx(ssk)->fail_tout, 0);
+	unlock_sock_fast(ssk, slow);
+}
+
+static void mptcp_do_fastclose(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow, *tmp;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	mptcp_for_each_subflow_safe(msk, subflow, tmp)
+		__mptcp_close_ssk(sk, mptcp_subflow_tcp_sock(subflow),
+				  subflow, MPTCP_CF_FASTCLOSE);
+}
+
+static void mptcp_worker(struct work_struct *work)
+{
+	struct mptcp_sock *msk = container_of(work, struct mptcp_sock, work);
+	struct sock *sk = &msk->sk.icsk_inet.sk;
+	unsigned long fail_tout;
+	int state;
+
+	lock_sock(sk);
+	state = sk->sk_state;
+	if (unlikely((1 << state) & (TCPF_CLOSE | TCPF_LISTEN)))
+		goto unlock;
+
+	mptcp_check_fastclose(msk);
+
+	mptcp_pm_nl_work(msk);
+
+	if (test_and_clear_bit(MPTCP_WORK_EOF, &msk->flags))
+		mptcp_check_for_eof(msk);
+
+	mptcp_check_send_data_fin(sk);
+	mptcp_check_data_fin_ack(sk);
+	mptcp_check_data_fin(sk);
+
+	if (test_and_clear_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags))
+		__mptcp_close_subflow(sk);
+
+	if (mptcp_close_tout_expired(sk)) {
+		inet_sk_state_store(sk, TCP_CLOSE);
+		mptcp_do_fastclose(sk);
+		mptcp_close_wake_up(sk);
+	}
+
+	if (sock_flag(sk, SOCK_DEAD) && sk->sk_state == TCP_CLOSE) {
+		__mptcp_destroy_sock(sk);
+		goto unlock;
+	}
+
+	if (test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))
+		__mptcp_retrans(sk);
+
+	fail_tout = msk->first ? READ_ONCE(mptcp_subflow_ctx(msk->first)->fail_tout) : 0;
+	if (fail_tout && time_after(jiffies, fail_tout))
+		mptcp_mp_fail_no_response(msk);
+
+unlock:
+	release_sock(sk);
+	sock_put(sk);
+}
+
+static int __mptcp_init_sock(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	INIT_LIST_HEAD(&msk->conn_list);
+	INIT_LIST_HEAD(&msk->join_list);
+	INIT_LIST_HEAD(&msk->rtx_queue);
+	INIT_WORK(&msk->work, mptcp_worker);
+	__skb_queue_head_init(&msk->receive_queue);
+	msk->out_of_order_queue = RB_ROOT;
+	msk->first_pending = NULL;
+	msk->rmem_fwd_alloc = 0;
+	WRITE_ONCE(msk->rmem_released, 0);
+	msk->timer_ival = TCP_RTO_MIN;
+
+	WRITE_ONCE(msk->first, NULL);
+	inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss;
+	WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk)));
+	WRITE_ONCE(msk->allow_infinite_fallback, true);
+	msk->recovery = false;
+
+	mptcp_pm_data_init(msk);
+
+	/* 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);
+
+	return 0;
+}
+
+static void mptcp_ca_reset(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	tcp_assign_congestion_control(sk);
+	strcpy(mptcp_sk(sk)->ca_name, icsk->icsk_ca_ops->name);
+
+	/* no need to keep a reference to the ops, the name will suffice */
+	tcp_cleanup_congestion_control(sk);
+	icsk->icsk_ca_ops = NULL;
+}
+
+static int mptcp_init_sock(struct sock *sk)
+{
+	struct net *net = sock_net(sk);
+	int ret;
+
+	ret = __mptcp_init_sock(sk);
+	if (ret)
+		return ret;
+
+	if (!mptcp_is_enabled(net))
+		return -ENOPROTOOPT;
+
+	if (unlikely(!net->mib.mptcp_statistics) && !mptcp_mib_alloc(net))
+		return -ENOMEM;
+
+	ret = __mptcp_socket_create(mptcp_sk(sk));
+	if (ret)
+		return ret;
+
+	/* fetch the ca name; do it outside __mptcp_init_sock(), so that clone will
+	 * propagate the correct value
+	 */
+	mptcp_ca_reset(sk);
+
+	sk_sockets_allocated_inc(sk);
+	sk->sk_rcvbuf = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[1]);
+	sk->sk_sndbuf = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_wmem[1]);
+
+	return 0;
+}
+
+static void __mptcp_clear_xmit(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_data_frag *dtmp, *dfrag;
+
+	WRITE_ONCE(msk->first_pending, NULL);
+	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list)
+		dfrag_clear(sk, dfrag);
+}
+
+void mptcp_cancel_work(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (cancel_work_sync(&msk->work))
+		__sock_put(sk);
+}
+
+void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how)
+{
+	lock_sock(ssk);
+
+	switch (ssk->sk_state) {
+	case TCP_LISTEN:
+		if (!(how & RCV_SHUTDOWN))
+			break;
+		fallthrough;
+	case TCP_SYN_SENT:
+		WARN_ON_ONCE(tcp_disconnect(ssk, O_NONBLOCK));
+		break;
+	default:
+		if (__mptcp_check_fallback(mptcp_sk(sk))) {
+			pr_debug("Fallback");
+			ssk->sk_shutdown |= how;
+			tcp_shutdown(ssk, how);
+
+			/* simulate the data_fin ack reception to let the state
+			 * machine move forward
+			 */
+			WRITE_ONCE(mptcp_sk(sk)->snd_una, mptcp_sk(sk)->snd_nxt);
+			mptcp_schedule_work(sk);
+		} else {
+			pr_debug("Sending DATA_FIN on subflow %p", ssk);
+			tcp_send_ack(ssk);
+			if (!mptcp_rtx_timer_pending(sk))
+				mptcp_reset_rtx_timer(sk);
+		}
+		break;
+	}
+
+	release_sock(ssk);
+}
+
+static const unsigned char new_state[16] = {
+	/* current state:     new state:      action:	*/
+	[0 /* (Invalid) */] = TCP_CLOSE,
+	[TCP_ESTABLISHED]   = TCP_FIN_WAIT1 | TCP_ACTION_FIN,
+	[TCP_SYN_SENT]      = TCP_CLOSE,
+	[TCP_SYN_RECV]      = TCP_FIN_WAIT1 | TCP_ACTION_FIN,
+	[TCP_FIN_WAIT1]     = TCP_FIN_WAIT1,
+	[TCP_FIN_WAIT2]     = TCP_FIN_WAIT2,
+	[TCP_TIME_WAIT]     = TCP_CLOSE,	/* should not happen ! */
+	[TCP_CLOSE]         = TCP_CLOSE,
+	[TCP_CLOSE_WAIT]    = TCP_LAST_ACK  | TCP_ACTION_FIN,
+	[TCP_LAST_ACK]      = TCP_LAST_ACK,
+	[TCP_LISTEN]        = TCP_CLOSE,
+	[TCP_CLOSING]       = TCP_CLOSING,
+	[TCP_NEW_SYN_RECV]  = TCP_CLOSE,	/* should not happen ! */
+};
+
+static int mptcp_close_state(struct sock *sk)
+{
+	int next = (int)new_state[sk->sk_state];
+	int ns = next & TCP_STATE_MASK;
+
+	inet_sk_state_store(sk, ns);
+
+	return next & TCP_ACTION_FIN;
+}
+
+static void mptcp_check_send_data_fin(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	pr_debug("msk=%p snd_data_fin_enable=%d pending=%d snd_nxt=%llu write_seq=%llu",
+		 msk, msk->snd_data_fin_enable, !!mptcp_send_head(sk),
+		 msk->snd_nxt, msk->write_seq);
+
+	/* we still need to enqueue subflows or not really shutting down,
+	 * skip this
+	 */
+	if (!msk->snd_data_fin_enable || msk->snd_nxt + 1 != msk->write_seq ||
+	    mptcp_send_head(sk))
+		return;
+
+	WRITE_ONCE(msk->snd_nxt, msk->write_seq);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
+
+		mptcp_subflow_shutdown(sk, tcp_sk, SEND_SHUTDOWN);
+	}
+}
+
+static void __mptcp_wr_shutdown(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	pr_debug("msk=%p snd_data_fin_enable=%d shutdown=%x state=%d pending=%d",
+		 msk, msk->snd_data_fin_enable, sk->sk_shutdown, sk->sk_state,
+		 !!mptcp_send_head(sk));
+
+	/* will be ignored by fallback sockets */
+	WRITE_ONCE(msk->write_seq, msk->write_seq + 1);
+	WRITE_ONCE(msk->snd_data_fin_enable, 1);
+
+	mptcp_check_send_data_fin(sk);
+}
+
+static void __mptcp_destroy_sock(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	pr_debug("msk=%p", msk);
+
+	might_sleep();
+
+	mptcp_stop_rtx_timer(sk);
+	sk_stop_timer(sk, &sk->sk_timer);
+	msk->pm.status = 0;
+
+	sk->sk_prot->destroy(sk);
+
+	WARN_ON_ONCE(msk->rmem_fwd_alloc);
+	WARN_ON_ONCE(msk->rmem_released);
+	sk_stream_kill_queues(sk);
+	xfrm_sk_free_policy(sk);
+
+	sk_refcnt_debug_release(sk);
+	sock_put(sk);
+}
+
+void __mptcp_unaccepted_force_close(struct sock *sk)
+{
+	sock_set_flag(sk, SOCK_DEAD);
+	inet_sk_state_store(sk, TCP_CLOSE);
+	mptcp_do_fastclose(sk);
+	__mptcp_destroy_sock(sk);
+}
+
+static __poll_t mptcp_check_readable(struct mptcp_sock *msk)
+{
+	/* Concurrent splices from sk_receive_queue into receive_queue will
+	 * always show at least one non-empty queue when checked in this order.
+	 */
+	if (skb_queue_empty_lockless(&((struct sock *)msk)->sk_receive_queue) &&
+	    skb_queue_empty_lockless(&msk->receive_queue))
+		return 0;
+
+	return EPOLLIN | EPOLLRDNORM;
+}
+
+static void mptcp_check_listen_stop(struct sock *sk)
+{
+	struct sock *ssk;
+
+	if (inet_sk_state_load(sk) != TCP_LISTEN)
+		return;
+
+	ssk = mptcp_sk(sk)->first;
+	if (WARN_ON_ONCE(!ssk || inet_sk_state_load(ssk) != TCP_LISTEN))
+		return;
+
+	lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);
+	tcp_set_state(ssk, TCP_CLOSE);
+	mptcp_subflow_queue_clean(sk, ssk);
+	inet_csk_listen_stop(ssk);
+	release_sock(ssk);
+}
+
+bool __mptcp_close(struct sock *sk, long timeout)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool do_cancel_work = false;
+	int subflows_alive = 0;
+
+	WRITE_ONCE(sk->sk_shutdown, SHUTDOWN_MASK);
+
+	if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE)) {
+		mptcp_check_listen_stop(sk);
+		inet_sk_state_store(sk, TCP_CLOSE);
+		goto cleanup;
+	}
+
+	if (mptcp_check_readable(msk)) {
+		/* the msk has read data, do the MPTCP equivalent of TCP reset */
+		inet_sk_state_store(sk, TCP_CLOSE);
+		mptcp_do_fastclose(sk);
+	} else if (mptcp_close_state(sk)) {
+		__mptcp_wr_shutdown(sk);
+	}
+
+	sk_stream_wait_close(sk, timeout);
+
+cleanup:
+	/* orphan all the subflows */
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow = lock_sock_fast_nested(ssk);
+
+		subflows_alive += ssk->sk_state != TCP_CLOSE;
+
+		/* since the close timeout takes precedence on the fail one,
+		 * cancel the latter
+		 */
+		if (ssk == msk->first)
+			subflow->fail_tout = 0;
+
+		/* detach from the parent socket, but allow data_ready to
+		 * push incoming data into the mptcp stack, to properly ack it
+		 */
+		ssk->sk_socket = NULL;
+		ssk->sk_wq = NULL;
+		unlock_sock_fast(ssk, slow);
+	}
+	sock_orphan(sk);
+
+	/* all the subflows are closed, only timeout can change the msk
+	 * state, let's not keep resources busy for no reasons
+	 */
+	if (subflows_alive == 0)
+		inet_sk_state_store(sk, TCP_CLOSE);
+
+	sock_hold(sk);
+	pr_debug("msk=%p state=%d", sk, sk->sk_state);
+	if (mptcp_sk(sk)->token)
+		mptcp_event(MPTCP_EVENT_CLOSED, msk, NULL, GFP_KERNEL);
+
+	if (sk->sk_state == TCP_CLOSE) {
+		__mptcp_destroy_sock(sk);
+		do_cancel_work = true;
+	} else {
+		mptcp_start_tout_timer(sk);
+	}
+
+	return do_cancel_work;
+}
+
+static void mptcp_close(struct sock *sk, long timeout)
+{
+	bool do_cancel_work;
+
+	lock_sock(sk);
+
+	do_cancel_work = __mptcp_close(sk, timeout);
+	release_sock(sk);
+	if (do_cancel_work)
+		mptcp_cancel_work(sk);
+
+	sock_put(sk);
+}
+
+static void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
+{
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	const struct ipv6_pinfo *ssk6 = inet6_sk(ssk);
+	struct ipv6_pinfo *msk6 = inet6_sk(msk);
+
+	msk->sk_v6_daddr = ssk->sk_v6_daddr;
+	msk->sk_v6_rcv_saddr = ssk->sk_v6_rcv_saddr;
+
+	if (msk6 && ssk6) {
+		msk6->saddr = ssk6->saddr;
+		msk6->flow_label = ssk6->flow_label;
+	}
+#endif
+
+	inet_sk(msk)->inet_num = inet_sk(ssk)->inet_num;
+	inet_sk(msk)->inet_dport = inet_sk(ssk)->inet_dport;
+	inet_sk(msk)->inet_sport = inet_sk(ssk)->inet_sport;
+	inet_sk(msk)->inet_daddr = inet_sk(ssk)->inet_daddr;
+	inet_sk(msk)->inet_saddr = inet_sk(ssk)->inet_saddr;
+	inet_sk(msk)->inet_rcv_saddr = inet_sk(ssk)->inet_rcv_saddr;
+}
+
+static int mptcp_disconnect(struct sock *sk, int flags)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	/* We are on the fastopen error path. We can't call straight into the
+	 * subflows cleanup code due to lock nesting (we are already under
+	 * msk->firstsocket lock).
+	 */
+	if (msk->fastopening)
+		return -EBUSY;
+
+	mptcp_check_listen_stop(sk);
+	inet_sk_state_store(sk, TCP_CLOSE);
+
+	mptcp_stop_rtx_timer(sk);
+	mptcp_stop_tout_timer(sk);
+
+	if (mptcp_sk(sk)->token)
+		mptcp_event(MPTCP_EVENT_CLOSED, mptcp_sk(sk), NULL, GFP_KERNEL);
+
+	/* msk->subflow is still intact, the following will not free the first
+	 * subflow
+	 */
+	mptcp_destroy_common(msk, MPTCP_CF_FASTCLOSE);
+	msk->last_snd = NULL;
+	WRITE_ONCE(msk->flags, 0);
+	msk->cb_flags = 0;
+	msk->push_pending = 0;
+	msk->recovery = false;
+	msk->can_ack = false;
+	msk->fully_established = false;
+	msk->rcv_data_fin = false;
+	msk->snd_data_fin_enable = false;
+	msk->rcv_fastclose = false;
+	msk->use_64bit_ack = false;
+	WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk)));
+	mptcp_pm_data_reset(msk);
+	mptcp_ca_reset(sk);
+
+	WRITE_ONCE(sk->sk_shutdown, 0);
+	sk_error_report(sk);
+	return 0;
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+static struct ipv6_pinfo *mptcp_inet6_sk(const struct sock *sk)
+{
+	unsigned int offset = sizeof(struct mptcp6_sock) - sizeof(struct ipv6_pinfo);
+
+	return (struct ipv6_pinfo *)(((u8 *)sk) + offset);
+}
+#endif
+
+struct sock *mptcp_sk_clone_init(const struct sock *sk,
+				 const struct mptcp_options_received *mp_opt,
+				 struct sock *ssk,
+				 struct request_sock *req)
+{
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+	struct sock *nsk = sk_clone_lock(sk, GFP_ATOMIC);
+	struct mptcp_sock *msk;
+	u64 ack_seq;
+
+	if (!nsk)
+		return NULL;
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (nsk->sk_family == AF_INET6)
+		inet_sk(nsk)->pinet6 = mptcp_inet6_sk(nsk);
+#endif
+
+	__mptcp_init_sock(nsk);
+
+	msk = mptcp_sk(nsk);
+	msk->local_key = subflow_req->local_key;
+	msk->token = subflow_req->token;
+	WRITE_ONCE(msk->subflow, NULL);
+	msk->in_accept_queue = 1;
+	WRITE_ONCE(msk->fully_established, false);
+	if (mp_opt->suboptions & OPTION_MPTCP_CSUMREQD)
+		WRITE_ONCE(msk->csum_enabled, true);
+
+	msk->write_seq = subflow_req->idsn + 1;
+	msk->snd_nxt = msk->write_seq;
+	msk->snd_una = msk->write_seq;
+	msk->wnd_end = msk->snd_nxt + req->rsk_rcv_wnd;
+	msk->setsockopt_seq = mptcp_sk(sk)->setsockopt_seq;
+
+	if (mp_opt->suboptions & OPTIONS_MPTCP_MPC) {
+		msk->can_ack = true;
+		msk->remote_key = mp_opt->sndr_key;
+		mptcp_crypto_key_sha(msk->remote_key, NULL, &ack_seq);
+		ack_seq++;
+		WRITE_ONCE(msk->ack_seq, ack_seq);
+		atomic64_set(&msk->rcv_wnd_sent, ack_seq);
+	}
+
+	sock_reset_flag(nsk, SOCK_RCU_FREE);
+	security_inet_csk_clone(nsk, req);
+
+	/* this can't race with mptcp_close(), as the msk is
+	 * not yet exposted to user-space
+	 */
+	inet_sk_state_store(nsk, TCP_ESTABLISHED);
+
+	/* The msk maintain a ref to each subflow in the connections list */
+	WRITE_ONCE(msk->first, ssk);
+	list_add(&mptcp_subflow_ctx(ssk)->node, &msk->conn_list);
+	sock_hold(ssk);
+
+	/* new mpc subflow takes ownership of the newly
+	 * created mptcp socket
+	 */
+	mptcp_token_accept(subflow_req, msk);
+
+	/* set msk addresses early to ensure mptcp_pm_get_local_id()
+	 * uses the correct data
+	 */
+	mptcp_copy_inaddrs(nsk, ssk);
+	mptcp_propagate_sndbuf(nsk, ssk);
+
+	mptcp_rcv_space_init(msk, ssk);
+	bh_unlock_sock(nsk);
+
+	/* note: the newly allocated socket refcount is 2 now */
+	return nsk;
+}
+
+void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk)
+{
+	const struct tcp_sock *tp = tcp_sk(ssk);
+
+	msk->rcvq_space.copied = 0;
+	msk->rcvq_space.rtt_us = 0;
+
+	msk->rcvq_space.time = tp->tcp_mstamp;
+
+	/* initial rcv_space offering made to peer */
+	msk->rcvq_space.space = min_t(u32, tp->rcv_wnd,
+				      TCP_INIT_CWND * tp->advmss);
+	if (msk->rcvq_space.space == 0)
+		msk->rcvq_space.space = TCP_INIT_CWND * TCP_MSS_DEFAULT;
+
+	WRITE_ONCE(msk->wnd_end, msk->snd_nxt + tcp_sk(ssk)->snd_wnd);
+}
+
+static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
+				 bool kern)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct socket *listener;
+	struct sock *newsk;
+
+	listener = READ_ONCE(msk->subflow);
+	if (WARN_ON_ONCE(!listener)) {
+		*err = -EINVAL;
+		return NULL;
+	}
+
+	pr_debug("msk=%p, listener=%p", msk, mptcp_subflow_ctx(listener->sk));
+	newsk = inet_csk_accept(listener->sk, flags, err, kern);
+	if (!newsk)
+		return NULL;
+
+	pr_debug("msk=%p, subflow is mptcp=%d", msk, sk_is_mptcp(newsk));
+	if (sk_is_mptcp(newsk)) {
+		struct mptcp_subflow_context *subflow;
+		struct sock *new_mptcp_sock;
+
+		subflow = mptcp_subflow_ctx(newsk);
+		new_mptcp_sock = subflow->conn;
+
+		/* is_mptcp should be false if subflow->conn is missing, see
+		 * subflow_syn_recv_sock()
+		 */
+		if (WARN_ON_ONCE(!new_mptcp_sock)) {
+			tcp_sk(newsk)->is_mptcp = 0;
+			goto out;
+		}
+
+		newsk = new_mptcp_sock;
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
+	} else {
+		MPTCP_INC_STATS(sock_net(sk),
+				MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
+	}
+
+out:
+	newsk->sk_kern_sock = kern;
+	return newsk;
+}
+
+void mptcp_destroy_common(struct mptcp_sock *msk, unsigned int flags)
+{
+	struct mptcp_subflow_context *subflow, *tmp;
+	struct sock *sk = (struct sock *)msk;
+
+	__mptcp_clear_xmit(sk);
+
+	/* 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);
+
+	/* move to sk_receive_queue, sk_stream_kill_queues will purge it */
+	mptcp_data_lock(sk);
+	skb_queue_splice_tail_init(&msk->receive_queue, &sk->sk_receive_queue);
+	__skb_queue_purge(&sk->sk_receive_queue);
+	skb_rbtree_purge(&msk->out_of_order_queue);
+	mptcp_data_unlock(sk);
+
+	/* move all the rx fwd alloc into the sk_mem_reclaim_final in
+	 * inet_sock_destruct() will dispose it
+	 */
+	sk_forward_alloc_add(sk, msk->rmem_fwd_alloc);
+	WRITE_ONCE(msk->rmem_fwd_alloc, 0);
+	mptcp_token_destroy(msk);
+	mptcp_pm_free_anno_list(msk);
+	mptcp_free_local_addr_list(msk);
+}
+
+static void mptcp_destroy(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	/* clears msk->subflow, allowing the following to close
+	 * even the initial subflow
+	 */
+	mptcp_dispose_initial_subflow(msk);
+	mptcp_destroy_common(msk, 0);
+	sk_sockets_allocated_dec(sk);
+}
+
+void __mptcp_data_acked(struct sock *sk)
+{
+	if (!sock_owned_by_user(sk))
+		__mptcp_clean_una(sk);
+	else
+		__set_bit(MPTCP_CLEAN_UNA, &mptcp_sk(sk)->cb_flags);
+
+	if (mptcp_pending_data_fin_ack(sk))
+		mptcp_schedule_work(sk);
+}
+
+void __mptcp_check_push(struct sock *sk, struct sock *ssk)
+{
+	if (!mptcp_send_head(sk))
+		return;
+
+	if (!sock_owned_by_user(sk)) {
+		struct sock *xmit_ssk = mptcp_subflow_get_send(mptcp_sk(sk));
+
+		if (xmit_ssk == ssk)
+			__mptcp_subflow_push_pending(sk, ssk);
+		else if (xmit_ssk)
+			mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk), MPTCP_DELEGATE_SEND);
+	} else {
+		__set_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->cb_flags);
+	}
+}
+
+#define MPTCP_FLAGS_PROCESS_CTX_NEED (BIT(MPTCP_PUSH_PENDING) | \
+				      BIT(MPTCP_RETRANSMIT) | \
+				      BIT(MPTCP_FLUSH_JOIN_LIST))
+
+/* processes deferred events and flush wmem */
+static void mptcp_release_cb(struct sock *sk)
+	__must_hold(&sk->sk_lock.slock)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	for (;;) {
+		unsigned long flags = (msk->cb_flags & MPTCP_FLAGS_PROCESS_CTX_NEED) |
+				      msk->push_pending;
+		struct list_head join_list;
+
+		if (!flags)
+			break;
+
+		INIT_LIST_HEAD(&join_list);
+		list_splice_init(&msk->join_list, &join_list);
+
+		/* the following actions acquire the subflow socket lock
+		 *
+		 * 1) can't be invoked in atomic scope
+		 * 2) must avoid ABBA deadlock with msk socket spinlock: the RX
+		 *    datapath acquires the msk socket spinlock while helding
+		 *    the subflow socket lock
+		 */
+		msk->push_pending = 0;
+		msk->cb_flags &= ~flags;
+		spin_unlock_bh(&sk->sk_lock.slock);
+
+		if (flags & BIT(MPTCP_FLUSH_JOIN_LIST))
+			__mptcp_flush_join_list(sk, &join_list);
+		if (flags & BIT(MPTCP_PUSH_PENDING))
+			__mptcp_push_pending(sk, 0);
+		if (flags & BIT(MPTCP_RETRANSMIT))
+			__mptcp_retrans(sk);
+
+		cond_resched();
+		spin_lock_bh(&sk->sk_lock.slock);
+	}
+
+	if (__test_and_clear_bit(MPTCP_CLEAN_UNA, &msk->cb_flags))
+		__mptcp_clean_una_wakeup(sk);
+	if (unlikely(msk->cb_flags)) {
+		/* be sure to set the current sk state before tacking actions
+		 * depending on sk_state, that is processing MPTCP_ERROR_REPORT
+		 */
+		if (__test_and_clear_bit(MPTCP_CONNECTED, &msk->cb_flags))
+			__mptcp_set_connected(sk);
+		if (__test_and_clear_bit(MPTCP_ERROR_REPORT, &msk->cb_flags))
+			__mptcp_error_report(sk);
+		if (__test_and_clear_bit(MPTCP_RESET_SCHEDULER, &msk->cb_flags))
+			msk->last_snd = NULL;
+	}
+
+	__mptcp_update_rmem(sk);
+}
+
+/* MP_JOIN client subflow must wait for 4th ack before sending any data:
+ * TCP can't schedule delack timer before the subflow is fully established.
+ * MPTCP uses the delack timer to do 3rd ack retransmissions
+ */
+static void schedule_3rdack_retransmission(struct sock *ssk)
+{
+	struct inet_connection_sock *icsk = inet_csk(ssk);
+	struct tcp_sock *tp = tcp_sk(ssk);
+	unsigned long timeout;
+
+	if (mptcp_subflow_ctx(ssk)->fully_established)
+		return;
+
+	/* reschedule with a timeout above RTT, as we must look only for drop */
+	if (tp->srtt_us)
+		timeout = usecs_to_jiffies(tp->srtt_us >> (3 - 1));
+	else
+		timeout = TCP_TIMEOUT_INIT;
+	timeout += jiffies;
+
+	WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
+	icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
+	icsk->icsk_ack.timeout = timeout;
+	sk_reset_timer(ssk, &icsk->icsk_delack_timer, timeout);
+}
+
+void mptcp_subflow_process_delegated(struct sock *ssk, long status)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct sock *sk = subflow->conn;
+
+	if (status & BIT(MPTCP_DELEGATE_SEND)) {
+		mptcp_data_lock(sk);
+		if (!sock_owned_by_user(sk))
+			__mptcp_subflow_push_pending(sk, ssk);
+		else
+			__set_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->cb_flags);
+		mptcp_data_unlock(sk);
+	}
+	if (status & BIT(MPTCP_DELEGATE_ACK))
+		schedule_3rdack_retransmission(ssk);
+}
+
+static int mptcp_hash(struct sock *sk)
+{
+	/* should never be called,
+	 * we hash the TCP subflows not the master socket
+	 */
+	WARN_ON_ONCE(1);
+	return 0;
+}
+
+static void mptcp_unhash(struct sock *sk)
+{
+	/* called from sk_common_release(), but nothing to do here */
+}
+
+static int mptcp_get_port(struct sock *sk, unsigned short snum)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct socket *ssock;
+
+	ssock = msk->subflow;
+	pr_debug("msk=%p, subflow=%p", msk, ssock);
+	if (WARN_ON_ONCE(!ssock))
+		return -EINVAL;
+
+	return inet_csk_get_port(ssock->sk, snum);
+}
+
+void mptcp_finish_connect(struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk;
+	struct sock *sk;
+	u64 ack_seq;
+
+	subflow = mptcp_subflow_ctx(ssk);
+	sk = subflow->conn;
+	msk = mptcp_sk(sk);
+
+	pr_debug("msk=%p, token=%u", sk, subflow->token);
+
+	mptcp_crypto_key_sha(subflow->remote_key, NULL, &ack_seq);
+	ack_seq++;
+	subflow->map_seq = ack_seq;
+	subflow->map_subflow_seq = 1;
+
+	/* the socket is not connected yet, no msk/subflow ops can access/race
+	 * accessing the field below
+	 */
+	WRITE_ONCE(msk->remote_key, subflow->remote_key);
+	WRITE_ONCE(msk->local_key, subflow->local_key);
+	WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
+	WRITE_ONCE(msk->snd_nxt, msk->write_seq);
+	WRITE_ONCE(msk->ack_seq, ack_seq);
+	WRITE_ONCE(msk->can_ack, 1);
+	WRITE_ONCE(msk->snd_una, msk->write_seq);
+	atomic64_set(&msk->rcv_wnd_sent, ack_seq);
+
+	mptcp_pm_new_connection(msk, ssk, 0);
+
+	mptcp_rcv_space_init(msk, ssk);
+}
+
+void mptcp_sock_graft(struct sock *sk, struct socket *parent)
+{
+	write_lock_bh(&sk->sk_callback_lock);
+	rcu_assign_pointer(sk->sk_wq, &parent->wq);
+	sk_set_socket(sk, parent);
+	sk->sk_uid = SOCK_INODE(parent)->i_uid;
+	write_unlock_bh(&sk->sk_callback_lock);
+}
+
+bool mptcp_finish_join(struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct sock *parent = (void *)msk;
+	bool ret = true;
+
+	pr_debug("msk=%p, subflow=%p", msk, subflow);
+
+	/* mptcp socket already closing? */
+	if (!mptcp_is_fully_established(parent)) {
+		subflow->reset_reason = MPTCP_RST_EMPTCP;
+		return false;
+	}
+
+	/* active subflow, already present inside the conn_list */
+	if (!list_empty(&subflow->node)) {
+		mptcp_subflow_joined(msk, ssk);
+		return true;
+	}
+
+	if (!mptcp_pm_allow_new_subflow(msk))
+		goto err_prohibited;
+
+	/* If we can't acquire msk socket lock here, let the release callback
+	 * handle it
+	 */
+	mptcp_data_lock(parent);
+	if (!sock_owned_by_user(parent)) {
+		ret = __mptcp_finish_join(msk, ssk);
+		if (ret) {
+			sock_hold(ssk);
+			list_add_tail(&subflow->node, &msk->conn_list);
+		}
+	} else {
+		sock_hold(ssk);
+		list_add_tail(&subflow->node, &msk->join_list);
+		__set_bit(MPTCP_FLUSH_JOIN_LIST, &msk->cb_flags);
+	}
+	mptcp_data_unlock(parent);
+
+	if (!ret) {
+err_prohibited:
+		subflow->reset_reason = MPTCP_RST_EPROHIBIT;
+		return false;
+	}
+
+	return true;
+}
+
+static void mptcp_shutdown(struct sock *sk, int how)
+{
+	pr_debug("sk=%p, how=%d", sk, how);
+
+	if ((how & SEND_SHUTDOWN) && mptcp_close_state(sk))
+		__mptcp_wr_shutdown(sk);
+}
+
+static int mptcp_forward_alloc_get(const struct sock *sk)
+{
+	return READ_ONCE(sk->sk_forward_alloc) +
+	       READ_ONCE(mptcp_sk(sk)->rmem_fwd_alloc);
+}
+
+static int mptcp_ioctl_outq(const struct mptcp_sock *msk, u64 v)
+{
+	const struct sock *sk = (void *)msk;
+	u64 delta;
+
+	if (sk->sk_state == TCP_LISTEN)
+		return -EINVAL;
+
+	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
+		return 0;
+
+	delta = msk->write_seq - v;
+	if (__mptcp_check_fallback(msk) && msk->first) {
+		struct tcp_sock *tp = tcp_sk(msk->first);
+
+		/* the first subflow is disconnected after close - see
+		 * __mptcp_close_ssk(). tcp_disconnect() moves the write_seq
+		 * so ignore that status, too.
+		 */
+		if (!((1 << msk->first->sk_state) &
+		      (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_CLOSE)))
+			delta += READ_ONCE(tp->write_seq) - tp->snd_una;
+	}
+	if (delta > INT_MAX)
+		delta = INT_MAX;
+
+	return (int)delta;
+}
+
+static int mptcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool slow;
+	int answ;
+
+	switch (cmd) {
+	case SIOCINQ:
+		if (sk->sk_state == TCP_LISTEN)
+			return -EINVAL;
+
+		lock_sock(sk);
+		__mptcp_move_skbs(msk);
+		answ = mptcp_inq_hint(sk);
+		release_sock(sk);
+		break;
+	case SIOCOUTQ:
+		slow = lock_sock_fast(sk);
+		answ = mptcp_ioctl_outq(msk, READ_ONCE(msk->snd_una));
+		unlock_sock_fast(sk, slow);
+		break;
+	case SIOCOUTQNSD:
+		slow = lock_sock_fast(sk);
+		answ = mptcp_ioctl_outq(msk, msk->snd_nxt);
+		unlock_sock_fast(sk, slow);
+		break;
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	return put_user(answ, (int __user *)arg);
+}
+
+static void mptcp_subflow_early_fallback(struct mptcp_sock *msk,
+					 struct mptcp_subflow_context *subflow)
+{
+	subflow->request_mptcp = 0;
+	__mptcp_do_fallback(msk);
+}
+
+static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct socket *ssock;
+	int err = -EINVAL;
+
+	ssock = __mptcp_nmpc_socket(msk);
+	if (!ssock)
+		return -EINVAL;
+
+	mptcp_token_destroy(msk);
+	inet_sk_state_store(sk, TCP_SYN_SENT);
+	subflow = mptcp_subflow_ctx(ssock->sk);
+#ifdef CONFIG_TCP_MD5SIG
+	/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
+	 * TCP option space.
+	 */
+	if (rcu_access_pointer(tcp_sk(ssock->sk)->md5sig_info))
+		mptcp_subflow_early_fallback(msk, subflow);
+#endif
+	if (subflow->request_mptcp && mptcp_token_new_connect(ssock->sk)) {
+		MPTCP_INC_STATS(sock_net(ssock->sk), MPTCP_MIB_TOKENFALLBACKINIT);
+		mptcp_subflow_early_fallback(msk, subflow);
+	}
+	if (likely(!__mptcp_check_fallback(msk)))
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVE);
+
+	/* if reaching here via the fastopen/sendmsg path, the caller already
+	 * acquired the subflow socket lock, too.
+	 */
+	if (msk->fastopening)
+		err = __inet_stream_connect(ssock, uaddr, addr_len, O_NONBLOCK, 1);
+	else
+		err = inet_stream_connect(ssock, uaddr, addr_len, O_NONBLOCK);
+	inet_sk(sk)->defer_connect = inet_sk(ssock->sk)->defer_connect;
+
+	/* on successful connect, the msk state will be moved to established by
+	 * subflow_finish_connect()
+	 */
+	if (unlikely(err && err != -EINPROGRESS)) {
+		inet_sk_state_store(sk, inet_sk_state_load(ssock->sk));
+		return err;
+	}
+
+	mptcp_copy_inaddrs(sk, ssock->sk);
+
+	/* silence EINPROGRESS and let the caller inet_stream_connect
+	 * handle the connection in progress
+	 */
+	return 0;
+}
+
+static struct proto mptcp_prot = {
+	.name		= "MPTCP",
+	.owner		= THIS_MODULE,
+	.init		= mptcp_init_sock,
+	.connect	= mptcp_connect,
+	.disconnect	= mptcp_disconnect,
+	.close		= mptcp_close,
+	.accept		= mptcp_accept,
+	.setsockopt	= mptcp_setsockopt,
+	.getsockopt	= mptcp_getsockopt,
+	.shutdown	= mptcp_shutdown,
+	.destroy	= mptcp_destroy,
+	.sendmsg	= mptcp_sendmsg,
+	.ioctl		= mptcp_ioctl,
+	.recvmsg	= mptcp_recvmsg,
+	.release_cb	= mptcp_release_cb,
+	.hash		= mptcp_hash,
+	.unhash		= mptcp_unhash,
+	.get_port	= mptcp_get_port,
+	.forward_alloc_get	= mptcp_forward_alloc_get,
+	.sockets_allocated	= &mptcp_sockets_allocated,
+
+	.memory_allocated	= &tcp_memory_allocated,
+	.per_cpu_fw_alloc	= &tcp_memory_per_cpu_fw_alloc,
+
+	.memory_pressure	= &tcp_memory_pressure,
+	.sysctl_wmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_wmem),
+	.sysctl_rmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_rmem),
+	.sysctl_mem	= sysctl_tcp_mem,
+	.obj_size	= sizeof(struct mptcp_sock),
+	.slab_flags	= SLAB_TYPESAFE_BY_RCU,
+	.no_autobind	= true,
+};
+
+static int mptcp_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
+{
+	struct mptcp_sock *msk = mptcp_sk(sock->sk);
+	struct socket *ssock;
+	int err;
+
+	lock_sock(sock->sk);
+	ssock = __mptcp_nmpc_socket(msk);
+	if (!ssock) {
+		err = -EINVAL;
+		goto unlock;
+	}
+
+	err = ssock->ops->bind(ssock, uaddr, addr_len);
+	if (!err)
+		mptcp_copy_inaddrs(sock->sk, ssock->sk);
+
+unlock:
+	release_sock(sock->sk);
+	return err;
+}
+
+static int mptcp_listen(struct socket *sock, int backlog)
+{
+	struct mptcp_sock *msk = mptcp_sk(sock->sk);
+	struct sock *sk = sock->sk;
+	struct socket *ssock;
+	int err;
+
+	pr_debug("msk=%p", msk);
+
+	lock_sock(sk);
+
+	err = -EINVAL;
+	if (sock->state != SS_UNCONNECTED || sock->type != SOCK_STREAM)
+		goto unlock;
+
+	ssock = __mptcp_nmpc_socket(msk);
+	if (!ssock) {
+		err = -EINVAL;
+		goto unlock;
+	}
+
+	mptcp_token_destroy(msk);
+	inet_sk_state_store(sk, TCP_LISTEN);
+	sock_set_flag(sk, SOCK_RCU_FREE);
+
+	err = ssock->ops->listen(ssock, backlog);
+	inet_sk_state_store(sk, inet_sk_state_load(ssock->sk));
+	if (!err)
+		mptcp_copy_inaddrs(sk, ssock->sk);
+
+unlock:
+	release_sock(sk);
+	return err;
+}
+
+static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
+			       int flags, bool kern)
+{
+	struct mptcp_sock *msk = mptcp_sk(sock->sk);
+	struct socket *ssock;
+	int err;
+
+	pr_debug("msk=%p", msk);
+
+	/* Buggy applications can call accept on socket states other then LISTEN
+	 * but no need to allocate the first subflow just to error out.
+	 */
+	ssock = READ_ONCE(msk->subflow);
+	if (!ssock)
+		return -EINVAL;
+
+	err = ssock->ops->accept(sock, newsock, flags, kern);
+	if (err == 0 && !mptcp_is_tcpsk(newsock->sk)) {
+		struct mptcp_sock *msk = mptcp_sk(newsock->sk);
+		struct mptcp_subflow_context *subflow;
+		struct sock *newsk = newsock->sk;
+
+		msk->in_accept_queue = 0;
+
+		lock_sock(newsk);
+
+		/* set ssk->sk_socket of accept()ed flows to mptcp socket.
+		 * This is needed so NOSPACE flag can be set from tcp stack.
+		 */
+		mptcp_for_each_subflow(msk, subflow) {
+			struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+			if (!ssk->sk_socket)
+				mptcp_sock_graft(ssk, newsock);
+		}
+
+		/* Do late cleanup for the first subflow as necessary. Also
+		 * deal with bad peers not doing a complete shutdown.
+		 */
+		if (msk->first &&
+		    unlikely(inet_sk_state_load(msk->first) == TCP_CLOSE)) {
+			__mptcp_close_ssk(newsk, msk->first,
+					  mptcp_subflow_ctx(msk->first), 0);
+			if (unlikely(list_empty(&msk->conn_list)))
+				inet_sk_state_store(newsk, TCP_CLOSE);
+		}
+
+		release_sock(newsk);
+	}
+
+	return err;
+}
+
+static __poll_t mptcp_check_writeable(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+
+	if (sk_stream_is_writeable(sk))
+		return EPOLLOUT | EPOLLWRNORM;
+
+	mptcp_set_nospace(sk);
+	smp_mb__after_atomic(); /* msk->flags is changed by write_space cb */
+	if (sk_stream_is_writeable(sk))
+		return EPOLLOUT | EPOLLWRNORM;
+
+	return 0;
+}
+
+static __poll_t mptcp_poll(struct file *file, struct socket *sock,
+			   struct poll_table_struct *wait)
+{
+	struct sock *sk = sock->sk;
+	struct mptcp_sock *msk;
+	__poll_t mask = 0;
+	u8 shutdown;
+	int state;
+
+	msk = mptcp_sk(sk);
+	sock_poll_wait(file, sock, wait);
+
+	state = inet_sk_state_load(sk);
+	pr_debug("msk=%p state=%d flags=%lx", msk, state, msk->flags);
+	if (state == TCP_LISTEN) {
+		struct socket *ssock = READ_ONCE(msk->subflow);
+
+		if (WARN_ON_ONCE(!ssock || !ssock->sk))
+			return 0;
+
+		return inet_csk_listen_poll(ssock->sk);
+	}
+
+	shutdown = READ_ONCE(sk->sk_shutdown);
+	if (shutdown == SHUTDOWN_MASK || state == TCP_CLOSE)
+		mask |= EPOLLHUP;
+	if (shutdown & RCV_SHUTDOWN)
+		mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;
+
+	if (state != TCP_SYN_SENT && state != TCP_SYN_RECV) {
+		mask |= mptcp_check_readable(msk);
+		if (shutdown & SEND_SHUTDOWN)
+			mask |= EPOLLOUT | EPOLLWRNORM;
+		else
+			mask |= mptcp_check_writeable(msk);
+	} else if (state == TCP_SYN_SENT && inet_sk(sk)->defer_connect) {
+		/* cf tcp_poll() note about TFO */
+		mask |= EPOLLOUT | EPOLLWRNORM;
+	}
+
+	/* This barrier is coupled with smp_wmb() in __mptcp_error_report() */
+	smp_rmb();
+	if (READ_ONCE(sk->sk_err))
+		mask |= EPOLLERR;
+
+	return mask;
+}
+
+static const struct proto_ops mptcp_stream_ops = {
+	.family		   = PF_INET,
+	.owner		   = THIS_MODULE,
+	.release	   = inet_release,
+	.bind		   = mptcp_bind,
+	.connect	   = inet_stream_connect,
+	.socketpair	   = sock_no_socketpair,
+	.accept		   = mptcp_stream_accept,
+	.getname	   = inet_getname,
+	.poll		   = mptcp_poll,
+	.ioctl		   = inet_ioctl,
+	.gettstamp	   = sock_gettstamp,
+	.listen		   = mptcp_listen,
+	.shutdown	   = inet_shutdown,
+	.setsockopt	   = sock_common_setsockopt,
+	.getsockopt	   = sock_common_getsockopt,
+	.sendmsg	   = inet_sendmsg,
+	.recvmsg	   = inet_recvmsg,
+	.mmap		   = sock_no_mmap,
+	.sendpage	   = inet_sendpage,
+};
+
+static struct inet_protosw mptcp_protosw = {
+	.type		= SOCK_STREAM,
+	.protocol	= IPPROTO_MPTCP,
+	.prot		= &mptcp_prot,
+	.ops		= &mptcp_stream_ops,
+	.flags		= INET_PROTOSW_ICSK,
+};
+
+static int mptcp_napi_poll(struct napi_struct *napi, int budget)
+{
+	struct mptcp_delegated_action *delegated;
+	struct mptcp_subflow_context *subflow;
+	int work_done = 0;
+
+	delegated = container_of(napi, struct mptcp_delegated_action, napi);
+	while ((subflow = mptcp_subflow_delegated_next(delegated)) != NULL) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		bh_lock_sock_nested(ssk);
+		if (!sock_owned_by_user(ssk)) {
+			mptcp_subflow_process_delegated(ssk, xchg(&subflow->delegated_status, 0));
+		} else {
+			/* tcp_release_cb_override already processed
+			 * the action or will do at next release_sock().
+			 * In both case must dequeue the subflow here - on the same
+			 * CPU that scheduled it.
+			 */
+			smp_wmb();
+			clear_bit(MPTCP_DELEGATE_SCHEDULED, &subflow->delegated_status);
+		}
+		bh_unlock_sock(ssk);
+		sock_put(ssk);
+
+		if (++work_done == budget)
+			return budget;
+	}
+
+	/* always provide a 0 'work_done' argument, so that napi_complete_done
+	 * will not try accessing the NULL napi->dev ptr
+	 */
+	napi_complete_done(napi, 0);
+	return work_done;
+}
+
+void __init mptcp_proto_init(void)
+{
+	struct mptcp_delegated_action *delegated;
+	int cpu;
+
+	mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo;
+
+	if (percpu_counter_init(&mptcp_sockets_allocated, 0, GFP_KERNEL))
+		panic("Failed to allocate MPTCP pcpu counter\n");
+
+	init_dummy_netdev(&mptcp_napi_dev);
+	for_each_possible_cpu(cpu) {
+		delegated = per_cpu_ptr(&mptcp_delegated_actions, cpu);
+		INIT_LIST_HEAD(&delegated->head);
+		netif_napi_add_tx(&mptcp_napi_dev, &delegated->napi,
+				  mptcp_napi_poll);
+		napi_enable(&delegated->napi);
+	}
+
+	mptcp_subflow_init();
+	mptcp_pm_init();
+	mptcp_token_init();
+
+	if (proto_register(&mptcp_prot, 1) != 0)
+		panic("Failed to register MPTCP proto.\n");
+
+	inet_register_protosw(&mptcp_protosw);
+
+	BUILD_BUG_ON(sizeof(struct mptcp_skb_cb) > sizeof_field(struct sk_buff, cb));
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+static const struct proto_ops mptcp_v6_stream_ops = {
+	.family		   = PF_INET6,
+	.owner		   = THIS_MODULE,
+	.release	   = inet6_release,
+	.bind		   = mptcp_bind,
+	.connect	   = inet_stream_connect,
+	.socketpair	   = sock_no_socketpair,
+	.accept		   = mptcp_stream_accept,
+	.getname	   = inet6_getname,
+	.poll		   = mptcp_poll,
+	.ioctl		   = inet6_ioctl,
+	.gettstamp	   = sock_gettstamp,
+	.listen		   = mptcp_listen,
+	.shutdown	   = inet_shutdown,
+	.setsockopt	   = sock_common_setsockopt,
+	.getsockopt	   = sock_common_getsockopt,
+	.sendmsg	   = inet6_sendmsg,
+	.recvmsg	   = inet6_recvmsg,
+	.mmap		   = sock_no_mmap,
+	.sendpage	   = inet_sendpage,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	   = inet6_compat_ioctl,
+#endif
+};
+
+static struct proto mptcp_v6_prot;
+
+static struct inet_protosw mptcp_v6_protosw = {
+	.type		= SOCK_STREAM,
+	.protocol	= IPPROTO_MPTCP,
+	.prot		= &mptcp_v6_prot,
+	.ops		= &mptcp_v6_stream_ops,
+	.flags		= INET_PROTOSW_ICSK,
+};
+
+int __init mptcp_proto_v6_init(void)
+{
+	int err;
+
+	mptcp_v6_prot = mptcp_prot;
+	strcpy(mptcp_v6_prot.name, "MPTCPv6");
+	mptcp_v6_prot.slab = NULL;
+	mptcp_v6_prot.obj_size = sizeof(struct mptcp6_sock);
+
+	err = proto_register(&mptcp_v6_prot, 1);
+	if (err)
+		return err;
+
+	err = inet6_register_protosw(&mptcp_v6_protosw);
+	if (err)
+		proto_unregister(&mptcp_v6_prot);
+
+	return err;
+}
+#endif