OSCL-LXR linux-6.0.1/​net/​mptcp/​protocol.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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, &ssock);
     if (err)
         return err;
 
     msk->first = ssock->sk;
     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_charge(struct sock *sk, int size)
 {
     mptcp_sk(sk)->rmem_fwd_alloc -= 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_sk(sk)->rmem_fwd_alloc -= 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;
 
     msk->rmem_fwd_alloc += 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;
 
     msk->rmem_fwd_alloc += 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_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 !__mptcp_check_fallback(msk) &&
            ((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;
 
     if (__mptcp_check_fallback(msk))
         return ret;
 
     /* 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);
 
         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;
         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) {
             /* if no data is found, a racing workqueue/recvmsg
              * already processed the new data, stop here or we
              * can enter an infinite loop
              */
             if (!moved)
                 done = true;
             break;
         }
 
         if (__mptcp_check_fallback(msk)) {
             /* if we are running under the workqueue, TCP could have
              * collapsed skbs between dummy map creation and now
              * be sure to adjust the 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;
 }
 
 /* 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 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_propagate_sndbuf((struct sock *)msk, ssk);
     mptcp_sockopt_sync_locked(msk, ssk);
     return true;
 }
 
 static void __mptcp_flush_join_list(struct sock *sk)
 {
     struct mptcp_subflow_context *tmp, *subflow;
     struct mptcp_sock *msk = mptcp_sk(sk);
 
     list_for_each_entry_safe(subflow, tmp, &msk->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_timer_pending(struct sock *sk)
 {
     return timer_pending(&inet_csk(sk)->icsk_retransmit_timer);
 }
 
 static void mptcp_reset_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
          */
         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_timer_pending(sk) && !mptcp_data_fin_enabled(msk))
             mptcp_stop_timer(sk);
     } else {
         mptcp_reset_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);
 }
 
 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 */
     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_remove_empty_skb(ssk);
             return 0;
         }
 
         zero_window_probe = true;
         data_seq = snd_una - 1;
         copy = 1;
 
         /* all mptcp-level data is acked, no skbs should be present into the
          * ssk write queue
          */
         WARN_ON_ONCE(reuse_skb);
     }
 
     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;
         WARN_ON_ONCE(zero_window_probe);
         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,
     };
     struct mptcp_data_frag *dfrag;
     int len, copied = 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;
 
             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;
             }
 
             info.sent += ret;
             copied += 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_timer_pending(sk))
         mptcp_reset_timer(sk);
     if (copied)
         __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_timer_pending(sk))
             mptcp_reset_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_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 {
     struct mptcp_sock *msk = mptcp_sk(sk);
     struct page_frag *pfrag;
     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);
 
     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 out;
     }
 
     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;
 
         if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)) {
             ret = -EPIPE;
             goto out;
         }
 
         /* 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 out;
         }
 
         /* data successfully copied into the write queue */
         sk->sk_forward_alloc -= 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 out;
     }
 
     if (copied)
         __mptcp_push_pending(sk, msg->msg_flags);
 
 out:
     release_sock(sk);
     return copied ? : ret;
 }
 
 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_timeout_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));
         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)
 
 /* 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 need_push, dispose_it;
 
     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)
         subflow->send_fastclose = 1;
 
     need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk);
     if (!dispose_it) {
         tcp_disconnect(ssk, 0);
         msk->subflow->state = SS_UNCONNECTED;
         mptcp_subflow_ctx_reset(subflow);
         release_sock(ssk);
 
         goto out;
     }
 
     /* if we are invoked by the msk cleanup code, the subflow is
      * already orphaned
      */
     if (ssk->sk_socket)
         sock_orphan(ssk);
 
     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) {
         kfree_rcu(subflow, rcu);
     } else {
         /* otherwise tcp will dispose of the ssk and subflow ctx */
         if (ssk->sk_state == TCP_LISTEN) {
             tcp_set_state(ssk, TCP_CLOSE);
             mptcp_subflow_queue_clean(ssk);
             inet_csk_listen_stop(ssk);
         }
         __tcp_close(ssk, 0);
 
         /* close acquired an extra ref */
         __sock_put(ssk);
     }
     release_sock(ssk);
 
     sock_put(ssk);
 
     if (ssk == msk->first)
         msk->first = NULL;
 
 out:
     if (ssk == msk->last_snd)
         msk->last_snd = NULL;
 
     if (need_push)
         __mptcp_push_pending(sk, 0);
 }
 
 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 mptcp_sock *msk)
 {
     struct mptcp_subflow_context *subflow, *tmp;
 
     might_sleep();
 
     list_for_each_entry_safe(subflow, tmp, &msk->conn_list, node) {
         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((struct sock *)msk, ssk, subflow);
     }
 }
 
 static bool mptcp_check_close_timeout(const struct sock *sk)
 {
     s32 delta = tcp_jiffies32 - inet_csk(sk)->icsk_mtup.probe_timestamp;
     struct mptcp_subflow_context *subflow;
 
     if (delta >= TCP_TIMEWAIT_LEN)
         return true;
 
     /* if all subflows are in closed status don't bother with additional
      * timeout
      */
     mptcp_for_each_subflow(mptcp_sk(sk), subflow) {
         if (inet_sk_state_load(mptcp_subflow_tcp_sock(subflow)) !=
             TCP_CLOSE)
             return false;
     }
     return true;
 }
 
 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);
 
     list_for_each_entry_safe(subflow, tmp, &msk->conn_list, node) {
         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);
     }
 
     inet_sk_state_store(sk, TCP_CLOSE);
     sk->sk_shutdown = SHUTDOWN_MASK;
     smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
     set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags);
 
     mptcp_close_wake_up(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_timer_pending(sk))
         mptcp_reset_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_timeout(struct mptcp_sock *msk, unsigned long fail_tout)
 {
     struct sock *sk = (struct sock *)msk;
     unsigned long timeout, close_timeout;
 
     if (!fail_tout && !sock_flag(sk, SOCK_DEAD))
         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 = sock_flag(sk, SOCK_DEAD) ? 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);
 
     mptcp_reset_timeout(msk, 0);
 }
 
 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(state == TCP_CLOSE))
         goto unlock;
 
     mptcp_check_data_fin_ack(sk);
 
     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(sk);
 
     /* There is no point in keeping around an orphaned sk timedout or
      * closed, but we need the msk around to reply to incoming DATA_FIN,
      * even if it is orphaned and in FIN_WAIT2 state
      */
     if (sock_flag(sk, SOCK_DEAD) &&
         (mptcp_check_close_timeout(sk) || sk->sk_state == TCP_CLOSE)) {
         inet_sk_state_store(sk, TCP_CLOSE);
         __mptcp_destroy_sock(sk);
         goto unlock;
     }
 
     if (test_and_clear_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags))
         __mptcp_close_subflow(msk);
 
     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;
 
     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_timeout_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:
         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);
         } else {
             pr_debug("Sending DATA_FIN on subflow %p", ssk);
             tcp_send_ack(ssk);
             if (!mptcp_timer_pending(sk))
                 mptcp_reset_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);
 
     /* fallback socket will not get data_fin/ack, can move to the next
      * state now
      */
     if (__mptcp_check_fallback(msk)) {
         WRITE_ONCE(msk->snd_una, msk->write_seq);
         if ((1 << sk->sk_state) & (TCPF_CLOSING | TCPF_LAST_ACK)) {
             inet_sk_state_store(sk, TCP_CLOSE);
             mptcp_close_wake_up(sk);
         } else if (sk->sk_state == TCP_FIN_WAIT1) {
             inet_sk_state_store(sk, TCP_FIN_WAIT2);
         }
     }
 
     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_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);
 }
 
 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;
 
     sk->sk_shutdown = SHUTDOWN_MASK;
 
     if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE)) {
         inet_sk_state_store(sk, TCP_CLOSE);
         goto cleanup;
     }
 
     if (mptcp_close_state(sk))
         __mptcp_wr_shutdown(sk);
 
     sk_stream_wait_close(sk, timeout);
 
 cleanup:
     /* orphan all the subflows */
     inet_csk(sk)->icsk_mtup.probe_timestamp = tcp_jiffies32;
     mptcp_for_each_subflow(msk, subflow) {
         struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
         bool slow = lock_sock_fast_nested(ssk);
 
         /* since the close timeout takes precedence on the fail one,
          * cancel the latter
          */
         if (ssk == msk->first)
             subflow->fail_tout = 0;
 
         sock_orphan(ssk);
         unlock_sock_fast(ssk, slow);
     }
     sock_orphan(sk);
 
     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_reset_timeout(msk, 0);
     }
 
     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);
 
     inet_sk_state_store(sk, TCP_CLOSE);
 
     mptcp_stop_timer(sk);
     sk_stop_timer(sk, &sk->sk_timer);
 
     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);
 
     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(const struct sock *sk,
                 const struct mptcp_options_received *mp_opt,
                 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;
     msk->subflow = NULL;
     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);
     /* will be fully established after successful MPC subflow creation */
     inet_sk_state_store(nsk, TCP_SYN_RECV);
 
     security_inet_csk_clone(nsk, req);
     bh_unlock_sock(nsk);
 
     /* keep a single reference */
     __sock_put(nsk);
     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 = __mptcp_nmpc_socket(msk);
     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;
         }
 
         /* acquire the 2nd reference for the owning socket */
         sock_hold(new_mptcp_sock);
         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 */
     list_for_each_entry_safe(subflow, tmp, &msk->conn_list, node)
         __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->sk_forward_alloc += msk->rmem_fwd_alloc;
     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;
         if (!flags)
             break;
 
         /* 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);
         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)
 {
     struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
     struct sock *sk = subflow->conn;
 
     if (test_bit(MPTCP_DELEGATE_SEND, &subflow->delegated_status)) {
         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);
         mptcp_subflow_delegated_done(subflow, MPTCP_DELEGATE_SEND);
     }
     if (test_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status)) {
         schedule_3rdack_retransmission(ssk);
         mptcp_subflow_delegated_done(subflow, MPTCP_DELEGATE_ACK);
     }
 }
 
 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 = __mptcp_nmpc_socket(msk);
     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;
     }
 
     if (!list_empty(&subflow->node))
         goto out;
 
     if (!mptcp_pm_allow_new_subflow(msk))
         goto err_prohibited;
 
     /* active connections are already on conn_list.
      * 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;
     }
 
     subflow->map_seq = READ_ONCE(msk->ack_seq);
     WRITE_ONCE(msk->allow_infinite_fallback, false);
 
 out:
     mptcp_event(MPTCP_EVENT_SUB_ESTABLISHED, msk, ssk, GFP_ATOMIC);
     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 sk->sk_forward_alloc + 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 struct proto mptcp_prot = {
     .name       = "MPTCP",
     .owner      = THIS_MODULE,
     .init       = mptcp_init_sock,
     .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 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_stream_connect(struct socket *sock, struct sockaddr *uaddr,
                 int addr_len, int flags)
 {
     struct mptcp_sock *msk = mptcp_sk(sock->sk);
     struct mptcp_subflow_context *subflow;
     struct socket *ssock;
     int err = -EINVAL;
 
     lock_sock(sock->sk);
     if (uaddr) {
         if (addr_len < sizeof(uaddr->sa_family))
             goto unlock;
 
         if (uaddr->sa_family == AF_UNSPEC) {
             err = mptcp_disconnect(sock->sk, flags);
             sock->state = err ? SS_DISCONNECTING : SS_UNCONNECTED;
             goto unlock;
         }
     }
 
     if (sock->state != SS_UNCONNECTED && msk->subflow) {
         /* pending connection or invalid state, let existing subflow
          * cope with that
          */
         ssock = msk->subflow;
         goto do_connect;
     }
 
     ssock = __mptcp_nmpc_socket(msk);
     if (!ssock)
         goto unlock;
 
     mptcp_token_destroy(msk);
     inet_sk_state_store(sock->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(sock->sk), MPTCP_MIB_MPCAPABLEACTIVE);
 
 do_connect:
     err = ssock->ops->connect(ssock, uaddr, addr_len, flags);
     sock->state = ssock->state;
 
     /* on successful connect, the msk state will be moved to established by
      * subflow_finish_connect()
      */
     if (!err || err == -EINPROGRESS)
         mptcp_copy_inaddrs(sock->sk, ssock->sk);
     else
         inet_sk_state_store(sock->sk, inet_sk_state_load(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 socket *ssock;
     int err;
 
     pr_debug("msk=%p", msk);
 
     lock_sock(sock->sk);
     ssock = __mptcp_nmpc_socket(msk);
     if (!ssock) {
         err = -EINVAL;
         goto unlock;
     }
 
     mptcp_token_destroy(msk);
     inet_sk_state_store(sock->sk, TCP_LISTEN);
     sock_set_flag(sock->sk, SOCK_RCU_FREE);
 
     err = ssock->ops->listen(ssock, backlog);
     inet_sk_state_store(sock->sk, inet_sk_state_load(ssock->sk));
     if (!err)
         mptcp_copy_inaddrs(sock->sk, ssock->sk);
 
 unlock:
     release_sock(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);
 
     ssock = __mptcp_nmpc_socket(msk);
     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;
 
         lock_sock(newsk);
 
         /* PM/worker can now acquire the first subflow socket
          * lock without racing with listener queue cleanup,
          * we can notify it, if needed.
          *
          * Even if remote has reset the initial subflow by now
          * the refcnt is still at least one.
          */
         subflow = mptcp_subflow_ctx(msk->first);
         list_add(&subflow->node, &msk->conn_list);
         sock_hold(msk->first);
         if (mptcp_is_fully_established(newsk))
             mptcp_pm_fully_established(msk, msk->first, GFP_KERNEL);
 
         mptcp_copy_inaddrs(newsk, msk->first);
         mptcp_rcv_space_init(msk, msk->first);
         mptcp_propagate_sndbuf(newsk, msk->first);
 
         /* 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);
         }
         release_sock(newsk);
     }
 
     return err;
 }
 
 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 __poll_t mptcp_check_writeable(struct mptcp_sock *msk)
 {
     struct sock *sk = (struct sock *)msk;
 
     if (unlikely(sk->sk_shutdown & SEND_SHUTDOWN))
         return EPOLLOUT | EPOLLWRNORM;
 
     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;
     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) {
         if (WARN_ON_ONCE(!msk->subflow || !msk->subflow->sk))
             return 0;
 
         return inet_csk_listen_poll(msk->subflow->sk);
     }
 
     if (state != TCP_SYN_SENT && state != TCP_SYN_RECV) {
         mask |= mptcp_check_readable(msk);
         mask |= mptcp_check_writeable(msk);
     }
     if (sk->sk_shutdown == SHUTDOWN_MASK || state == TCP_CLOSE)
         mask |= EPOLLHUP;
     if (sk->sk_shutdown & RCV_SHUTDOWN)
         mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;
 
     /* This barrier is coupled with smp_wmb() in tcp_reset() */
     smp_rmb();
     if (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       = mptcp_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_has_delegated_action(subflow))
             mptcp_subflow_process_delegated(ssk);
         /* ... elsewhere 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.
          */
         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       = mptcp_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 void mptcp_v6_destroy(struct sock *sk)
 {
     mptcp_destroy(sk);
     inet6_destroy_sock(sk);
 }
 
 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.destroy = mptcp_v6_destroy;
     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