/**
 * sk_stream_wait_connect - Wait for a socket to get into the connected state
 * @sk: sock to wait on
 * @timeo_p: for how long to wait
 *
 * Must be called with the socket locked.
 */
int sk_stream_wait_connect(struct sock *sk, long *timeo_p)
{
	struct task_struct *tsk = current;
	DEFINE_WAIT(wait);
	int done;

	do {
		int err = sock_error(sk);
		if (err)
			return err;
		if ((1 << sk->sk_state) & ~(TCPF_SYN_SENT | TCPF_SYN_RECV))
			return -EPIPE;
		if (!*timeo_p)
			return -EAGAIN;
		if (signal_pending(tsk))
			return sock_intr_errno(*timeo_p);

		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
		sk->sk_write_pending++;
		done = sk_wait_event(sk, timeo_p,
				     !sk->sk_err &&
				     !((1 << sk->sk_state) &
				       ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)));
		finish_wait(sk_sleep(sk), &wait);
		sk->sk_write_pending--;
	} while (!done);
	return 0;
}

static int pep_wait_connreq(struct sock *sk, int noblock)
{
	struct task_struct *tsk = current;
	struct pep_sock *pn = pep_sk(sk);
	long timeo = sock_rcvtimeo(sk, noblock);

	for (;;) {
		DEFINE_WAIT(wait);

		if (sk->sk_state != TCP_LISTEN)
			return -EINVAL;
		if (!hlist_empty(&pn->ackq))
			break;
		if (!timeo)
			return -EWOULDBLOCK;
		if (signal_pending(tsk))
			return sock_intr_errno(timeo);

		prepare_to_wait_exclusive(sk_sleep(sk), &wait,
						TASK_INTERRUPTIBLE);
		release_sock(sk);
		timeo = schedule_timeout(timeo);
		lock_sock(sk);
		finish_wait(sk_sleep(sk), &wait);
	}

	return 0;
}

/*
 * wait for space to appear in the transmit/ACK window
 * - caller holds the socket locked
 */
static int rxrpc_wait_for_tx_window(struct rxrpc_sock *rx,
				    struct rxrpc_call *call,
				    long *timeo)
{
	DECLARE_WAITQUEUE(myself, current);
	int ret;

	_enter(",{%d},%ld",
	       CIRC_SPACE(call->acks_head, call->acks_tail, call->acks_winsz),
	       *timeo);

	add_wait_queue(&call->tx_waitq, &myself);

	for (;;) {
		set_current_state(TASK_INTERRUPTIBLE);
		ret = 0;
		if (CIRC_SPACE(call->acks_head, call->acks_tail,
			       call->acks_winsz) > 0)
			break;
		if (signal_pending(current)) {
			ret = sock_intr_errno(*timeo);
			break;
		}

		release_sock(&rx->sk);
		*timeo = schedule_timeout(*timeo);
		lock_sock(&rx->sk);
	}

	remove_wait_queue(&call->tx_waitq, &myself);
	set_current_state(TASK_RUNNING);
	_leave(" = %d", ret);
	return ret;
}

int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
{
	int err = 0;
	long vm_wait = 0;
	long current_timeo = *timeo_p;
	DEFINE_WAIT(wait);

	if (sk_stream_memory_free(sk))
		current_timeo = vm_wait = (net_random() % (HZ / 5)) + 2;

	while (1) {
		set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);

		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

		if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
			goto do_error;
		if (!*timeo_p)
			goto do_nonblock;
		if (signal_pending(current))
			goto do_interrupted;
		clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
		if (sk_stream_memory_free(sk) && !vm_wait)
			break;

		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
		sk->sk_write_pending++;
		sk_wait_event(sk, &current_timeo, sk->sk_err ||
						  (sk->sk_shutdown & SEND_SHUTDOWN) ||
						  (sk_stream_memory_free(sk) &&
						  !vm_wait));
		sk->sk_write_pending--;

		if (vm_wait) {
			vm_wait -= current_timeo;
			current_timeo = *timeo_p;
			if (current_timeo != MAX_SCHEDULE_TIMEOUT &&
			    (current_timeo -= vm_wait) < 0)
				current_timeo = 0;
			vm_wait = 0;
		}
		*timeo_p = current_timeo;
	}
out:
	finish_wait(sk_sleep(sk), &wait);
	return err;

do_error:
	err = -EPIPE;
	goto out;
do_nonblock:
	err = -EAGAIN;
	goto out;
do_interrupted:
	err = sock_intr_errno(*timeo_p);
	goto out;
}

static int l2cap_sock_accept(struct socket *sock, struct socket *newsock,
			     int flags)
{
	DEFINE_WAIT_FUNC(wait, woken_wake_function);
	struct sock *sk = sock->sk, *nsk;
	long timeo;
	int err = 0;

	lock_sock_nested(sk, L2CAP_NESTING_PARENT);

	timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);

	BT_DBG("sk %p timeo %ld", sk, timeo);

	/* Wait for an incoming connection. (wake-one). */
	add_wait_queue_exclusive(sk_sleep(sk), &wait);
	while (1) {
		if (sk->sk_state != BT_LISTEN) {
			err = -EBADFD;
			break;
		}

		nsk = bt_accept_dequeue(sk, newsock);
		if (nsk)
			break;

		if (!timeo) {
			err = -EAGAIN;
			break;
		}

		if (signal_pending(current)) {
			err = sock_intr_errno(timeo);
			break;
		}

		release_sock(sk);

		timeo = wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);

		lock_sock_nested(sk, L2CAP_NESTING_PARENT);
	}
	remove_wait_queue(sk_sleep(sk), &wait);

	if (err)
		goto done;

	newsock->state = SS_CONNECTED;

	BT_DBG("new socket %p", nsk);

done:
	release_sock(sk);
	return err;
}

/*
 * Wrapper for the above, for allocs of data skbs. We try and get the
 * whole size thats been asked for (plus 11 bytes of header). If this
 * fails, then we try for any size over 16 bytes for SOCK_STREAMS.
 */
struct sk_buff *dn_alloc_send_skb(struct sock *sk, size_t *size, int noblock, long timeo, int *err)
{
	int space;
	int len;
	struct sk_buff *skb = NULL;

	*err = 0;

	while(skb == NULL) {
		if (signal_pending(current)) {
			*err = sock_intr_errno(timeo);
			break;
		}

		if (sk->sk_shutdown & SEND_SHUTDOWN) {
			*err = EINVAL;
			break;
		}

		if (sk->sk_err)
			break;

		len = *size + 11;
		space = sk->sk_sndbuf - atomic_read(&sk->sk_wmem_alloc);

		if (space < len) {
			if ((sk->sk_socket->type == SOCK_STREAM) &&
			    (space >= (16 + 11)))
				len = space;
		}

		if (space < len) {
			set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
			if (noblock) {
				*err = EWOULDBLOCK;
				break;
			}

			clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
			SOCK_SLEEP_PRE(sk)

			if ((sk->sk_sndbuf - atomic_read(&sk->sk_wmem_alloc)) <
			    len)
				schedule();

			SOCK_SLEEP_POST(sk)
			continue;
		}

		if ((skb = dn_alloc_skb(sk, len, sk->sk_allocation)) == NULL)
			continue;

		*size = len - 11;
	}

/*
 * Wait for a packet..
 */
static int wait_for_packet(struct sock *sk, int *err, long *timeo_p)
{
	int error;
	DEFINE_WAIT_FUNC(wait, receiver_wake_function);
    /* 
     前面的操作都是初始化wait，为将socket加入wait队列作准备，这部分代码牵涉到进程调度。关于进程调度，我      只是知道一些皮毛，留在以后学习。这里只需要将其看作是一些加入wait队列的准备工作即可，并不影响理解代码      。
     */
	prepare_to_wait_exclusive(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

	/* Socket errors? */
	error = sock_error(sk);
	if (error)
		goto out_err;
    /* 一个完备检测。在决定wait和调用wait之间，有数据包到了，那么就不需要wait，所以这里再次检查socket      的队列是否为空 */

	if (!skb_queue_empty(&sk->sk_receive_queue))
		goto out;

	/* Socket shut down? */
	/* 完备检测。也许socket无数据包读取，因为socket已经被另外的线程关闭了。这样可以保证关闭socket的时      候，不会导致其他的socket的读写操作被阻塞。*/
	if (sk->sk_shutdown & RCV_SHUTDOWN)
		goto out_noerr;

	/* Sequenced packets can come disconnected.
	 * If so we report the problem
	 *//* 对于面向连接的socket进行检查。如果是面向连接的socket，如果不是已经建立连接或者正在监听状态的so       cket是不可能有数据包的。不然即出错*/
	error = -ENOTCONN;
	if (connection_based(sk) &&
	    !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN))
		goto out_err;

	/* handle signals */
	if (signal_pending(current))/* 检查是否有pending的signal，保证阻塞时，进程可以被signal唤醒 */
		goto interrupted;

	error = 0;
	*timeo_p = schedule_timeout(*timeo_p); /* sleep本进程，直至满足唤醒条件或者被信号唤醒——因为前面设置了TASK_INTERRUPTIBLE*/
out:
	finish_wait(sk_sleep(sk), &wait); /* wait队列的清理工作 */
	return error;
interrupted:
	error = sock_intr_errno(*timeo_p);
out_err:
	*err = error;
	goto out;
out_noerr:
	*err = 0;
	error = 1;
	goto out;
}

/* blocks sndbuf producer until at least one byte of free space available */
static int smc_tx_wait_memory(struct smc_sock *smc, int flags)
{
	DEFINE_WAIT_FUNC(wait, woken_wake_function);
	struct smc_connection *conn = &smc->conn;
	struct sock *sk = &smc->sk;
	bool noblock;
	long timeo;
	int rc = 0;

	/* similar to sk_stream_wait_memory */
	timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
	noblock = timeo ? false : true;
	add_wait_queue(sk_sleep(sk), &wait);
	while (1) {
		sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
		if (sk->sk_err ||
		    (sk->sk_shutdown & SEND_SHUTDOWN) ||
		    conn->local_tx_ctrl.conn_state_flags.peer_done_writing) {
			rc = -EPIPE;
			break;
		}
		if (smc_cdc_rxed_any_close(conn)) {
			rc = -ECONNRESET;
			break;
		}
		if (!timeo) {
			if (noblock)
				set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
			rc = -EAGAIN;
			break;
		}
		if (signal_pending(current)) {
			rc = sock_intr_errno(timeo);
			break;
		}
		sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
		if (atomic_read(&conn->sndbuf_space))
			break; /* at least 1 byte of free space available */
		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
		sk_wait_event(sk, &timeo,
			      sk->sk_err ||
			      (sk->sk_shutdown & SEND_SHUTDOWN) ||
			      smc_cdc_rxed_any_close(conn) ||
			      atomic_read(&conn->sndbuf_space),
			      &wait);
	}
	remove_wait_queue(sk_sleep(sk), &wait);
	return rc;
}

/*
 * Wait for the last received packet to be different from skb
 */
static int wait_for_more_packets(struct sock *sk, int *err, long *timeo_p,
				 const struct sk_buff *skb)
{
	int error;
	DEFINE_WAIT_FUNC(wait, receiver_wake_function);

	prepare_to_wait_exclusive(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

	/* Socket errors? */
	error = sock_error(sk);
	if (error)
		goto out_err;

	if (sk->sk_receive_queue.prev != skb)
		goto out;

	/* Socket shut down? */
	if (sk->sk_shutdown & RCV_SHUTDOWN)
		goto out_noerr;

	/* Sequenced packets can come disconnected.
	 * If so we report the problem
	 */
	error = -ENOTCONN;
	if (connection_based(sk) &&
	    !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN))
		goto out_err;

	/* handle signals */
	if (signal_pending(current))
		goto interrupted;

	error = 0;
	*timeo_p = schedule_timeout(*timeo_p);
out:
	finish_wait(sk_sleep(sk), &wait);
	return error;
interrupted:
	error = sock_intr_errno(*timeo_p);
out_err:
	*err = error;
	goto out;
out_noerr:
	*err = 0;
	error = 1;
	goto out;
}

static int wait_for_packet(struct sock *sk, int *err, long *timeo_p)
{
	int error;
	DEFINE_WAIT_FUNC(wait, receiver_wake_function);

	prepare_to_wait_exclusive(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

	
	error = sock_error(sk);
	if (error)
		goto out_err;

	if (!skb_queue_empty(&sk->sk_receive_queue))
		goto out;

	
	if (sk->sk_shutdown & RCV_SHUTDOWN)
		goto out_noerr;

	error = -ENOTCONN;
	if (connection_based(sk) &&
	    !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN))
		goto out_err;

	
	if (signal_pending(current))
		goto interrupted;

	error = 0;
	*timeo_p = schedule_timeout(*timeo_p);
out:
	finish_wait(sk_sleep(sk), &wait);
	return error;
interrupted:
	error = sock_intr_errno(*timeo_p);
out_err:
	*err = error;
	goto out;
out_noerr:
	*err = 0;
	error = 1;
	goto out;
}

static int pep_sendmsg(struct kiocb *iocb, struct sock *sk,
			struct msghdr *msg, size_t len)
{
	struct pep_sock *pn = pep_sk(sk);
	struct sk_buff *skb;
	long timeo;
	int flags = msg->msg_flags;
	int err, done;

	if ((msg->msg_flags & ~(MSG_DONTWAIT|MSG_EOR|MSG_NOSIGNAL|
				MSG_CMSG_COMPAT)) ||
			!(msg->msg_flags & MSG_EOR))
		return -EOPNOTSUPP;

	skb = sock_alloc_send_skb(sk, MAX_PNPIPE_HEADER + len,
					flags & MSG_DONTWAIT, &err);
	if (!skb)
		return -ENOBUFS;

	skb_reserve(skb, MAX_PHONET_HEADER + 3);
	err = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len);
	if (err < 0)
		goto outfree;

	lock_sock(sk);
	timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
	if ((1 << sk->sk_state) & (TCPF_LISTEN|TCPF_CLOSE)) {
		err = -ENOTCONN;
		goto out;
	}
	if (sk->sk_state != TCP_ESTABLISHED) {
		/* Wait until the pipe gets to enabled state */
disabled:
		err = sk_stream_wait_connect(sk, &timeo);
		if (err)
			goto out;

		if (sk->sk_state == TCP_CLOSE_WAIT) {
			err = -ECONNRESET;
			goto out;
		}
	}
	BUG_ON(sk->sk_state != TCP_ESTABLISHED);

	/* Wait until flow control allows TX */
	done = atomic_read(&pn->tx_credits);
	while (!done) {
		DEFINE_WAIT(wait);

		if (!timeo) {
			err = -EAGAIN;
			goto out;
		}
		if (signal_pending(current)) {
			err = sock_intr_errno(timeo);
			goto out;
		}

		prepare_to_wait(sk_sleep(sk), &wait,
				TASK_INTERRUPTIBLE);
		done = sk_wait_event(sk, &timeo, atomic_read(&pn->tx_credits));
		finish_wait(sk_sleep(sk), &wait);

		if (sk->sk_state != TCP_ESTABLISHED)
			goto disabled;
	}

	err = pipe_skb_send(sk, skb);
	if (err >= 0)
		err = len; /* success! */
	skb = NULL;
out:
	release_sock(sk);
outfree:
	kfree_skb(skb);
	return err;
}

//.........这里部分代码省略.........

	err = transport->notify_recv_init(vsk, target, &recv_data);
	if (err < 0)
		goto out;


	while (1) {
		s64 ready;

		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
		ready = vsock_stream_has_data(vsk);

		if (ready == 0) {
			if (sk->sk_err != 0 ||
			    (sk->sk_shutdown & RCV_SHUTDOWN) ||
			    (vsk->peer_shutdown & SEND_SHUTDOWN)) {
				finish_wait(sk_sleep(sk), &wait);
				break;
			}
			/* Don't wait for non-blocking sockets. */
			if (timeout == 0) {
				err = -EAGAIN;
				finish_wait(sk_sleep(sk), &wait);
				break;
			}

			err = transport->notify_recv_pre_block(
					vsk, target, &recv_data);
			if (err < 0) {
				finish_wait(sk_sleep(sk), &wait);
				break;
			}
			release_sock(sk);
			timeout = schedule_timeout(timeout);
			lock_sock(sk);

			if (signal_pending(current)) {
				err = sock_intr_errno(timeout);
				finish_wait(sk_sleep(sk), &wait);
				break;
			} else if (timeout == 0) {
				err = -EAGAIN;
				finish_wait(sk_sleep(sk), &wait);
				break;
			}
		} else {
			ssize_t read;

			finish_wait(sk_sleep(sk), &wait);

			if (ready < 0) {
				/* Invalid queue pair content. XXX This should
				* be changed to a connection reset in a later
				* change.
				*/

				err = -ENOMEM;
				goto out;
			}

			err = transport->notify_recv_pre_dequeue(
					vsk, target, &recv_data);
			if (err < 0)
				break;

			read = transport->stream_dequeue(
					vsk, msg,
					len - copied, flags);
			if (read < 0) {
				err = -ENOMEM;
				break;
			}

			copied += read;

			err = transport->notify_recv_post_dequeue(
					vsk, target, read,
					!(flags & MSG_PEEK), &recv_data);
			if (err < 0)
				goto out;

			if (read >= target || flags & MSG_PEEK)
				break;

			target -= read;
		}
	}

	if (sk->sk_err)
		err = -sk->sk_err;
	else if (sk->sk_shutdown & RCV_SHUTDOWN)
		err = 0;

	if (copied > 0)
		err = copied;

out:
	release_sock(sk);
	return err;
}

static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
				size_t len)
{
	struct sock *sk;
	struct vsock_sock *vsk;
	ssize_t total_written;
	long timeout;
	int err;
	struct vsock_transport_send_notify_data send_data;
	DEFINE_WAIT_FUNC(wait, woken_wake_function);

	sk = sock->sk;
	vsk = vsock_sk(sk);
	total_written = 0;
	err = 0;

	if (msg->msg_flags & MSG_OOB)
		return -EOPNOTSUPP;

	lock_sock(sk);

	/* Callers should not provide a destination with stream sockets. */
	if (msg->msg_namelen) {
		err = sk->sk_state == TCP_ESTABLISHED ? -EISCONN : -EOPNOTSUPP;
		goto out;
	}

	/* Send data only if both sides are not shutdown in the direction. */
	if (sk->sk_shutdown & SEND_SHUTDOWN ||
	    vsk->peer_shutdown & RCV_SHUTDOWN) {
		err = -EPIPE;
		goto out;
	}

	if (sk->sk_state != TCP_ESTABLISHED ||
	    !vsock_addr_bound(&vsk->local_addr)) {
		err = -ENOTCONN;
		goto out;
	}

	if (!vsock_addr_bound(&vsk->remote_addr)) {
		err = -EDESTADDRREQ;
		goto out;
	}

	/* Wait for room in the produce queue to enqueue our user's data. */
	timeout = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);

	err = transport->notify_send_init(vsk, &send_data);
	if (err < 0)
		goto out;

	while (total_written < len) {
		ssize_t written;

		add_wait_queue(sk_sleep(sk), &wait);
		while (vsock_stream_has_space(vsk) == 0 &&
		       sk->sk_err == 0 &&
		       !(sk->sk_shutdown & SEND_SHUTDOWN) &&
		       !(vsk->peer_shutdown & RCV_SHUTDOWN)) {

			/* Don't wait for non-blocking sockets. */
			if (timeout == 0) {
				err = -EAGAIN;
				remove_wait_queue(sk_sleep(sk), &wait);
				goto out_err;
			}

			err = transport->notify_send_pre_block(vsk, &send_data);
			if (err < 0) {
				remove_wait_queue(sk_sleep(sk), &wait);
				goto out_err;
			}

			release_sock(sk);
			timeout = wait_woken(&wait, TASK_INTERRUPTIBLE, timeout);
			lock_sock(sk);
			if (signal_pending(current)) {
				err = sock_intr_errno(timeout);
				remove_wait_queue(sk_sleep(sk), &wait);
				goto out_err;
			} else if (timeout == 0) {
				err = -EAGAIN;
				remove_wait_queue(sk_sleep(sk), &wait);
				goto out_err;
			}
		}
		remove_wait_queue(sk_sleep(sk), &wait);

		/* These checks occur both as part of and after the loop
		 * conditional since we need to check before and after
		 * sleeping.
		 */
		if (sk->sk_err) {
			err = -sk->sk_err;
			goto out_err;
		} else if ((sk->sk_shutdown & SEND_SHUTDOWN) ||
			   (vsk->peer_shutdown & RCV_SHUTDOWN)) {
			err = -EPIPE;
			goto out_err;
//.........这里部分代码省略.........

static int vsock_accept(struct socket *sock, struct socket *newsock, int flags,
			bool kern)
{
	struct sock *listener;
	int err;
	struct sock *connected;
	struct vsock_sock *vconnected;
	long timeout;
	DEFINE_WAIT(wait);

	err = 0;
	listener = sock->sk;

	lock_sock(listener);

	if (sock->type != SOCK_STREAM) {
		err = -EOPNOTSUPP;
		goto out;
	}

	if (listener->sk_state != TCP_LISTEN) {
		err = -EINVAL;
		goto out;
	}

	/* Wait for children sockets to appear; these are the new sockets
	 * created upon connection establishment.
	 */
	timeout = sock_sndtimeo(listener, flags & O_NONBLOCK);
	prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE);

	while ((connected = vsock_dequeue_accept(listener)) == NULL &&
	       listener->sk_err == 0) {
		release_sock(listener);
		timeout = schedule_timeout(timeout);
		finish_wait(sk_sleep(listener), &wait);
		lock_sock(listener);

		if (signal_pending(current)) {
			err = sock_intr_errno(timeout);
			goto out;
		} else if (timeout == 0) {
			err = -EAGAIN;
			goto out;
		}

		prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE);
	}
	finish_wait(sk_sleep(listener), &wait);

	if (listener->sk_err)
		err = -listener->sk_err;

	if (connected) {
		listener->sk_ack_backlog--;

		lock_sock_nested(connected, SINGLE_DEPTH_NESTING);
		vconnected = vsock_sk(connected);

		/* If the listener socket has received an error, then we should
		 * reject this socket and return.  Note that we simply mark the
		 * socket rejected, drop our reference, and let the cleanup
		 * function handle the cleanup; the fact that we found it in
		 * the listener's accept queue guarantees that the cleanup
		 * function hasn't run yet.
		 */
		if (err) {
			vconnected->rejected = true;
		} else {
			newsock->state = SS_CONNECTED;
			sock_graft(connected, newsock);
		}

		release_sock(connected);
		sock_put(connected);
	}

out:
	release_sock(listener);
	return err;
}

static int vsock_stream_connect(struct socket *sock, struct sockaddr *addr,
				int addr_len, int flags)
{
	int err;
	struct sock *sk;
	struct vsock_sock *vsk;
	struct sockaddr_vm *remote_addr;
	long timeout;
	DEFINE_WAIT(wait);

	err = 0;
	sk = sock->sk;
	vsk = vsock_sk(sk);

	lock_sock(sk);

	/* XXX AF_UNSPEC should make us disconnect like AF_INET. */
	switch (sock->state) {
	case SS_CONNECTED:
		err = -EISCONN;
		goto out;
	case SS_DISCONNECTING:
		err = -EINVAL;
		goto out;
	case SS_CONNECTING:
		/* This continues on so we can move sock into the SS_CONNECTED
		 * state once the connection has completed (at which point err
		 * will be set to zero also).  Otherwise, we will either wait
		 * for the connection or return -EALREADY should this be a
		 * non-blocking call.
		 */
		err = -EALREADY;
		break;
	default:
		if ((sk->sk_state == TCP_LISTEN) ||
		    vsock_addr_cast(addr, addr_len, &remote_addr) != 0) {
			err = -EINVAL;
			goto out;
		}

		/* The hypervisor and well-known contexts do not have socket
		 * endpoints.
		 */
		if (!transport->stream_allow(remote_addr->svm_cid,
					     remote_addr->svm_port)) {
			err = -ENETUNREACH;
			goto out;
		}

		/* Set the remote address that we are connecting to. */
		memcpy(&vsk->remote_addr, remote_addr,
		       sizeof(vsk->remote_addr));

		err = vsock_auto_bind(vsk);
		if (err)
			goto out;

		sk->sk_state = TCP_SYN_SENT;

		err = transport->connect(vsk);
		if (err < 0)
			goto out;

		/* Mark sock as connecting and set the error code to in
		 * progress in case this is a non-blocking connect.
		 */
		sock->state = SS_CONNECTING;
		err = -EINPROGRESS;
	}

	/* The receive path will handle all communication until we are able to
	 * enter the connected state.  Here we wait for the connection to be
	 * completed or a notification of an error.
	 */
	timeout = vsk->connect_timeout;
	prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

	while (sk->sk_state != TCP_ESTABLISHED && sk->sk_err == 0) {
		if (flags & O_NONBLOCK) {
			/* If we're not going to block, we schedule a timeout
			 * function to generate a timeout on the connection
			 * attempt, in case the peer doesn't respond in a
			 * timely manner. We hold on to the socket until the
			 * timeout fires.
			 */
			sock_hold(sk);
			INIT_DELAYED_WORK(&vsk->dwork,
					  vsock_connect_timeout);
			schedule_delayed_work(&vsk->dwork, timeout);

			/* Skip ahead to preserve error code set above. */
			goto out_wait;
		}

		release_sock(sk);
		timeout = schedule_timeout(timeout);
		lock_sock(sk);

		if (signal_pending(current)) {
			err = sock_intr_errno(timeout);
//.........这里部分代码省略.........

int netlink_unicast(struct sock *ssk, struct sk_buff *skb, u32 pid, int nonblock)
{
	struct sock *sk;
	int len = skb->len;
	int protocol = ssk->protocol;
	long timeo;
        DECLARE_WAITQUEUE(wait, current);

	timeo = sock_sndtimeo(ssk, nonblock);

retry:
	sk = netlink_lookup(protocol, pid);
	if (sk == NULL)
		goto no_dst;

#ifdef NL_EMULATE_DEV
	if (sk->protinfo.af_netlink->handler) {
		skb_orphan(skb);
		len = sk->protinfo.af_netlink->handler(protocol, skb);
		sock_put(sk);
		return len;
	}
#endif

	if (atomic_read(&sk->rmem_alloc) > sk->rcvbuf ||
	    test_bit(0, &sk->protinfo.af_netlink->state)) {
		if (!timeo) {
			if (ssk->protinfo.af_netlink->pid == 0)
				netlink_overrun(sk);
			sock_put(sk);
			kfree_skb(skb);
			return -EAGAIN;
		}

		__set_current_state(TASK_INTERRUPTIBLE);
		add_wait_queue(&sk->protinfo.af_netlink->wait, &wait);

		if ((atomic_read(&sk->rmem_alloc) > sk->rcvbuf ||
		    test_bit(0, &sk->protinfo.af_netlink->state)) &&
		    !sk->dead)
			timeo = schedule_timeout(timeo);

		__set_current_state(TASK_RUNNING);
		remove_wait_queue(&sk->protinfo.af_netlink->wait, &wait);
		sock_put(sk);

		if (signal_pending(current)) {
			kfree_skb(skb);
			return sock_intr_errno(timeo);
		}
		goto retry;
	}

	skb_orphan(skb);
	skb_set_owner_r(skb, sk);
	skb_queue_tail(&sk->receive_queue, skb);
	sk->data_ready(sk, len);
	sock_put(sk);
	return len;

no_dst:
	kfree_skb(skb);
	return -ECONNREFUSED;
}

int dccp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
		 size_t len, int nonblock, int flags, int *addr_len)
{
	const struct dccp_hdr *dh;
	long timeo;

	lock_sock(sk);

	if (sk->sk_state == DCCP_LISTEN) {
		len = -ENOTCONN;
		goto out;
	}

	timeo = sock_rcvtimeo(sk, nonblock);

	do {
		struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);

		if (skb == NULL)
			goto verify_sock_status;

		dh = dccp_hdr(skb);

		switch (dh->dccph_type) {
		case DCCP_PKT_DATA:
		case DCCP_PKT_DATAACK:
			goto found_ok_skb;

		case DCCP_PKT_CLOSE:
		case DCCP_PKT_CLOSEREQ:
			if (!(flags & MSG_PEEK))
				dccp_finish_passive_close(sk);
			/* fall through */
		case DCCP_PKT_RESET:
			dccp_pr_debug("found fin (%s) ok!\n",
				      dccp_packet_name(dh->dccph_type));
			len = 0;
			goto found_fin_ok;
		default:
			dccp_pr_debug("packet_type=%s\n",
				      dccp_packet_name(dh->dccph_type));
			sk_eat_skb(sk, skb, false);
		}
verify_sock_status:
		if (sock_flag(sk, SOCK_DONE)) {
			len = 0;
			break;
		}

		if (sk->sk_err) {
			len = sock_error(sk);
			break;
		}

		if (sk->sk_shutdown & RCV_SHUTDOWN) {
			len = 0;
			break;
		}

		if (sk->sk_state == DCCP_CLOSED) {
			if (!sock_flag(sk, SOCK_DONE)) {
				/* This occurs when user tries to read
				 * from never connected socket.
				 */
				len = -ENOTCONN;
				break;
			}
			len = 0;
			break;
		}

		if (!timeo) {
			len = -EAGAIN;
			break;
		}

		if (signal_pending(current)) {
			len = sock_intr_errno(timeo);
			break;
		}

		sk_wait_data(sk, &timeo);
		continue;
	found_ok_skb:
		if (len > skb->len)
			len = skb->len;
		else if (len < skb->len)
			msg->msg_flags |= MSG_TRUNC;

		if (skb_copy_datagram_iovec(skb, 0, msg->msg_iov, len)) {
			/* Exception. Bailout! */
			len = -EFAULT;
			break;
		}
		if (flags & MSG_TRUNC)
			len = skb->len;
	found_fin_ok:
		if (!(flags & MSG_PEEK))
			sk_eat_skb(sk, skb, false);
		break;
//.........这里部分代码省略.........