stream.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 *     SUCS NET3:
  4 *
  5 *     Generic stream handling routines. These are generic for most
  6 *     protocols. Even IP. Tonight 8-).
  7 *     This is used because TCP, LLC (others too) layer all have mostly
  8 *     identical sendmsg() and recvmsg() code.
  9 *     So we (will) share it here.
 10 *
 11 *     Authors:        Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 12 *                     (from old tcp.c code)
 13 *                     Alan Cox <alan@lxorguk.ukuu.org.uk> (Borrowed comments 8-))
 14 */
 15
 16#include <linux/module.h>
 17#include <linux/sched/signal.h>
 18#include <linux/net.h>
 19#include <linux/signal.h>
 20#include <linux/tcp.h>
 21#include <linux/wait.h>
 22#include <net/sock.h>
 23
 24/**
 25 * sk_stream_write_space - stream socket write_space callback.
 26 * @sk: pointer to the socket structure
 27 *
 28 * This function is invoked when there's space available in the socket's
 29 * send buffer for writing. It first checks if the socket is writable,
 30 * clears the SOCK_NOSPACE flag indicating that memory for writing
 31 * is now available, wakes up any processes waiting for write operations
 32 * and sends asynchronous notifications if needed.
 33 */
 34void sk_stream_write_space(struct sock *sk)
 35{
 36	struct socket *sock = sk->sk_socket;
 37	struct socket_wq *wq;
 38
 39	if (__sk_stream_is_writeable(sk, 1) && sock) {
 40		clear_bit(SOCK_NOSPACE, &sock->flags);
 41
 42		rcu_read_lock();
 43		wq = rcu_dereference(sk->sk_wq);
 44		if (skwq_has_sleeper(wq))
 45			wake_up_interruptible_poll(&wq->wait, EPOLLOUT |
 46						EPOLLWRNORM | EPOLLWRBAND);
 47		if (wq && wq->fasync_list && !(sk->sk_shutdown & SEND_SHUTDOWN))
 48			sock_wake_async(wq, SOCK_WAKE_SPACE, POLL_OUT);
 49		rcu_read_unlock();
 50	}
 51}
 52
 53/**
 54 * sk_stream_wait_connect - Wait for a socket to get into the connected state
 55 * @sk: sock to wait on
 56 * @timeo_p: for how long to wait
 57 *
 58 * Must be called with the socket locked.
 59 */
 60int sk_stream_wait_connect(struct sock *sk, long *timeo_p)
 61{
 62	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 63	struct task_struct *tsk = current;
 64	int done;
 65
 66	do {
 67		int err = sock_error(sk);
 68		if (err)
 69			return err;
 70		if ((1 << sk->sk_state) & ~(TCPF_SYN_SENT | TCPF_SYN_RECV))
 71			return -EPIPE;
 72		if (!*timeo_p)
 73			return -EAGAIN;
 74		if (signal_pending(tsk))
 75			return sock_intr_errno(*timeo_p);
 76
 77		add_wait_queue(sk_sleep(sk), &wait);
 78		sk->sk_write_pending++;
 79		done = sk_wait_event(sk, timeo_p,
 80				     !READ_ONCE(sk->sk_err) &&
 81				     !((1 << READ_ONCE(sk->sk_state)) &
 82				       ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)), &wait);
 83		remove_wait_queue(sk_sleep(sk), &wait);
 84		sk->sk_write_pending--;
 85	} while (!done);
 86	return done < 0 ? done : 0;
 87}
 88EXPORT_SYMBOL(sk_stream_wait_connect);
 89
 90/**
 91 * sk_stream_closing - Return 1 if we still have things to send in our buffers.
 92 * @sk: socket to verify
 93 */
 94static int sk_stream_closing(const struct sock *sk)
 95{
 96	return (1 << READ_ONCE(sk->sk_state)) &
 97	       (TCPF_FIN_WAIT1 | TCPF_CLOSING | TCPF_LAST_ACK);
 98}
 99
100void sk_stream_wait_close(struct sock *sk, long timeout)
101{
102	if (timeout) {
103		DEFINE_WAIT_FUNC(wait, woken_wake_function);
104
105		add_wait_queue(sk_sleep(sk), &wait);
106
107		do {
108			if (sk_wait_event(sk, &timeout, !sk_stream_closing(sk), &wait))
109				break;
110		} while (!signal_pending(current) && timeout);
111
112		remove_wait_queue(sk_sleep(sk), &wait);
113	}
114}
115EXPORT_SYMBOL(sk_stream_wait_close);
116
117/**
118 * sk_stream_wait_memory - Wait for more memory for a socket
119 * @sk: socket to wait for memory
120 * @timeo_p: for how long
121 */
122int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
123{
124	int ret, err = 0;
125	long vm_wait = 0;
126	long current_timeo = *timeo_p;
127	DEFINE_WAIT_FUNC(wait, woken_wake_function);
128
129	if (sk_stream_memory_free(sk))
130		current_timeo = vm_wait = get_random_u32_below(HZ / 5) + 2;
131
132	add_wait_queue(sk_sleep(sk), &wait);
133
134	while (1) {
135		sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
136
137		if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
138			goto do_error;
139		if (!*timeo_p)
140			goto do_eagain;
141		if (signal_pending(current))
142			goto do_interrupted;
143		sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
144		if (sk_stream_memory_free(sk) && !vm_wait)
145			break;
146
147		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
148		sk->sk_write_pending++;
149		ret = sk_wait_event(sk, &current_timeo, READ_ONCE(sk->sk_err) ||
150				    (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN) ||
151				    (sk_stream_memory_free(sk) && !vm_wait),
152				    &wait);
153		sk->sk_write_pending--;
154		if (ret < 0)
155			goto do_error;
156
157		if (vm_wait) {
158			vm_wait -= current_timeo;
159			current_timeo = *timeo_p;
160			if (current_timeo != MAX_SCHEDULE_TIMEOUT &&
161			    (current_timeo -= vm_wait) < 0)
162				current_timeo = 0;
163			vm_wait = 0;
164		}
165		*timeo_p = current_timeo;
166	}
167out:
168	if (!sock_flag(sk, SOCK_DEAD))
169		remove_wait_queue(sk_sleep(sk), &wait);
170	return err;
171
172do_error:
173	err = -EPIPE;
174	goto out;
175do_eagain:
176	/* Make sure that whenever EAGAIN is returned, EPOLLOUT event can
177	 * be generated later.
178	 * When TCP receives ACK packets that make room, tcp_check_space()
179	 * only calls tcp_new_space() if SOCK_NOSPACE is set.
180	 */
181	set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
182	err = -EAGAIN;
183	goto out;
184do_interrupted:
185	err = sock_intr_errno(*timeo_p);
186	goto out;
187}
188EXPORT_SYMBOL(sk_stream_wait_memory);
189
190int sk_stream_error(struct sock *sk, int flags, int err)
191{
192	if (err == -EPIPE)
193		err = sock_error(sk) ? : -EPIPE;
194	if (err == -EPIPE && !(flags & MSG_NOSIGNAL))
195		send_sig(SIGPIPE, current, 0);
196	return err;
197}
198EXPORT_SYMBOL(sk_stream_error);
199
200void sk_stream_kill_queues(struct sock *sk)
201{
202	/* First the read buffer. */
203	__skb_queue_purge(&sk->sk_receive_queue);
204
205	/* Next, the error queue.
206	 * We need to use queue lock, because other threads might
207	 * add packets to the queue without socket lock being held.
208	 */
209	skb_queue_purge(&sk->sk_error_queue);
210
211	/* Next, the write queue. */
212	WARN_ON_ONCE(!skb_queue_empty(&sk->sk_write_queue));
213
214	/* Account for returned memory. */
215	sk_mem_reclaim_final(sk);
216
217	WARN_ON_ONCE(sk->sk_wmem_queued);
218
219	/* It is _impossible_ for the backlog to contain anything
220	 * when we get here.  All user references to this socket
221	 * have gone away, only the net layer knows can touch it.
222	 */
223}
224EXPORT_SYMBOL(sk_stream_kill_queues);