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: socket
27 *
28 * FIXME: write proper description
29 */
30void sk_stream_write_space(struct sock *sk)
31{
32	struct socket *sock = sk->sk_socket;
33	struct socket_wq *wq;
34
35	if (__sk_stream_is_writeable(sk, 1) && sock) {
36		clear_bit(SOCK_NOSPACE, &sock->flags);
37
38		rcu_read_lock();
39		wq = rcu_dereference(sk->sk_wq);
40		if (skwq_has_sleeper(wq))
41			wake_up_interruptible_poll(&wq->wait, EPOLLOUT |
42						EPOLLWRNORM | EPOLLWRBAND);
43		if (wq && wq->fasync_list && !(sk->sk_shutdown & SEND_SHUTDOWN))
44			sock_wake_async(wq, SOCK_WAKE_SPACE, POLL_OUT);
45		rcu_read_unlock();
46	}
47}
48
49/**
50 * sk_stream_wait_connect - Wait for a socket to get into the connected state
51 * @sk: sock to wait on
52 * @timeo_p: for how long to wait
53 *
54 * Must be called with the socket locked.
55 */
56int sk_stream_wait_connect(struct sock *sk, long *timeo_p)
57{
58	DEFINE_WAIT_FUNC(wait, woken_wake_function);
59	struct task_struct *tsk = current;
60	int done;
61
62	do {
63		int err = sock_error(sk);
64		if (err)
65			return err;
66		if ((1 << sk->sk_state) & ~(TCPF_SYN_SENT | TCPF_SYN_RECV))
67			return -EPIPE;
68		if (!*timeo_p)
69			return -EAGAIN;
70		if (signal_pending(tsk))
71			return sock_intr_errno(*timeo_p);
72
73		add_wait_queue(sk_sleep(sk), &wait);
74		sk->sk_write_pending++;
75		done = sk_wait_event(sk, timeo_p,
76				     !READ_ONCE(sk->sk_err) &&
77				     !((1 << READ_ONCE(sk->sk_state)) &
78				       ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)), &wait);
79		remove_wait_queue(sk_sleep(sk), &wait);
80		sk->sk_write_pending--;
81	} while (!done);
82	return done < 0 ? done : 0;
83}
84EXPORT_SYMBOL(sk_stream_wait_connect);
85
86/**
87 * sk_stream_closing - Return 1 if we still have things to send in our buffers.
88 * @sk: socket to verify
89 */
90static int sk_stream_closing(const struct sock *sk)
91{
92	return (1 << READ_ONCE(sk->sk_state)) &
93	       (TCPF_FIN_WAIT1 | TCPF_CLOSING | TCPF_LAST_ACK);
94}
95
96void sk_stream_wait_close(struct sock *sk, long timeout)
97{
98	if (timeout) {
99		DEFINE_WAIT_FUNC(wait, woken_wake_function);
100
101		add_wait_queue(sk_sleep(sk), &wait);
102
103		do {
104			if (sk_wait_event(sk, &timeout, !sk_stream_closing(sk), &wait))
105				break;
106		} while (!signal_pending(current) && timeout);
107
108		remove_wait_queue(sk_sleep(sk), &wait);
109	}
110}
111EXPORT_SYMBOL(sk_stream_wait_close);
112
113/**
114 * sk_stream_wait_memory - Wait for more memory for a socket
115 * @sk: socket to wait for memory
116 * @timeo_p: for how long
117 */
118int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
119{
120	int ret, err = 0;
121	long vm_wait = 0;
122	long current_timeo = *timeo_p;
123	DEFINE_WAIT_FUNC(wait, woken_wake_function);
124
125	if (sk_stream_memory_free(sk))
126		current_timeo = vm_wait = get_random_u32_below(HZ / 5) + 2;
127
128	add_wait_queue(sk_sleep(sk), &wait);
129
130	while (1) {
131		sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
132
133		if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
134			goto do_error;
135		if (!*timeo_p)
136			goto do_eagain;
137		if (signal_pending(current))
138			goto do_interrupted;
139		sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
140		if (sk_stream_memory_free(sk) && !vm_wait)
141			break;
142
143		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
144		sk->sk_write_pending++;
145		ret = sk_wait_event(sk, &current_timeo, READ_ONCE(sk->sk_err) ||
146				    (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN) ||
147				    (sk_stream_memory_free(sk) && !vm_wait),
148				    &wait);
149		sk->sk_write_pending--;
150		if (ret < 0)
151			goto do_error;
152
153		if (vm_wait) {
154			vm_wait -= current_timeo;
155			current_timeo = *timeo_p;
156			if (current_timeo != MAX_SCHEDULE_TIMEOUT &&
157			    (current_timeo -= vm_wait) < 0)
158				current_timeo = 0;
159			vm_wait = 0;
160		}
161		*timeo_p = current_timeo;
162	}
163out:
164	if (!sock_flag(sk, SOCK_DEAD))
165		remove_wait_queue(sk_sleep(sk), &wait);
166	return err;
167
168do_error:
169	err = -EPIPE;
170	goto out;
171do_eagain:
172	/* Make sure that whenever EAGAIN is returned, EPOLLOUT event can
173	 * be generated later.
174	 * When TCP receives ACK packets that make room, tcp_check_space()
175	 * only calls tcp_new_space() if SOCK_NOSPACE is set.
176	 */
177	set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
178	err = -EAGAIN;
179	goto out;
180do_interrupted:
181	err = sock_intr_errno(*timeo_p);
182	goto out;
183}
184EXPORT_SYMBOL(sk_stream_wait_memory);
185
186int sk_stream_error(struct sock *sk, int flags, int err)
187{
188	if (err == -EPIPE)
189		err = sock_error(sk) ? : -EPIPE;
190	if (err == -EPIPE && !(flags & MSG_NOSIGNAL))
191		send_sig(SIGPIPE, current, 0);
192	return err;
193}
194EXPORT_SYMBOL(sk_stream_error);
195
196void sk_stream_kill_queues(struct sock *sk)
197{
198	/* First the read buffer. */
199	__skb_queue_purge(&sk->sk_receive_queue);
200
201	/* Next, the error queue.
202	 * We need to use queue lock, because other threads might
203	 * add packets to the queue without socket lock being held.
204	 */
205	skb_queue_purge(&sk->sk_error_queue);
206
207	/* Next, the write queue. */
208	WARN_ON_ONCE(!skb_queue_empty(&sk->sk_write_queue));
209
210	/* Account for returned memory. */
211	sk_mem_reclaim_final(sk);
212
213	WARN_ON_ONCE(sk->sk_wmem_queued);
214
215	/* It is _impossible_ for the backlog to contain anything
216	 * when we get here.  All user references to this socket
217	 * have gone away, only the net layer knows can touch it.
218	 */
219}
220EXPORT_SYMBOL(sk_stream_kill_queues);
221