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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 <[email protected]>
12 * (from old tcp.c code)
13 * Alan Cox <[email protected]> (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}
115
116/**
117 * sk_stream_wait_memory - Wait for more memory for a socket
118 * @sk: socket to wait for memory
119 * @timeo_p: for how long
120 */
121int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
122{
123 int ret, err = 0;
124 long vm_wait = 0;
125 long current_timeo = *timeo_p;
126 DEFINE_WAIT_FUNC(wait, woken_wake_function);
127
128 if (sk_stream_memory_free(sk))
129 current_timeo = vm_wait = get_random_u32_below(HZ / 5) + 2;
130
131 add_wait_queue(sk_sleep(sk), &wait);
132
133 while (1) {
134 sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
135
136 if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
137 goto do_error;
138 if (!*timeo_p)
139 goto do_eagain;
140 if (signal_pending(current))
141 goto do_interrupted;
142 sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
143 if (sk_stream_memory_free(sk) && !vm_wait)
144 break;
145
146 set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
147 sk->sk_write_pending++;
148 ret = sk_wait_event(sk, &current_timeo, READ_ONCE(sk->sk_err) ||
149 (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN) ||
150 (sk_stream_memory_free(sk) && !vm_wait),
151 &wait);
152 sk->sk_write_pending--;
153 if (ret < 0)
154 goto do_error;
155
156 if (vm_wait) {
157 vm_wait -= current_timeo;
158 current_timeo = *timeo_p;
159 if (current_timeo != MAX_SCHEDULE_TIMEOUT &&
160 (current_timeo -= vm_wait) < 0)
161 current_timeo = 0;
162 vm_wait = 0;
163 }
164 *timeo_p = current_timeo;
165 }
166out:
167 if (!sock_flag(sk, SOCK_DEAD))
168 remove_wait_queue(sk_sleep(sk), &wait);
169 return err;
170
171do_error:
172 err = -EPIPE;
173 goto out;
174do_eagain:
175 /* Make sure that whenever EAGAIN is returned, EPOLLOUT event can
176 * be generated later.
177 * When TCP receives ACK packets that make room, tcp_check_space()
178 * only calls tcp_new_space() if SOCK_NOSPACE is set.
179 */
180 set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
181 err = -EAGAIN;
182 goto out;
183do_interrupted:
184 err = sock_intr_errno(*timeo_p);
185 goto out;
186}
187EXPORT_SYMBOL(sk_stream_wait_memory);
188
189int sk_stream_error(struct sock *sk, int flags, int err)
190{
191 if (err == -EPIPE)
192 err = sock_error(sk) ? : -EPIPE;
193 if (err == -EPIPE && !(flags & MSG_NOSIGNAL))
194 send_sig(SIGPIPE, current, 0);
195 return err;
196}
197EXPORT_SYMBOL(sk_stream_error);
198
199void sk_stream_kill_queues(struct sock *sk)
200{
201 /* First the read buffer. */
202 __skb_queue_purge(&sk->sk_receive_queue);
203
204 /* Next, the error queue.
205 * We need to use queue lock, because other threads might
206 * add packets to the queue without socket lock being held.
207 */
208 skb_queue_purge(&sk->sk_error_queue);
209
210 /* Next, the write queue. */
211 WARN_ON_ONCE(!skb_queue_empty(&sk->sk_write_queue));
212
213 /* Account for returned memory. */
214 sk_mem_reclaim_final(sk);
215
216 WARN_ON_ONCE(sk->sk_wmem_queued);
217
218 /* It is _impossible_ for the backlog to contain anything
219 * when we get here. All user references to this socket
220 * have gone away, only the net layer knows can touch it.
221 */
222}
223EXPORT_SYMBOL(sk_stream_kill_queues);