net/core/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: socket
  27  *
  28  * FIXME: write proper description
  29  */
  30 void 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  */
  56 int 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 0;
  83 }
  84 EXPORT_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  */
  90 static 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
  96 void 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 }
 111 EXPORT_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  */
 118 int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
 119 {
 120         int 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 = prandom_u32_max(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                 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) &&
 148                                                   !vm_wait), &wait);
 149                 sk->sk_write_pending--;
 150
 151                 if (vm_wait) {
 152                         vm_wait -= current_timeo;
 153                         current_timeo = *timeo_p;
 154                         if (current_timeo != MAX_SCHEDULE_TIMEOUT &&
 155                             (current_timeo -= vm_wait) < 0)
 156                                 current_timeo = 0;
 157                         vm_wait = 0;
 158                 }
 159                 *timeo_p = current_timeo;
 160         }
 161 out:
 162         if (!sock_flag(sk, SOCK_DEAD))
 163                 remove_wait_queue(sk_sleep(sk), &wait);
 164         return err;
 165
 166 do_error:
 167         err = -EPIPE;
 168         goto out;
 169 do_eagain:
 170         /* Make sure that whenever EAGAIN is returned, EPOLLOUT event can
 171          * be generated later.
 172          * When TCP receives ACK packets that make room, tcp_check_space()
 173          * only calls tcp_new_space() if SOCK_NOSPACE is set.
 174          */
 175         set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 176         err = -EAGAIN;
 177         goto out;
 178 do_interrupted:
 179         err = sock_intr_errno(*timeo_p);
 180         goto out;
 181 }
 182 EXPORT_SYMBOL(sk_stream_wait_memory);
 183
 184 int sk_stream_error(struct sock *sk, int flags, int err)
 185 {
 186         if (err == -EPIPE)
 187                 err = sock_error(sk) ? : -EPIPE;
 188         if (err == -EPIPE && !(flags & MSG_NOSIGNAL))
 189                 send_sig(SIGPIPE, current, 0);
 190         return err;
 191 }
 192 EXPORT_SYMBOL(sk_stream_error);
 193
 194 void sk_stream_kill_queues(struct sock *sk)
 195 {
 196         /* First the read buffer. */
 197         __skb_queue_purge(&sk->sk_receive_queue);
 198
 199         /* Next, the error queue.
 200          * We need to use queue lock, because other threads might
 201          * add packets to the queue without socket lock being held.
 202          */
 203         skb_queue_purge(&sk->sk_error_queue);
 204
 205         /* Next, the write queue. */
 206         WARN_ON_ONCE(!skb_queue_empty(&sk->sk_write_queue));
 207
 208         /* Account for returned memory. */
 209         sk_mem_reclaim_final(sk);
 210
 211         WARN_ON_ONCE(sk->sk_wmem_queued);
 212
 213         /* It is _impossible_ for the backlog to contain anything
 214          * when we get here.  All user references to this socket
 215          * have gone away, only the net layer knows can touch it.
 216          */
 217 }
 218 EXPORT_SYMBOL(sk_stream_kill_queues);