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 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         }
 163 out:
 164         if (!sock_flag(sk, SOCK_DEAD))
 165                 remove_wait_queue(sk_sleep(sk), &wait);
 166         return err;
 167
 168 do_error:
 169         err = -EPIPE;
 170         goto out;
 171 do_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;
 180 do_interrupted:
 181         err = sock_intr_errno(*timeo_p);
 182         goto out;
 183 }
 184 EXPORT_SYMBOL(sk_stream_wait_memory);
 185
 186 int 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 }
 194 EXPORT_SYMBOL(sk_stream_error);
 195
 196 void 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 }
 220 EXPORT_SYMBOL(sk_stream_kill_queues);