net/core/stream.c

   1 /*
   2  *     SUCS NET3:
   3  *
   4  *     Generic stream handling routines. These are generic for most
   5  *     protocols. Even IP. Tonight 8-).
   6  *     This is used because TCP, LLC (others too) layer all have mostly
   7  *     identical sendmsg() and recvmsg() code.
   8  *     So we (will) share it here.
   9  *
  10  *     Authors:        Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  11  *                     (from old tcp.c code)
  12  *                     Alan Cox <alan@lxorguk.ukuu.org.uk> (Borrowed comments 8-))
  13  */
  14
  15 #include <linux/module.h>
  16 #include <linux/net.h>
  17 #include <linux/signal.h>
  18 #include <linux/tcp.h>
  19 #include <linux/wait.h>
  20 #include <net/sock.h>
  21
  22 /**
  23  * sk_stream_write_space - stream socket write_space callback.
  24  * @sk: socket
  25  *
  26  * FIXME: write proper description
  27  */
  28 void sk_stream_write_space(struct sock *sk)
  29 {
  30         struct socket *sock = sk->sk_socket;
  31         struct socket_wq *wq;
  32
  33         if (sk_stream_is_writeable(sk) && sock) {
  34                 clear_bit(SOCK_NOSPACE, &sock->flags);
  35
  36                 rcu_read_lock();
  37                 wq = rcu_dereference(sk->sk_wq);
  38                 if (skwq_has_sleeper(wq))
  39                         wake_up_interruptible_poll(&wq->wait, POLLOUT |
  40                                                 POLLWRNORM | POLLWRBAND);
  41                 if (wq && wq->fasync_list && !(sk->sk_shutdown & SEND_SHUTDOWN))
  42                         sock_wake_async(wq, SOCK_WAKE_SPACE, POLL_OUT);
  43                 rcu_read_unlock();
  44         }
  45 }
  46
  47 /**
  48  * sk_stream_wait_connect - Wait for a socket to get into the connected state
  49  * @sk: sock to wait on
  50  * @timeo_p: for how long to wait
  51  *
  52  * Must be called with the socket locked.
  53  */
  54 int sk_stream_wait_connect(struct sock *sk, long *timeo_p)
  55 {
  56         struct task_struct *tsk = current;
  57         DEFINE_WAIT(wait);
  58         int done;
  59
  60         do {
  61                 int err = sock_error(sk);
  62                 if (err)
  63                         return err;
  64                 if ((1 << sk->sk_state) & ~(TCPF_SYN_SENT | TCPF_SYN_RECV))
  65                         return -EPIPE;
  66                 if (!*timeo_p)
  67                         return -EAGAIN;
  68                 if (signal_pending(tsk))
  69                         return sock_intr_errno(*timeo_p);
  70
  71                 prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
  72                 sk->sk_write_pending++;
  73                 done = sk_wait_event(sk, timeo_p,
  74                                      !sk->sk_err &&
  75                                      !((1 << sk->sk_state) &
  76                                        ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)));
  77                 finish_wait(sk_sleep(sk), &wait);
  78                 sk->sk_write_pending--;
  79         } while (!done);
  80         return 0;
  81 }
  82 EXPORT_SYMBOL(sk_stream_wait_connect);
  83
  84 /**
  85  * sk_stream_closing - Return 1 if we still have things to send in our buffers.
  86  * @sk: socket to verify
  87  */
  88 static inline int sk_stream_closing(struct sock *sk)
  89 {
  90         return (1 << sk->sk_state) &
  91                (TCPF_FIN_WAIT1 | TCPF_CLOSING | TCPF_LAST_ACK);
  92 }
  93
  94 void sk_stream_wait_close(struct sock *sk, long timeout)
  95 {
  96         if (timeout) {
  97                 DEFINE_WAIT(wait);
  98
  99                 do {
 100                         prepare_to_wait(sk_sleep(sk), &wait,
 101                                         TASK_INTERRUPTIBLE);
 102                         if (sk_wait_event(sk, &timeout, !sk_stream_closing(sk)))
 103                                 break;
 104                 } while (!signal_pending(current) && timeout);
 105
 106                 finish_wait(sk_sleep(sk), &wait);
 107         }
 108 }
 109 EXPORT_SYMBOL(sk_stream_wait_close);
 110
 111 /**
 112  * sk_stream_wait_memory - Wait for more memory for a socket
 113  * @sk: socket to wait for memory
 114  * @timeo_p: for how long
 115  */
 116 int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
 117 {
 118         int err = 0;
 119         long vm_wait = 0;
 120         long current_timeo = *timeo_p;
 121         DEFINE_WAIT(wait);
 122
 123         if (sk_stream_memory_free(sk))
 124                 current_timeo = vm_wait = (prandom_u32() % (HZ / 5)) + 2;
 125
 126         while (1) {
 127                 sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 128
 129                 prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 130
 131                 if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
 132                         goto do_error;
 133                 if (!*timeo_p)
 134                         goto do_eagain;
 135                 if (signal_pending(current))
 136                         goto do_interrupted;
 137                 sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 138                 if (sk_stream_memory_free(sk) && !vm_wait)
 139                         break;
 140
 141                 set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 142                 sk->sk_write_pending++;
 143                 sk_wait_event(sk, &current_timeo, sk->sk_err ||
 144                                                   (sk->sk_shutdown & SEND_SHUTDOWN) ||
 145                                                   (sk_stream_memory_free(sk) &&
 146                                                   !vm_wait));
 147                 sk->sk_write_pending--;
 148
 149                 if (vm_wait) {
 150                         vm_wait -= current_timeo;
 151                         current_timeo = *timeo_p;
 152                         if (current_timeo != MAX_SCHEDULE_TIMEOUT &&
 153                             (current_timeo -= vm_wait) < 0)
 154                                 current_timeo = 0;
 155                         vm_wait = 0;
 156                 }
 157                 *timeo_p = current_timeo;
 158         }
 159 out:
 160         finish_wait(sk_sleep(sk), &wait);
 161         return err;
 162
 163 do_error:
 164         err = -EPIPE;
 165         goto out;
 166 do_eagain:
 167         /* Make sure that whenever EAGAIN is returned, EPOLLOUT event can
 168          * be generated later.
 169          * When TCP receives ACK packets that make room, tcp_check_space()
 170          * only calls tcp_new_space() if SOCK_NOSPACE is set.
 171          */
 172         set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 173         err = -EAGAIN;
 174         goto out;
 175 do_interrupted:
 176         err = sock_intr_errno(*timeo_p);
 177         goto out;
 178 }
 179 EXPORT_SYMBOL(sk_stream_wait_memory);
 180
 181 int sk_stream_error(struct sock *sk, int flags, int err)
 182 {
 183         if (err == -EPIPE)
 184                 err = sock_error(sk) ? : -EPIPE;
 185         if (err == -EPIPE && !(flags & MSG_NOSIGNAL))
 186                 send_sig(SIGPIPE, current, 0);
 187         return err;
 188 }
 189 EXPORT_SYMBOL(sk_stream_error);
 190
 191 void sk_stream_kill_queues(struct sock *sk)
 192 {
 193         /* First the read buffer. */
 194         __skb_queue_purge(&sk->sk_receive_queue);
 195
 196         /* Next, the write queue. */
 197         WARN_ON(!skb_queue_empty(&sk->sk_write_queue));
 198
 199         /* Account for returned memory. */
 200         sk_mem_reclaim(sk);
 201
 202         WARN_ON(sk->sk_wmem_queued);
 203         WARN_ON(sk->sk_forward_alloc);
 204
 205         /* It is _impossible_ for the backlog to contain anything
 206          * when we get here.  All user references to this socket
 207          * have gone away, only the net layer knows can touch it.
 208          */
 209 }
 210 EXPORT_SYMBOL(sk_stream_kill_queues);