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 (wq_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 EXPORT_SYMBOL(sk_stream_write_space);
  47
  48 /**
  49  * sk_stream_wait_connect - Wait for a socket to get into the connected state
  50  * @sk: sock to wait on
  51  * @timeo_p: for how long to wait
  52  *
  53  * Must be called with the socket locked.
  54  */
  55 int sk_stream_wait_connect(struct sock *sk, long *timeo_p)
  56 {
  57         struct task_struct *tsk = current;
  58         DEFINE_WAIT(wait);
  59         int done;
  60
  61         do {
  62                 int err = sock_error(sk);
  63                 if (err)
  64                         return err;
  65                 if ((1 << sk->sk_state) & ~(TCPF_SYN_SENT | TCPF_SYN_RECV))
  66                         return -EPIPE;
  67                 if (!*timeo_p)
  68                         return -EAGAIN;
  69                 if (signal_pending(tsk))
  70                         return sock_intr_errno(*timeo_p);
  71
  72                 prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
  73                 sk->sk_write_pending++;
  74                 done = sk_wait_event(sk, timeo_p,
  75                                      !sk->sk_err &&
  76                                      !((1 << sk->sk_state) &
  77                                        ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)));
  78                 finish_wait(sk_sleep(sk), &wait);
  79                 sk->sk_write_pending--;
  80         } while (!done);
  81         return 0;
  82 }
  83 EXPORT_SYMBOL(sk_stream_wait_connect);
  84
  85 /**
  86  * sk_stream_closing - Return 1 if we still have things to send in our buffers.
  87  * @sk: socket to verify
  88  */
  89 static inline int sk_stream_closing(struct sock *sk)
  90 {
  91         return (1 << sk->sk_state) &
  92                (TCPF_FIN_WAIT1 | TCPF_CLOSING | TCPF_LAST_ACK);
  93 }
  94
  95 void sk_stream_wait_close(struct sock *sk, long timeout)
  96 {
  97         if (timeout) {
  98                 DEFINE_WAIT(wait);
  99
 100                 do {
 101                         prepare_to_wait(sk_sleep(sk), &wait,
 102                                         TASK_INTERRUPTIBLE);
 103                         if (sk_wait_event(sk, &timeout, !sk_stream_closing(sk)))
 104                                 break;
 105                 } while (!signal_pending(current) && timeout);
 106
 107                 finish_wait(sk_sleep(sk), &wait);
 108         }
 109 }
 110 EXPORT_SYMBOL(sk_stream_wait_close);
 111
 112 /**
 113  * sk_stream_wait_memory - Wait for more memory for a socket
 114  * @sk: socket to wait for memory
 115  * @timeo_p: for how long
 116  */
 117 int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
 118 {
 119         int err = 0;
 120         long vm_wait = 0;
 121         long current_timeo = *timeo_p;
 122         bool noblock = (*timeo_p ? false : true);
 123         DEFINE_WAIT(wait);
 124
 125         if (sk_stream_memory_free(sk))
 126                 current_timeo = vm_wait = (prandom_u32() % (HZ / 5)) + 2;
 127
 128         while (1) {
 129                 sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 130
 131                 prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 132
 133                 if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
 134                         goto do_error;
 135                 if (!*timeo_p) {
 136                         if (noblock)
 137                                 set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 138                         goto do_nonblock;
 139                 }
 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                 sk_wait_event(sk, &current_timeo, sk->sk_err ||
 149                                                   (sk->sk_shutdown & SEND_SHUTDOWN) ||
 150                                                   (sk_stream_memory_free(sk) &&
 151                                                   !vm_wait));
 152                 sk->sk_write_pending--;
 153
 154                 if (vm_wait) {
 155                         vm_wait -= current_timeo;
 156                         current_timeo = *timeo_p;
 157                         if (current_timeo != MAX_SCHEDULE_TIMEOUT &&
 158                             (current_timeo -= vm_wait) < 0)
 159                                 current_timeo = 0;
 160                         vm_wait = 0;
 161                 }
 162                 *timeo_p = current_timeo;
 163         }
 164 out:
 165         finish_wait(sk_sleep(sk), &wait);
 166         return err;
 167
 168 do_error:
 169         err = -EPIPE;
 170         goto out;
 171 do_nonblock:
 172         err = -EAGAIN;
 173         goto out;
 174 do_interrupted:
 175         err = sock_intr_errno(*timeo_p);
 176         goto out;
 177 }
 178 EXPORT_SYMBOL(sk_stream_wait_memory);
 179
 180 int sk_stream_error(struct sock *sk, int flags, int err)
 181 {
 182         if (err == -EPIPE)
 183                 err = sock_error(sk) ? : -EPIPE;
 184         if (err == -EPIPE && !(flags & MSG_NOSIGNAL))
 185                 send_sig(SIGPIPE, current, 0);
 186         return err;
 187 }
 188 EXPORT_SYMBOL(sk_stream_error);
 189
 190 void sk_stream_kill_queues(struct sock *sk)
 191 {
 192         /* First the read buffer. */
 193         __skb_queue_purge(&sk->sk_receive_queue);
 194
 195         /* Next, the error queue. */
 196         __skb_queue_purge(&sk->sk_error_queue);
 197
 198         /* Next, the write queue. */
 199         WARN_ON(!skb_queue_empty(&sk->sk_write_queue));
 200
 201         /* Account for returned memory. */
 202         sk_mem_reclaim(sk);
 203
 204         WARN_ON(sk->sk_wmem_queued);
 205         WARN_ON(sk->sk_forward_alloc);
 206
 207         /* It is _impossible_ for the backlog to contain anything
 208          * when we get here.  All user references to this socket
 209          * have gone away, only the net layer knows can touch it.
 210          */
 211 }
 212 EXPORT_SYMBOL(sk_stream_kill_queues);