[DCCP]: Initial dccp_poll implementation

Tested with a patched netcat, no horror stories so far 8)
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dccp/input.c

@@ -34,6 +34,7 @@ static void dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
 	dccp_v4_send_reset(sk, DCCP_RESET_CODE_CLOSED);
 	dccp_fin(sk, skb);
 	dccp_set_state(sk, DCCP_CLOSED);
+	sk_wake_async(sk, 1, POLL_HUP);
 }
 
 static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)

net/dccp/proto.c

@@ -140,6 +140,62 @@ int dccp_disconnect(struct sock *sk, int flags)
 	return err;
 }
 
+/*
+ *	Wait for a DCCP event.
+ *
+ *	Note that we don't need to lock the socket, as the upper poll layers
+ *	take care of normal races (between the test and the event) and we don't
+ *	go look at any of the socket buffers directly.
+ */
+static unsigned int dccp_poll(struct file *file, struct socket *sock,
+			      poll_table *wait)
+{
+	unsigned int mask;
+	struct sock *sk = sock->sk;
+
+	poll_wait(file, sk->sk_sleep, wait);
+	if (sk->sk_state == DCCP_LISTEN)
+		return inet_csk_listen_poll(sk);
+
+	/* Socket is not locked. We are protected from async events
+	   by poll logic and correct handling of state changes
+	   made by another threads is impossible in any case.
+	 */
+
+	mask = 0;
+	if (sk->sk_err)
+		mask = POLLERR;
+
+	if (sk->sk_shutdown == SHUTDOWN_MASK || sk->sk_state == DCCP_CLOSED)
+		mask |= POLLHUP;
+	if (sk->sk_shutdown & RCV_SHUTDOWN)
+		mask |= POLLIN | POLLRDNORM;
+
+	/* Connected? */
+	if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_RESPOND)) {
+		if (atomic_read(&sk->sk_rmem_alloc) > 0)
+			mask |= POLLIN | POLLRDNORM;
+
+		if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
+			if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)) {
+				mask |= POLLOUT | POLLWRNORM;
+			} else {  /* send SIGIO later */
+				set_bit(SOCK_ASYNC_NOSPACE,
+					&sk->sk_socket->flags);
+				set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+
+				/* Race breaker. If space is freed after
+				 * wspace test but before the flags are set,
+				 * IO signal will be lost.
+				 */
+				if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk))
+					mask |= POLLOUT | POLLWRNORM;
+			}
+		}
+	}
+	return mask;
+}
+
 int dccp_ioctl(struct sock *sk, int cmd, unsigned long arg)
 {
 	dccp_pr_debug("entry\n");
@@ -478,7 +534,8 @@ static struct proto_ops inet_dccp_ops = {
 	.socketpair	= sock_no_socketpair,
 	.accept		= inet_accept,
 	.getname	= inet_getname,
-	.poll		= sock_no_poll,
+	/* FIXME: work on tcp_poll to rename it to inet_csk_poll */
+	.poll		= dccp_poll,
 	.ioctl		= inet_ioctl,
 	/* FIXME: work on inet_listen to rename it to sock_common_listen */
 	.listen		= inet_dccp_listen,