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Commit f662c070 authored by Allan Stephens's avatar Allan Stephens Committed by David S. Miller
Browse files

tipc: correct problems with misleading flags returned using poll() 



Prevent TIPC from incorrectly setting returned flags to poll()
in the following cases:

- an unconnected socket no longer indicates that it is always readable

- an unconnected, connecting, or listening socket no longer indicates
  that it is always writable

Signed-off-by: default avatarAllan Stephens <allan.stephens@windriver.com>
Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 35997e31

net/tipc/socket.c

+40 −21
Original line number Diff line number Diff line
@@ -429,36 +429,55 @@ static int get_name(struct socket *sock, struct sockaddr *uaddr, 
 * to handle any preventable race conditions, so TIPC will do the same ...

 *

 * TIPC sets the returned events as follows:

 * a) POLLRDNORM and POLLIN are set if the socket's receive queue is non-empty

 *    or if a connection-oriented socket is does not have an active connection

 *    (i.e. a read operation will not block).

 * b) POLLOUT is set except when a socket's connection has been terminated

 *    (i.e. a write operation will not block).

 * c) POLLHUP is set when a socket's connection has been terminated.

 *

 * IMPORTANT: The fact that a read or write operation will not block does NOT

 * imply that the operation will succeed!

 *

 * socket state		flags set

 * ------------		---------

 * unconnected		no read flags

 *			no write flags

 *

 * connecting		POLLIN/POLLRDNORM if ACK/NACK in rx queue

 *			no write flags

 *

 * connected		POLLIN/POLLRDNORM if data in rx queue

 *			POLLOUT if port is not congested

 *

 * disconnecting	POLLIN/POLLRDNORM/POLLHUP

 *			no write flags

 *

 * listening		POLLIN if SYN in rx queue

 *			no write flags

 *

 * ready		POLLIN/POLLRDNORM if data in rx queue

 * [connectionless]	POLLOUT (since port cannot be congested)

 *

 * IMPORTANT: The fact that a read or write operation is indicated does NOT

 * imply that the operation will succeed, merely that it should be performed

 * and will not block.

 */



static unsigned int poll(struct file *file, struct socket *sock,

			 poll_table *wait)

{

	struct sock *sk = sock->sk;

	u32 mask;

	u32 mask = 0;



	poll_wait(file, sk_sleep(sk), wait);



	if (!skb_queue_empty(&sk->sk_receive_queue) ||

	    (sock->state == SS_UNCONNECTED) ||

	    (sock->state == SS_DISCONNECTING))

		mask = (POLLRDNORM | POLLIN);

	else

		mask = 0;



	if (sock->state == SS_DISCONNECTING)

		mask |= POLLHUP;

	else

	switch ((int)sock->state) {

	case SS_READY:

	case SS_CONNECTED:

		if (!tipc_sk_port(sk)->congested)

			mask |= POLLOUT;

		/* fall thru' */

	case SS_CONNECTING:

	case SS_LISTENING:

		if (!skb_queue_empty(&sk->sk_receive_queue))

			mask |= (POLLIN | POLLRDNORM);

		break;

	case SS_DISCONNECTING:

		mask = (POLLIN | POLLRDNORM | POLLHUP);

		break;

	}



	return mask;

}