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

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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: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Allan Stephens 2010-08-17 11:00:06 +00:00 committed by David S. Miller
parent 35997e3157
commit f662c07058
1 changed files with 39 additions and 20 deletions
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59
net/tipc/socket.c
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@ -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
mask |= POLLOUT;
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;
}