tipc: return POLLOUT for sockets in an unconnected state

If an implied connect is attempted on a nonblocking STREAM/SEQPACKET
socket during link congestion, the connect message will be discarded
and sendmsg will return EAGAIN. This is normal behavior, and the
application is expected to poll the socket until POLLOUT is set,
after which the connection attempt can be retried.
However, the POLLOUT flag is never set for unconnected sockets and
poll() always returns a zero mask. The application is then left without
a trigger for when it can make another attempt at sending the message.

The solution is to check if we're polling on an unconnected socket
and set the POLLOUT flag if the TIPC port owned by this socket
is not congested. The TIPC ports waiting on a specific link will be
marked as 'not congested' when the link congestion have abated.

Signed-off-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index b5fc8ed1d1fec0dbccc524ed2645f91d9fbeed55..59adc76905e0d022211f68056175041fde326c4d 100644 (file)
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -412,7 +412,7 @@ static int get_name(struct socket *sock, struct sockaddr *uaddr,
  * socket state                flags set
  * ------------                ---------
  * unconnected         no read flags
- *                     no write flags
+ *                     POLLOUT if port is not congested
  *
  * connecting          POLLIN/POLLRDNORM if ACK/NACK in rx queue
  *                     no write flags
@@ -442,6 +442,10 @@ static unsigned int poll(struct file *file, struct socket *sock,
        sock_poll_wait(file, sk_sleep(sk), wait);
 
        switch ((int)sock->state) {
+       case SS_UNCONNECTED:
+               if (!tipc_sk_port(sk)->congested)
+                       mask |= POLLOUT;
+               break;
        case SS_READY:
        case SS_CONNECTED:
                if (!tipc_sk_port(sk)->congested)