sctp: Disallow new connection on a closing socket

If a socket has a lot of association that are in the process of
of being closed/aborted, it is possible for a remote to establish
new associations during the time period that the old ones are shutting
down.  If this was a result of a close() call, there will be no socket
and will cause a memory leak.  We'll prevent this by setting the
socket state to CLOSING and disallow new associations when in this state.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

include/net/sctp/constants.h

@@ -231,7 +231,7 @@ typedef enum {
 	SCTP_SS_LISTENING      = TCP_LISTEN,
 	SCTP_SS_ESTABLISHING   = TCP_SYN_SENT,
 	SCTP_SS_ESTABLISHED    = TCP_ESTABLISHED,
-	SCTP_SS_DISCONNECTING  = TCP_CLOSING,
+	SCTP_SS_CLOSING        = TCP_CLOSING,
 } sctp_sock_state_t;
 
 /* These functions map various type to printable names.  */