sctp: flush out queue once assoc state falls into SHUTDOWN_PENDING

This patch is to flush out queue when assoc state falls into
SHUTDOWN_PENDING if there are still chunks in it, so that the
data can be sent out as soon as possible before sending SHUTDOWN
chunk.

When sctp supports MSG_MORE flag in next patch, this improvement
can also solve the problem that the chunks with MSG_MORE flag
may be stuck in queue when closing an assoc.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/sm_sideeffect.c

@@ -872,6 +872,10 @@ static void sctp_cmd_new_state(sctp_cmd_seq_t *cmds,
 		if (!sctp_style(sk, UDP))
 			sk->sk_state_change(sk);
 	}
+
+	if (sctp_state(asoc, SHUTDOWN_PENDING) &&
+	    !sctp_outq_is_empty(&asoc->outqueue))
+		sctp_outq_uncork(&asoc->outqueue, GFP_ATOMIC);
 }
 
 /* Helper function to delete an association. */