ovn-controller: avoid crash when vswitchd connection is lost

When ovs-vswitchd has dropped its connection to ovn-controller,
rconn_get_version() will return -1. OpenFlow messages built by
ofctrl_put() in this condition will have an invalid OpenFlow version
value of 255, which eventually leads to ovn-controller crashing
due to an assertion failure in raw_instance_get().

Avoid this crash by improving the ofctrl_can_put() test to ensure
that the negotiated version is available. (Note that checking
rconn_is_connected() would not be sufficient since rconn S_IDLE
state is considered "connected" but version negotiation is not
necessarily complete).

Signed-off-by: Lance Richardson <[email protected]>
Signed-off-by: Ben Pfaff <[email protected]>

ovn/controller/ofctrl.c

@@ -817,7 +817,8 @@ bool
 ofctrl_can_put(void)
 {
     if (state != S_UPDATE_FLOWS
-        || rconn_packet_counter_n_packets(tx_counter)) {
+        || rconn_packet_counter_n_packets(tx_counter)
+        || rconn_get_version(swconn) < 0) {
         return false;
     }
     return true;