connmgr: Fix vswitchd abort when a port is added and the controller is down

connmgr: Fix vswitchd abort when a port is added and the controller is down

We see the below trace when a port is added to a bridge and the configured
controller is down

0x00007fb002f8b207 in raise () from /lib64/libc.so.6
0x00007fb002f8c8f8 in abort () from /lib64/libc.so.6
0x00007fb004953026 in ofputil_protocol_to_ofp_version () from /lib64/libopenvswitch-2.10.so.0
0x00007fb00494e38e in ofputil_encode_port_status () from /lib64/libopenvswitch-2.10.so.0
0x00007fb004ef1c5b in connmgr_send_port_status () from /lib64/libofproto-2.10.so.0
0x00007fb004efa9f4 in ofport_install () from /lib64/libofproto-2.10.so.0
0x00007fb004efbfb2 in update_port () from /lib64/libofproto-2.10.so.0
0x00007fb004efc7f9 in ofproto_port_add () from /lib64/libofproto-2.10.so.0
0x0000556d540a3f95 in bridge_add_ports__ ()
0x0000556d540a5a47 in bridge_reconfigure ()
0x0000556d540a9199 in bridge_run ()
0x0000556d540a02a5 in main ()

The abort is because of ofputil_protocol_to_ofp_version() is called with invalid
protocol - OFPUTIL_P_NONE. Please see [1] for more details. Similar aborts are
seen as reported in [2].

The commit [3] changed the behavior of the function rconn_get_version().
Before the commit [3], the function ofconn_receives_async_msg() would always
return false if the connection to the controller was down, since
rconn_get_version() used to return -1. This patch now checks the rconn
connection status in ofconn_receives_async_msg() and returns false if not
connected. This would avoid the aborts seen in the above stack trace.

The issue can be reproduced by running the test added in this patch
without the fix.

[1] - https://bugzilla.redhat.com/show_bug.cgi?id=1640045
[2] - https://bugzilla.redhat.com/show_bug.cgi?id=1637926

[3] - 476d2551ab ("rconn: Introduce new invariant to fix assertion failure in corner case.")

Signed-off-by: Numan Siddique <nusiddiq@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Eelco Chaudron <echaudro@redhat.com>