[ovs-discuss] Bug in error logging

[Josh Hershberg]

In the file lib/dpif-netlink.c in the function dpif_netlink_init the value
of error is not initialized. If ovsthread_once_start return false, a random
error code is returned. This occurred in my setup when running "ovs-vsctl
add-br br1". Here's the stack trace:
#0  ofproto_tunnel_init () at ofproto/tunnel.c:138
#1  0x0000556adf5a417d in construct (ofproto_=0x556ae07bd960) at
ofproto/ofproto-dpif.c:1306
#2  0x0000556adf591f6c in ofproto_create (datapath_name=0x556ae07b6a80
"br1", datapath_type=<optimized out>, ofprotop=ofprotop at entry=0x556ae07e08a8)
at ofproto/ofproto.c:578
#3  0x0000556adf583d33 in bridge_reconfigure
(ovs_cfg=ovs_cfg at entry=0x556ae07e1450)
at vswitchd/bridge.c:633
#4  0x0000556adf5851cf in bridge_run () at vswitchd/bridge.c:2975
#5  0x0000556adf57b5f5 in main (argc=2, argv=0x7ffc9c326ad8) at
vswitchd/ovs-vswitchd.c:120

and the error reported was (errno 2) when in reality it's the fact that the
lock fails:
2016-05-29T11:50:33Z|00770|ofproto|ERR|failed to open datapath br1: No such
file or directory
2016-05-29T11:50:33Z|00771|bridge|ERR|failed to create bridge br1: No such
file or directory

[root at 2cf66ac4a8aa ~]# ovs-vswitchd --version
ovs-vswitchd (Open vSwitch) 2.5.1
Compiled Mar 20 2016 13:36:00

[jhershbe at josh-laptop ovs]$ git rev-parse HEAD
890effbb949b19bea1b47c95d02934609bb21973

[root at 2cf66ac4a8aa ~]# cat /proc/version
Linux version 4.4.4-200.fc22.x86_64 (
mockbuild at bkernel02.phx2.fedoraproject.org) (gcc version 5.3.1 20151207
(Red Hat 5.3.1-2) (GCC) ) #1 SMP Fri Mar 4 20:06:29 UTC 2016
...but running inside a docker container

[root at 2cf66ac4a8aa ~]# ovs-dpctl show
2016-05-29T11:59:43Z|00001|dpif_netlink|ERR|Generic Netlink family
'ovs_datapath' does not exist. The Open vSwitch kernel module is probably
not loaded.
2016-05-29T11:59:43Z|00002|dpif|WARN|failed to enumerate system datapaths:
No such file or directory

I assume ^^^ this is the root cause of the command not working but the
error should still be correctly reported.
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