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[libvirt] [PATCH] network: prevent infinite hang if ovs-vswitchd isn't running

This fixes https://bugzilla.redhat.com/show_bug.cgi?id=852984

If a network or interface is configured to use Open vSwitch, but
ovs-vswitchd (the Open vSwitch database service) isn't running, the
ovs-vsctl add-port/del-port commands will hang indefinitely rather
than returning an error. There is a --nowait option, but that appears
to have no effect on add-port and del-port commands, so instead we add
a --timeout=5 to the commands - they will retry for up to 5 seconds,
then fail if there is no response.

I'm not sure if 5 seconds is a reasonable timeout for this, but it
seems to work okay for me (in a very lightly loaded environment, but a
successful return is always effectively instantaneous...).
Unfortunately there doesn't seem to be another way to bound the wait
time of ovs-vsctl. :-(

 src/util/virnetdevopenvswitch.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/util/virnetdevopenvswitch.c b/src/util/virnetdevopenvswitch.c
index 764f478..97b9d52 100644
--- a/src/util/virnetdevopenvswitch.c
+++ b/src/util/virnetdevopenvswitch.c
@@ -105,7 +105,7 @@ int virNetDevOpenvswitchAddPort(const char *brname, const char *ifname,
     cmd = virCommandNew(OVSVSCTL);
-    virCommandAddArgList(cmd, "--", "--may-exist", "add-port",
+    virCommandAddArgList(cmd, "--timeout=5", "--", "--may-exist", "add-port",
                         brname, ifname, NULL);
     if (virBufferUse(&buf) != 0)
@@ -166,7 +166,7 @@ int virNetDevOpenvswitchRemovePort(const char *brname ATTRIBUTE_UNUSED, const ch
     virCommandPtr cmd = NULL;
     cmd = virCommandNew(OVSVSCTL);
-    virCommandAddArgList(cmd, "--", "--if-exists", "del-port", ifname, NULL);
+    virCommandAddArgList(cmd, "--timeout=5", "--", "--if-exists", "del-port", ifname, NULL);
     if (virCommandRun(cmd, NULL) < 0) {

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