Introduced by f6a2f97e

Problem Description:
After multiple times of migrating a domain, which has an ovs interface with no 
portData set,
with non-shared disk, nbd ports got overflowed.

The steps to reproduce the problem:
1 define and start a domain with its network configured as:
    <interface type='bridge'>
          <source bridge='br0'/>
          <virtualport type='openvswitch'>
          </virtualport>
          <model type='virtio'/>
          <driver name='vhost' queues='4'/>
    </interface>
2 do not set the network's portData.
3 migrate(ToURI2) it with flag 91(1011011), which means:
  VIR_MIGRATE_LIVE
  VIR_MIGRATE_PEER2PEER
  VIR_MIGRATE_PERSIST_DEST
  VIR_MIGRATE_UNDEFINE_SOURCE
  VIR_MIGRATE_NON_SHARED_DISK
4 migrate success, but we got an error log in libvirtd.log:
  error : virCommandWait:2423 : internal error: Child process (ovs-vsctl 
--timeout=5 get Interface
  vnet1 external_ids:PortData) unexpected exit status 1: ovs-vsctl: no key 
"PortData" in Interface
  record "vnet1" column external_ids
5 migrate it back, migrate it , migrate it back, .......
6 nbd port got overflowed.

The reasons for the problem is :
1 virNetDevOpenvswitchGetMigrateData() takes it as wrong if no portData is 
available for  the ovs
 interface of a domain. (We think it's not appropriate, as portData is just 
OPTIONAL)
2 in func qemuMigrationBakeCookie(), it fails in 
qemuMigrationCookieAddNetwork(), and returns with -1.
 qemuMigrationCookieAddNBD() is not called thereafter, and mig->nbd is still 
NULL.
3 However, qemuMigrationRun() just *WARN* if qemuMigrationBakeCookie() fails, 
migration still successes.
 cookie is NULL, it's not baked on the src side.
4 On the destination side, it would alloc a port first and then free the nbd 
port in COOKIE.
 But the cookie is NULL due to qemuMigrationCookieAddNetwork() failure at src 
side. thus the nbd port
 is not freed.

In this patch, we add "--if-exists" option to make ovs-vsctl not raise error if 
there's no portData available.
Further more, because portData may be NULL in the cookie at the dest side, 
check it before setting portData.


Signed-off-by: Zhou Yimin <zhouyi...@huawei.com>
Signed-off-by: Zhang Bo <oscar.zhan...@huawei.com>
---
V1 here:
     https://www.redhat.com/archives/libvir-list/2015-February/msg00388.html
V2:
   Add "--if-exists" option to ovs-vsctl cmd,  making ovs-vsctl not raise error 
if there's no portData
   available. Suggested by Martin.
   We Tested the patch, it works.
   link: https://www.redhat.com/archives/libvir-list/2015-March/msg00104.html
V3:
   move V1/V2/V3 description from above the patch to here. It did not show the 
detailed description above
   after apply PATCH v2.
---
 src/util/virnetdevopenvswitch.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/util/virnetdevopenvswitch.c b/src/util/virnetdevopenvswitch.c
index e5c87bb..722d0dd 100644
--- a/src/util/virnetdevopenvswitch.c
+++ b/src/util/virnetdevopenvswitch.c
@@ -30,9 +30,12 @@
 #include "virerror.h"
 #include "virmacaddr.h"
 #include "virstring.h"
+#include "virlog.h"

 #define VIR_FROM_THIS VIR_FROM_NONE

+VIR_LOG_INIT("util.netdevopenvswitch");
+
 /**
  * virNetDevOpenvswitchAddPort:
  * @brname: the bridge name
@@ -206,7 +209,7 @@ int virNetDevOpenvswitchGetMigrateData(char **migrate, 
const char *ifname)
     virCommandPtr cmd = NULL;
     int ret = -1;

-    cmd = virCommandNewArgList(OVSVSCTL, "--timeout=5", "get", "Interface",
+    cmd = virCommandNewArgList(OVSVSCTL, "--timeout=5", "--if-exists", "get", 
"Interface",
                                ifname, "external_ids:PortData", NULL);

     virCommandSetOutputBuffer(cmd, migrate);
@@ -241,6 +244,12 @@ int virNetDevOpenvswitchSetMigrateData(char *migrate, 
const char *ifname)
     virCommandPtr cmd = NULL;
     int ret = -1;

+    if (!migrate) {
+        VIR_DEBUG("No OVS port data for interface %s", ifname);
+        return 0;
+    }
+
     cmd = virCommandNewArgList(OVSVSCTL, "--timeout=5", "set",
                                "Interface", ifname, NULL);
     virCommandAddArgFormat(cmd, "external_ids:PortData=%s", migrate);
-- 
1.7.12.4


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