[libvirt] Using Libvirt to change the bridge a virtual network card of a running vm is connected to

[Hendrik Schwartke]

I was sure that I did that before. Apparently I was wrong. Sorry for that.

diff --git a/.gnulib b/.gnulib
index d5612c7..e9e8aba 160000
--- a/.gnulib
+++ b/.gnulib
@@ -1 +1 @@
-Subproject commit d5612c714c87555f1059d71d347e20271dced322
+Subproject commit e9e8aba12af3c903edd422fa036a356c5b2f313a
diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index 1e56354..de54710 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -40,6 +40,8 @@
  #include "qemu_cgroup.h"
  #include "locking/domain_lock.h"
  #include "network/bridge_driver.h"
+#include "util/virnetdev.h"
+#include "util/virnetdevbridge.h"
  #include "virnetdevtap.h"

  #define VIR_FROM_THIS VIR_FROM_QEMU
@@ -1191,6 +1193,44 @@ static virDomainNetDefPtr qemuDomainFindNet(virDomainObjPtr vm,
      return NULL;
  }

+int qemuDomainChangeNetBridge(virDomainNetDefPtr olddev,
+                              virDomainNetDefPtr newdev)
+{
+    const char *oldbridge = olddev->data.bridge.brname;
+    const char *newbridge = newdev->data.bridge.brname;
+
+    VIR_DEBUG("Change bridge for interface %s: %s ->  %s",
+              olddev->ifname, oldbridge, newbridge);
+
+    if (!virNetDevExists(newbridge)) {
+        qemuReportError(VIR_ERR_OPERATION_FAILED, "%s",
+                        _("unable to remove port from bridge"));
+        return -1;
+    }
+
+    if (oldbridge&&
+        virNetDevBridgeRemovePort(oldbridge, olddev->ifname)<  0) {
+        qemuReportError(VIR_ERR_OPERATION_FAILED,
+                        _("unable to remove port from bridge %s"), oldbridge);
+        return -1;
+    }
+    if (virNetDevBridgeAddPort(newbridge, newdev->ifname)<  0) {
+        qemuReportError(VIR_ERR_OPERATION_FAILED,
+                        _("unable to add port to bridge %s"), newbridge);
+        if (virNetDevBridgeAddPort(oldbridge, olddev->ifname)<  0) {
+            qemuReportError(VIR_ERR_OPERATION_FAILED,
+                            _("unable to recover former state by adding port to bridge %s"), oldbridge);
+            VIR_FREE(olddev->data.bridge.brname);
+        }
+        return -1;
+    }
+    VIR_FREE(olddev->data.bridge.brname);
+    olddev->data.bridge.brname = newdev->data.bridge.brname;
+    newdev->data.bridge.brname = NULL;
+    return 0;
+}
+
+
  int qemuDomainChangeNetLinkState(struct qemud_driver *driver,
                                   virDomainObjPtr vm,
                                   virDomainNetDefPtr dev,
@@ -1321,6 +1361,13 @@ int qemuDomainChangeNet(struct qemud_driver *driver,
          return -1;
      }

+    if (olddev->type == VIR_DOMAIN_NET_TYPE_BRIDGE
+&&  dev->type == VIR_DOMAIN_NET_TYPE_BRIDGE
+&&  STRNEQ_NULLABLE(olddev->data.bridge.brname, dev->data.bridge.brname)) {
+    	if ((ret = qemuDomainChangeNetBridge(olddev, dev))<  0)
+    		return ret;
+    }
+
      if (olddev->linkstate != dev->linkstate) {
          if ((ret = qemuDomainChangeNetLinkState(driver, vm, olddev, dev->linkstate))<  0)
              return ret;
diff --git a/src/qemu/qemu_hotplug.h b/src/qemu/qemu_hotplug.h
index 0310361..1e1f75c 100644
--- a/src/qemu/qemu_hotplug.h
+++ b/src/qemu/qemu_hotplug.h
@@ -80,6 +80,8 @@ int qemuDomainChangeNetLinkState(struct qemud_driver *driver,
                                   virDomainObjPtr vm,
                                   virDomainNetDefPtr dev,
                                   int linkstate);
+int qemuDomainChangeNetBridge(virDomainNetDefPtr olddev,
+                              virDomainNetDefPtr newdev);
  int qemuDomainDetachPciDiskDevice(struct qemud_driver *driver,
                                    virDomainObjPtr vm,
                                    virDomainDeviceDefPtr dev);






On 16.03.2012 00:06, Eric Blake wrote:
> On 01/26/2012 04:10 AM, Daniel P. Berrange wrote:
>> On Wed, Jan 25, 2012 at 04:09:22PM +0100, Hendrik Schwartke wrote:
>>> I wrote a patch to change the mapping between a virtual bridge
>>> interface and the host bridge while the host is up. It's based on
>>> commit 6fba577e505611e6c25c68e322942eab7754de7e. The host and the
>>> interface definition I used for testing are also attached.
>>> I would be glad if the patch could be added to the repo.
>> Great !
>>
> ...
>
>> Various whitespace fixes
>>
>>   - For assignment, we prefer 'foo = bar' instead of 'foo=bar'
>>   - For conditionals  'if (' instead of 'if('
>>   - For tests  "foo<  0" instead of "foo<0"
>>
>>
>> So all in all I think I'd write this as
>>
>>    int qemuDomainChangeNetBridge(virDomainNetDefPtr olddev,
>>                                  virDomainNetDefPtr newdev)
>>    {
> ...
>
> Are you planning on resubmitting this patch with the noted improvements?
>