xend: Prevent XenD touching externally managed bridges

With current XenD 3.0.4 or later try the following:

    brctl addbr demo
    ifconfig demo up

    /etc/init.d/xend start
    /etc/init.d/xend stop

    ifconfig demo down
    brctl delbr demo

Now, start XenD again....

    /etc/init.d/xend start

And watch in horror as it re-creates your 'demo' bridge.

The problem is that the 'XendNetwork' class does not distinguish
between bridge devices that it is managing (ie those created via
XenAPI) and those which it does not manage (ie those created by OS
distro init scripts, or by apps like  libvirt).

While initially I thought I could just make XenD ignore
externally-managed bridges completely, it seems to needs to know about
them otherwise it can't hook up guest VIFs to them correctly. So the
attached patch adds a 'managed' flag to the XendNetwork
class. Externally managed bridges have this set to False. At startup
XenD will now only re-create bridge devices which have the 'managed'
flag set to 'True'  - ie those created via XenAPI.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
xen-unstable changeset:   16625:44a98411d230b3214be49b42e66d7c42e01ab59f
xen-unstable date:        Sat Dec 15 18:26:52 2007 +0000

diff --git a/tools/python/xen/xend/XendNetwork.py b/tools/python/xen/xend/XendNetwork.py
index 1858fbfbb0d881c4be777293510ab3ce25a29bfe..197c5cf89eefe79b0d8512c6194ed46e88d34607 100644 (file)
--- a/tools/python/xen/xend/XendNetwork.py
+++ b/tools/python/xen/xend/XendNetwork.py
@@ -52,7 +52,8 @@ class XendNetwork(XendBase):
 
     def getAttrRO(self):
         attrRO =  ['VIFs',
-                   'PIFs']
+                   'PIFs',
+                   'managed']
         return XendBase.getAttrRO() + attrRO
 
     def getAttrInst(self):
@@ -88,7 +89,8 @@ class XendNetwork(XendBase):
                 'name_description': '',
                 'other_config':     {},
                 'default_gateway':  '',
-                'default_netmask':  ''
+                'default_netmask':  '',
+                'managed':          False,
             }
         network = XendNetwork(record, uuid)
 
@@ -106,7 +108,10 @@ class XendNetwork(XendBase):
 
         # Create network if it doesn't already exist
         if not bridge_exists(network.name_label):
-            Brctl.bridge_create(network.name_label)
+            if network.managed:
+                Brctl.bridge_create(network.name_label)
+            else:
+                log.info("Not recreating missing unmanaged network %s" % network.name_label)
 
         return uuid
 
@@ -137,7 +142,13 @@ class XendNetwork(XendBase):
     recreate    = classmethod(recreate)
     create      = classmethod(create)
         
-    def __init__(self, record, uuid):       
+    def __init__(self, record, uuid):
+        # This is a read-only attr, so we need to
+        # set it here, as super class won't try to
+        if record.has_key("managed"):
+            self.managed = record["managed"]
+        else:
+            self.managed = True
         XendBase.__init__(self, uuid, record)
         
     #
@@ -171,6 +182,9 @@ class XendNetwork(XendBase):
         self.name_description = new_desc
         XendNode.instance().save_networks()
 
+    def get_managed(self):
+        return self.managed
+
     def get_VIFs(self):
         result = []
         vms = XendDomain.instance().get_all_vms()