PATCH: Prevent XenD touching externally managed bridges

PATCH: Prevent XenD touching externally managed bridges

[Daniel P. Berrange]

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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>

Dan.
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diff -rup xen-unstable-16606.orig/tools/python/xen/xend/XendNetwork.py xen-unstable-16606.new/tools/python/xen/xend/XendNetwork.py
--- xen-unstable-16606.orig/tools/python/xen/xend/XendNetwork.py	2007-12-13 04:31:03.000000000 -0500
+++ xen-unstable-16606.new/tools/python/xen/xend/XendNetwork.py	2007-12-14 13:51:08.000000000 -0500
@@ -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
 
@@ -143,7 +148,13 @@ class XendNetwork(XendBase):
     create            = classmethod(create)
     get_by_name_label = classmethod(get_by_name_label)
         
-    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)
         
     #
@@ -177,6 +188,9 @@ 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()

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