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[Xen-changelog] [xen-unstable] xend: Prevent XenD touching externally ma

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Subject: [Xen-changelog] [xen-unstable] xend: Prevent XenD touching externally managed bridges
From: Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 19 Dec 2007 05:40:14 -0800
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# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1197743212 0
# Node ID 44a98411d230b3214be49b42e66d7c42e01ab59f
# Parent  257ca4017b416b26120f4a271cf608a23cf23468
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@xxxxxxxxxx>
 tools/python/xen/xend/XendNetwork.py |   22 ++++++++++++++++++----
 1 files changed, 18 insertions(+), 4 deletions(-)

diff -r 257ca4017b41 -r 44a98411d230 tools/python/xen/xend/XendNetwork.py
--- a/tools/python/xen/xend/XendNetwork.py      Sat Dec 15 18:23:13 2007 +0000
+++ b/tools/python/xen/xend/XendNetwork.py      Sat Dec 15 18:26:52 2007 +0000
@@ -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" % 
         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)
@@ -176,6 +187,9 @@ class XendNetwork(XendBase):
     def set_name_description(self, new_desc):
         self.name_description = new_desc
+    def get_managed(self):
+        return self.managed
     def get_VIFs(self):
         result = []

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