bug 8347: skip ebtables if kernel doesn't support it

scripts/vm/hypervisor/xenserver/vmops

@@ -5,12 +5,12 @@
 import os, sys, time
 import XenAPIPlugin
 sys.path.extend(["/opt/xensource/sm/", "/usr/local/sbin/", "/sbin/"])
-from util import CommandException
+import base64
 import hostvmstats
 import socket
 import stat
-import base64
 import tempfile
+import util
 
 def echo(fn):
     def wrapped(*v, **k):
@@ -482,7 +482,11 @@ def default_ebtables_rules(vm_name, vif, vm_ip, vm_mac):
         try:
             util.pread2(['ebtables', '-t', 'nat', '-N', chain])
         except:
-            util.pread2(['ebtables', '-t',  'nat',  '-F', chain]) 
+            try:
+                util.pread2(['ebtables', '-t',  'nat',  '-F', chain])
+            except:
+                util.SMlog("Failed to create ebtables nat rule, skipping")
+                return 'true'
 
     try:
         # -s ! 52:54:0:56:44:32 -j DROP 
@@ -513,6 +517,8 @@ def default_ebtables_rules(vm_name, vif, vm_ip, vm_mac):
     except:
         util.SMlog("Failed to program default ebtables OUT rules")
         return 'false' 
+    
+    return 'true'
 
 @echo
 def default_network_rules_systemvm(session, args):