Fixed bug in simnet when installing iptables rules in the host namespace

-- Insert rather than append the iptables rules that redirect packets to the simnet
sn-FORWARD table.  This ensures packets flow through the simnet rules before any system
firewall rules installed in the host namespace.

Author: Jay Logue

src/tools/simnet/simnet.py

@@ -1877,7 +1877,7 @@ def initSimnetIPTables(nsName=None):
     # Create the simnet IPv4 FORWARD chain and add it to the default FORWARD chain.
     runCmd([ 'iptables', '-N', namePrefix + 'FORWARD' ], nsName=nsName, 
            errMsg='Unable to create simnet iptables FORWARD chain in namespace %s' % nsName)
-    runCmd([ 'iptables', '-A', 'FORWARD', '-j', namePrefix + 'FORWARD' ], nsName=nsName, 
+    runCmd([ 'iptables', '-I', 'FORWARD', '-j', namePrefix + 'FORWARD' ], nsName=nsName, 
            errMsg='Unable to add simnet iptables FORWARD chain to default FORWARD chain in namespace %s' % nsName)
 
     # Set the policy on the default IPv4 FORWARD chain to DROP.
@@ -1893,7 +1893,7 @@ def initSimnetIPTables(nsName=None):
     # Create the simnet IPv6 FORWARD chain and add it to the default FORWARD chain.
     runCmd([ 'ip6tables', '-N', namePrefix + 'FORWARD' ], nsName=nsName, 
            errMsg='Unable to create simnet ip6tables FORWARD chain in namespace %s' % nsName)
-    runCmd([ 'ip6tables', '-A', 'FORWARD', '-j', namePrefix + 'FORWARD' ], nsName=nsName, 
+    runCmd([ 'ip6tables', '-I', 'FORWARD', '-j', namePrefix + 'FORWARD' ], nsName=nsName, 
            errMsg='Unable to add simnet ip6tables FORWARD chain to default FORWARD chain in namespace %s' % nsName)
 
     # Set the policy on the default IPv6 FORWARD chains to DROP.