Enable NAT to use all interfaces.

Also put the net.ipv4.ip_forward option back to what it was before on exit,
rather than always setting back to 0.

mininet/nodelib.py

@@ -73,18 +73,17 @@ class LinuxBridge( Switch ):
 class NAT( Node ):
     "NAT: Provides connectivity to external network"
 
-    def __init__( self, name, inetIntf=None, subnet='10.0/8',
+    def __init__( self, name, subnet='10.0/8',
                   localIntf=None, flush=False, **params):
         """Start NAT/forwarding between Mininet and external network
-           inetIntf: interface for internet access
            subnet: Mininet subnet (default 10.0/8)
            flush: flush iptables before installing NAT rules"""
         super( NAT, self ).__init__( name, **params )
 
-        self.inetIntf = inetIntf if inetIntf else self.getGatewayIntf()
         self.subnet = subnet
         self.localIntf = localIntf
         self.flush = flush
+        self.forwardState = self.cmd( 'sysctl -n net.ipv4.ip_forward' ).strip()
 
     def config( self, **params ):
         """Configure the NAT and iptables"""
@@ -93,9 +92,9 @@ class NAT( Node ):
         if not self.localIntf:
             self.localIntf = self.defaultIntf()
 
-        self.cmd( 'sysctl net.ipv4.ip_forward=0' )
-
         if self.flush:
+            self.cmd( 'sysctl net.ipv4.ip_forward=0' )
+            
             self.cmd( 'iptables -F' )
             self.cmd( 'iptables -t nat -F' )
             # Create default entries for unmatched traffic
@@ -109,9 +108,9 @@ class NAT( Node ):
         self.cmd( 'iptables -A FORWARD',
                   '-i', self.localIntf, '-s', self.subnet, '-j ACCEPT' )
         self.cmd( 'iptables -A FORWARD',
-                  '-i', self.inetIntf, '-d', self.subnet, '-j ACCEPT' )
+                  '-o', self.localIntf, '-d', self.subnet,'-j ACCEPT' )
         self.cmd( 'iptables -t nat -A POSTROUTING',
-                  '-o', self.inetIntf, '-s', self.subnet, '-j MASQUERADE' )
+                  '-s', self.subnet, '\'!\'', '-d', self.subnet, '-j MASQUERADE' )
 
         # Instruct the kernel to perform forwarding
         self.cmd( 'sysctl net.ipv4.ip_forward=1' )
@@ -130,18 +129,6 @@ class NAT( Node ):
         # hopefully this won't disconnect you
         self.cmd( 'service network-manager restart' )
 
-    def getGatewayIntf( self, fallback='eth0' ):
-        """Return gateway interface name
-           fallback: default device to fall back to"""
-        routes = self.cmd( 'ip route show' )
-        match = re.search( r'default via \S+ dev (\S+)', routes )
-        if match:
-            return match.group( 1 )
-        else:
-            warn( 'There is no default route set.',
-                  'Using', fallback, 'as gateway interface...\n' )
-            return fallback
-
     def terminate( self ):
         "Stop NAT/forwarding between Mininet and external network"
         # Remote NAT rules
@@ -150,9 +137,9 @@ class NAT( Node ):
         self.cmd( 'iptables -D FORWARD',
                   '-i', self.localIntf, '-s', self.subnet, '-j ACCEPT' )
         self.cmd( 'iptables -D FORWARD',
-                   '-i', self.inetIntf, '-d', self.subnet, '-j ACCEPT' )
+                  '-o', self.localIntf, '-d', self.subnet,'-j ACCEPT' )
         self.cmd( 'iptables -t nat -D POSTROUTING',
-                   '-o', self.inetIntf, '-s', self.subnet, '-j MASQUERADE' )
-        # Instruct the kernel to stop forwarding
-        self.cmd( 'sysctl net.ipv4.ip_forward=0' )
+                  '-s', self.subnet, '\'!\'', '-d', self.subnet, '-j MASQUERADE' )
+        # Put the forwarding state back to what it was
+        self.cmd( 'sysctl net.ipv4.ip_forward=%s' % self.forwardState )
         super( NAT, self ).terminate()