Adding NAT class

Includes automatic NAT feature (mn --nat) and addNAT convenience method for topologies
fixes #111

bin/mn

@@ -193,6 +193,9 @@ class MininetRunner( object ):
         opts.add_option( '--pin', action='store_true',
                          default=False, help="pin hosts to CPU cores "
                          "(requires --host cfs or --host rt)" )
+        opts.add_option( '--nat', action='store_true',
+                         default=False, help="adds a NAT to the topology "
+                         "that connects Mininet to the physical network" )
         opts.add_option( '--version', action='callback', callback=version )
 
         self.options, self.args = opts.parse_args()
@@ -223,6 +226,8 @@ class MininetRunner( object ):
         start = time.time()
 
         topo = buildTopo( TOPOS, self.options.topo )
+        if self.options.nat:
+          topo.addNAT()
         switch = customConstructor( SWITCHES, self.options.switch )
         host = customConstructor( HOSTS, self.options.host )
         controller = customConstructor( CONTROLLERS, self.options.controller )

mininet/net.py

@@ -95,7 +95,7 @@ from itertools import chain
 
 from mininet.cli import CLI
 from mininet.log import info, error, debug, output
-from mininet.node import Host, OVSKernelSwitch, Controller
+from mininet.node import Host, OVSKernelSwitch, Controller, NAT
 from mininet.link import Link, Intf
 from mininet.util import quietRun, fixLimits, numCores, ensureRoot
 from mininet.util import macColonHex, ipStr, ipParse, netParse, ipAdd
@@ -112,7 +112,8 @@ class Mininet( object ):
                   build=True, xterms=False, cleanup=False, ipBase='10.0.0.0/8',
                   inNamespace=False,
                   autoSetMacs=False, autoStaticArp=False, autoPinCpus=False,
-                  listenPort=None ):
+                  listenPort=None,
+                  gateway=None ):
         """Create Mininet object.
            topo: Topo (topology) object or None
            switch: default Switch class
@@ -129,7 +130,8 @@ class Mininet( object ):
            autoStaticArp: set all-pairs static MAC addrs?
            autoPinCpus: pin hosts to (real) cores (requires CPULimitedHost)?
            listenPort: base listening port to open; will be incremented for
-               each additional switch in the net if inNamespace=False"""
+               each additional switch in the net if inNamespace=False
+           gateway: node that provides connectivity to the Internet"""
         self.topo = topo
         self.switch = switch
         self.host = host
@@ -148,6 +150,7 @@ class Mininet( object ):
         self.numCores = numCores()
         self.nextCore = 0  # next core for pinning hosts to CPUs
         self.listenPort = listenPort
+        self.gateway = gateway
 
         self.hosts = []
         self.switches = []
@@ -163,6 +166,9 @@ class Mininet( object ):
         if topo and build:
             self.build()
 
+    # list of Node subclasses that provide gateway service
+    gateways = [ NAT ]
+
     def addHost( self, name, cls=None, **params ):
         """Add host.
            name: name of host to add
@@ -175,17 +181,22 @@ class Mininet( object ):
                                   prefixLen=self.prefixLen ) +
                                   '/%s' % self.prefixLen }
         if self.autoSetMacs:
-            defaults[ 'mac'] = macColonHex( self.nextIP )
+            defaults[ 'mac' ] = macColonHex( self.nextIP )
         if self.autoPinCpus:
             defaults[ 'cores' ] = self.nextCore
             self.nextCore = ( self.nextCore + 1 ) % self.numCores
         self.nextIP += 1
         defaults.update( params )
+        # TODO: clean this up
+        if params.get( 'isNAT', False ):
+            cls = NAT
         if not cls:
             cls = self.host
         h = cls( name, **defaults )
         self.hosts.append( h )
         self.nameToNode[ name ] = h
+        if cls in self.gateways:
+            self.gateway = h
         return h
 
     def addSwitch( self, name, cls=None, **params ):
@@ -227,6 +238,16 @@ class Mininet( object ):
             self.nameToNode[ name ] = controller_new
         return controller_new
 
+    # TODO: incomplete
+    def addNAT( self, name='nat0', connect=True, **params ):
+        nat = self.addHost( name, cls=NAT, **params )
+        # find first switch and create link
+        print "net/addNAT"
+        if connect:
+            #connect the nat to the first switch
+            self.addLink( nat, self.switches[ 0 ] )
+        return nat
+
     # BL: We now have four ways to look up nodes
     # This may (should?) be cleaned up in the future.
     def getNodeByName( self, *args ):
@@ -305,6 +326,19 @@ class Mininet( object ):
             host.cmd( 'ifconfig lo up' )
         info( '\n' )
 
+    def configGateway( self ):
+        """Add gateway routes to all hosts if the networks has a gateway."""
+        if self.gateway:
+            gatewayIP = self.gateway.defaultIntf().IP()
+            for host in self.hosts:
+                if host.inNamespace and self.gateway:
+                    host.cmd( 'ip route flush root 0/0' )
+                    host.cmd( 'route add -net', self.ipBase, 'dev', host.defaultIntf() )
+                    host.cmd( 'route add default gw', gatewayIP )
+                else:
+                    # Don't mess with hosts in the root namespace
+                    pass
+
     def buildFromTopo( self, topo=None ):
         """Build mininet from a topology object
            At the end of this function, everything should be connected
@@ -363,6 +397,7 @@ class Mininet( object ):
             self.startTerms()
         if self.autoStaticArp:
             self.staticArp()
+        self.configGateway()
         self.built = True
 
     def startTerms( self ):

mininet/node.py

@@ -1243,3 +1243,67 @@ class RemoteController( Controller ):
             warn( "Unable to contact the remote controller"
                   " at %s:%d\n" % ( self.ip, self.port ) )
 
+class NAT( Node ):
+    """NAT: Provides connectivity to external network"""
+
+    def __init__( self, name, inetIntf='eth0', subnet='10.0/8', **params):
+        super( NAT, self ).__init__( name, **params )
+
+        """Start NAT/forwarding between Mininet and external network
+        inetIntf: interface for internet access
+        subnet: Mininet subnet (default 10.0/8)="""
+        self.inetIntf = inetIntf
+        self.subnet = subnet #TODO: get subnet from Mininet directly
+
+    def config( self, inetIntf='eth0', subnet='10.0/8', **params ):
+        super( NAT, self).config( **params )
+        """Configure the NAT and iptables"""
+
+        # Identify the interface connecting to the mininet network
+        localIntf =  self.defaultIntf()
+        self.cmd( 'sysctl net.ipv4.ip_forward=0' )
+
+        # Flush any currently active rules
+        # TODO: is this safe?
+        self.cmd( 'iptables -F' )
+        self.cmd( 'iptables -t nat -F' )
+
+        # Create default entries for unmatched traffic
+        self.cmd( 'iptables -P INPUT ACCEPT' )
+        self.cmd( 'iptables -P OUTPUT ACCEPT' )
+        self.cmd( 'iptables -P FORWARD DROP' )
+
+        # Configure NAT
+        self.cmd( 'iptables -I FORWARD -i', localIntf, '-d', self.subnet, '-j DROP' )
+        self.cmd( 'iptables -A FORWARD -i', localIntf, '-s', self.subnet, '-j ACCEPT' )
+        self.cmd( 'iptables -A FORWARD -i', self.inetIntf, '-d', self.subnet, '-j ACCEPT' )
+        self.cmd( 'iptables -t nat -A POSTROUTING -o ', self.inetIntf, '-j MASQUERADE' )
+
+        # Instruct the kernel to perform forwarding
+        self.cmd( 'sysctl net.ipv4.ip_forward=1' )
+
+        # Prevent network-manager from messing with our interface
+        # by specifying manual configuration in /etc/network/interfaces
+        intf = localIntf
+        cfile = '/etc/network/interfaces'
+        line = '\niface %s inet manual\n' % intf
+        config = open( cfile ).read()
+        if ( line ) not in config:
+            info( '*** Adding "' + line.strip() + '" to ' + cfile )
+            with open( cfile, 'a' ) as f:
+                f.write( line )
+        # Probably need to restart network-manager to be safe -
+        # hopefully this won't disconnect you
+        self.cmd( 'service network-manager restart' )
+
+    def terminate( self ):
+        """Stop NAT/forwarding between Mininet and external network"""
+        # Flush any currently active rules
+        # TODO: is this safe?
+        self.cmd( 'iptables -F' )
+        self.cmd( 'iptables -t nat -F' )
+
+        # Instruct the kernel to stop forwarding
+        self.cmd( 'sysctl net.ipv4.ip_forward=0' )
+
+        super( NAT, self ).terminate()

mininet/topo.py

@@ -89,6 +89,16 @@ class Topo(object):
         result = self.addNode(name, isSwitch=True, **opts)
         return result
 
+    def addNAT(self, name='nat', connect=True, **opts):
+        """Convenience method: Add NAT to graph.
+           name: NAT name
+           connect: True will automatically connect to the first switch"""
+        nat = self.addNode(name, isNAT=True, inNamespace=False)
+        if connect:
+            # connect the NAT to the first switch
+            self.addLink(name, self.switches()[ 0 ])
+        return nat
+
     def addLink(self, node1, node2, port1=None, port2=None,
                 **opts):
         """node1, node2: nodes to link together