mininet/net.py

"""

    Mininet: A simple networking testbed for OpenFlow/SDN!

author: Bob Lantz (rlantz@cs.stanford.edu)
author: Brandon Heller (brandonh@stanford.edu)

Mininet creates scalable OpenFlow test networks by using
process-based virtualization and network namespaces.

Simulated hosts are created as processes in separate network
namespaces. This allows a complete OpenFlow network to be simulated on
top of a single Linux kernel.

Each host has:

A virtual console (pipes to a shell)
A virtual interfaces (half of a veth pair)
A parent shell (and possibly some child processes) in a namespace

Hosts have a network interface which is configured via ifconfig/ip
link/etc.

This version supports both the kernel and user space datapaths
from the OpenFlow reference implementation (openflowswitch.org)
as well as OpenVSwitch (openvswitch.org.)

In kernel datapath mode, the controller and switches are simply
processes in the root namespace.

Kernel OpenFlow datapaths are instantiated using dpctl(8), and are
attached to the one side of a veth pair; the other side resides in the
host namespace. In this mode, switch processes can simply connect to the
controller via the loopback interface.

In user datapath mode, the controller and switches can be full-service
nodes that live in their own network namespaces and have management
interfaces and IP addresses on a control network (e.g. 192.168.123.1,
currently routed although it could be bridged.)

In addition to a management interface, user mode switches also have
several switch interfaces, halves of veth pairs whose other halves
reside in the host nodes that the switches are connected to.

Consistent, straightforward naming is important in order to easily
identify hosts, switches and controllers, both from the CLI and
from program code. Interfaces are named to make it easy to identify
which interfaces belong to which node.

The basic naming scheme is as follows:

    Host nodes are named h1-hN
    Switch nodes are named s1-sN
    Controller nodes are named c0-cN
    Interfaces are named {nodename}-eth0 .. {nodename}-ethN

Note: If the network topology is created using mininet.topo, then
node numbers are unique among hosts and switches (e.g. we have
h1..hN and SN..SN+M) and also correspond to their default IP addresses
of 10.x.y.z/8 where x.y.z is the base-256 representation of N for
hN. This mapping allows easy determination of a node's IP
address from its name, e.g. h1 -> 10.0.0.1, h257 -> 10.0.1.1.

Note also that 10.0.0.1 can often be written as 10.1 for short, e.g.
"ping 10.1" is equivalent to "ping 10.0.0.1".

Currently we wrap the entire network in a 'mininet' object, which
constructs a simulated network based on a network topology created
using a topology object (e.g. LinearTopo) from mininet.topo or
mininet.topolib, and a Controller which the switches will connect
to. Several configuration options are provided for functions such as
automatically setting MAC addresses, populating the ARP table, or
even running a set of terminals to allow direct interaction with nodes.

After the network is created, it can be started using start(), and a
variety of useful tasks maybe performed, including basic connectivity
and bandwidth tests and running the mininet CLI.

Once the network is up and running, test code can easily get access
to host and switch objects which can then be used for arbitrary
experiments, typically involving running a series of commands on the
hosts.

After all desired tests or activities have been completed, the stop()
method may be called to shut down the network.

"""

import os
import re
import select
import signal
from time import sleep

from mininet.cli import CLI
from mininet.log import info, error, debug, output
from mininet.node import Host, OVSKernelSwitch, Controller
from mininet.link import Link, Intf
from mininet.util import quietRun, fixLimits, numCores, ensureRoot
from mininet.util import macColonHex, ipStr, ipParse, netParse, ipAdd, nextCCNnet
from mininet.term import cleanUpScreens, makeTerms
import pdb

# Mininet version: should be consistent with README and LICENSE
VERSION = "2.0.0"

class Mininet( object ):
    "Network emulation with hosts spawned in network namespaces."

    def __init__( self, topo=None, switch=OVSKernelSwitch, host=Host,
                  controller=Controller, link=Link, intf=Intf,
                  build=True, xterms=False, cleanup=False, ipBase='10.0.0.0/8',
                  inNamespace=False,
                  autoSetMacs=False, autoStaticArp=False, autoPinCpus=False,
                  listenPort=None ):
        """Create Mininet object.
           topo: Topo (topology) object or None
           switch: default Switch class
           host: default Host class/constructor
           controller: default Controller class/constructor
           link: default Link class/constructor
           intf: default Intf class/constructor
           ipBase: base IP address for hosts,
           build: build now from topo?
           xterms: if build now, spawn xterms?
           cleanup: if build now, cleanup before creating?
           inNamespace: spawn switches and controller in net namespaces?
           autoSetMacs: set MAC addrs automatically like IP addresses?
           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"""
        self.topo = topo
        self.switch = switch
        self.host = host
        self.controller = controller
        self.link = link
        self.intf = intf
        self.ipBase = ipBase
        self.ipBaseNum, self.prefixLen = netParse( self.ipBase )
        self.nextIP = 1  # start for address allocation
        self.ccnNetBase = '1.0.0.0'
        self.inNamespace = inNamespace
        self.xterms = xterms
        self.cleanup = cleanup
        self.autoSetMacs = autoSetMacs
        self.autoStaticArp = autoStaticArp
        self.autoPinCpus = autoPinCpus
        self.numCores = numCores()
        self.nextCore = 0  # next core for pinning hosts to CPUs
        self.listenPort = listenPort

        self.hosts = []
        self.switches = []
        self.controllers = []

        self.nameToNode = {}  # name to Node (Host/Switch) objects

        self.terms = []  # list of spawned xterm processes

        Mininet.init()  # Initialize Mininet if necessary

        self.built = False
        if topo and build:
            self.build()

    def isNdnhost(self, node):
        if 'fib' in node.params:
            return True
        else:
            return False
        
    def addHost( self, name, cls=None, **params ):
        """Add host.
           name: name of host to add
           cls: custom host class/constructor (optional)
           params: parameters for host
           returns: added host"""
        # Default IP and MAC addresses
	#pdb.set_trace()
        #defaults = { 'ip': ipAdd( self.nextIP,
                                  #ipBaseNum=self.ipBaseNum,
                                  #prefixLen=self.prefixLen ) +
                                  #'/%s' % self.prefixLen }
        #if self.autoSetMacs:
            #defaults[ 'mac'] = macColonHex( self.nextIP )
        #if self.autoPinCpus:
            #defaults[ 'cores' ] = self.nextCore
            #self.nextCore = ( self.nextCore + 1 ) % self.numCores        
        #self.nextIP += 1
	defaults = {}
        defaults.update( params )

        if not cls:
            cls = self.host
        h = cls( name, **defaults )
        self.hosts.append( h )
        self.nameToNode[ name ] = h
        return h

    def addSwitch( self, name, cls=None, **params ):
        """Add switch.
           name: name of switch to add
           cls: custom switch class/constructor (optional)
           returns: added switch
           side effect: increments listenPort ivar ."""
        defaults = { 'listenPort': self.listenPort,
                     'inNamespace': self.inNamespace }
        defaults.update( params )
        if not cls:
            cls = self.switch
        sw = cls( name, **defaults )
        if not self.inNamespace and self.listenPort:
            self.listenPort += 1
        self.switches.append( sw )
        self.nameToNode[ name ] = sw
        return sw

    def addController( self, name='c0', controller=None, **params ):
        """Add controller.
           controller: Controller class"""
        if not controller:
            controller = self.controller
        controller_new = controller( name, **params )
        if controller_new:  # allow controller-less setups
            self.controllers.append( controller_new )
            self.nameToNode[ name ] = controller_new
        return controller_new

    # BL: is this better than just using nameToNode[] ?
    # Should it have a better name?
    def getNodeByName( self, *args ):
        "Return node(s) with given name(s)"
        if len( args ) == 1:
            return self.nameToNode[ args[ 0 ] ]
        return [ self.nameToNode[ n ] for n in args ]

    def get( self, *args ):
        "Convenience alias for getNodeByName"
        return self.getNodeByName( *args )

    def addLink( self, node1, node2, port1=None, port2=None,
                 cls=None, **params ):
        """"Add a link from node1 to node2
            node1: source node
            node2: dest node
            port1: source port
            port2: dest port
            returns: link object"""
        defaults = { 'port1': port1,
                     'port2': port2,
                     'intf': self.intf }
        defaults.update( params )
        if not cls:
            cls = self.link
        return cls( node1, node2, **defaults )

    def configHosts( self ):
        "Configure a set of hosts."
        for host in self.hosts:
            info( host.name + ' ' )
            intf = host.defaultIntf()
            if self.isNdnhost(host):
                host.configNdn()
                host.configDefault(ip=None,mac=None)         
            elif intf:
                host.configDefault( defaultRoute=intf )
            else:
                # Don't configure nonexistent intf
                host.configDefault( ip=None, mac=None )
            # You're low priority, dude!
            # BL: do we want to do this here or not?
            # May not make sense if we have CPU lmiting...
            # quietRun( 'renice +18 -p ' + repr( host.pid ) )
            # This may not be the right place to do this, but
            # it needs to be done somewhere.
            host.cmd( 'ifconfig lo up' )
        info( '\n' )

    def buildFromTopo( self, topo=None ):
        """Build mininet from a topology object
           At the end of this function, everything should be connected
           and up."""

        # Possibly we should clean up here and/or validate
        # the topo
        if self.cleanup:
            pass

        info( '*** Creating network\n' )

        #if not self.controllers:
            # Add a default controller
            #info( '*** Adding controller\n' )
            #classes = self.controller
            #if type( classes ) is not list:
            #    classes = [ classes ]
            #for i, cls in enumerate( classes ):
            #    self.addController( 'c%d' % i, cls )

        info( '*** Adding hosts:\n' )
        for hostName in topo.hosts():
	    #pdb.set_trace()
            self.addHost( hostName, **topo.nodeInfo( hostName ) )
            info( hostName + ' ' )

        info( '\n*** Adding switches:\n' )
        for switchName in topo.switches():
            self.addSwitch( switchName, **topo.nodeInfo( switchName) )
            info( switchName + ' ' )

        info( '\n*** Adding links:\n' )
        for srcName, dstName in topo.links(sort=True):
            src, dst = self.nameToNode[ srcName ], self.nameToNode[ dstName ]
            params = topo.linkInfo( srcName, dstName )
            srcPort, dstPort = topo.port( srcName, dstName )
            self.addLink( src, dst, srcPort, dstPort, **params )
            if self.isNdnhost(src):
                src.setIP(ipStr(ipParse(self.ccnNetBase) + 1) + '/30', intf=src.name + '-eth' + str(srcPort))
                dst.setIP(ipStr(ipParse(self.ccnNetBase) + 2) + '/30', intf=dst.name + '-eth' + str(dstPort))
                self.ccnNetBase=nextCCNnet(self.ccnNetBase)
                
            info( '(%s, %s) ' % ( src.name, dst.name ) )

        info( '\n' )
        
        
    def configureControlNetwork( self ):
        "Control net config hook: override in subclass"
        raise Exception( 'configureControlNetwork: '
                         'should be overriden in subclass', self )

    def build( self ):
        "Build mininet."

        if self.topo:
            self.buildFromTopo( self.topo )
        if ( self.inNamespace ):
            self.configureControlNetwork()
        info( '*** Configuring hosts\n' )
        self.configHosts()
        if self.xterms:
            self.startTerms()
        if self.autoStaticArp:
            self.staticArp()
        self.built = True

    def startTerms( self ):
        "Start a terminal for each node."
        info( "*** Running terms on %s\n" % os.environ[ 'DISPLAY' ] )
        cleanUpScreens()
        self.terms += makeTerms( self.controllers, 'controller' )
        self.terms += makeTerms( self.switches, 'switch' )
        self.terms += makeTerms( self.hosts, 'host' )

    def stopXterms( self ):
        "Kill each xterm."
        for term in self.terms:
            os.kill( term.pid, signal.SIGKILL )
        cleanUpScreens()

    def staticArp( self ):
        "Add all-pairs ARP entries to remove the need to handle broadcast."
        for src in self.hosts:
            for dst in self.hosts:
                if src != dst:
                    src.setARP( ip=dst.IP(), mac=dst.MAC() )

    def start( self ):
        "Start controller and switches."
        if not self.built:
            self.build()
        info( '*** Starting controller\n' )
        for controller in self.controllers:
            controller.start()
        info( '*** Starting %s switches\n' % len( self.switches ) )
        for switch in self.switches:
            info( switch.name + ' ')
            switch.start( self.controllers )
        info( '\n' )

    def stop( self ):
        "Stop the controller(s), switches and hosts"
        if self.terms:
            info( '*** Stopping %i terms\n' % len( self.terms ) )
            self.stopXterms()
        info( '*** Stopping %i hosts\n' % len( self.hosts ) )
        for host in self.hosts:
            info( host.name + ' ' )
            host.terminate()
        info( '\n' )
        info( '*** Stopping %i switches\n' % len( self.switches ) )
        for switch in self.switches:
            info( switch.name + ' ' )
            switch.stop()
        info( '\n' )
        info( '*** Stopping %i controllers\n' % len( self.controllers ) )
        for controller in self.controllers:
            info( controller.name + ' ' )
            controller.stop()
        info( '\n*** Done\n' )

    def run( self, test, *args, **kwargs ):
        "Perform a complete start/test/stop cycle."
        self.start()
        info( '*** Running test\n' )
        result = test( *args, **kwargs )
        self.stop()
        return result

    def monitor( self, hosts=None, timeoutms=-1 ):
        """Monitor a set of hosts (or all hosts by default),
           and return their output, a line at a time.
           hosts: (optional) set of hosts to monitor
           timeoutms: (optional) timeout value in ms
           returns: iterator which returns host, line"""
        if hosts is None:
            hosts = self.hosts
        poller = select.poll()
        Node = hosts[ 0 ]  # so we can call class method fdToNode
        for host in hosts:
            poller.register( host.stdout )
        while True:
            ready = poller.poll( timeoutms )
            for fd, event in ready:
                host = Node.fdToNode( fd )
                if event & select.POLLIN:
                    line = host.readline()
                    if line is not None:
                        yield host, line
            # Return if non-blocking
            if not ready and timeoutms >= 0:
                yield None, None

    # XXX These test methods should be moved out of this class.
    # Probably we should create a tests.py for them

    @staticmethod
    def _parsePing( pingOutput ):
        "Parse ping output and return packets sent, received."
        # Check for downed link
        if 'connect: Network is unreachable' in pingOutput:
            return (1, 0)
        r = r'(\d+) packets transmitted, (\d+) received'
        m = re.search( r, pingOutput )
        if m is None:
            error( '*** Error: could not parse ping output: %s\n' %
                   pingOutput )
            return (1, 0)
        sent, received = int( m.group( 1 ) ), int( m.group( 2 ) )
        return sent, received

    def ping( self, hosts=None, timeout=None ):
        """Ping between all specified hosts.
           hosts: list of hosts
           timeout: time to wait for a response, as string
           returns: ploss packet loss percentage"""
        # should we check if running?
        packets = 0
        lost = 0
        ploss = None
        if not hosts:
            hosts = self.hosts
            output( '*** Ping: testing ping reachability\n' )
        for node in hosts:
            output( '%s -> ' % node.name )
            for dest in hosts:
                if node != dest:
                    opts = ''
                    if timeout:
                        opts = '-W %s' % timeout
                    result = node.cmd( 'ping -c1 %s %s' % (opts, dest.IP()) )
                    sent, received = self._parsePing( result )
                    packets += sent
                    if received > sent:
                        error( '*** Error: received too many packets' )
                        error( '%s' % result )
                        node.cmdPrint( 'route' )
                        exit( 1 )
                    lost += sent - received
                    output( ( '%s ' % dest.name ) if received else 'X ' )
            output( '\n' )
            ploss = 100 * lost / packets
        output( "*** Results: %i%% dropped (%d/%d lost)\n" %
                ( ploss, lost, packets ) )
        return ploss

    @staticmethod
    def _parsePingFull( pingOutput ):
        "Parse ping output and return all data."
        # Check for downed link
        if 'connect: Network is unreachable' in pingOutput:
            return (1, 0)
        r = r'(\d+) packets transmitted, (\d+) received'
        m = re.search( r, pingOutput )
        if m is None:
            error( '*** Error: could not parse ping output: %s\n' %
                   pingOutput )
            return (1, 0, 0, 0, 0, 0)
        sent, received = int( m.group( 1 ) ), int( m.group( 2 ) )
        r = r'rtt min/avg/max/mdev = '
        r += r'(\d+\.\d+)/(\d+\.\d+)/(\d+\.\d+)/(\d+\.\d+) ms'
        m = re.search( r, pingOutput )
        rttmin = float( m.group( 1 ) )
        rttavg = float( m.group( 2 ) )
        rttmax = float( m.group( 3 ) )
        rttdev = float( m.group( 4 ) )
        return sent, received, rttmin, rttavg, rttmax, rttdev

    def pingFull( self, hosts=None, timeout=None ):
        """Ping between all specified hosts and return all data.
           hosts: list of hosts
           timeout: time to wait for a response, as string
           returns: all ping data; see function body."""
        # should we check if running?
        # Each value is a tuple: (src, dsd, [all ping outputs])
        all_outputs = []
        if not hosts:
            hosts = self.hosts
            output( '*** Ping: testing ping reachability\n' )
        for node in hosts:
            output( '%s -> ' % node.name )
            for dest in hosts:
                if node != dest:
                    opts = ''
                    if timeout:
                        opts = '-W %s' % timeout
                    result = node.cmd( 'ping -c1 %s %s' % (opts, dest.IP()) )
                    outputs = self._parsePingFull( result )
                    sent, received, rttmin, rttavg, rttmax, rttdev = outputs
                    all_outputs.append( (node, dest, outputs) )
                    output( ( '%s ' % dest.name ) if received else 'X ' )
            output( '\n' )
        output( "*** Results: \n" )
        for outputs in all_outputs:
            src, dest, ping_outputs = outputs
            sent, received, rttmin, rttavg, rttmax, rttdev = ping_outputs
            output( " %s->%s: %s/%s, " % (src, dest, sent, received ) )
            output( "rtt min/avg/max/mdev %0.3f/%0.3f/%0.3f/%0.3f ms\n" %
                    (rttmin, rttavg, rttmax, rttdev) )
        return all_outputs

    def pingAll( self ):
        """Ping between all hosts.
           returns: ploss packet loss percentage"""
        return self.ping()

    def pingPair( self ):
        """Ping between first two hosts, useful for testing.
           returns: ploss packet loss percentage"""
        hosts = [ self.hosts[ 0 ], self.hosts[ 1 ] ]
        return self.ping( hosts=hosts )

    def pingAllFull( self ):
        """Ping between all hosts.
           returns: ploss packet loss percentage"""
        return self.pingFull()

    def pingPairFull( self ):
        """Ping between first two hosts, useful for testing.
           returns: ploss packet loss percentage"""
        hosts = [ self.hosts[ 0 ], self.hosts[ 1 ] ]
        return self.pingFull( hosts=hosts )

    @staticmethod
    def _parseIperf( iperfOutput ):
        """Parse iperf output and return bandwidth.
           iperfOutput: string
           returns: result string"""
        r = r'([\d\.]+ \w+/sec)'
        m = re.findall( r, iperfOutput )
        if m:
            return m[-1]
        else:
            # was: raise Exception(...)
            error( 'could not parse iperf output: ' + iperfOutput )
            return ''

    # XXX This should be cleaned up

    def iperf( self, hosts=None, l4Type='TCP', udpBw='10M' ):
        """Run iperf between two hosts.
           hosts: list of hosts; if None, uses opposite hosts
           l4Type: string, one of [ TCP, UDP ]
           returns: results two-element array of server and client speeds"""
        if not quietRun( 'which telnet' ):
            error( 'Cannot find telnet in $PATH - required for iperf test' )
            return
        if not hosts:
            hosts = [ self.hosts[ 0 ], self.hosts[ -1 ] ]
        else:
            assert len( hosts ) == 2
        client, server = hosts
        output( '*** Iperf: testing ' + l4Type + ' bandwidth between ' )
        output( "%s and %s\n" % ( client.name, server.name ) )
        server.cmd( 'killall -9 iperf' )
        iperfArgs = 'iperf '
        bwArgs = ''
        if l4Type == 'UDP':
            iperfArgs += '-u '
            bwArgs = '-b ' + udpBw + ' '
        elif l4Type != 'TCP':
            raise Exception( 'Unexpected l4 type: %s' % l4Type )
        server.sendCmd( iperfArgs + '-s', printPid=True )
        servout = ''
        while server.lastPid is None:
            servout += server.monitor()
        if l4Type == 'TCP':
            while 'Connected' not in client.cmd(
                    'sh -c "echo A | telnet -e A %s 5001"' % server.IP()):
                output('waiting for iperf to start up...')
                sleep(.5)
        cliout = client.cmd( iperfArgs + '-t 5 -c ' + server.IP() + ' ' +
                             bwArgs )
        debug( 'Client output: %s\n' % cliout )
        server.sendInt()
        servout += server.waitOutput()
        debug( 'Server output: %s\n' % servout )
        result = [ self._parseIperf( servout ), self._parseIperf( cliout ) ]
        if l4Type == 'UDP':
            result.insert( 0, udpBw )
        output( '*** Results: %s\n' % result )
        return result

    def runCpuLimitTest( self, cpu, duration=5 ):
        """run CPU limit test with 'while true' processes.
        cpu: desired CPU fraction of each host
        duration: test duration in seconds
        returns a single list of measured CPU fractions as floats.
        """
        pct = cpu * 100
        info('*** Testing CPU %.0f%% bandwidth limit\n' % pct)
        hosts = self.hosts
        for h in hosts:
            h.cmd( 'while true; do a=1; done &' )
        pids = [h.cmd( 'echo $!' ).strip() for h in hosts]
        pids_str = ",".join(["%s" % pid for pid in pids])
        cmd = 'ps -p %s -o pid,%%cpu,args' % pids_str
        # It's a shame that this is what pylint prefers
        outputs = []
        for _ in range( duration ):
            sleep( 1 )
            outputs.append( quietRun( cmd ).strip() )
        for h in hosts:
            h.cmd( 'kill %1' )
        cpu_fractions = []
        for test_output in outputs:
            # Split by line.  Ignore first line, which looks like this:
            # PID %CPU COMMAND\n
            for line in test_output.split('\n')[1:]:
                r = r'\d+\s*(\d+\.\d+)'
                m = re.search( r, line )
                if m is None:
                    error( '*** Error: could not extract CPU fraction: %s\n' %
                           line )
                    return None
                cpu_fractions.append( float( m.group( 1 ) ) )
        output( '*** Results: %s\n' % cpu_fractions )
        return cpu_fractions

    # BL: I think this can be rewritten now that we have
    # a real link class.
    def configLinkStatus( self, src, dst, status ):
        """Change status of src <-> dst links.
           src: node name
           dst: node name
           status: string {up, down}"""
        if src not in self.nameToNode:
            error( 'src not in network: %s\n' % src )
        elif dst not in self.nameToNode:
            error( 'dst not in network: %s\n' % dst )
        else:
            if type( src ) is str:
                src = self.nameToNode[ src ]
            if type( dst ) is str:
                dst = self.nameToNode[ dst ]
            connections = src.connectionsTo( dst )
            if len( connections ) == 0:
                error( 'src and dst not connected: %s %s\n' % ( src, dst) )
            for srcIntf, dstIntf in connections:
                result = srcIntf.ifconfig( status )
                if result:
                    error( 'link src status change failed: %s\n' % result )
                result = dstIntf.ifconfig( status )
                if result:
                    error( 'link dst status change failed: %s\n' % result )

    def interact( self ):
        "Start network and run our simple CLI."
        self.start()
        result = CLI( self )
        self.stop()
        return result

    inited = False

    @classmethod
    def init( cls ):
        "Initialize Mininet"
        if cls.inited:
            return
        ensureRoot()
        fixLimits()
        cls.inited = True


class MininetWithControlNet( Mininet ):

    """Control network support:

       Create an explicit control network. Currently this is only
       used/usable with the user datapath.

       Notes:

       1. If the controller and switches are in the same (e.g. root)
          namespace, they can just use the loopback connection.

       2. If we can get unix domain sockets to work, we can use them
          instead of an explicit control network.

       3. Instead of routing, we could bridge or use 'in-band' control.

       4. Even if we dispense with this in general, it could still be
          useful for people who wish to simulate a separate control
          network (since real networks may need one!)

       5. Basically nobody ever used this code, so it has been moved
          into its own class.

       6. Ultimately we may wish to extend this to allow us to create a
          control network which every node's control interface is
          attached to."""

    def configureControlNetwork( self ):
        "Configure control network."
        self.configureRoutedControlNetwork()

    # We still need to figure out the right way to pass
    # in the control network location.

    def configureRoutedControlNetwork( self, ip='192.168.123.1',
                                       prefixLen=16 ):
        """Configure a routed control network on controller and switches.
           For use with the user datapath only right now."""
        controller = self.controllers[ 0 ]
        info( controller.name + ' <->' )
        cip = ip
        snum = ipParse( ip )
        for switch in self.switches:
            info( ' ' + switch.name )
            link = self.link( switch, controller, port1=0 )
            sintf, cintf = link.intf1, link.intf2
            switch.controlIntf = sintf
            snum += 1
            while snum & 0xff in [ 0, 255 ]:
                snum += 1
            sip = ipStr( snum )
            cintf.setIP( cip, prefixLen )
            sintf.setIP( sip, prefixLen )
            controller.setHostRoute( sip, cintf )
            switch.setHostRoute( cip, sintf )
        info( '\n' )
        info( '*** Testing control network\n' )
        while not cintf.isUp():
            info( '*** Waiting for', cintf, 'to come up\n' )
            sleep( 1 )
        for switch in self.switches:
            while not sintf.isUp():
                info( '*** Waiting for', sintf, 'to come up\n' )
                sleep( 1 )
            if self.ping( hosts=[ switch, controller ] ) != 0:
                error( '*** Error: control network test failed\n' )
                exit( 1 )
        info( '\n' )