NePA TesT: Community Network Emulator

"""

Node Library for Mininet

This contains additional Node types which you may find to be useful.

"""

from mininet.node import Node, Switch

from mininet.log import info, warn

from mininet.moduledeps import pathCheck

import re

class LinuxBridge( Switch ):

    "Linux Bridge (with optional spanning tree)"

    nextPrio = 100  # next bridge priority for spanning tree

    def __init__( self, name, stp=False, prio=None, **kwargs ):

        """stp: use spanning tree protocol? (default False)

           prio: optional explicit bridge priority for STP"""

        self.stp = stp

        if prio:

            self.prio = prio

        else:

            self.prio = LinuxBridge.nextPrio

            LinuxBridge.nextPrio += 1

        Switch.__init__( self, name, **kwargs )

    def connected( self ):

        "Are we forwarding yet?"

        if self.stp:

            return 'forwarding' in self.cmd( 'brctl showstp', self )

        else:

            return True

    def start( self, _controllers ):

        "Start Linux bridge"

        self.cmd( 'ifconfig', self, 'down' )

        self.cmd( 'brctl delbr', self )

        self.cmd( 'brctl addbr', self )

        if self.stp:

            self.cmd( 'brctl setbridgeprio', self.prio )

            self.cmd( 'brctl stp', self, 'on' )

        for i in self.intfList():

            if self.name in i.name:

                self.cmd( 'brctl addif', self, i )

        self.cmd( 'ifconfig', self, 'up' )

    def stop( self, deleteIntfs=True ):

        """Stop Linux bridge

           deleteIntfs: delete interfaces? (True)"""

        self.cmd( 'ifconfig', self, 'down' )

        self.cmd( 'brctl delbr', self )

        super( LinuxBridge, self ).stop( deleteIntfs )

    def dpctl( self, *args ):

        "Run brctl command"

        return self.cmd( 'brctl', *args )

    @classmethod

    def setup( cls ):

        "Make sure our class dependencies are available"

        pathCheck( 'brctl', moduleName='bridge-utils' )

class NAT( Node ):

    "NAT: Provides connectivity to external network"

    def __init__( self, name, inetIntf=None, subnet='10.0/8',

                  localIntf=None, **params):

        """Start NAT/forwarding between Mininet and external network

           inetIntf: interface for internet access

           subnet: Mininet subnet (default 10.0/8)="""

        super( NAT, self ).__init__( name, **params )

        self.inetIntf = inetIntf if inetIntf else self.getGatewayIntf()

        self.subnet = subnet

        self.localIntf = localIntf

    def config( self, **params ):

        """Configure the NAT and iptables"""

        super( NAT, self).config( **params )

        if not self.localIntf:

            self.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', self.localIntf, '-d', self.subnet, '-j DROP' )

        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' )

        self.cmd( 'iptables -t nat -A POSTROUTING',

                  '-o', self.inetIntf, '-s', self.subnet, '-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 = self.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 + '\n' )

            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 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"""

        # 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()