mininet-project/mininet/nodelib.py

"""
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
from mininet.util import quietRun


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 ):
        "Check dependencies and warn about firewalling"
        pathCheck( 'brctl', moduleName='bridge-utils' )
        # Disable Linux bridge firewalling so that traffic can flow!
        for table in 'arp', 'ip', 'ip6':
            cmd = 'sysctl net.bridge.bridge-nf-call-%stables' % table
            out = quietRun( cmd ).strip()
            if out.endswith( '1' ):
                warn( 'Warning: Linux bridge may not work with', out, '\n' )


class NAT( Node ):
    "NAT: Provides connectivity to external network"

    def __init__( self, name, subnet='10.0/8',
                  localIntf=None, flush=False, **params):
        """Start NAT/forwarding between Mininet and external network
           subnet: Mininet subnet (default 10.0/8)
           flush: flush iptables before installing NAT rules"""
        super( NAT, self ).__init__( name, **params )

        self.subnet = subnet
        self.localIntf = localIntf
        self.flush = flush
        self.forwardState = self.cmd( 'sysctl -n net.ipv4.ip_forward' ).strip()

    def setManualConfig( self, intf ):
        """Prevent network-manager/networkd from messing with our interface
           by specifying manual configuration in /etc/network/interfaces"""
        cfile = '/etc/network/interfaces'
        line = '\niface %s inet manual\n' % intf
        try:
            with open( cfile ) as f:
                config = f.read()
        except IOError:
            config = ''
        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 || netplan apply' )

    # pylint: disable=arguments-differ
    def config( self, **params ):
        """Configure the NAT and iptables"""

        if not self.localIntf:
            self.localIntf = self.defaultIntf()

        self.setManualConfig( self.localIntf )

        # Now we can configure manually without interference
        super( NAT, self).config( **params )

        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
            self.cmd( 'iptables -P INPUT ACCEPT' )
            self.cmd( 'iptables -P OUTPUT ACCEPT' )
            self.cmd( 'iptables -P FORWARD DROP' )

        # Install NAT rules
        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',
                  '-o', self.localIntf, '-d', self.subnet, '-j ACCEPT' )
        self.cmd( 'iptables -t nat -A POSTROUTING',
                  '-s', self.subnet, "'!'", '-d', self.subnet,
                  '-j MASQUERADE' )

        # Instruct the kernel to perform forwarding
        self.cmd( 'sysctl net.ipv4.ip_forward=1' )

    def terminate( self ):
        "Stop NAT/forwarding between Mininet and external network"
        # Remote NAT rules
        self.cmd( 'iptables -D FORWARD',
                   '-i', self.localIntf, '-d', self.subnet, '-j DROP' )
        self.cmd( 'iptables -D FORWARD',
                  '-i', self.localIntf, '-s', self.subnet, '-j ACCEPT' )
        self.cmd( 'iptables -D FORWARD',
                  '-o', self.localIntf, '-d', self.subnet, '-j ACCEPT' )
        self.cmd( 'iptables -t nat -D POSTROUTING',
                  '-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()