# 1router_net.py: L. Seng and A. Sekercioglu
# Last modified on: 20200303

import os

from mininet.cli import CLI
from mininet.link import TCLink, Intf
from mininet.log import setLogLevel, info
from mininet.net import Mininet
from mininet.node import Node, Controller, CPULimitedHost

class LinuxRouter( Node ):	# from the Mininet library
    "A Node with IP forwarding enabled."

    def config( self, **params ):
        super( LinuxRouter, self).config( **params )
        # Enable forwarding on the router
        info ('enabling forwarding on ', self)
        self.cmd( 'sysctl net.ipv4.ip_forward=1' )

    def terminate( self ):
        self.cmd( 'sysctl net.ipv4.ip_forward=0' )
        super( LinuxRouter, self ).terminate()

def MyNetwork():
    "Create an empty network and add nodes to it."

    net = Mininet(host=CPULimitedHost, link=TCLink, autoStaticArp=False)

    info( '*** Adding controller:\n' )
    # turns OVS switch into an Ethernet bridge/learning bridge
    net.addController('c0')

    info( '*** Adding hosts:\n' )
    s1 = net.addSwitch('s1')
    s2 = net.addSwitch('s2')

    # Router has multiple interfaces, we assign IP addresses later.
    r1 = net.addHost('r1', cls=LinuxRouter)

    # Here, we assign the IP address and set the subnet mask at the
    # same time: The first 24 bits of the subnet mask bits set to 1, or
    # 255.255.255.0
    h1 = net.addHost('h1', ip='172.16.0.2/24', defaultRoute="via 172.16.0.1")
    h2 = net.addHost('h2', ip='172.16.0.3/24')
    h3 = net.addHost('h3', ip='172.16.1.2/24', defaultRoute="via 172.16.1.1")
    h4 = net.addHost('h4', ip='172.16.1.3/24', defaultRoute="via 172.16.1.1")

    info( '*** Creating links:\n' )
    net.addLink(r1, s1, intfName1="r1-wan0")
    net.addLink(r1, s2, intfName1="r1-wan1")
    net.addLink(h1, s1)
    net.addLink(h2, s1)
    net.addLink(h3, s2)
    net.addLink(h4, s2)

    info( '*** Starting network:\n')
    net.start()

    info( '*** Configuring router:\n' )
    r1.cmd('ifconfig r1-wan0 172.16.0.1/24')
    r1.cmd('ifconfig r1-wan1 172.16.1.1/24')

    info( '*** Running CLI:\n' )
    CLI(net)

    info( '*** Stopping network:\n' )
    net.stop()

if __name__ == '__main__':
    os.system("sudo mn -c")
    setLogLevel( 'info' )
    MyNetwork()