[Python] Generate ICMPv6 Packet Too Big Error in Mininet Topology

How do I get my router in Mininet to send the "Packet Too Big" error back to the host before the host fragments the packet?

In Wireshark, I am only able to view the fragmented packets when I use the command "h1 ping6 -s 2001:db8::254".

Any assistance would be appreciated as I am extremely new to networking. Thank you.


# Run with sudo ./topo.py

import os
import subprocess
from mininet.net import Mininet
from mininet.node import Controller, OVSSwitch, RemoteController
from mininet.cli import CLI
from mininet.log import setLogLevel, info

# Ensure Open vSwitch service is running
def start_ovs():
info("*** Starting Open vSwitch service\n")
os.system("service openvswitch-switch start") # Alternative: subprocess.run(["service", "openvswitch-switch", "start"])

def dfpsTopology():
net = Mininet(controller=Controller, switch=OVSSwitch)

info("*** Adding controller\n")
net.addController('c0')

info("*** Adding hosts\n")
attacker = net.addHost('h1', ip='2001:db8::1/64')
router = net.addHost('h2', ip='2001:db8::254/64') # Acting as router
victim = net.addHost('h3', ip='2001:db8::2/64')

info("*** Adding switch\n")
s1 = net.addSwitch('s1')

info("*** Creating links\n")
net.addLink(attacker, s1)
net.addLink(router, s1)
net.addLink(victim, s1)

info("*** Starting network\n")
net.start()

info("*** Configuring global IPv6 addresses on each host\n")
attacker.cmd('ip -6 addr add 2001:db8::1/64 dev h1-eth0')
router.cmd('ip -6 addr add 2001:db8::254/64 dev h2-eth0')
victim.cmd('ip -6 addr add 2001:db8::2/64 dev h3-eth0')

info("*** Configuring router (h2) to forward packets\n")
router.cmd('sysctl -w net.ipv6.conf.all.forwarding=1')

print("[*] Launching fragmentation attack simulator on h1...")
h1 = net.get("h1")
h1.cmd("xterm -e 'python3 simGUI.py' &") # Run simGUI.py in xterm

print("[*] Launching decision tree system on h3...")
h3 = net.get("h3")
h3.cmd("xterm -e 'python3 monGUI.py' &") # Run monGUI.py in xterm

info("*** Running CLI\n")
CLI(net)

info("*** Stopping network\n")
net.stop()

if __name__ == '__main__':
setLogLevel('info')
start_ovs() # Start Open vSwitch before running the topology
dfpsTopology()

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