Hello everyone, I am trying to code a fake gateway to send packets
between h1(10.1.1.2) and h2(10.1.4.2) in mininet
My gateway has two interfaces, one in 10.1.1.0/24 (ip: 10.1.1.1) and one
in 10.1.4.0/24 (ip:10.1.4.1)
I am trying with h1 to download a video from apache webserver running on h2.
When I do so, h1 sends an ARP request to find who has 10.1.1.1?
I already coded a function to reply to these arp requests and my
switch answers: 00:00:00:00:00:01 (S1-eth0 mac)
Now h1 sends TCP packets with src 10.1.1.2 to 10.1.4.2 and h2 receives
them but drops them because the dst mac is 00:00:00:00:00:01. I added
something to change the mac to 00:00:00:00:00:02 in my code but so far
it is not working and the mac stays 00:00:00:00:00:01 according to tcpdump.
Could someone please tell me if my reasoning is wrong? Moreover what is
wrong with my code? If there is a working example of something similar
could you please send me a link? I found the ryu rest router but it is
not very prone to modification which is why I started coding this.
My code is in the py file attached.
(You will have to configure routing for h1 and h2 in order for s1 to get
packets)
Thank you in advance.
Regards,
warsang
# Copyright (C) 2011 Nippon Telegraph and Telephone Corporation.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.lib.packet import arp
from ryu.ofproto import ofproto_v1_4
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet
from ryu.lib.packet import ether_types
from ryu.lib.packet import ipv4
from ryu.lib.packet import icmp
from ryu.lib.packet.arp import arp
from ryu.lib.packet.packet import Packet
import array
HOST_IPADDR1 = "10.1.1.2"
HOST_IPADDR2 = "10.1.4.2"
ROUTER_IPADDR1 = "10.1.1.1"
ROUTER_IPADDR2 = "10.1.4.1"
ROUTER_MACADDR1 = "00:00:00:00:00:01"
ROUTER_MACADDR2 = "00:00:00:00:00:02"
ROUTER_PORT1 = 1
ROUTER_PORT2 = 2
class SimpleSwitch14(app_manager.RyuApp):
OFP_VERSIONS = [ofproto_v1_4.OFP_VERSION]
def __init__(self, *args, **kwargs):
super(SimpleSwitch14, self).__init__(*args, **kwargs)
self.mac_to_port = {}
self.arpTable = {}#ip to mac
@set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
def switch_features_handler(self, ev):
datapath = ev.msg.datapath
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
# install table-miss flow entry
#
# We specify NO BUFFER to max_len of the output action due to
# OVS bug. At this moment, if we specify a lesser number, e.g.,
# 128, OVS will send Packet-In with invalid buffer_id and
# truncated packet data. In that case, we cannot output packets
# correctly. The bug has been fixed in OVS v2.1.0.
match = parser.OFPMatch()
actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
ofproto.OFPCML_NO_BUFFER)]
self.add_flow(datapath, 0, match, actions)
def add_flow(self, datapath, priority, match, actions):
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
actions)]
mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
match=match, instructions=inst)
datapath.send_msg(mod)
def receive_arp(self,datapath,packet,etherFrame,inPort):
arpPacket = packet.get_protocol(arp)
if arpPacket.opcode == 1 :
arp_dstIp = arpPacket.dst_ip
self.logger.debug('received ARP Request %s => %s (port%d)'%(etherFrame.src,etherFrame.dst,inPort))
self.reply_arp(datapath,etherFrame,arpPacket,arp_dstIp,inPort)
elif arpPacket.opcode == 2 :
pass
def reply_arp(self, datapath, etherFrame, arpPacket, arp_dstIp, inPort):
dstIp = arpPacket.src_ip
srcIp = arpPacket.dst_ip
dstMac = etherFrame.src
self.logger.debug("ARP dstIp: %s"%arp_dstIp)
if arp_dstIp == ROUTER_IPADDR1:
srcMac = ROUTER_MACADDR1
outPort = ROUTER_PORT1
elif arp_dstIp == ROUTER_IPADDR2:
srcMac = ROUTER_MACADDR2
outPort = ROUTER_PORT2
else:
self.logger.debug("unknown arp request received !")
self.send_arp(datapath, 2, srcMac, srcIp, dstMac, dstIp, outPort)
self.logger.debug("send ARP reply %s => %s (port%d)" %(srcMac, dstMac, outPort))
def send_arp(self, datapath, opcode, srcMac, srcIp, dstMac, dstIp, outPort):
if opcode == 1:
targetMac = "00:00:00:00:00:00"
targetIp = dstIp
elif opcode == 2:
targetMac = dstMac
targetIp = dstIp
e = ethernet.ethernet(dstMac, srcMac, ether_types.ETH_TYPE_ARP)
a = arp(1, 0x0800, 6, 4, opcode, srcMac, srcIp, targetMac, targetIp)
p = Packet()
p.add_protocol(e)
p.add_protocol(a)
p.serialize()
actions = [datapath.ofproto_parser.OFPActionOutput(outPort, 0)]
out = datapath.ofproto_parser.OFPPacketOut(
datapath=datapath,
buffer_id=0xffffffff,
in_port=datapath.ofproto.OFPP_CONTROLLER,
actions=actions,
data=p.data)
datapath.send_msg(out)
def _send_packet(self, datapath, port, pkt):
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
pkt.serialize()
self.logger.info("packet-out %s" % (pkt,))
data = pkt.data
actions = [parser.OFPActionOutput(port=port)]
out = parser.OFPPacketOut(datapath=datapath,
buffer_id=ofproto.OFP_NO_BUFFER,
in_port=ofproto.OFPP_CONTROLLER,
actions=actions,
data=data)
datapath.send_msg(out)
def _handle_icmp(self, datapath, port, pkt_ethernet, pkt_ipv4, pkt_icmp):
if pkt_icmp.type != icmp.ICMP_ECHO_REQUEST:
return
pkt = packet.Packet()
pkt.add_protocol(ethernet.ethernet(ethertype=pkt_ethernet.ethertype,
dst=pkt_ethernet.src,
src=ROUTER_MACADDR1))
pkt.add_protocol(ipv4.ipv4(dst=pkt_ipv4.src,
src=ROUTER_IPADDR1,
proto=pkt_ipv4.proto))
pkt.add_protocol(icmp.icmp(type_=icmp.ICMP_ECHO_REPLY,
code=icmp.ICMP_ECHO_REPLY_CODE,
csum=0,
data=pkt_icmp.data))
self._send_packet(datapath, port, pkt)
@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
def _packet_in_handler(self, ev):
msg = ev.msg
datapath = msg.datapath
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
in_port = msg.match['in_port']
pkt = packet.Packet(msg.data)
eth = pkt.get_protocols(ethernet.ethernet)[0]
self.logger.info('%s'%eth.ethertype)
dst = eth.dst
src = eth.src
dpid = datapath.id
self.mac_to_port.setdefault(dpid, {})
if eth.ethertype == ether_types.ETH_TYPE_LLDP:
# ignore lldp packet
return
self.logger.info("packet in dpid: %s, srce: %s, dest: %s, in_port: %s", dpid, src, dst, in_port)
# learn a mac address to avoid FLOOD next time.
self.mac_to_port[dpid][src] = in_port
if eth.ethertype == ether_types.ETH_TYPE_ARP:
self.receive_arp(datapath,pkt,eth,in_port)
#learn mac to ip
if eth.ethertype == ether_types.ETH_TYPE_IP:
ipv4_pak = pkt.get_protocol(ipv4.ipv4)
icmp_pak = pkt.get_protocol(icmp.icmp)
self.logger.info('packet_in_handler: --> %s'%ipv4_pak)
if dst == ROUTER_MACADDR1:
out_port = 2
actions.append( OFPActionSetField(eth_src=ROUTER_MACADDR2) )
actions.append( OFPActionSetField(eth_dst='b2:64:b7:5f:5a:97') )
elif dst == ROUTER_MACADDR2:
out_port = 1
actions.append( OFPActionSetField(eth_src=ROUTER_MACADDR1) )
actions.append( OFPActionSetField(eth_dst='a2:86:fb:29:dc:57 ') )
else:
self.logger.info('Not working')
return
out = parser.OFPPacketOut(datapath = datapath,
buffer_id = ofproto.OFP_NO_BUFFER,
in_port = in_port,
actions = actions,
data = msg.data)
self.logger.info('packet_out:--> %s'%out)
datapath.send_msg(out)
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