I am trying to code a fake gateway similar to this one in pox: 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.
(You will have to configure routing for h1 and h2 in order for s1 to get packets) Thank you in advance.
My code is the following
# 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)
Thank you in advance.
