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Introduction

fakeroute is a simple tool that simulates network topologies by intercepting traceroute-like probes towards a set of IP addresses. Topologies are made of text files describing the successive links, allowing for the presence of load balancers. The tool has been designed to test traceroute-like programs.

Installation

1. Install needed packages

• Debian: run as root the following commands:

aptitude update
aptitude safe-upgrade
aptitude install git python python-setuptools python-netfilter python-nfqueue python-dpkt

• Note: if a python module is not available, no worries, setup.py will install it automatically (see step 3).

2. Get the sources:

mkdir ~/git
cd ~/git
git clone https://github.com/libparistraceroute/fakeroute.git

3. Then run as root:

cd ~/git/fakeroute
python setup.py install

This will install missing python module and configure fakeroute.

Run fakeroute

fakeroute emulates topologies that you can "probe" by performing traceroute measurements. By default, `fakeroutè propose some samples using the following targets IPs (see here):

• in IPv4: 1.1.1.1, 1.1.1.2, 1.1.1.3, 1.1.1.4, 1.1.1.5, 1.1.1.6, 1.1.1.7, 1.1.1.8, 1.1.1.9
• in IPv6: 2001:db8:85a3::8a2e:370:7338

IPv4

1. If your primary network interface (let say eth0) has no IPv4 address, you cannot route the fakeroute destinations. In our samples, each nodes belong to 1.1.1.0/24, so you may run as root:

ifconfig eth0:1 1.1.1.28/24

2. Then run fakeroute as root:

cd ~/git/fakeroute/
./fakeroute/fakeroute -4

You should see something like this:

I: Handling IPv4 probe packets...
   [                          1.1.1.4 ] Weird load balancer
   [                          1.1.1.1 ] Simple asymmetric load balancer
   [                          1.1.1.2 ] Simple load balancer
   [                          1.1.1.3 ] Two-levels simple load balancers
I: Adding iptables rules for handled destinations (see "iptables -nL" and "ip6tables -nL")
I: Running...

To simulate random load-balancing, fakeroute uses a random number generator. By default, the generator will be seeded with current linux time. If you would like to define your own seed, add the option --seed SEED.

./fakeroute/fakeroute -4 --seed 123

3. Run a traceroute measurement toward one of these destinations:

paris-traceroute 1.1.1.1

4. Press ctrl-c to stop fakeroute.

IPv6

1. If your primary network interface (let say eth0) has no IPv6 address, you cannot route the fakeroute destinations. In our samples each nodes belong to 2001:0db8:85a3:0000:0000:8a2e:0370:7330/64, so you may run as root:

ifconfig eth0 inet6 add 2001:0db8:85a3:0000:0000:8a2e:0370:7330/64

2. Run fakeroute as root:

cd ~/git/fakeroute/
./fakeroute/fakeroute -6

You should see something like this:

I: Handling IPv6 prove packets...
   [     2001:db8:85a3::8a2e:370:7338 ] IPv6 test
I: Adding iptables rules for handled destinations (see "iptables -nL" and "ip6tables -nL")
I: Running...

To simulate random load-balancing, fakeroute uses a random number generator. By default, the generator will be seeded with current linux time. If you would like to define your own seed, add the option [--seed seed].

./fakeroute/fakeroute -6 --seed 123

3. Run a traceroute measurement toward this destination:

traceroute6 2001:db8:85a3::8a2e:370:7338

4. Press ctrl-c to stop fakeroute.

How to define custom network topologies

Fakeroute explores successively the following directories until finding some valid configuration files:

• "./targets",
• "~/.fakeroute/targets"
• "/etc/fakeroute/targets"

Write your own file in one of these directory. The filename must respect the following pattern:

<ip_address>-<description>

... (for example "1.1.1.1-asymlb"), otherwise this file will be ignored by fakeroute. ip_address denotes a fakeroute destination that you can probe with a traceroute-like tool.

The first line of your file should be:

#DESC Description of your network topology

Then, write one line per arc. An arc involves a source vertex (which may be either "start" or an IP address) and a target vertex (which may be "end" or an IP address) separated by a space character.

• start stands for the node running traceroute measurements
• end stands for the target node of the traceroute

Full example:

# DESC Simple asymmetric load balancer
start 10.0.0.1
10.0.0.1 10.0.0.2
10.0.0.2 10.0.1.3
10.0.0.2 10.0.2.3
10.0.1.3 10.0.1.4
10.0.2.3 10.0.0.5
10.0.1.4 10.0.0.5
10.0.0.5 10.0.0.6
10.0.0.6 10.0.0.7
10.0.0.7 end

You may use plot script (see next section) to draw the corresponding network topology into a png file.

Drawing fakeroute topologies

1. Install fakeroute and python-pydot package.

• Debian: run as root the following commands

aptitude update
aptitude safe-upgrade
aptitude install python-pydot

2. Go to the fakeroute directory and run plot by passing as parameter the fakeroute target IP (for instance 1.1.1.1):

cd ~git/fakeroute/
./fakeroute/plot 1.1.1.1

3. You should see the following output:

I: Converting './targets/1.1.1.1-asymlb' into '1.1.1.1-asymlb.png'

Fakeroute and wireshark

Thanks to wireshark, you can observe packets returned by fakeroute by sniffing "lo" interface.