blob: a10f63b1944423dee7bdad6bd2354fd8e7a0b6bd [file] [log] [blame]
# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
DOC = """\
lansim is a LAN simulator that runs over a TAP network interface and
allows to simulate network traffic on that interface from Python code.
A TAP interface is a virtual network kernel device that acts as any
other network interface, except that instead of sending and receiving
the traffic through a hardware interface it allows a given program to
handle that traffic through a socket. It is essentially a
bi-directional pipe where one side is a network interface and the
other side is a socket on a program.
The lansim Simulator class allows a Python function to attend all the
outbound traffic matching certain rules and take an action over that
like send back a packet to this interface. The kernel network stack
will see this packet as an inbound packet from the fake interface.
These actions can also be time driven, like a simulation timeout or
send a ping packet every second.
This simulator is useful on situations where you can't fake a network
service using the normal kernel network stack. For example, if you
need to fake a network of several hosts publishing services via mDNS
with multicast you can write those services using this simulator but
it's more complicated to do the same using the system's network stack
since an outbound multicast packet will be sent out on the real
The Simulator class requires a TAP network interface and allows other
Python classes to subscribe to its traffic. The TAP interface needs to
be up when the Simulator runs.
For example, to create a tap interface you can do the following:
tap = tuntap.TunTap(tuntap.IFF_TAP, name="faketap")
print "Interface running on",
This will create a TAP interface with a name like "faketap0". You can
then configure it manually, or just bring it up without an IP address
if you have a Python class implementing a fake DHCP server to
configure it later. To set the IP address manually, you can use any
system command like "ip" or "ifconfig", or from Python in this way:
A very simple example of the usage of this simulator is the
following, where three hosts are created on the faketap0 interface
and will respond to ARP requests. Running the command
"arping -I faketap0" will show two responses for that
given IP address:
simu = simulator.SimulatorThread(tap)
host_a = host.SimpleHost(simu, '12:34:56:78:90:AB', '')
host_b = host.SimpleHost(simu, '12:34:56:78:90:CD', '')
host_c = host.SimpleHost(simu, '12:34:56:78:90:EF', '')
simu.start() # Run the thread.
print "Press enter to stop the simulation."