iwd/README

Wireless daemon for Linux
*************************

Copyright (C) 2013-2014  Intel Corporation. All rights reserved.


Compilation and installation
============================

In order to compile the source code you need following software packages:
	- GCC compiler
	- GNU C library
	- Embedded Linux library

To configure run:
	./configure --prefix=/usr

Configure automatically searches for all required components and packages.

To compile and install run:
	make && make install


Embedded Linux library
======================

In order to compile the daemon and control utility the development version
of Embedded Linux library is required to be present. The development
repositories can be found here:

	git://git.kernel.org/pub/scm/libs/ell/ell.git
	https://kernel.googlesource.com/pub/scm/libs/ell/ell.git

The build systems requires that the Embedded Linux library source code
is available on the same top level directory as the Wireless daemon
source code:

	.
	|--- ell
	|    |--- ell
	|    `--- unit
	`--- iwd
	     |--- src
	     `--- client

It is not required to build or install Embedded Linux library. The build
will happen when building the Wireless daemon and it will then be linked
internally.


Kernel dependencies
===================

In order to use this daemon and control utility the kdbus kernel module
is required. The development repositories can be found here:

	https://github.com/gregkh/kdbus
	https://code.google.com/p/d-bus/

The daemon will start its own private bus that is located at the /dev/kdbus
device hierarchy:

	/dev/kdbus
	|--- control
	`--- 0-iwd
	     `--- bus

When started as root, the new private bus will be /dev/kdbus/0-iwd/bus
and it can be verified with the busctl utility from systemd:

	# busctl --address=kernel:path=/dev/kdbus/0-iwd/bus
	NAME       PID  PROCESS     USER      CONNECTION    CONNECTION-NAME
	:1.1     62151  iwd         root      :1.1          iwd
	:1.2     62153  busctl      root      :1.2          sd-busctl

Clients talking to the daemon must specifiy the private bus address.


Netlink monitoring
==================

The included iwmon utility can be used to monitor the 802.11 subsystem
generic netlink commands and events. It uses the nlmon kernel driver
from Linux 3.10 and later.

In order to use iwmon to create traces, the nlmon network interface
needs to be created:

	ip link add name nlmon type nlmon
	ip link set dev nlmon allmulticast on
	ip link set dev nlmon up

For now it is important that the netlink monitor interace is actually
named nlmon. Future version might relax this requirement.

It is possible to create netlink traces in PCAP format using tcpdump
and then read them via iwmon utility:

	tcpdump -i nlmon -w trace-file.pcap

The resulting PCAP files will use Linux cooked packet format containing
packets with ARPHRD_NETLINK type. They can be read using iwmon:

	iwmon -r trace-file.pcap

At this time iwmon is not able to write PCAP files by itself. This might
change in future versions.

When also the authentication protocol traffic on port 0x888e (ETH_P_PAE)
is needed, then a second capture is required:

	tcpdump -i any 'ether proto 0x888e' -w trace-pae.pcap

It is possible to combine these two PCAP files using the mergecap utility
and create a combined trace file:

	mergecap -F pcap -w trace.pcap trace-file.pcap trace-pae.pcap

This will create a trace.pcap file that includes the complete picture
of nl80211 netlink traffic and authentication messages. All packets are
merged in chronological order based on timestamps.

Unfortunately it is not possible to instruct tcpdump filtering to do
this in a single capture. Post-processing of the PCAP files is required
at the moment.


Simulating devices
==================

The Linux driver mac80211_hwsim provides the functionality to simulate
Wireless devices using fake virtual air. Just load the module.

	modprobe mac80211_hwsim radios=0

Provding the radios=0 is important since otherwise it starts out with
two new Wireless radios by default.

With the provided hwsim utility it is now possible to add and remove
virtual radio devices.

	hwsim --create
	hwsim --destroy=<radio-id>

The radio id assigned to each virtual device is its internal id used
by the Wireless device.