[linux-block.git] / Documentation / networking / ieee802154.txt


		Linux IEEE 802.15.4 implementation


Introduction
============
The IEEE 802.15.4 working group focuses on standardization of the bottom
two layers: Medium Access Control (MAC) and Physical access (PHY). And there
are mainly two options available for upper layers:
 - ZigBee - proprietary protocol from the ZigBee Alliance
 - 6LoWPAN - IPv6 networking over low rate personal area networks

The goal of the Linux-wpan is to provide a complete implementation
of the IEEE 802.15.4 and 6LoWPAN protocols. IEEE 802.15.4 is a stack
of protocols for organizing Low-Rate Wireless Personal Area Networks.

The stack is composed of three main parts:
 - IEEE 802.15.4 layer;  We have chosen to use plain Berkeley socket API,
   the generic Linux networking stack to transfer IEEE 802.15.4 data
   messages and a special protocol over netlink for configuration/management
 - MAC - provides access to shared channel and reliable data delivery
 - PHY - represents device drivers


Socket API
==========

int sd = socket(PF_IEEE802154, SOCK_DGRAM, 0);
.....

The address family, socket addresses etc. are defined in the
include/net/af_ieee802154.h header or in the special header
in the userspace package (see either http://wpan.cakelab.org/ or the
git tree at https://github.com/linux-wpan/wpan-tools).


Kernel side
=============

Like with WiFi, there are several types of devices implementing IEEE 802.15.4.
1) 'HardMAC'. The MAC layer is implemented in the device itself, the device
   exports a management (e.g. MLME) and data API.
2) 'SoftMAC' or just radio. These types of devices are just radio transceivers
   possibly with some kinds of acceleration like automatic CRC computation and
   comparation, automagic ACK handling, address matching, etc.

Those types of devices require different approach to be hooked into Linux kernel.


HardMAC
=======

See the header include/net/ieee802154_netdev.h. You have to implement Linux
net_device, with .type = ARPHRD_IEEE802154. Data is exchanged with socket family
code via plain sk_buffs. On skb reception skb->cb must contain additional
info as described in the struct ieee802154_mac_cb. During packet transmission
the skb->cb is used to provide additional data to device's header_ops->create
function. Be aware that this data can be overridden later (when socket code
submits skb to qdisc), so if you need something from that cb later, you should
store info in the skb->data on your own.

To hook the MLME interface you have to populate the ml_priv field of your
net_device with a pointer to struct ieee802154_mlme_ops instance. The fields
assoc_req, assoc_resp, disassoc_req, start_req, and scan_req are optional.
All other fields are required.


SoftMAC
=======

The MAC is the middle layer in the IEEE 802.15.4 Linux stack. This moment it
provides interface for drivers registration and management of slave interfaces.

NOTE: Currently the only monitor device type is supported - it's IEEE 802.15.4
stack interface for network sniffers (e.g. WireShark).

This layer is going to be extended soon.

See header include/net/mac802154.h and several drivers in
drivers/net/ieee802154/.


Device drivers API
==================

The include/net/mac802154.h defines following functions:
 - struct ieee802154_hw *
   ieee802154_alloc_hw(size_t priv_data_len, const struct ieee802154_ops *ops):
   allocation of IEEE 802.15.4 compatible hardware device

 - void ieee802154_free_hw(struct ieee802154_hw *hw):
   freeing allocated hardware device

 - int ieee802154_register_hw(struct ieee802154_hw *hw):
   register PHY which is the allocated hardware device, in the system

 - void ieee802154_unregister_hw(struct ieee802154_hw *hw):
   freeing registered PHY

 - void ieee802154_rx_irqsafe(struct ieee802154_hw *hw, struct sk_buff *skb,
                              u8 lqi):
   telling 802.15.4 module there is a new received frame in the skb with
   the RF Link Quality Indicator (LQI) from the hardware device

 - void ieee802154_xmit_complete(struct ieee802154_hw *hw, struct sk_buff *skb,
                                 bool ifs_handling):
   telling 802.15.4 module the frame in the skb is or going to be
   transmitted through the hardware device

The device driver must implement the following callbacks in the IEEE 802.15.4
operations structure at least:
struct ieee802154_ops {
	...
	int	(*start)(struct ieee802154_hw *hw);
	void	(*stop)(struct ieee802154_hw *hw);
	...
	int	(*xmit_async)(struct ieee802154_hw *hw, struct sk_buff *skb);
	int	(*ed)(struct ieee802154_hw *hw, u8 *level);
	int	(*set_channel)(struct ieee802154_hw *hw, u8 page, u8 channel);
	...
};

 - int start(struct ieee802154_hw *hw):
   handler that 802.15.4 module calls for the hardware device initialization.

 - void stop(struct ieee802154_hw *hw):
   handler that 802.15.4 module calls for the hardware device cleanup.

 - int xmit_async(struct ieee802154_hw *hw, struct sk_buff *skb):
   handler that 802.15.4 module calls for each frame in the skb going to be
   transmitted through the hardware device.

 - int ed(struct ieee802154_hw *hw, u8 *level):
   handler that 802.15.4 module calls for Energy Detection from the hardware
   device.

 - int set_channel(struct ieee802154_hw *hw, u8 page, u8 channel):
   set radio for listening on specific channel of the hardware device.

Moreover IEEE 802.15.4 device operations structure should be filled.

Fake drivers
============

In addition there is a driver available which simulates a real device with
SoftMAC (fakelb - IEEE 802.15.4 loopback driver) interface. This option
provides a possibility to test and debug the stack without usage of real hardware.

See sources in drivers/net/ieee802154 folder for more details.


6LoWPAN Linux implementation
============================

The IEEE 802.15.4 standard specifies an MTU of 127 bytes, yielding about 80
octets of actual MAC payload once security is turned on, on a wireless link
with a link throughput of 250 kbps or less.  The 6LoWPAN adaptation format
[RFC4944] was specified to carry IPv6 datagrams over such constrained links,
taking into account limited bandwidth, memory, or energy resources that are
expected in applications such as wireless Sensor Networks.  [RFC4944] defines
a Mesh Addressing header to support sub-IP forwarding, a Fragmentation header
to support the IPv6 minimum MTU requirement [RFC2460], and stateless header
compression for IPv6 datagrams (LOWPAN_HC1 and LOWPAN_HC2) to reduce the
relatively large IPv6 and UDP headers down to (in the best case) several bytes.

In September 2011 the standard update was published - [RFC6282].
It deprecates HC1 and HC2 compression and defines IPHC encoding format which is
used in this Linux implementation.

All the code related to 6lowpan you may find in files: net/6lowpan/*
and net/ieee802154/6lowpan/*

To setup a 6LoWPAN interface you need:
1. Add IEEE802.15.4 interface and set channel and PAN ID;
2. Add 6lowpan interface by command like:
   # ip link add link wpan0 name lowpan0 type lowpan
3. Bring up 'lowpan0' interface
Commit	Line	Data
	1
	2	Linux IEEE 802.15.4 implementation
	3
	4
	5	Introduction
	6	============
	7	The IEEE 802.15.4 working group focuses on standardization of the bottom
	8	two layers: Medium Access Control (MAC) and Physical access (PHY). And there
	9	are mainly two options available for upper layers:
	10	- ZigBee - proprietary protocol from the ZigBee Alliance
	11	- 6LoWPAN - IPv6 networking over low rate personal area networks
	12
	13	The goal of the Linux-wpan is to provide a complete implementation
	14	of the IEEE 802.15.4 and 6LoWPAN protocols. IEEE 802.15.4 is a stack
	15	of protocols for organizing Low-Rate Wireless Personal Area Networks.
	16
	17	The stack is composed of three main parts:
	18	- IEEE 802.15.4 layer; We have chosen to use plain Berkeley socket API,
	19	the generic Linux networking stack to transfer IEEE 802.15.4 data
	20	messages and a special protocol over netlink for configuration/management
	21	- MAC - provides access to shared channel and reliable data delivery
	22	- PHY - represents device drivers
	23
	24
	25	Socket API
	26	==========
	27
	28	int sd = socket(PF_IEEE802154, SOCK_DGRAM, 0);
	29	.....
	30
	31	The address family, socket addresses etc. are defined in the
	32	include/net/af_ieee802154.h header or in the special header
	33	in the userspace package (see either http://wpan.cakelab.org/ or the
	34	git tree at https://github.com/linux-wpan/wpan-tools).
	35
	36
	37	Kernel side
	38	=============
	39
	40	Like with WiFi, there are several types of devices implementing IEEE 802.15.4.
	41	1) 'HardMAC'. The MAC layer is implemented in the device itself, the device
	42	exports a management (e.g. MLME) and data API.
	43	2) 'SoftMAC' or just radio. These types of devices are just radio transceivers
	44	possibly with some kinds of acceleration like automatic CRC computation and
	45	comparation, automagic ACK handling, address matching, etc.
	46
	47	Those types of devices require different approach to be hooked into Linux kernel.
	48
	49
	50	HardMAC
	51	=======
	52
	53	See the header include/net/ieee802154_netdev.h. You have to implement Linux
	54	net_device, with .type = ARPHRD_IEEE802154. Data is exchanged with socket family
	55	code via plain sk_buffs. On skb reception skb->cb must contain additional
	56	info as described in the struct ieee802154_mac_cb. During packet transmission
	57	the skb->cb is used to provide additional data to device's header_ops->create
	58	function. Be aware that this data can be overridden later (when socket code
	59	submits skb to qdisc), so if you need something from that cb later, you should
	60	store info in the skb->data on your own.
	61
	62	To hook the MLME interface you have to populate the ml_priv field of your
	63	net_device with a pointer to struct ieee802154_mlme_ops instance. The fields
	64	assoc_req, assoc_resp, disassoc_req, start_req, and scan_req are optional.
	65	All other fields are required.
	66
	67
	68	SoftMAC
	69	=======
	70
	71	The MAC is the middle layer in the IEEE 802.15.4 Linux stack. This moment it
	72	provides interface for drivers registration and management of slave interfaces.
	73
	74	NOTE: Currently the only monitor device type is supported - it's IEEE 802.15.4
	75	stack interface for network sniffers (e.g. WireShark).
	76
	77	This layer is going to be extended soon.
	78
	79	See header include/net/mac802154.h and several drivers in
	80	drivers/net/ieee802154/.
	81
	82
	83	Device drivers API
	84	==================
	85
	86	The include/net/mac802154.h defines following functions:
	87	- struct ieee802154_hw *
	88	ieee802154_alloc_hw(size_t priv_data_len, const struct ieee802154_ops *ops):
	89	allocation of IEEE 802.15.4 compatible hardware device
	90
	91	- void ieee802154_free_hw(struct ieee802154_hw *hw):
	92	freeing allocated hardware device
	93
	94	- int ieee802154_register_hw(struct ieee802154_hw *hw):
	95	register PHY which is the allocated hardware device, in the system
	96
	97	- void ieee802154_unregister_hw(struct ieee802154_hw *hw):
	98	freeing registered PHY
	99
	100	- void ieee802154_rx_irqsafe(struct ieee802154_hw hw, struct sk_buff skb,
	101	u8 lqi):
	102	telling 802.15.4 module there is a new received frame in the skb with
	103	the RF Link Quality Indicator (LQI) from the hardware device
	104
	105	- void ieee802154_xmit_complete(struct ieee802154_hw hw, struct sk_buff skb,
	106	bool ifs_handling):
	107	telling 802.15.4 module the frame in the skb is or going to be
	108	transmitted through the hardware device
	109
	110	The device driver must implement the following callbacks in the IEEE 802.15.4
	111	operations structure at least:
	112	struct ieee802154_ops {
	113	...
	114	int (start)(struct ieee802154_hw hw);
	115	void (stop)(struct ieee802154_hw hw);
	116	...
	117	int (xmit_async)(struct ieee802154_hw hw, struct sk_buff *skb);
	118	int (ed)(struct ieee802154_hw hw, u8 *level);
	119	int (set_channel)(struct ieee802154_hw hw, u8 page, u8 channel);
	120	...
	121	};
	122
	123	- int start(struct ieee802154_hw *hw):
	124	handler that 802.15.4 module calls for the hardware device initialization.
	125
	126	- void stop(struct ieee802154_hw *hw):
	127	handler that 802.15.4 module calls for the hardware device cleanup.
	128
	129	- int xmit_async(struct ieee802154_hw hw, struct sk_buff skb):
	130	handler that 802.15.4 module calls for each frame in the skb going to be
	131	transmitted through the hardware device.
	132
	133	- int ed(struct ieee802154_hw hw, u8 level):
	134	handler that 802.15.4 module calls for Energy Detection from the hardware
	135	device.
	136
	137	- int set_channel(struct ieee802154_hw *hw, u8 page, u8 channel):
	138	set radio for listening on specific channel of the hardware device.
	139
	140	Moreover IEEE 802.15.4 device operations structure should be filled.
	141
	142	Fake drivers
	143	============
	144
	145	In addition there is a driver available which simulates a real device with
	146	SoftMAC (fakelb - IEEE 802.15.4 loopback driver) interface. This option
	147	provides a possibility to test and debug the stack without usage of real hardware.
	148
	149	See sources in drivers/net/ieee802154 folder for more details.
	150
	151
	152	6LoWPAN Linux implementation
	153	============================
	154
	155	The IEEE 802.15.4 standard specifies an MTU of 127 bytes, yielding about 80
	156	octets of actual MAC payload once security is turned on, on a wireless link
	157	with a link throughput of 250 kbps or less. The 6LoWPAN adaptation format
	158	[RFC4944] was specified to carry IPv6 datagrams over such constrained links,
	159	taking into account limited bandwidth, memory, or energy resources that are
	160	expected in applications such as wireless Sensor Networks. [RFC4944] defines
	161	a Mesh Addressing header to support sub-IP forwarding, a Fragmentation header
	162	to support the IPv6 minimum MTU requirement [RFC2460], and stateless header
	163	compression for IPv6 datagrams (LOWPAN_HC1 and LOWPAN_HC2) to reduce the
	164	relatively large IPv6 and UDP headers down to (in the best case) several bytes.
	165
	166	In September 2011 the standard update was published - [RFC6282].
	167	It deprecates HC1 and HC2 compression and defines IPHC encoding format which is
	168	used in this Linux implementation.
	169
	170	All the code related to 6lowpan you may find in files: net/6lowpan/*
	171	and net/ieee802154/6lowpan/*
	172
	173	To setup a 6LoWPAN interface you need:
	174	1. Add IEEE802.15.4 interface and set channel and PAN ID;
	175	2. Add 6lowpan interface by command like:
	176	# ip link add link wpan0 name lowpan0 type lowpan
	177	3. Bring up 'lowpan0' interface