From 9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 Mon Sep 17 00:00:00 2001 From: Yunhong Jiang Date: Tue, 4 Aug 2015 12:17:53 -0700 Subject: Add the rt linux 4.1.3-rt3 as base Import the rt linux 4.1.3-rt3 as OPNFV kvm base. It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and the base is: commit 0917f823c59692d751951bf5ea699a2d1e2f26a2 Author: Sebastian Andrzej Siewior Date: Sat Jul 25 12:13:34 2015 +0200 Prepare v4.1.3-rt3 Signed-off-by: Sebastian Andrzej Siewior We lose all the git history this way and it's not good. We should apply another opnfv project repo in future. Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423 Signed-off-by: Yunhong Jiang --- kernel/Documentation/networking/ieee802154.txt | 151 +++++++++++++++++++++++++ 1 file changed, 151 insertions(+) create mode 100644 kernel/Documentation/networking/ieee802154.txt (limited to 'kernel/Documentation/networking/ieee802154.txt') diff --git a/kernel/Documentation/networking/ieee802154.txt b/kernel/Documentation/networking/ieee802154.txt new file mode 100644 index 000000000..22bbc7225 --- /dev/null +++ b/kernel/Documentation/networking/ieee802154.txt @@ -0,0 +1,151 @@ + + Linux IEEE 802.15.4 implementation + + +Introduction +============ +The IEEE 802.15.4 working group focuses on standardization of bottom +two layers: Medium Access Control (MAC) and Physical (PHY). And there +are mainly two options available for upper layers: + - ZigBee - proprietary protocol from ZigBee Alliance + - 6LowPAN - IPv6 networking over low rate personal area networks + +The Linux-ZigBee project goal is to provide complete implementation +of 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 messages + and a special protocol over genetlink 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 our userspace package (see either linux-zigbee sourceforge download page +or git tree at git://linux-zigbee.git.sourceforge.net/gitroot/linux-zigbee). + +One can use SOCK_RAW for passing raw data towards device xmit function. YMMV. + + +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 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. + + +MLME - MAC Level Management +============================ + +Most of IEEE 802.15.4 MLME interfaces are directly mapped on netlink commands. +See the include/net/nl802154.h header. Our userspace tools package +(see above) provides CLI configuration utility for radio interfaces and simple +coordinator for IEEE 802.15.4 networks as an example users of MLME protocol. + + +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. + +We provide an example of simple HardMAC driver at drivers/ieee802154/fakehard.c + + +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/ieee802154/. + + +Device drivers API +================== + +The include/net/mac802154.h defines following functions: + - struct ieee802154_dev *ieee802154_alloc_device + (size_t priv_size, struct ieee802154_ops *ops): + allocation of IEEE 802.15.4 compatible device + + - void ieee802154_free_device(struct ieee802154_dev *dev): + freeing allocated device + + - int ieee802154_register_device(struct ieee802154_dev *dev): + register PHY in the system + + - void ieee802154_unregister_device(struct ieee802154_dev *dev): + freeing registered PHY + +Moreover IEEE 802.15.4 device operations structure should be filled. + +Fake drivers +============ + +In addition there are two drivers available which simulate real devices with +HardMAC (fakehard) and SoftMAC (fakelb - IEEE 802.15.4 loopback driver) +interfaces. This option provides possibility to test and debug stack without +usage of real hardware. + +See sources in drivers/ieee802154 folder for more details. + + +6LoWPAN Linux implementation +============================ + +The IEEE 802.15.4 standard specifies an MTU of 128 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 Semptember 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/ieee802154/6lowpan.* + +To setup 6lowpan interface you need (busybox release > 1.17.0): +1. Add IEEE802.15.4 interface and initialize PANid; +2. Add 6lowpan interface by command like: + # ip link add link wpan0 name lowpan0 type lowpan +3. Set MAC (if needs): + # ip link set lowpan0 address de:ad:be:ef:ca:fe:ba:be +4. Bring up 'lowpan0' interface -- cgit 1.2.3-korg