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MADWIFI: Multimode Atheros Driver for WiFi on Linux =================================================== * Copyright (c) 2002-2005 Sam Leffler. All rights reserved. Read the file COPYRIGHT for the complete copyright. WARNING: THIS IS A BETA DISTRIBUTION. THIS SOFTWARE HAS KNOWN PROBLEMS WARNING: AND LIMITATIONS THAT WILL BE CORRECTED BEFORE A PRODUCTION WARNING: RELEASE. DON'T BLAME US IF THE SOFTWARE EATS YOUR SYSTEM, WARNING: DESTROYS YOUR DISK OR MAKES YOUR CORN-FLAKES SOGGY. WARNING: USE AT YOUR OWN RISK! Introduction ------------ This software contains a Linux kernel driver for Atheros-based Wireless LAN devices. The driver supports station, AP, ad-hoc, and monitor modes of operation. The Atheros driver depends on a device-independent implementation of the 802.11 protocols that originated in the BSD community (NetBSD in particular). The driver functions as a normal network device and uses the Wireless Extensions API. As such normal Linux tools can and should be used with it. Where the wireless extensions are lacking private ioctls have been added. There is only one driver included here; it supports PCI, MiniPCI and Cardbus devices - USB devices are currently not supported by this driver! The driver can be built as a module or linked directly into the kernel. Note however that the net80211 layer is device-independent; there is no reason it cannot be used with any 802.11 device (in fact this is the case on BSD systems). This software is broken into multiple modules. The Atheros-specific device support is found in the ath_pci module; it should be loaded when an Atheros wireless device is recognized. The ath_pci module requires an additional device specific module, ath_hal, which is described more below. In addition the driver requires the wlan module which contains the 802.11 state machine, protocol support, and other device-independent support needed by any 802.11 device. This code is derived from work that first appeared in NetBSD and then FreeBSD. The wlan module may also force the loading of additional modules for crypto support (wlan_wep, wlan_tkip, wlan_ccmp, etc.), for MAC-based ACL support (wlan_acl), and for 802.1x authenticator support (wlan_xauth). The latter modules are only used when operating as an AP. The crypto modules are loaded when keys of that type are created. The ath_hal module contains the Atheros Hardware Access Layer (HAL). This code manages much of the chip-specific operation of the driver. The HAL is provided in a binary-only form in order to comply with FCC regulations. In particular, a radio transmitter can only be operated at power levels and on frequency channels for which it is approved. The FCC requires that a software-defined radio cannot be configured by the user to operate outside the approved power levels and frequency channels. This makes it difficult to open-source code that enforces limits on the power levels, frequency channels and other parameters of the radio transmitter. See http://ftp.fcc.gov/Bureaus/Engineering_Technology/Orders/2001/fcc01264.pdf for the specific FCC regulation. Because the module is provided in a binary-only form it is marked "Proprietary"; this means when you load it you will see messages that your system is now "tainted". A detailed discussion of the pros and cons of this design can be found at http://madwifi-project.org/wiki/HAL If you wish to use this driver on a platform for which an ath_hal module is not already provided please contact the author. Note that this is only necessary for new _architectures_; the HAL is not tied to any specific version of Linux - in fact the identical HAL binary code is used unchanged with other operating systems. Atheros Hardware ---------------- There are currently three "programming generations" of Atheros 802.11 wireless devices (some of these have multiple hardware implementations but otherwise appear identical to users): 5210 supports 11a only 5211 supports both 11a and 11b 5212 supports 11a, 11b, and 11g These parts have been incorporated in a variety of retail products including Cardbus cards from D-Link, Linksys, Netgear, Orinoco, Proxim, and 3Com; and mini-pci cards from some of these same vendors. In addition, many laptop vendors use Atheros mini-pci cards for their built-in wireless support. For an up-to-date list of cards based on Atheros parts visit: http://customerproducts.atheros.com/customerproducts A list of products that have been reported to be supported by MadWifi can be found here: http://madwifi-project.org/wiki/Compatibility In general, if a device is identified as ``11a only'', it is almost certain to contain an Atheros 5210 part in it. Most retail a+b products use the 5211. Many a+b+g combo products use the 5212 though other vendors have started to offer dual-band support. When in doubt, check the PCI vendor ID with a tool like lspci, the Atheros vendor ID is 0x168c; e.g. 00:13.0 Ethernet controller: Unknown device 168c:0012 (rev 01) but beware that some vendors use alternate vendor IDs (e.g 3Com, IBM). The file ath_hal/ah_devid.h has a list of known PCI IDs. Building the driver ------------------- The procedure to build the driver is described in the file INSTALL. Using the driver ---------------- The driver should support any Atheros-based Cardbus or PCI device. This version of the driver is managed and controlled by the usual Linux tools (ifconfig, iwconfig, iwpriv) plus the wlanconfig tool, which is included with the driver in the tools directory and gets installed on your system with make install. First, run "modprobe ath_pci" or the equivalent using "insmod". When the driver is successfully loaded it creates two devices, named "wifi0" and "ath0". The output from iwconfig should look like this: lo no wireless extensions. wifi0 no wireless extensions. ath0 IEEE 802.11b ESSID:"" Mode:Managed Channel:0 Access Point: Not-Associated Bit Rate:0 kb/s Tx-Power:50 dBm Sensitivity=0/3 Retry:off RTS thr:off Fragment thr:off Power Management:off Link Quality=0/94 Signal level=-95 dBm Noise level=-95 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 This driver uses wifi%d only as a placeholder for the physical device, and will create one wifi device for each wireless NIC in the system. These wifi devices will reject ifconfig and iwconfig commands. The wifi interface indicates the existence of a physical MadWifi device, but it is not of any functional interest other than as the starting point for VAP creation via wlanconfig (see Virtual AP section below). By default, an ath%d Managed mode interface is also created. This device is a "virtual ap" (VAP) of the wifi%d physical device, and is configurable by the standard networking tools - ifconfig, iwconfig, iwpriv. The autocreation function can be manipulated to create any one of the other supported device types automatically by using the autocreate=mode option when the ath_pci module is first loaded. The following example will cause ath%d to be in Master mode: modprobe ath_pci autocreate=ap Autocreation can be disabled: modprobe ath_pci autocreate=none Please see the following link for more information: http://madwifi-project.org/wiki/UserDocs/autocreate Virtual APs (VAPs) and wlanconfig --------------------------------- An interesting feature of MadWifi is Virtual AP (VAP) mode, which allows the operation of multiple concurrent (virtual) access points, and concurrent interfaces running in both AP and station mode. To manipulate VAPs, MadWifi comes with a tool called wlanconfig which is used to create and destroy VAPS with various different modes. The following examples assume that the "autocreate=none" option has been parsed to the module at load time. This allows fine control over management of VAPs, as the creation of a Managed mode station should be delayed until all other required VAPs are first created, as only one sta mode VAP can exist per physical device. To create an access point, use: wlanconfig ath0 create wlandev wifi0 wlanmode ap To create an access point and a station, use: wlanconfig ath0 create wlandev wifi0 wlanmode ap wlanconfig ath1 create wlandev wifi0 wlanmode sta To create APs that share a single MAC address, just create the VAPs: wlanconfig ath0 create wlandev wifi0 wlanmode ap wlanconfig ath1 create wlandev wifi0 wlanmode ap To create an VAP with a unique MAC address, use the bssid parameter: wlanconfig ath0 create wlandev wifi0 wlanmode ap wlanconfig ath1 create wlandev wifi0 wlanmode ap bssid Finally, to destroy a VAP, issue the command: wlanconfig ath0 destroy For more information about Virtual APs, please refer to the users-guide document distributed with the MadWifi source code. For more information about wlanconfig, see its manpage, it is installed when you run "make install". Operating Mode -------------- If you have a multi-mode card, use one of the following commands to lock the operating mode to one of 11a, 11b, or 11g: iwpriv ath0 mode 1 lock operation to 11a only iwpriv ath0 mode 2 lock operation to 11b only iwpriv ath0 mode 3 lock operation to 11g only iwpriv ath0 mode 0 autoselect from 11a/b/g (default) Debugging --------- There are some debugging mechanisms for the curious/masochistic: sysctl -w dev.ath.debug=0xXXX enable console msgs from the driver sysctl -w net.wlan0.debug=0xYYY enable console msgs from the wlan module The values specified for 0XXX and 0xYYY are bit masks that enable debugging in various parts of each module. For the wlan module these values are found in the file net80211/ieee80211_var.h (search for MSG_). For the ath driver look in ath/if_ath.c (search for ATH_DEBUG). Beware that enabling some debugging msgs can affect the operation of the software by slowing it down too much. A more comfortable way to manipulate the debug settings is to make use of athdebug and 80211debug tools. Call them with the parameter "-h" to learn how they are used, or refer to the appropriate man pages. In addition the programs tools/athstats and tools/80211stats can be very useful in understanding what is going on. In particular, something like athstats 1 will give a running display of the most interesting statistics sampled every 1 second. Running athstats without any options will display a summary of all non-zero statistics from the time the driver was loaded. By default the ath0 device is used; to override this use the -i option. A wiki page describes common MadWifi debugging methods here: http://madwifi-project.org/wiki/DevDocs/AthDebug Security/Crypto Support ----------------------- All Atheros devices implement fixed/shared key WEP in hardware. Newer Atheros hardware is capable of much more (e.g. AES, TKIP and Michael). When hardware support is not available for a cipher the net80211 layer will automatically do the work in software. WPA/802.11i station operation (aka supplicant) is supported using Jouni Malinen's wpa_supplicant program. This can be obtained from: http://hostap.epitest.fi/wpa_supplicant/ wpa_supplicant also supports a wide range of 802.1x EAP methods, either together with WPA/WPA2 or without; consult the wpa_supplicant documentation for an up to date list. MadWifi supports the use of the Wireless Extensions ioctls equal to or greater than WE18 (Linux 2.6.13). When using wpa_supplicant with a recent linux kernel, it is preferred to use the 'wext' driver backend, rather than the private MadWifi ioctls. This means that '-D wext' option should be used with wpa_supplicant. NOTE: the in-kernel authenticator is being replaced; to use it you need to follow the directions in net80211/Makefile. When operating as an AP, you can use fixed/shared key ciphers and/or 802.1x authentication. The authentication mode is specified using iwpriv: iwpriv ath0 authmode 1 # open authentication iwpriv ath0 authmode 2 # shared key authentication iwpriv ath0 authmode 3 # 802.1x authentication To use the 802.1x authenticator you must install and configure the hostapd program from the same place you got wpa_supplicant from. Consult the hostapd documentation for further information. Live Monitoring and Writing Raw 802.11 Packets ---------------------------------------------- The driver can be used in a live "monitor" mode, by creating a monitor VAP and sending packets to it. All packets sent to a monitor mode VAP will bypass any state machine. To create a monitor VAP, use: wlanconfig ath1 create wlandev wifi0 wlanmode monitor ifconfig ath1 up Finally, you can choose to receive packets on ath1 in several different packet formats: echo '801' > /proc/sys/net/ath1/dev_type # only 802.11 headers echo '802' > /proc/sys/net/ath1/dev_type # prism2 headers echo '803' > /proc/sys/net/ath1/dev_type # radiotap headers echo '804' > /proc/sys/net/ath1/dev_type # atheros descriptors Known Problems -------------- [All these problems are to be fixed in future revisions.] 1. Ad-hoc mode is broken; symptoms are intermittent operation. Other issues might be mentioned in our ticket tracker: http://madwifi-project.org/report/1 Getting Support --------------- User support is provided via the madwifi-users mailing list, which can be reached at: email@example.com Contact this mailing list if you need help in getting your installation up and running. We suggest that you subscribe to the list before sending your request (see below). We also offer an IRC channel that might be a better help in urgent cases. Learn more about the different ways to get support by visiting: http://madwifi-project.org/wiki/Support When sending a support request or problem report be sure to include the version of the driver and the part identification the driver prints to the console when the module is loaded. For example: ath_hal: 0.8.2.0 wlan: 0.7.0.0 ath_pci: 0.8.2.0 PCI: Found IRQ 11 for device 00:13.0 ath0: 11a rates: 6Mbps 9Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps ath0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps ath0: 802.11 address: 00:05:5d:6f:99:5f ath0: Atheros 5211: mem=0xfebf0000, irq=11 This says the HAL module is version 0.8.2, the wlan module is version 0.7, the driver is version 0.8.2 and the hardware uses an Atheros 5211 chip (which supports 11a and 11b modes). We will try to respond in a timely manner but understand this software is provided as-is, without any promise of support. Feedback and Contributions -------------------------- Reports about reproducible bugs, feature requests and patches should be submitted in the form of a trouble ticket: http://madwifi-project.org/wiki/TicketSubmissionGuidelines Fixes and enhancements are encouraged.