IEEE 802.11 standard compliant 4 address WDS frame

From: Jouni Malinen (jkmaline_at_cc.hut.fi)
Date: 2002-06-29 09:38:34 UTC


I just added support for IEEE 802.11 standard compliant four address WDS frame in _other_ than Host AP (Master) mode. Host AP mode is still limited to using non-compliant frame format (4th address after the payload) when sending WDS frames, but it can now receive standard compliant frames.

It looks like some station firmware versions are able to send valid WDS frames in pseudo ad-hoc mode, but some versions zero addr3 (=DA). I have thus added support for new operations mode for WDS. I used IW_MODE_REPEATER since it was free and even though not necessarily exactly correct but at least close. This mode can be selected with module parameters iw_mode=4 or using 'iwconfig wlan0 mode Repeater'. wlan# interface cannot be used for data transmit in Repeater mode (you need to make WDS links and use wlan#wds# interfaces). This mode does not send beacons and it can be used only with WDS links.

I haven't tested new version with any wlan device that would use 802.11 WDS frames (since I do not happen to have one ;-). However, the frames looked to be correct when I sniffed frames sent between two hosts using Host AP driver. If anyone happens to test this with other devices, please let me know about the results.

I see at least two configuration, in which this mode might be useful:

  1. using two WLAN cards in AP and using one in Master mode for associating to stations and the other in Repeater mode for WDS link to another AP
  2. bridging to Ethernets, but no need for supporting WLAN stations (i.e., no need to use Master mode and beacons)

Following commands should be enough to brind up a 802.11 compliant WDS link to 00:11:22:33:44:55:

iwconfig wlan0 mode Repeater
iwpriv wlan0 wds_add 00:11:22:33:44:55
ifconfig wlan0wds0 up
# add IP addr if you want to use it also on IP layer 

-- 
Jouni Malinen                                            PGP id EFC895FA
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