On Mon, 2009-12-14 at 11:35 -0500, Alan Stern wrote: > I just tried to set up ethernet bridging between the wireless interface > and the wired ethernet interface on my laptop machine. It didn't work. > As far as I could tell from the tcpdump output, the wireless stack > doesn't want to transmit packets with a foreign link-layer source > address. > > Is there any way around this restriction? Or must I resort to IP > forwarding instead? There's no standard way around this restriction, the on-air packets are required to be transmitted with the correct TA (transmitter address) [1] which also must be the SA (sender address) in the regular frame format, since the DA (destination address) and RA (receiver address) must be present and the format only has three addresses. In recent kernels (what will be 2.6.33), we have added code to disallow such configurations since they cannot work. However, if you control both the AP and and the station (e.g. laptop), and your AP and station both run mac80211, then you can use the four-address hack that Felix has been developing. It will then use the standardised four-address frame format that normally cannot be used between a station and an AP to transfer different TA/SA. I'm not sure if he has documentation on this yet. There's also ebtables NAT, but I have no idea if/how that works. johannes [1] otherwise the ACK mechanism cannot work
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