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Low level air interface access?


Nicholas Weaver
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I'm looking at doing a development project, where I need a small WiFi device with a (somewhat) directional antenna and a gyroscope.

 

The DS (with the gyroscope/3-axis accelerometer card) appears to fit the bill.

 

But I need to do low level access to the air interface, a'la Kismet et al...

 

Namely, I need to be able to tune to a channel, receive all packets in promiscuous mode (with signal strength, no decryption required) and send raw packets.

 

Before I start digging through API documentation, does DSWifi library give this capability?

 

Thanks.

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Not quite - the wifi lib can provide channel changing but doesn't currently receive all packets in promiscuous mode.

 

(There is a way to do this, but it's not documented and requires some lower level hacking at this point - I haven't confirmed that it works yet, either...)

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Not quite - the wifi lib can provide channel changing but doesn't currently receive all packets in promiscuous mode.

 

Admin edit: spam and swearing removed. You have been warned.

Edited by Robert
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Not quite - the wifi lib can provide channel changing but doesn't currently receive all packets in promiscuous mode.

 

(There is a way to do this, but it's not documented and requires some lower level hacking at this point - I haven't confirmed that it works yet, either...)

 

For non-promiscuous packet receiving, is it possible to get the signal-strength issue?

 

(Promiscuous mode would be a win, but wouldn't be essential, for what I want to do, as I can fake it with some ARP spamming)

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For non-promiscuous packet receiving, is it possible to get the signal-strength issue?

 

(Promiscuous mode would be a win, but wouldn't be essential, for what I want to do, as I can fake it with some ARP spamming)

 

Yup, And actually if you are connected to an AP, you can receive all 1-2mbit packets "attached" to that AP.

When you enable raw packet capture you have the ability to get a header including the speed.. though it's a little bit of a hack.

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For non-promiscuous packet receiving, is it possible to get the signal-strength issue?

 

(Promiscuous mode would be a win, but wouldn't be essential, for what I want to do, as I can fake it with some ARP spamming)

 

Yup, And actually if you are connected to an AP, you can receive all 1-2mbit packets "attached" to that AP.

When you enable raw packet capture you have the ability to get a header including the speed.. though it's a little bit of a hack.

 

but does header also give signal strenght? Basically, I want to hunt-down some WiFi sources in the building.

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Oh right - yes, the header does provide signal strength. And it's a bit of a hack to get to it, but it's right next to the speed (I meant to say strength, not speed - but managed to confuse them in my reply)

See here (though not entirely accurate): http://akkit.org/info/dswifi.htm#FmtRx

 

The wifi RX header is in the buffer right -before- the pointer the "raw" API gives you, so you have to compute the address and read it. Next version will provide easier access.

(Also the RSSI readings are more complex than indicated, I'll document this sometime.)

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Oh right - yes, the header does provide signal strength. And it's a bit of a hack to get to it, but it's right next to the speed (I meant to say strength, not speed - but managed to confuse them in my reply)

See here (though not entirely accurate): http://akkit.org/info/dswifi.htm#FmtRx

 

The wifi RX header is in the buffer right -before- the pointer the "raw" API gives you, so you have to compute the address and read it. Next version will provide easier access.

(Also the RSSI readings are more complex than indicated, I'll document this sometime.)

 

EXCELLENT!

 

Time to go order me a DS. :)

 

Oh, and how directional is the internal antenna?

 

Any luck on tricking it into 11 Mbps receive mode?

 

Thanks for all your help!

Edited by Nicholas Weaver
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