Subject: Re: access point list from Lucent wireless cards
To: Atsushi Onoe <>
From: Andrew Brown <>
List: current-users
Date: 09/19/2001 01:27:03
>> I'd like to have a device (/dev/wi0 or something) that can be used as
>> a method to pass data into and out of the kernel.  I'd use this as a
>> way to pass along packets that perhaps I don't want to send to the
>> IP stack (management, encrypted or undecryptable frames, etc) as
>> well as a general purpose async notification pipe for monitoring
>> AP associations, signal strengths, etc.
>I've heard BSD/OS uses BPF to capture 802.11 packets, which is basically
>the right way, IMHO.

we currently have the bpf tap attached after the pseudo ethernet
header is constructed, so 802.11 packets end up looking like regular
ethernet packets.  would it be outlandish for me to suggest an ioctl
to frob this?

>But it is hard to send 802.11 frame via BPF because it is not clear
>what field should be filled by the driver.  Obviously, some information
>such as seqence control should be consistent with the normal IP packets.
>And there may be a discussion who should take care of encryption.
>Some device cannot skip hardware encryption/decryption engine.

there's an ioctl (SIOCSWAVELAN, i think) that allows you to construct
arbitrary 802.11 frames.  at least...that's what it looked like to me.

>And if we change the bpf type from DLT_EN10MB, the application like
>dhclient(8) must be updated.  So I'm thinking the way to creating switch
>controlled by ioctl for bpf device.

yeah.  me too.  :)

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