Monitor Mode for bcmdhd Driver

[Jinghao Shi]

Hi,

I am working on enabling monitor mode for bcmdhd driver on Android phones (Nexus 5) for a research project. I've used the WLC_SET_MONITOR ioctl command to tell the firmware send up every 802.11 frame it has decoded, and this works well. Now I'm trying to get per packet RSSI, and this is where I get stuck. I'd appreciate it if anybody can shed some light on this.

I found that after setting tlv iovar with WLFC_FLAGS_RSSI_SINGALS, the firmware is supposed to report per packet RSSI in the wlfc header, which it indeed does in normal manged mode,  However, after enabling monitor mode, each packet's RSSI becomes invalid (0). And I have no clue of what's going on there.

For your information, my modifications are based on recent kernel release for KitKat 4.4, commit id 8217cfa3b560b102b53258156dee3dab530fc00b.

Regards,

Jinghao

[Allan Park]

What do you mean rssi packet? Rssi is the received signal strength indicater. So its value came from the host side. It calibrate from host. May u can parse rssi value in wpa supplicant and dhd driver. 

2014년 8월 5일 화요일, Jinghao Shi<jhs...@gmail.com>님이 작성한 메시지:

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[Jinghao Shi]

You can get the RSSI value of each Access Point from the scan result data. However, in monitor mode, you will overhear packets from both Access Points and other devices. So ideally the firmware should report per-packet RSSI so that I know the signal strength of each terminals within certain range.

On Wednesday, October 1, 2014 1:06:47 PM UTC-4, allan park wrote:

What do you mean rssi packet? Rssi is the received signal strength indicater. So its value came from the host side. It calibrate from host. May u can parse rssi value in wpa supplicant and dhd driver. 

2014년 8월 5일 화요일, Jinghao Shi<jhs...@gmail.com>님이 작성한 메시지:

Hi,

I am working on enabling monitor mode for bcmdhd driver on Android phones (Nexus 5) for a research project. I've used the WLC_SET_MONITOR ioctl command to tell the firmware send up every 802.11 frame it has decoded, and this works well. Now I'm trying to get per packet RSSI, and this is where I get stuck. I'd appreciate it if anybody can shed some light on this.

I found that after setting tlv iovar with WLFC_FLAGS_RSSI_SINGALS, the firmware is supposed to report per packet RSSI in the wlfc header, which it indeed does in normal manged mode,  However, after enabling monitor mode, each packet's RSSI becomes invalid (0). And I have no clue of what's going on there.

For your information, my modifications are based on recent kernel release for KitKat 4.4, commit id 8217cfa3b560b102b53258156dee3dab530fc00b.

Regards,

Jinghao

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[Jinghao Shi]

I poked around the web and found this thread.

http://www.spinics.net/lists/linux-wireless/msg68768.html

In particular, this sentence:

"For some other protocols, rssi in BDC header is zero,meaning we cannot get correct rssi for them."

It seems the firmware just won't report per-packet RSSI in monitor mode. Sad.

[Allan Park]

If want to set monitor mode, need a another firmware. Nexus5 has only 2 firmware(STA-P2P, SotfAP). The broadcom would not provide the monitor firmware.

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