Correct wireless stats in i3status.

[jhb]

Summary

Fix multiple issues with the wireless information reported by i3status for
an interface:

• Instead of hoping that the currently associated AP will show up as the first AP in the list of scan results, fetch the BSSID of the currently associated AP and use that to fetch station info for the AP. This provides more frequently updated signal strength information than scan results and reliably provides information when multiple APs are in range.
• Do not treat the RSSI value as a raw signal value in dBm. Instead, use the same formula as ifconfig(8) to compute a signal value.
• Do not report the beacon interval value as a signal quality level.

Test Plan

• Run i3status on my laptop while associated to "Warren" with this scan list:

SSID/MESH ID BSSID CHAN RATE S:N INT CAPS
HOME-4412 90:0d:cb:2a:44:10 1 54M -84:-95 100 EP WPS HTCAP WPA RSN WME

92:0d:cb:2a:44:10    1   54M -86:-95  100 EP   HTCAP RSN WME

xfinitywifi 96:0d:cb:2a:44:10 1 54M -86:-95 100 E HTCAP WME
ATTBgRvXPi cc:65:ad:63:f2:80 6 54M -60:-95 100 EP RSN HTCAP WPA WME
Warren 6c:70:9f:e9:9d:90 11 54M -60:-95 100 EP RSN HTCAP WPA WME
d crab f8:35:dd:36:55:05 11 54M -86:-95 100 EP RSN HTCAP WPS WME
HOME-E452 00:ac:e0:3a:e4:50 11 54M -87:-95 100 EP WPS HTCAP WPA RSN WME
raben 00:0c:41:82:61:39 7 54M -79:-95 100 EPS RSN
Warren 6c:70:9f:e9:9d:91 149 54M -66:-95 100 EP RSN HTCAP WPA WME

Previously the status was reported as "? at Warren". If Warren happened to
be the first AP it would have been repored with a quality of '100' always
(regardless of signal strength since it was using the 'INT' column from
ifconfig). Now with my format string set to display %signal instead of
%quality I get "-60 dBm at Warren" as my status text.

In addition, after changing from scan results to station info, the signal strength changes
periodically whereas before it changed rarely (I believe I have bgscan disabled, so it was
only scanning when trying to associate).

[jhb]

x11/i3status/Makefile

17 ↗

(On Diff #7905)

Oops, this wasn't meant to be there.

[jhb]

Remove debugging.

[adrian]

hi,

you can have >1 SSID with the same BSSID. It's silly, but it happens. You may want to use both together as a key.

[jhb]

In D3369#68624, @adrian wrote:

hi,

you can have >1 SSID with the same BSSID. It's silly, but it happens. You may want to use both together as a key.

Bizarre. Does the stack "know" which AP you are connected to such that we could provide an ioctl to return the scan_results for just the AP you are connected to? I imagine that is something lots lof little widgets would like to use. If nothing else, we should possibly provide a wrapper API in a library that does that instead of duplicating this logic in N different places.

[jhb]

Use STA_INFO instead of SCAN_RESULTS. This results in simpler logic and
also gives more realtime signal strength info.

[jhb]

Ensure this is updated.

[jhb]

Last update removed "fail" debugging printfs. Those were sent to the output stream resulting in JSON parsing errors in i3 itself at which point i3 killed i3status (e.g. when wlan0 reassociated)