[Cerowrt-devel] figuring out who's actually on an ap

Dave Taht dave.taht at gmail.com
Sat Jan 26 13:22:17 EST 2013

Once upon a time it was possible to write quick and dirty tools in shell.
You used to just be able to open a port, write a tiny little daemon, and
go. And we used to have handy tools like rwho and finger to figure out who
was online, ruptime to check uptime, etc, etc.

That's too insecure nowadays...
so we have 3 different levels of snmp which you can use (if you can secure
it), and
run a shell command from that, remotely, then parse... or use ssh, and

And then we have dhcp, which hands out leases, but is not tied to how wifi
goes up
and down.

This morning I had a need to figure who was actually on a couple cerowrt
and a few statistics as to their connected rate...

I haven't got so as figuring out how to do all that via snmpd yet, but as
this uses
an obscure feature of the mac802.11 stack, I thought I'd document this much.

If there is a better way, a mib, something, let me know....

# rup: quickly see whos really on the wifi

A=`ls /sys/kernel/debug/ieee80211/phy*/netdev:*/stations | \
    cut -f8 -d/ | tr '\n' '|'`
# cut off last |
egrep ${A%?} /tmp/dhcp.leases | awk '{print $3 " " $4 }'

Dave Täht

Fixing bufferbloat with cerowrt:
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