How to log missing ACKs

Installing and Using OpenWrt
1

Hello,

we used an older OpenWRT version and had problem with losing the connection due to missing ACKs.
Now we upgraded to LEDE and hope that the problems are gone, but we would like to see if any ACKs are missing in a log file, so that we understand if there is a problem (could be due to motors running close to the antennas).

Is there a setting to enable logging of these events (not only, if there are too many missing, but any missing ACK)?

We are using the router WPJ342a-16M from Compex.

Thanks for your help!

Uwe

2

This is enabled by default. You will see entries in the system log like so:

01:02:03:04:05:06 IEEE 802.11: disconnected due to excessive missing ACKs

3

Ok, I now that, but I would like to see missing ACKs BEFORE there are so many of them, that I get disconnected. Any idea?

4

Hm, difficult. You can find some simple "missing ACK" counters in /sys/kernel/debug/ieee80211/phy*/statistics/dot11ACKFailureCount but that is a global per-phy counter, not tied to the stations.

The "missing ACK" condition is triggered when more than 50 transmitted packets are not ACKed since the last successful ACK. You can find the code for that in net/mac80211/status.c, functions ieee80211_lost_packet() and ieee80211_tx_status_noskb().

5

Thanks for your useful answer!
We have a one-to-one link (groundstation to flying wind drone). Max distance 1000 m.
I will look into this failure counter tomorrow!

Today we have seen a ratio of retried transmissions of 5-10%. Is this acceptable?

Uwe