On a previously known-to-working AP with openwrt built from trunk in late September, we started seeing connection issues with a few clients.
The connection appears to "freeze" on the client side.
Here's an excerpt from ping's output:
64 bytes from 192.168.3.1: icmp_seq=4 ttl=64 time=2347.642 ms
64 bytes from 192.168.3.1: icmp_seq=5 ttl=64 time=1347.545 ms
64 bytes from 192.168.3.1: icmp_seq=6 ttl=64 time=345.336 ms
64 bytes from 192.168.3.1: icmp_seq=7 ttl=64 time=2120.560 ms
64 bytes from 192.168.3.1: icmp_seq=8 ttl=64 time=1117.109 ms
64 bytes from 192.168.3.1: icmp_seq=9 ttl=64 time=112.861 ms
64 bytes from 192.168.3.1: icmp_seq=10 ttl=64 time=13.704 ms
64 bytes from 192.168.3.1: icmp_seq=11 ttl=64 time=25.534 ms
64 bytes from 192.168.3.1: icmp_seq=12 ttl=64 time=30.433 ms
64 bytes from 192.168.3.1: icmp_seq=13 ttl=64 time=8.212 ms
However, everything looks normal on the AP (decrypted tcpdump from monitor interface):
Noise is -105dBm (as per iw survey dump) and there's no airtime problem (iw station dump) [1].
To me, this looks as if the client is causing the delay.
We tested using two different macbooks and an iphone.
I wasn't able to reproduce that behaviour with my linux/lenovo laptop, android phone, or an older iphone (iOS 15.1) on an AP of the exact same type.
The problem got a bit better after restarting the AP.
What's the next step?
Is there a way that that sort of delay can happen between handing the data to the driver and the transmission?
Is it worth using third device for monitoring to make sure there's no unusual delay before the wifi chip actually transmits the data?
Wireshark on the macbook?
[1]
Station a4:5e:60:d2:d6:c5 (on nw5_0-1)
inactive time: 80 ms
rx bytes: 5804668
rx packets: 30135
tx bytes: 58326289
tx packets: 42522
tx retries: 881
tx failed: 9
rx drop misc: 1
signal: -68 [-68, -71, -98, -98] dBm
signal avg: -67 [-67, -70, -97, -97] dBm
tx bitrate: 585.1 MBit/s VHT-MCS 6 80MHz short GI VHT-NSS 2
tx duration: 1512052 us
rx bitrate: 24.0 MBit/s
rx duration: 1660124 us
airtime weight: 256
authorized: yes
authenticated: yes
associated: yes
preamble: long
WMM/WME: yes
MFP: no
TDLS peer: no
DTIM period: 2
beacon interval:100
short slot time:yes
connected time: 389 seconds
associated at [boottime]: 804872.989s
associated at: 18446725625939099384 ms
current time: 18446744071878302679 ms
Station b8:e8:56:30:95:0e (on nw5_0-1)
inactive time: 0 ms
rx bytes: 1378529909
rx packets: 1097255