Re: rtwn/rtl8821au: strange issue with 5GHz channels
Date: Thu, 28 Aug 2025 08:41:05 UTC
On 19/08/2025 15:46, Andriy Gapon wrote: > This may be unsurprising becomes the adapter sees a wrong / strange channel > number comparing to what's configured on the AP. It's almost always +4. > And only rarely it's the correct number. In those cases the connection works. > > E.g., right now: > $ ifconfig wlan0 scan | sort -t '' -k 1.66,1.67n | head -2 > SSID/MESH ID BSSID CHAN RATE S:N INT CAPS > HolyLan 7a:d2:94:80:1f:ec 153 54M -70:-95 100 > EPS RSN BSSLOAD HTCAP VHTCAP VHTOPMODE VHTPWRENV WME I've observed how a scan can get a wrong frequency / channel for an AP. In this case the channel is very different (not +4) and I have no idea what could the issue. Evidence: Aug 27 21:01:35 rock64b kernel: [78:d2:94:80:1f:ec] new probe_resp on chan 36 (bss chan 36) "ThePromisedLan" rssi 53 Aug 27 21:01:35 rock64b kernel: [78:d2:94:80:1f:ec] caps 0x11 bintval 100 erp 0x0 country [UA 36-43,20 100-110,20 144,0 149-153,20] Aug 27 21:01:35 rock64b kernel: [78:d2:94:80:1f:ec] new probe_resp on chan 36 (bss chan 36) "ThePromisedLan" rssi 53 Aug 27 21:01:35 rock64b kernel: [78:d2:94:80:1f:ec] caps 0x11 bintval 100 erp 0x0 country [UA 36-43,20 100-110,20 144,0 149-153,20] Aug 27 21:01:35 rock64b kernel: [78:d2:94:80:1f:ec] new probe_resp on chan 36 (bss chan 36) "ThePromisedLan" rssi 53 Aug 27 21:01:35 rock64b kernel: [78:d2:94:80:1f:ec] caps 0x11 bintval 100 erp 0x0 country [UA 36-43,20 100-110,20 144,0 149-153,20] Aug 27 21:01:35 rock64b kernel: [78:d2:94:80:1f:ec] new probe_resp on chan 36 (bss chan 36) "ThePromisedLan" rssi 53 Aug 27 21:01:35 rock64b kernel: [78:d2:94:80:1f:ec] caps 0x11 bintval 100 erp 0x0 country [UA 36-43,20 100-110,20 144,0 149-153,20] Aug 27 21:01:38 rock64b kernel: [78:d2:94:80:1f:ec] new beacon on chan 132 (bss chan 132) "ThePromisedLan" rssi 9 Aug 27 21:01:38 rock64b kernel: [78:d2:94:80:1f:ec] caps 0x11 bintval 100 erp 0x0 country [UA 36-43,20 100-110,20 144,0 149-153,20] Aug 27 21:01:39 rock64b kernel: wlan0: macaddr bssid chan rssi rate flag wep essid Aug 27 21:01:39 rock64b kernel: - 78:d2:94:80:1f:ec 78:d2:94:80:1f:ec 132 +49 54M ess wep "ThePromisedLan"! So, all messages are about the same AP (ThePromisedLan / 78:d2:94:80:1f:ec). Initially, the scan saw some probe responses on the correct channel (36) with strong signal (rssi 53). Later, after jumping many channels, the scan saw a beacon for the same AP on a wrong channel (132) with much weaker signal (rssi 9). But the last seen channel won. That beacon on the wrong channel is very puzzling. What could it be? Some problem on the AP side? Or some issue with switching channels on the adapter side? Or something in the environment? E.g., some spoofing / hacking equipment? -- Andriy Gapon