[Solved] D-Link DIR-860L B1 2.4 GHz WiFi issues on VoIP calls

[justme123]

Hello,

I'm experiencing instant disconnections only on the 2.4 GHz band when trying to call or receive calls through Signal Messenger (Open Whisper Systems) and Skype Lite (Microsoft) on an Android 9 (LineageOS) connected to the router.

The details:
D-Link DIR-860L, running:

# cat /etc/openwrt_release
DISTRIB_ID='OpenWrt'
DISTRIB_RELEASE='19.07.4'
DISTRIB_REVISION='r11208-ce6496d796'
DISTRIB_TARGET='ramips/mt7621'
DISTRIB_ARCH='mipsel_24kc'
DISTRIB_DESCRIPTION='OpenWrt 19.07.4 r11208-ce6496d796'
DISTRIB_TAINTS=''

• relevant section from /etc/config/wireless

config wifi-device 'radio1'
        option type 'mac80211'
        option hwmode '11g'
        option path 'pci0000:00/0000:00:01.0/0000:02:00.0'
        option htmode 'HT20'
        option txpower '20'
        option channel '1'
        option distance '20'
        option country 'DE'

• log snippet showing the disconnection - always the same and always reproducible

Sun Oct 25 17:07:04 2020 daemon.notice hostapd: wlan1: AP-STA-DISCONNECTED xx:xx:xx:xx:xx:xx
Sun Oct 25 17:07:08 2020 daemon.info hostapd: wlan1: STA xx:xx:xx:xx:xx:xx IEEE 802.11: authenticated
Sun Oct 25 17:07:08 2020 daemon.info hostapd: wlan1: STA xx:xx:xx:xx:xx:xx IEEE 802.11: associated (aid 1)
Sun Oct 25 17:07:08 2020 daemon.notice hostapd: wlan1: AP-STA-CONNECTED xx:xx:xx:xx:xx:xx
Sun Oct 25 17:07:08 2020 daemon.info hostapd: wlan1: STA xx:xx:xx:xx:xx:xx WPA: pairwise key handshake completed (RSN)
Sun Oct 25 17:07:08 2020 daemon.info dnsmasq-dhcp[2808]: DHCPDISCOVER(br-WIFI2) xx:xx:xx:xx:xx:xx
Sun Oct 25 17:07:08 2020 daemon.info dnsmasq-dhcp[2808]: DHCPOFFER(br-WIFI2) yyy.yyy.yyy.yyy xx:xx:xx:xx:xx:xx
Sun Oct 25 17:07:13 2020 daemon.info dnsmasq-dhcp[2808]: DHCPDISCOVER(br-WIFI2) xx:xx:xx:xx:xx:xx
Sun Oct 25 17:07:13 2020 daemon.info dnsmasq-dhcp[2808]: DHCPOFFER(br-WIFI2) yyy.yyy.yyy.yyy xx:xx:xx:xx:xx:xx
Sun Oct 25 17:07:17 2020 daemon.info dnsmasq-dhcp[2808]: DHCPREQUEST(br-WIFI2) yyy.yyy.yyy.yyy xx:xx:xx:xx:xx:xx
Sun Oct 25 17:07:17 2020 daemon.info dnsmasq-dhcp[2808]: DHCPACK(br-WIFI2) yyy.yyy.yyy.yyy xx:xx:xx:xx:xx:xx

Otherwise, the 2.4 GHz connection works flawlessly, I'm able to watch 10-15 Mbit FullHD DVB streams (streamed through tvheadend), able to watch YouTube, browse the net, no glitches.
On the 5 GHz band I'm not experiencing this issue.

What I tried so far without success:

• disabled the 5GHz interface
• set the 2,4 GHz interface settings on channel Auto (got a lot of errors in the log related to - unable to determine noise floor), TX power - driver default, disabled key reinstallation (KRACK) countermeasures, disabled Short Preamble
• loaded OpenWRT 19.07.3 (noticed some driver updates in 19.07.4)
• connected the Android through a local OpenVPN tunnel and routed all the traffic through it, inspected what's inside the tunnel with iptraf - noticed some 15-20 packets / second and ~ 20 kbps during call initialization and instant WiFi disconnection.

Up until a few days ago I used a TL-WR741ND router loaded with OpenWRT 18.06.8 with the same 2.4 GHz settings I have now on the D-Link DIR-860L and never experienced any issues. Also, I haven't done any changes on the the Android device, even the 2.4 GHz ESSID & password is the same.

Any help appreciated!

[maurer]

try latest build from here Optimized build for the D-Link DIR-860L (based on master)

[diizzy]

Your best bet is master although I gave up when using Android clients and ended up with IPQ4*** devices instead. It works quite well (SIP with UDP) but it's not flawless.

[justme123]

Thank you both for the inputs. I was actually looking for a way to debug what's happening on the WiFi and why the Android client gets disconnected.
The optimized build for the DIR-86L, while I do appreciate the development efforts, is something I wouldn't use on daily basis because I really need stability.

Meanwhile I managed to find out what's causing the issue and it's not related to OpenWRT.
The Android 9 based LineageOS apparently has issues when both BlueTooth and WiFi 2.4 are used at the same time and it's definitely a firmware/driver problem for the particular client (Samsung Phone). On other Android clients, including LineageOS and Stock ROMs I don't have this issue.

Sorry for the noise. I'll put this thread on resolved.