====== MT7621 arp broadcast issue ======

Symptoms:
  * all WiFi clients has internet access
  * after some time, cannot reach WiFi client from another client (WiFi or Wired)

Affected routers:
  * My devices: Netgear R6220 MediaTek MT7621 ver:1 eco:3
  * D-Link DIR-882 (MediaTek MT7621A SoC)
  * Cudy WR2100, MT7621 chipset, MT7603E Wifi.

Problem introduced by Kernel: [[https://lkml.org/lkml/2022/5/10/253|[PATCH v2] net: dsa: tag_mtk: add padding for tx packets]]

OpenWrt issue: 
  * [[https://github.com/openwrt/openwrt/issues/11942|ARP/broadcast issues for wireless clients on Mediatek-based routers using OpenWrt as dumb AP in pfSense/OPNsense bridged LAN firewall setups on 22.03.3 release, present since OpenWrt 22.03.0-rc2 #11942]]
  * [[https://forum.openwrt.org/t/device-stops-passing-broadcast-packets-to-wireless-interfaces-after-24h-of-uptime/79426|Device stops passing broadcast packets to wireless interfaces after 24H of uptime]]
  * Other chipsets - similar problem: [[https://github.com/openwrt/openwrt/issues/9555|ARP requests are not forwarded to Wifi Client after some time --> devices unreachable #9555]]
  * Maybe related [[https://forum.openwrt.org/t/clients-in-same-wlan-cant-reach-each-other/2501|Clients in same WLAN can’t reach each other]]

  * [[https://github.com/openwrt/mt76/issues/598|broadcasts delivery problem #598]]

Reported as fixed in:
  * r22186-9307c2753980
  * >= v22.03.4

Problem still occurs in:
  * OpenWrt 23.05-SNAPSHOT r24041-a07a531329

Potential fix: 
  * [[https://lore.kernel.org/linux-wireless/Z2Q9POuV-6MIdzRf@pilgrim/T/#t|Re: Potential Broadcast Issues After GTK Key Exchange on ath11k with IPQ8072A (QCN5024/QCN5054)]]
  * [[https://github.com/openwrt/openwrt/issues/9555#issuecomment-2563690019]]

Workaround:
  * execute command `wifi` on remote OpenWrt