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)

Problem introduced by Kernel: [PATCH v2] net: dsa: tag_mtk: add padding for tx packets

OpenWrt issue:

• 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
• Device stops passing broadcast packets to wireless interfaces after 24H of uptime

broadcasts delivery problem #598

Fixed in:

• r22186-9307c2753980
• >= v22.03.4