networkd enslaves the radio to br0 once, at link init. On real hardware
(GL-MT6000, mt798x-wmac) that happens while the netdev is still in station
mode, so the kernel rejects the bridge join (IFF_DONT_BRIDGE), the link is
parked in networkd's failed state and never retried: link_reconfigure_impl()
is a no-op while the matching .network file is unchanged, and the udev
'iw set type __ap' hook meant to pre-empt this loses the race. Wireless
clients associate but their DHCP never reaches vlan-lan.
Match on WLANInterfaceType=ap as well as the name. The station-mode netdev
then matches nothing (unmanaged) and the file first matches when hostapd
has switched the radio to AP and raised carrier, so the enslave succeeds
on the first try. Drop the udev hook.
Verified with checks.x86_64-linux.router (hwsim STA lease over the bridge).
kurogeek