OpenWrt support for Linksys MX4200

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Has anyone seen DHCP issues using the MX-{4200,4300} running on 24.10-SNAPSHOT when bridging WLAN and VLAN interfaces? I'm seeing an issue that sporadically causes wireless clients that connect to the MX4300 dumb AP to not receive DHCP responses and therefore fail over to a 169.254.x.x zeroconf style address.

Of course, it happens more often when I don't have debugging / packet capture enabled, but in almost all cases the DHCP response can be seen on the AP's WAN interface (which I'm bridging into br-lan since this is an AP), but just never makes it to the bridge or possibly doesn't make it to the wireless client itself.

This sounds very much like https://github.com/openwrt/openwrt/issues/11650 and https://github.com/openwrt/openwrt/issues/13756, but I haven't had a chance to dig into the bridge state before/after such events.... just discovered those tickets late last night after being frustrated with the flaky DHCP requests all of a sudden becoming less flaky as soon as I started running tcpdump on all interfaces in the chain up to the WLAN.

My /etc/config/network:

config interface 'loopback'
        option device 'lo'
        option proto 'static'
        option ipaddr '127.0.0.1'
        option netmask '255.0.0.0'

config globals 'globals'
        option packet_steering '1'

config device
        option name 'lan1'
        option macaddr 'my:ma:ca:dd:rr:3e'

config device
        option name 'lan2'
        option macaddr 'my:ma:ca:dd:rr:3e'

config device
        option name 'lan3'
        option macaddr 'my:ma:ca:dd:rr:3e'

config device
        option type '8021q'
        option ifname 'wan'
        option vid '1'
        option name 'wan.1'

config device
        option type '8021q'
        option ifname 'wan'
        option vid '3'
        option name 'wan.3'
        option ipv6 '0'

config device
        option type '8021q'
        option ifname 'wan'
        option vid '5'
        option name 'wan.5'
        option ipv6 '0'

config device
        option type 'bridge'
        option name 'br-lan'
        list ports 'lan1'
        list ports 'lan2'
        list ports 'lan3'
        list ports 'wan.1'
        option igmp_snooping '1'

config interface 'lan'
        option proto 'static'
        option device 'br-lan'
        option ipaddr '192.168.1.253'
        option netmask '255.255.255.0'
        option gateway '192.168.1.1'
        list dns '192.168.1.2'
        list dns '192.168.1.6'
        list ip6class 'lan6'
        option delegate '0'

config device
        option type 'bridge'
        option name 'br-iot'
        list ports 'wan.3'
        option ipv6 '0'
        option igmp_snooping '1'

config device
        option type 'bridge'
        option name 'br-guest'
        list ports 'wan.5'
        option ipv6 '0'
        option igmp_snooping '1'

config interface 'iot'
        option proto 'none'
        option device 'br-iot'

config interface 'guest'
        option proto 'none'
        option device 'br-guest'

config interface 'lan6'
        option proto 'dhcpv6'
        option device '@lan'
        option reqaddress 'try'
        option reqprefix 'auto'
        option norelease '1'
        option ip6assign '64'
        list ip6class 'lan6'

config device
        option name 'wan'
        option macaddr 'my:ma:ca:dd:rr:3e'

(yes, there is nothing bridged into the IoT network, because I started testing the primary WLAN bridge and the guest bridge and was seeing DHCP requests timing out)

NOTE: firewall, dnsmasq and odhcpd all disabled since this is a dump AP after all.

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