IPv6 DNS advertisement - possible regression?

Hi, All!

On my old WDR3600 Chaos Calmer nicely advertises both its GUA and ULA per RFC6106, when they are available. But when I put the 12.29 LEDE snapshot (r2709-b7677f0) on my new DIR-860L Windows 10 only picked up the router's LLA for IPv6 DNS. If you are wondering, I have DHCPv6 turned off everywhere, which just got broken anyway, and use RDNSSd instead. This is with a mostly default config. I then tried the workaround that was necessary on CC to get IPv6 working at all, setting for wan6 the custom @wan interface, but that didn't help.

This is uci show network for LEDE:

network.loopback=interface
network.loopback.ifname='lo'
network.loopback.proto='static'
network.loopback.ipaddr='127.0.0.1'
network.loopback.netmask='255.0.0.0'
network.globals=globals
network.globals.ula_prefix='fd4f:9bfb:d5b3::/48'
network.lan=interface
network.lan.type='bridge'
network.lan.ifname='eth0.1'
network.lan.proto='static'
network.lan.ipaddr='192.168.1.1'
network.lan.netmask='255.255.255.0'
network.lan.ip6assign='64'
network.lan_dev=device
network.lan_dev.name='eth0.1'
network.lan_dev.macaddr='aa:bb:cc:dd:ee:ff'
network.wan=interface
network.wan.ifname='eth0.2'
network.wan._orig_ifname='eth0.2'
network.wan._orig_bridge='false'
network.wan.proto='pppoe'
network.wan.username='ispname'
network.wan.password='isppass'
network.wan.ipv6='auto'
network.wan_dev=device
network.wan_dev.name='eth0.2'
network.wan_dev.macaddr='aa:bb:cc:dd:ee:ff'
network.wan6=interface
network.wan6.ifname='eth0.2'
network.wan6.proto='dhcpv6'
network.wan6.reqaddress='try'
network.wan6.reqprefix='auto'
network.@switch[0]=switch
network.@switch[0].name='switch0'
network.@switch[0].reset='1'
network.@switch[0].enable_vlan='1'
network.@switch_vlan[0]=switch_vlan
network.@switch_vlan[0].device='switch0'
network.@switch_vlan[0].vlan='1'
network.@switch_vlan[0].ports='1 2 3 4 6t'
network.@switch_vlan[1]=switch_vlan
network.@switch_vlan[1].device='switch0'
network.@switch_vlan[1].vlan='2'
network.@switch_vlan[1].ports='0 6t'

The workaround config instead had:

network.wan6._orig_ifname='eth0.2'
network.wan6._orig_bridge='false'
network.wan6.ifname='@wan'

For CC uci show network is:

network.loopback=interface
network.loopback.ifname='lo'
network.loopback.proto='static'
network.loopback.ipaddr='127.0.0.1'
network.loopback.netmask='255.0.0.0'
network.globals=globals
network.globals.ula_prefix='fd4f:9bfb:d5b3::/48'
network.lan=interface
network.lan.ifname='eth0.1'
network.lan.force_link='1'
network.lan.type='bridge'
network.lan.proto='static'
network.lan.ipaddr='192.168.1.1'
network.lan.netmask='255.255.255.0'
network.lan.ip6assign='64'
network.wan=interface
network.wan.ifname='eth0.2'
network.wan._orig_ifname='eth0.2'
network.wan._orig_bridge='false'
network.wan.proto='pppoe'
network.wan.username='ispname'
network.wan.password='isppass'
network.wan.ipv6='1'
network.wan6=interface
network.wan6._orig_ifname='eth0.2'
network.wan6._orig_bridge='false'
network.wan6.proto='dhcpv6'
network.wan6.ifname='@wan'
network.wan6.reqaddress='try'
network.wan6.reqprefix='auto'
network.@switch[0]=switch
network.@switch[0].name='switch0'
network.@switch[0].reset='1'
network.@switch[0].enable_vlan='1'
network.@switch_vlan[0]=switch_vlan
network.@switch_vlan[0].device='switch0'
network.@switch_vlan[0].vlan='1'
network.@switch_vlan[0].ports='0t 2 3 4 5'
network.@switch_vlan[1]=switch_vlan
network.@switch_vlan[1].device='switch0'
network.@switch_vlan[1].vlan='2'
network.@switch_vlan[1].ports='0t 1'

uci show dhcp is the same for both:

dhcp.@dnsmasq[0]=dnsmasq
dhcp.@dnsmasq[0].domainneeded='1'
dhcp.@dnsmasq[0].boguspriv='1'
dhcp.@dnsmasq[0].filterwin2k='0'
dhcp.@dnsmasq[0].localise_queries='1'
dhcp.@dnsmasq[0].rebind_protection='1'
dhcp.@dnsmasq[0].rebind_localhost='1'
dhcp.@dnsmasq[0].local='/lan/'
dhcp.@dnsmasq[0].domain='lan'
dhcp.@dnsmasq[0].expandhosts='1'
dhcp.@dnsmasq[0].nonegcache='0'
dhcp.@dnsmasq[0].authoritative='1'
dhcp.@dnsmasq[0].readethers='1'
dhcp.@dnsmasq[0].leasefile='/tmp/dhcp.leases'
dhcp.@dnsmasq[0].resolvfile='/tmp/resolv.conf.auto'
dhcp.@dnsmasq[0].localservice='1'
dhcp.lan=dhcp
dhcp.lan.interface='lan'
dhcp.lan.ra='server'
dhcp.lan.ra_default='1'
dhcp.lan.start='100'
dhcp.lan.limit='150'
dhcp.lan.leasetime='12h'
dhcp.wan=dhcp
dhcp.wan.interface='wan'
dhcp.wan.ignore='1'
dhcp.odhcpd=odhcpd
dhcp.odhcpd.maindhcp='0'
dhcp.odhcpd.leasefile='/tmp/hosts/odhcpd'
dhcp.odhcpd.leasetrigger='/usr/sbin/odhcpd-update' 

Any ideas?