Unexpected ipv6 address / Restricting IP addresses for umdns replies

Installing and Using OpenWrt
1

Hi, I just installed a snapshot of openwrt mainline on a Mangopi MQ Pro after seeing that it's now supported in version 24.10. Overall, it's working properly and was easy to set up. I'm running it as a client on my local network and I don't plan to use the device as a router. The device has ipv4 and ipv6 addresses provided by my main router using DHCP. I'm running umdns as the MDNS responder on the device.

Anyway, the problem I'm facing is that when resolving the device's mdns hostname from another system on the same network, the umdns server on the device sometimes responds with an ipv6 address that's unusable from the perspective of other hosts on the network. Specifically, resolving the hostname from another system on the network results in the following exchange:

avahi-resolve -6 -n mangopi.local
mangopi.local	::96a4:xxxx:yyyy:zzzz

In addition to that address, the mangopi has two other IPv6 addresses on the network interface that are working properly and accessible by the other hosts on my network, a link-local one (fe80::96a4::xxxx:yyyy:zzzz/64) and a public internet one (2601:aaaa:bbbb:cccc:96a4:xxxx:yyyy:zzzz/64).

Does anyone know why the ::96a4:xxxx:yyyy:zzzz/64 address is being added to my network interface? On other Linux computers that I run, I haven't seen any obtain a similar style of ipv6 address and I'm unfamiliar with that format in general. If they are valid, is it possible to prevent OpenWrt from assigning them? If not, is there any way to prevent umdns from advertising an IP address that's unusable by other hosts on the network or is this a bug in umdns that should be fixed?

This is my entire network configuration:

uci show network
network.loopback=interface
network.loopback.device='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='qqqq:wwww:eeee::/48'
network.wlan=interface
network.wlan.proto='dhcp'
network.wlan.device='wlan0'
network.wlan6=interface
network.wlan6.proto='dhcpv6'
network.wlan6.device='wlan0'

Thanks.

2

Anyway, I tested a similar setup on a Raspberry Pi 4b on the 24.10 release of OpenWrt, and I have the same results so this isn't specific to any single device or OpenWrt version. Also I took a look at my android phone when connected to the same network and it also has the same style of IPv6 addresses so it seems they are normal to obtain, unless I have configured something incorrectly on my home network's ipv6.
Either way, I guess it would still be useful for umdns to be able to exclude these kinds of IP addresses when considering which addresses to advertise.