Update IPv6 address extraction in radvd.inc

[cnbatch]

Fix #9523

Refactor to capture IPv6 configuration details more accurately.

[fichtner]

To my knowledge radvd forces /64 anyway because that’s what SLAAC uses. Feel free to check the radvd logs and source code.

[cnbatch]

These are the early tcpdump record. Prefix is '/62'

[fichtner]

The prefix can be /62 or similar but you don’t assign it. Use /64 nets everywhere. It’s what SLAAC is built for.

[cnbatch]

I do want to get a /64 net, but it seems radvd and/or some components elsewhere didn't generate it.

[fichtner]

You haven’t shown ifconfig output. There’s a /62 somewhere and there shouldn’t be.

[cnbatch]

[fichtner]

Yes, your LAN GUA is misconfigured. Use a single (or multiple if you need but under normal circumstances you want to pass another /64 to a different internal interface) /64 networks instead.

[cnbatch]

Ah, is /64 netmask generated by the PHP scripts? I don't see any textbox (except DHCPv6 but I want to use SLAAC on this LAN interface) that can manually input netmask length

[fichtner]

Yes, scripts correctly use /64 for tracking but it looks like static assignment from your end here.

[cnbatch]

But I have not set any static IPv6 address assignment on WAN and LAN interface: #9523

[fichtner]

I’ve never seen dhcp6c assign a non /64 either. Just not sure what to make of this. Missing context here.