[Dnsmasq-discuss] Problem: How do I disable RDNS being included in an RA without disabling the DNS component itself.
Kristof Mattei
kristofmattei at outlook.com
Sun Dec 6 17:08:29 GMT 2020
Hi all!
Consider the following dual stack network:
IPv4:
* 192.168.1.1/24
* DHCP on 192.168.1.1 with DNSMASQ
* DNS on 192.168.1.10 (pi-hole, docker)
* DNSMASQ has dhcp-option=6,192.168.1.10, so clients query the DNS directly. This allows pi-hole query DNSMASQ for the names of those clients.
IPv6:
* Changing prefix when the router/cable modem reboots, so I cannot hardcode the prefix.
* Even tried locking down the DUID. Doesn't work.
* DNSMASQ has dhcp-range=::,constructor:br0,ra-only,12h. (ra-only to my understanding here is the same as SLAAC)
* I did NOT set the dhcp-option=option6:23,[::]
Now the problem is that DNSMASQ still send the link-local address of br0 being the RDNS server as part of the RA.
The only way I found to disable this was to set the nameserver port to 0, essentially disabling the DNS component of DNSMASQ.
This however breaks the lookups that pi-hole does against DNSMASQ.
Is there another switch that I'm not seeing?
Other solutions I have considered:
* Set the dhcp-option=option6:23 to the link-local address of pi-hole. Working on that, but Docker and IPv6 aren't the best friends when it comes to changing prefixes.
* ULA on the network, DD-WRT doesn't support that.
* Make pi-hole the DHCP server for IPv4, so it has the client names, deferring to DNSMASQ only for IPv6. Actual viable solution.
--
Kristof
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