README.md

rDNS NS

This is a simple DNS server for providing reverse DNS for dynamic/SLAAC IPv6 addresses. It was created to provide reverse DNS for larger dynamic allocations (in my case, /56's routed to my house and for my VPN) as other reverse DNS servers (e.g. AllKnowingDNS) only work for prefix lengths divisible by 16.

Configuration

Each prefix that the DNS server should handle should be configured in config.json.

{
	"prefix": "2001:db8:1234:5600::/56",
	"recordFormat": "lon-{addr}.rdns.isp.example",
	"static": [
		{
			"address": "2001:db8:1234:5600::1",
			"record": "lon-router01.isp.example"
		}
	]
}

The record format must be unique for each prefix for the AAAA lookups to work properly. Similarly, the prefixes must be unique and not overlapping.

The listenOn and listenOnV6 configuration options are also required.

You should also configure the thisNS setting. Set this to the delegated nameserver record (see the DNS Delegation section below). These nameservers will be returned whenever an NS request is received for a prefix or root reverse DNS record defined in the config (e.g. 9.5.4.3.2.1.8.b.d.0.1.0.0.2.ip6.arpa and rdns.isp.example.com from the above example). If the prefix length is not divisible by 4, the NS will be returned for the subdomain of the ip6.arpa zone (e.g. 2001:db8:1234:5900::/57 will return NS on x.9.5.4.3.2.1.8.b.d.0.1.0.0.2.ip6.arpa where x is [0-9a-f]).

Optionally, the idServer setting can be configured. This will be returned when a TXT CH request for id.server is received.

To allow rDNS NS to bind to port 53, you will need to run the following command: sudo setcap 'cap_net_bind_service=+ep' $(readlink -f $(which node)).

DNS Delegation

You will need to delegate the DNS zones that rDNS NS should handle.

6.5.4.3.2.1.8.b.d.0.1.0.0.2.ip6.arpa. IN NS rdns-ns.isp.example.

rdns.isp.example. IN NS rdns-ns.isp.example.