Forwarding

Forwarding

Maybe some domain names must be sent to an internal DNS server to be resolved.

Maybe you'd like queries for your local domain to go to your router, and not to an upstream DNS resolver. By doing so, names of your local online devices can be found.

This also prevents internal names from being sent to 3rd party servers.

While all the DNS traffic is usually meant to be sent to secure channels, you can add "exceptions" that will be sent, unencrypted, as regular DNS queries, to specific hosts.

This is the purpose of the forwarding_rules parameter:

forwarding_rules = 'forwarding-rules.txt'

This loads a file named forwarding-rules.txt with a set of rules with the following syntax:

example.com 192.168.2.44
example.net 114.114.114.114

Here, queries for example.com and example.net or any of their subdomains will not go through DNSCrypt or DNS-over-HTTPS. They will be exceptions, sent using regular DNS, to other DNS servers: 192.168.2.44 and 114.114.114.114.

This is different from cloaking: the IP address is the IP address of a DNS resolver, not the IP address returned to the client.

Patterns are not supported. Suffix-matching is always done: www.example.com will go to 192.168.2.44 in the example above.

Multiple comma-separated IP addresses can be specified:

example.com 192.168.2.1,192.168.2.2

They will be tried in random order.

IPv6 addresses must include the port number:

info [2001:4860:4860::8888]:53

Forwarding can make encrypted DNS and services incompatible with encrypted DNS play well with each other.

But most people may want to only redirect their local domain (for example .localdomain or .lan) to their router IP address.

It will apply the first rule (although it may be not the most accurate) which matches the query. If you have several groups of forwarding rules used together, put the prior one in the front.

Forwarding reverse queries

A rule such as

lan 192.168.1.1

will forward any queries within the local .lan zone to 192.168.1.1, presumably, the router.

For example, the IP address of printer.lan cannot be resolved by public resolvers, but the router may know about it.

Similarly, the router knows that 192.168.1.7 (or whatever the printer IP address is) is the IP address of printer.lan. But a specific rule is required for dnscrypt-proxy to ask the router to resolve names for IP addresses within the local network ("reverse queries").

The rules should use the .in-addr.arpa zone:

# Resolve names of IP addresses in 10.* using the router 192.168.1.1
10.in-addr.arpa 192.168.1.1

# Resolve names of IP addresses in 192.* using the router 192.168.1.1
192.in-addr.arpa 192.168.1.1

# Resolve names of IP addresses in 169.254.* using the router 192.168.1.1
# Note that address components are in reverse order
254.169.in-addr.arpa 192.168.1.1

Forwarding and caching

Routers usually have their own DNS cache. But most importantly, they also act as DHCP servers, keeping track of all the devices on the local network.

As soon as a new device joins the network, the router adds it to their DNS records for the local zone. As soon as a DHCP lease expires, the relevant device names disappears from the local DNS zone.

For this reason, zones forwarded by dnscrypt-proxy are intentionally never cached by the proxy, leaving the router the only authority about what devices are active on the local network. This ensures that local devices can be immediately used when they get online, and protects against negative caching attacks.

Load-balancing options