ipref - recursively translate IPREF AA records into A/AAAA records by communicating with the IPREF mapper

Each incoming A/AAAA DNS query that reaches the ipref plugin will result in a recursive query to the configured upstream server for an IPREF AA record (encoded in TXT records beginning with "AA"). The ipref plugin will then communicate with the gateway mapper over a Unix domain socket to get the encoded address associated with the IPREF address returned by the upstream server, and then the encoded address is returned in an A/AAAA response.

If the query cannot be served by translating an IPREF address, then the next plugin in the chain is executed (even if the upstream has an A/AAAA record). If you'd like to combine IPREF translation with normal DNS resolution, see the forward plugin (example below).

This plugin can only be used once per Server Block.

This code includes technology covered by patent US 10,749,840 B2.

ipref [FROM...] {
    except IGNORED_NAMES...
    upstream ADDR
    ea-ipver 4|6
    gw-ipver 4|6
    mapper PATH
}

• FROM is the base domains to match for the request to be resolved. If not specified the zones from the server block are used.
• IGNORED_NAMES in except is a space-separated list of domains to exclude from resolving.
• upstream specifies the address of the upstream DNS server (eg. 8.8.8.8).
• ea-ipver and gw-ipver specify the IP versions (IPv4 or IPv6) to use for the encoded address network (local network) and IPREF gateway tunnel, respectively. The default for both is IPv4.
• mapper specifies the path to the Unix domain socket for communication with the gateway - the default is /run/ipref/mapper.sock.

If monitoring is enabled (via the prometheus directive) then the following metric is exported:

• coredns_ipref_request_duration_seconds{server} - duration per query.
• coredns_ipref_response_rcode_count_total{server, rcode} - count of RCODEs.

The server label indicates which server handled the request, see the metrics plugin for details.

Translate IPREF AA records for everything under example.com (except everything under www.example.com) using 8.8.8.8 as the upstream source for AA records. If no valid AA records are found, or if the domain is excluded, then the request is forwarded to 8.8.8.8. Note that this requires ipref to be above forward in plugin.cfg.

. {
    ipref example.com {
        except www.example.com
        upstream 8.8.8.8
        ea-ipver 4
        gw-ipver 4
    }
    forward . 8.8.8.8
}

To compile this with CoreDNS you can follow the normal procedure for external plugins.

You may need to add these dependencies to CoreDNS's go.mod:

require (
	github.com/ipref/common v1.3.1
)

IPREF needs new DNS resource record type. The plan is to register AA records with IANA. For now, as a workaround to allow development, the unavailable AA records are emulated by embedding them in TXT records. This is invisible to hosts requesting name resolution.

See https://github.com/ipref/dns for information on IPREF addressing.

This plugin was originally based on the unbound plugin, but it has since been rewritten to perform forwarding instead.