ens

coredns-ens

CoreDNS-ENS is a CoreDNS plugin that resolves DNS information over ENS. It has two primary purposes:

1. A general-purpose DNS resolver for DNS records stored on the Ethereum blockchain
2. A specialised resolver for IPFS content hashes and gatways

Details of the first feature can be found at http://www.wealdtech.com/articles/ethdns-an-ethereum-backend-for-the-domain-name-system/

The second feature provides a mechanism to map DNS domains to ENS domains by removing the relevant suffix, for example the DNS domain wealdtech.eth.link maps to the ENS domain wealdtech.eth, and returning information for IPFS gateways (if an A or AAAA record is requested) as well as IPFS and content hashes (if a TXT record is requested). The result of this is that IPFS content can be obtained from any web browser by simply

Building

The latest build is always available as a docker repository at wealdtech/coredns-ens. If you want to build a standalone copy of CoreDNS with this plugin enabled run the build-standalone.sh script, which should work on most unix-like systems.

Corefile

The plugin has a number of configuration options. An example annotated Corefile is shown below:

# This section enables DNS lookups for all domains on ENS
. {
  rewrite stop {
    # This rewrites any requests for *.eth.link domains to *.eth internally
    # prior to being processed by the main ENS resolver.
    name regex (.*)\.eth\.link {1}.eth
    answer name (.*)\.eth {1}.eth.link
  }
  ens {
    # connection is the connection to an Ethereum node.  It is *highly*
    # recommended that a local node is used, as remote connections can
    # cause DNS requests to time out.
    # This can be either a path to an IPC socket or a URL to a JSON-RPC
    # endpoint.
    connection /home/ethereum/.ethereum/geth.ipc

    # ethlinknameservers are the names of the nameservers that serve
    # EthLink domains.  This will usually be the name of this server,
    # plus potentially one or more others.
    ethlinknameservers ns1.ethdns.xyz ns2.ethdns.xyz

    # ipfsgatewaya is the address of an ENS-enabled IPFS gateway.
    # This value is returned when a request for an A record of an Ethlink
    # domain is received and the domain has a contenthash record in ENS but
    # no A record.  Multiple values can be supplied, separated by a space,
    # in which case all records will be returned.
    ipfsgatewaya 176.9.154.81

    # ipfsgatewayaaaa is the address of an ENS-enabled IPFS gateway.
    # This value is returned when a request for an AAAA record of an Ethlink
    # domain is received and the domain has a contenthash record in ENS but
    # no A record.  Multiple values can be supplied, separated by a space,
    # in which case all records will be returned.
    ipfsgatewayaaaa 2a01:4f8:160:4069::2
  }

  # This enables DNS forwarding.  It should only be enabled if this DNS server
  # is not exposed to the internet, otherwise it becomes an open DNS server and
  # will be flooded with attack packets.
  forward . 8.8.8.8

  errors
}

It is also possible to run the DNS server over TLS or over HTTPS; details on how to set up certificates the can be found in the CoreDNS documentation.

Running standalone

Running CoreDNS standalone is simply a case of starting the binary. See the CoreDNS documentation for further information.

Running with Docker

Running CoreDNS with Docker requires running the image created in the Building section. A sample command-line might be:

docker run -p 53:53/udp --volume=/home/coredns:/etc/coredns wealdtech/coredns-ens:latest

where /home/coredns is the directory on the server that contains the Corefile and certificates.