coredns

command module
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 Go to latest Published: Jan 25, 2018 License: Apache-2.0 Imports: 2 Imported by: 0

README

CoreDNS

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CoreDNS (written in Go) chains plugins. Each plugin performs a DNS function.

CoreDNS is a Cloud Native Computing Foundation inception level project.

CoreDNS is the successor to SkyDNS. SkyDNS is a thin layer that exposes services in etcd in the DNS. CoreDNS builds on this idea and is a generic DNS server that can talk to multiple backends (etcd, kubernetes, etc.).

CoreDNS aims to be a fast and flexible DNS server. The keyword here is flexible: with CoreDNS you are able to do what you want with your DNS data. And if not: write a plugin!

CoreDNS can listen for DNS request coming in over UDP/TCP (go'old DNS), TLS (RFC 7858) and gRPC (not a standard).

Currently CoreDNS is able to:

  • Serve zone data from a file; both DNSSEC (NSEC only) and DNS are supported (file).
  • Retrieve zone data from primaries, i.e., act as a secondary server (AXFR only) (secondary).
  • Sign zone data on-the-fly (dnssec).
  • Load balancing of responses (loadbalance).
  • Allow for zone transfers, i.e., act as a primary server (file).
  • Automatically load zone files from disk (auto).
  • Caching (cache).
  • Health checking endpoint (health).
  • Use etcd as a backend, i.e., a 101.5% replacement for SkyDNS (etcd).
  • Use k8s (kubernetes) as a backend (kubernetes).
  • Serve as a proxy to forward queries to some other (recursive) nameserver (proxy).
  • Provide metrics (by using Prometheus) (metrics).
  • Provide query (log) and error (error) logging.
  • Support the CH class: version.bind and friends (chaos).
  • Support the RFC 5001 DNS name server identifier (NSID) option (nsid).
  • Profiling support (pprof).
  • Rewrite queries (qtype, qclass and qname) (rewrite).
  • Echo back the IP address, transport and port number used (whoami). This is also the default plugin that gets loaded when CoreDNS can't find a Corefile to load.

Each of the plugins has a README.md of its own, see coredns.io/plugins for all in-tree plugins, and coredns.io/explugins for all out-of-tree plugins.

Status

CoreDNS can be used as an authoritative nameserver for your domains. CoreDNS should be able to provide you with enough functionality to replace parts of BIND 9, Knot, NSD or PowerDNS and SkyDNS.

Compilation

Check out the project and do dependency resolution with:

go get github.com/coredns/coredns

Some of the dependencies require Go version 1.8 or later.

(If you already have the source of CoreDNS checked out in the appropriate place in your GOPATH, you can get all dependencies with go get ./....)

Then use go build as you would normally do:

go build

This should yield a coredns binary.

Compilation with Docker

CoreDNS requires Go to compile. However, if you already have docker installed and prefer not to setup a Go environment, you could build coredns easily:

$ docker run --rm -i -t -v $PWD:/go/src/github.com/coredns/coredns \
      -w /go/src/github.com/coredns/coredns golang:1.9 make

The above command alone will have coredns binary generated.

Examples

When starting CoreDNS without any configuration, it loads the whoami plugin and starts listening on port 53 (override with -dns.port), it should show the following:

.:53
2016/09/18 09:20:50 [INFO] CoreDNS-001
CoreDNS-001

Any query send to port 53 should return some information; your sending address, port and protocol used.

If you have a Corefile without a port number specified it will, by default, use port 53, but you can override the port with the -dns.port flag:

./coredns -dns.port 1053, runs the server on port 1053.

Start a simple proxy, you'll need to be root to start listening on port 53.

Corefile contains:

.:53 {
    proxy . 8.8.8.8:53
    log
}

Just start CoreDNS: ./coredns. Then just query on that port (53). The query should be forwarded to 8.8.8.8 and the response will be returned. Each query should also show up in the log which is printed on standard output.

Serve the (NSEC) DNSSEC-signed example.org on port 1053, with errors and logging sent to standard output. Allow zone transfers to everybody, but specifically mention 1 IP address so that CoreDNS can send notifies to it.

example.org:1053 {
    file /var/lib/coredns/example.org.signed {
        transfer to *
        transfer to 2001:500:8f::53
    }
    errors
    log
}

Serve example.org on port 1053, but forward everything that does not match example.org to a recursive nameserver and rewrite ANY queries to HINFO.

.:1053 {
    rewrite ANY HINFO
    proxy . 8.8.8.8:53

    file /var/lib/coredns/example.org.signed example.org {
        transfer to *
        transfer to 2001:500:8f::53
    }
    errors
    log
}

IP addresses are also allowed. They are automatically converted to reverse zones:

10.0.0.0/24 {
    whoami
}

Means you are authoritative for 0.0.10.in-addr.arpa..

This also works for IPv6 addresses. If for some reason you want to serve a zone named 10.0.0.0/24 add the closing dot: 10.0.0.0/24. as this also stops the conversion.

This even works for CIDR (See RFC 1518 and 1519) addressing, i.e 10.0.0.0/25, CoreDNS will then check if the in-addr request falls in the correct range.

Listening on TLS and for gRPC? Use:

tls://example.org grpc://example.org {
    whoami
}

Specifying ports works in the same way:

grpc://example.org:1443 {
    # ...
}

When no transport protocol is specified the default dns:// is assumed.

Community

Deployment

Examples for deployment via systemd and other use cases can be found in the deployment repository.

Documentation

The Go Gopher

There is no documentation for this package.

Source Files

View all Source files

Directories

Path Synopsis
Package core registers the server and all plugins we support.
 Package core registers the server and all plugins we support.
dnsserver
Package dnsserver implements all the interfaces from Caddy, so that CoreDNS can be a servertype plugin.
 Package dnsserver implements all the interfaces from Caddy, so that CoreDNS can be a servertype plugin.
plugin
Package coremain contains the functions for starting CoreDNS.
 Package coremain contains the functions for starting CoreDNS.
Package pb is a generated protocol buffer package.
 Package pb is a generated protocol buffer package.
Package plugin provides some types and functions common among plugin.
 Package plugin provides some types and functions common among plugin.
auto
Package auto implements an on-the-fly loading file backend.
 Package auto implements an on-the-fly loading file backend.
autopath
Package autopath implements autopathing.
 Package autopath implements autopathing.
bind
Package bind allows binding to a specific interface instead of bind to all of them.
 Package bind allows binding to a specific interface instead of bind to all of them.
cache
Package cache implements a cache.
 Package cache implements a cache.
cache/freq
Package freq keeps track of last X seen events.
 Package freq keeps track of last X seen events.
chaos
Package chaos implements a plugin that answer to 'CH version.bind TXT' type queries.
 Package chaos implements a plugin that answer to 'CH version.bind TXT' type queries.
debug
dnssec
Package dnssec implements a plugin that signs responses on-the-fly using NSEC black lies.
 Package dnssec implements a plugin that signs responses on-the-fly using NSEC black lies.
dnstap
dnstap/dnstapio
dnstap/msg
Package msg helps to build a dnstap Message.
 Package msg helps to build a dnstap Message.
dnstap/taprw
Package taprw takes a query and intercepts the response.
 Package taprw takes a query and intercepts the response.
dnstap/test
erratic
Package erratic implements a plugin that returns erratic answers (delayed, dropped).
 Package erratic implements a plugin that returns erratic answers (delayed, dropped).
errors
Package errors implements an HTTP error handling plugin.
 Package errors implements an HTTP error handling plugin.
etcd
Package etcd provides the etcd backend plugin.
 Package etcd provides the etcd backend plugin.
etcd/msg
Package msg defines the Service structure which is used for service discovery.
 Package msg defines the Service structure which is used for service discovery.
federation
Package federation implements kubernetes federation.
 Package federation implements kubernetes federation.
file
Package file implements a file backend.
 Package file implements a file backend.
file/tree
Package tree implements Left-Leaning Red Black trees as described by Robert Sedgewick.
 Package tree implements Left-Leaning Red Black trees as described by Robert Sedgewick.
health
Package health implements an HTTP handler that responds to health checks.
 Package health implements an HTTP handler that responds to health checks.
hosts
kubernetes
Package kubernetes provides the kubernetes backend.
 Package kubernetes provides the kubernetes backend.
loadbalance
Package loadbalance is plugin for rewriting responses to do "load balancing" Package loadbalance shuffles A and AAAA records.
 Package loadbalance is plugin for rewriting responses to do "load balancing" Package loadbalance shuffles A and AAAA records.
log
Package log implements basic but useful request (access) logging plugin.
 Package log implements basic but useful request (access) logging plugin.
metrics
Package metrics implement a handler and plugin that provides Prometheus metrics.
 Package metrics implement a handler and plugin that provides Prometheus metrics.
metrics/test
Package test will scrape a target and you can inspect the variables.
 Package test will scrape a target and you can inspect the variables.
metrics/vars
nsid
Package nsid implements NSID protocol
 Package nsid implements NSID protocol
pkg/cache
Package cache implements a cache.
 Package cache implements a cache.
pkg/dnstest
Package dnstest allows for easy testing of DNS client against a test server.
 Package dnstest allows for easy testing of DNS client against a test server.
pkg/dnsutil
Package dnsutil contains DNS related helper functions.
 Package dnsutil contains DNS related helper functions.
pkg/edns
Package edns provides function useful for adding/inspecting OPT records to/in messages.
 Package edns provides function useful for adding/inspecting OPT records to/in messages.
pkg/fall
Package fall handles the fallthrough logic used in plugins that support it.
 Package fall handles the fallthrough logic used in plugins that support it.
pkg/fuzz
pkg/healthcheck
pkg/nonwriter
Package nonwriter implements a dns.ResponseWriter that never writes, but captures the dns.Msg being written.
 Package nonwriter implements a dns.ResponseWriter that never writes, but captures the dns.Msg being written.
pkg/parse
pkg/rcode
pkg/replacer
pkg/response
pkg/singleflight
Package singleflight provides a duplicate function call suppression mechanism.
 Package singleflight provides a duplicate function call suppression mechanism.
pkg/tls
pkg/trace
pprof
Package pprof implement a debug endpoint for getting profiles using the go pprof tooling.
 Package pprof implement a debug endpoint for getting profiles using the go pprof tooling.
proxy
Package proxy is plugin that proxies requests.
 Package proxy is plugin that proxies requests.
reverse
rewrite
Package rewrite is plugin for rewriting requests internally to something different.
 Package rewrite is plugin for rewriting requests internally to something different.
root
route53
Package route53 implements a plugin that returns resource records from AWS route53
 Package route53 implements a plugin that returns resource records from AWS route53
secondary
Package secondary implements a secondary plugin.
 Package secondary implements a secondary plugin.
template
test
Package test contains helper functions for writing plugin tests.
 Package test contains helper functions for writing plugin tests.
tls
trace
Package trace implements OpenTracing-based tracing
 Package trace implements OpenTracing-based tracing
whoami
Package whoami implements a plugin that returns details about the resolving querying it.
 Package whoami implements a plugin that returns details about the resolving querying it.
Package request abstracts a client's request so that all plugin will handle them in an unified way.
 Package request abstracts a client's request so that all plugin will handle them in an unified way.
Package test contains function and types useful for writing tests
 Package test contains function and types useful for writing tests

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