httpproxy

README

httpproxy

httpproxy proxies DNS request to a proxy using HTTPS (or HTTP/2 - not implemented). Usually this involves sending a JSON payload over this transport and translating the response back to DNS. The current supported backend is Google, using the URL: https://dns.google.com .

Syntax

In its most basic form, a simple http proxy uses this syntax:

httpproxy FROM TO

• FROM is the base domain to match for the request to be proxied.
• TO is the destination endpoint to proxy to, accepted values here are dns.google.com.

For changing the defaults you can use the expanded syntax:

proxy FROM TO {
    upstream ADDRESS...
}

• upstream defines upstream resolvers to be used (re-)resolve dns.google.com (or other names in the future) every 30 seconds. When not specified the combo 8.8.8.8, 8.8.4.4 is used.

Metrics

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

• coredns_httpproxy_request_count_total{zone, proto, family}

Examples

Proxy all requests within example.org to Google's dns.google.com.

proxy example.org dns.google.com

Proxy everything, and re-lookup dns.google.com every 30 seconds using the resolvers specified in /etc/resolv.conf.

proxy . dns.google.com {
    upstream /etc/resolv.conf
}

Debug queries

Debug queries are enabled by default and currently there is no way to turn them off. When CoreDNS receives a debug queries (i.e. the name is prefixed with o-o.debug. a TXT record with Comment from dns.google.com is added. Note this is not always set, but sometimes you'll see:

dig @localhost -p 1053 mx o-o.debug.example.org:

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;o-o.debug.example.org.		IN	MX

;; AUTHORITY SECTION:
example.org.		1799	IN	SOA	sns.dns.icann.org. noc.dns.icann.org. 2016110711 7200 3600 1209600 3600

;; ADDITIONAL SECTION:
.			0	CH	TXT	"Response from 199.43.133.53"

Documentation

Overview

Package httpproxy is middleware that proxies requests to a HTTPs server doing DNS.

Index

• Variables
• func OnStartupMetrics() error
• type Exchanger
• type Proxy
  • func (p Proxy) Name() string
  • func (p *Proxy) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error)

Variables

var (
	RequestDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
		Namespace: middleware.Namespace,
		Subsystem: subsystem,
		Name:      "request_duration_milliseconds",
		Buckets:   append(prometheus.DefBuckets, []float64{50, 100, 200, 500, 1000, 2000, 3000, 4000, 5000, 10000}...),
		Help:      "Histogram of the time (in milliseconds) each request took.",
	}, []string{"zone"})
)

Metrics the httpproxy middleware exports.

Functions

func OnStartupMetrics

func OnStartupMetrics() error

OnStartupMetrics sets up the metrics on startup.

Types

type Exchanger

type Exchanger interface {
	Exchange(request.Request) (*dns.Msg, error)

	SetUpstream(*simpleUpstream) error
	OnStartup() error
	OnShutdown() error
}

Exchanger is an interface that specifies a type implementing a DNS resolver that uses a HTTPS server.

type Proxy

type Proxy struct {
	Next middleware.Handler
	// contains filtered or unexported fields
}

Proxy represents a middleware instance that can proxy requests to HTTPS servers.

func (Proxy) Name

func (p Proxy) Name() string

Name implements the Handler interface.

func (*Proxy) ServeDNS

func (p *Proxy) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error)

ServeDNS satisfies the middleware.Handler interface.