dnstap

README

dnstap

Name

dnstap - enables logging to dnstap.

Description

dnstap is a flexible, structured binary log format for DNS software; see https://dnstap.info. With this plugin you make CoreDNS output dnstap logging.

Note that there is an internal buffer, so expect at least 13 requests before the server sends its dnstap messages to the socket.

Syntax

dnstap SOCKET [full]

• SOCKET is the socket path supplied to the dnstap command line tool.
• full to include the wire-format DNS message.

Examples

Log information about client requests and responses to /tmp/dnstap.sock.

dnstap /tmp/dnstap.sock

Log information including the wire-format DNS message about client requests and responses to /tmp/dnstap.sock.

dnstap unix:///tmp/dnstap.sock full

Log to a remote endpoint.

dnstap tcp://127.0.0.1:6000 full

Command Line Tool

Dnstap has a command line tool that can be used to inspect the logging. The tool can be found at Github: https://github.com/dnstap/golang-dnstap. It's written in Go.

The following command listens on the given socket and decodes messages to stdout.

$ dnstap -u /tmp/dnstap.sock

The following command listens on the given socket and saves message payloads to a binary dnstap-format log file.

$ dnstap -u /tmp/dnstap.sock -w /tmp/test.dnstap

Listen for dnstap messages on port 6000.

$ dnstap -l 127.0.0.1:6000

Using Dnstap in your plugin

import (
    "github.com/oleksandrblack/coredns/plugin/dnstap"
    "github.com/oleksandrblack/coredns/plugin/dnstap/msg"
)

func (h Dnstap) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
    // log client query to Dnstap
    if t := dnstap.TapperFromContext(ctx); t != nil {
        b := msg.New().Time(time.Now()).Addr(w.RemoteAddr())
        if t.Pack() {
            b.Msg(r)
        }
        if m, err := b.ToClientQuery(); err == nil {
            t.TapMessage(m)
        }
    }

    // ...
}

See Also

dnstap.info.

Documentation

Index

• func ContextWithTapper(ctx context.Context, t Tapper) context.Context
• type ContextKey
• type Dnstap
  • func (h Dnstap) Name() string
  • func (h Dnstap) Pack() bool
  • func (h Dnstap) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error)
  • func (h Dnstap) TapMessage(m *tap.Message)
• type IORoutine
• type Tapper
  • func TapperFromContext(ctx context.Context) Tapper

Functions

func ContextWithTapper

func ContextWithTapper(ctx context.Context, t Tapper) context.Context

ContextWithTapper returns a new `context.Context` that holds a reference to `t`'s Tapper.

Types

type ContextKey

type ContextKey string

ContextKey defines the type of key that is used to save data into the context.

const (
	// DnstapSendOption specifies the Dnstap message to be send.  Default is sent all.
	DnstapSendOption ContextKey = "dnstap-send-option"
)

type Dnstap

type Dnstap struct {
	Next plugin.Handler
	IO   IORoutine

	// Set to true to include the relevant raw DNS message into the dnstap messages.
	JoinRawMessage bool
}

Dnstap is the dnstap handler.

func (Dnstap) Name

func (h Dnstap) Name() string

Name returns dnstap.

func (Dnstap) Pack

func (h Dnstap) Pack() bool

Pack returns true if the raw DNS message should be included into the dnstap messages.

func (Dnstap) ServeDNS

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

ServeDNS logs the client query and response to dnstap and passes the dnstap Context.

func (Dnstap) TapMessage

func (h Dnstap) TapMessage(m *tap.Message)

TapMessage implements Tapper.

type IORoutine

type IORoutine interface {
	Dnstap(tap.Dnstap)
}

IORoutine is the dnstap I/O thread as defined by: <http://dnstap.info/Architecture>.

type Tapper

type Tapper interface {
	TapMessage(message *tap.Message)
	Pack() bool
}

Tapper is implemented by the Context passed by the dnstap handler.

func TapperFromContext

func TapperFromContext(ctx context.Context) Tapper

TapperFromContext returns the `Tapper` previously associated with `ctx`, or `nil` if no such `Tapper` could be found.