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151 lines
3.7 KiB
Markdown
151 lines
3.7 KiB
Markdown
# dnstap
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## Name
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*dnstap* - enables logging to dnstap.
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## Description
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dnstap is a flexible, structured binary log format for DNS software; see https://dnstap.info. With this
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plugin you make CoreDNS output dnstap logging.
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Every message is sent to the socket as soon as it comes in, the *dnstap* plugin has a buffer of
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10000 messages, above that number dnstap messages will be dropped (this is logged).
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## Syntax
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~~~ txt
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dnstap SOCKET [full] {
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[identity IDENTITY]
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[version VERSION]
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[skipverify]
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}
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~~~
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* **SOCKET** is the socket (path) supplied to the dnstap command line tool.
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* `full` to include the wire-format DNS message.
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* **IDENTITY** to override the identity of the server. Defaults to the hostname.
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* **VERSION** to override the version field. Defaults to the CoreDNS version.
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* `skipverify` to skip tls verification during connection. Default to be secure
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## Examples
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Log information about client requests and responses to */tmp/dnstap.sock*.
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~~~ txt
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dnstap /tmp/dnstap.sock
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~~~
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Log information including the wire-format DNS message about client requests and responses to */tmp/dnstap.sock*.
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~~~ txt
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dnstap unix:///tmp/dnstap.sock full
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~~~
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Log to a remote endpoint.
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~~~ txt
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dnstap tcp://127.0.0.1:6000 full
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~~~
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Log to a remote endpoint by FQDN.
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~~~ txt
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dnstap tcp://example.com:6000 full
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~~~
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Log to a socket, overriding the default identity and version.
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~~~ txt
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dnstap /tmp/dnstap.sock {
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identity my-dns-server1
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version MyDNSServer-1.2.3
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}
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~~~
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Log to a remote TLS endpoint.
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~~~ txt
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dnstap tls://127.0.0.1:6000 full {
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skipverify
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}
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~~~
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You can use _dnstap_ more than once to define multiple taps. The following logs information including the
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wire-format DNS message about client requests and responses to */tmp/dnstap.sock*,
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and also sends client requests and responses without wire-format DNS messages to a remote FQDN.
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~~~ txt
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dnstap /tmp/dnstap.sock full
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dnstap tcp://example.com:6000
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~~~
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## Command Line Tool
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Dnstap has a command line tool that can be used to inspect the logging. The tool can be found
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at Github: <https://github.com/dnstap/golang-dnstap>. It's written in Go.
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The following command listens on the given socket and decodes messages to stdout.
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~~~ sh
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$ dnstap -u /tmp/dnstap.sock
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~~~
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The following command listens on the given socket and saves message payloads to a binary dnstap-format log file.
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~~~ sh
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$ dnstap -u /tmp/dnstap.sock -w /tmp/test.dnstap
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~~~
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Listen for dnstap messages on port 6000.
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~~~ sh
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$ dnstap -l 127.0.0.1:6000
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~~~
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## Using Dnstap in your plugin
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In your setup function, collect and store a list of all *dnstap* plugins loaded in the config:
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~~~ go
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x := &ExamplePlugin{}
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c.OnStartup(func() error {
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if taph := dnsserver.GetConfig(c).Handler("dnstap"); taph != nil {
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for tapPlugin, ok := taph.(*dnstap.Dnstap); ok; tapPlugin, ok = tapPlugin.Next.(*dnstap.Dnstap) {
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x.tapPlugins = append(x.tapPlugins, tapPlugin)
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}
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}
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return nil
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})
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~~~
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And then in your plugin:
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~~~ go
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import (
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github.com/coredns/coredns/plugin/dnstap/msg
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tap "github.com/dnstap/golang-dnstap"
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)
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func (x ExamplePlugin) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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for _, tapPlugin := range x.tapPlugins {
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q := new(msg.Msg)
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msg.SetQueryTime(q, time.Now())
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msg.SetQueryAddress(q, w.RemoteAddr())
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if tapPlugin.IncludeRawMessage {
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buf, _ := r.Pack() // r has been seen packed/unpacked before, this should not fail
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q.QueryMessage = buf
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}
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msg.SetType(q, tap.Message_CLIENT_QUERY)
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tapPlugin.TapMessage(q)
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}
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// ...
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}
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~~~
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## See Also
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The website [dnstap.info](https://dnstap.info) has info on the dnstap protocol. The *forward*
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plugin's `dnstap.go` uses dnstap to tap messages sent to an upstream.
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