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a136b7128b
* plugin/dnstap: remove encoder*.go Those files reimplemented parts of the dnstap spec, we can just use the dnstap functions for that. This leaves all the queuing that is enabled and drops messages if the dnstap reader can't keep up. In the new code flush() would never return an error (at least I couldn't make it do so), so the reconnect functionally is moved to kick off when we get write errors. Some smaller cosmetic changes as well, `d.socket` is now `proto`, which makes the dial() function smaller. Total testing time is now <1s (which was the impetus to look into this plugin *again*). See #4238 The buffered channel needs to be sized correctly, as we may need to do some queing if the dnstap reader can't keep up. Signed-off-by: Miek Gieben <miek@miek.nl> * add missing file Signed-off-by: Miek Gieben <miek@miek.nl> * update doc on queing Signed-off-by: Miek Gieben <miek@miek.nl>
105 lines
2.5 KiB
Markdown
105 lines
2.5 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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~~~
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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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## 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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## 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, check to see if the *dnstap* plugin is loaded:
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~~~ go
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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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if tapPlugin, ok := taph.(dnstap.Dnstap); ok {
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f.tapPlugin = &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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func (x RandomPlugin) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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if tapPlugin != nil {
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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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