coredns/man/coredns-dnstap.7

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.TH "COREDNS-DNSTAP" 7 "October 2020" "CoreDNS" "CoreDNS Plugins"

.SH "NAME"
.PP
\fIdnstap\fP - enables logging to dnstap.

.SH "DESCRIPTION"
.PP
dnstap is a flexible, structured binary log format for DNS software; see https://dnstap.info
\[la]https://dnstap.info\[ra]. With this
plugin you make CoreDNS output dnstap logging.

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

.SH "SYNTAX"
.PP
.RS

.nf
dnstap SOCKET [full]

.fi
.RE

.IP \(bu 4
\fBSOCKET\fP is the socket path supplied to the dnstap command line tool.
.IP \(bu 4
\fB\fCfull\fR to include the wire-format DNS message.


.SH "EXAMPLES"
.PP
Log information about client requests and responses to \fI/tmp/dnstap.sock\fP.

.PP
.RS

.nf
dnstap /tmp/dnstap.sock

.fi
.RE

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

.PP
.RS

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

.fi
.RE

.PP
Log to a remote endpoint.

.PP
.RS

.nf
dnstap tcp://127.0.0.1:6000 full

.fi
.RE

.SH "COMMAND LINE TOOL"
.PP
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
\[la]https://github.com/dnstap/golang-dnstap\[ra]. It's written in Go.

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

.PP
.RS

.nf
$ dnstap \-u /tmp/dnstap.sock

.fi
.RE

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

.PP
.RS

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

.fi
.RE

.PP
Listen for dnstap messages on port 6000.

.PP
.RS

.nf
$ dnstap \-l 127.0.0.1:6000

.fi
.RE

.SH "USING DNSTAP IN YOUR PLUGIN"
.PP
In your setup function, check to see if the \fIdnstap\fP plugin is loaded:

.PP
.RS

.nf
c.OnStartup(func() error {
    if taph := dnsserver.GetConfig(c).Handler("dnstap"); taph != nil {
        if tapPlugin, ok := taph.(dnstap.Dnstap); ok {
            f.tapPlugin = \&tapPlugin
        }
    }
    return nil
})

.fi
.RE

.PP
And then in your plugin:

.PP
.RS

.nf
func (x RandomPlugin) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
    if tapPlugin != nil {
        q := new(msg.Msg)
        msg.SetQueryTime(q, time.Now())
        msg.SetQueryAddress(q, w.RemoteAddr())
        if tapPlugin.IncludeRawMessage {
            buf, \_ := r.Pack() // r has been seen packed/unpacked before, this should not fail
            q.QueryMessage = buf
        }
        msg.SetType(q, tap.Message\_CLIENT\_QUERY)
        tapPlugin.TapMessage(q)
    }
    // ...
}

.fi
.RE

.SH "SEE ALSO"
.PP
The website dnstap.info
\[la]https://dnstap.info\[ra] has info on the dnstap protocol.
The \fIforward\fP plugin's \fB\fCdnstap.go\fR uses dnstap to tap messages sent to an upstream.