table of contents
COREDNS-DNSTAP(7) | CoreDNS Plugins | COREDNS-DNSTAP(7) |
NAME¶
dnstap - enables logging to dnstap.
DESCRIPTION¶
dnstap is a flexible, structured binary log format for DNS software; see https://dnstap.info ⟨https://dnstap.info⟩. With this plugin you make CoreDNS output dnstap logging.
Every message is sent to the socket as soon as it comes in, the dnstap plugin has a buffer of 10000 messages, above that number dnstap messages will be dropped (this is logged).
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 ⟨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¶
In your setup function, check to see if the dnstap plugin is loaded:
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 })
And then in your plugin:
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)
}
// ... }
SEE ALSO¶
The website dnstap.info ⟨https://dnstap.info⟩ has info on the dnstap protocol. The forward plugin's dnstap.go uses dnstap to tap messages sent to an upstream.
March 2021 | CoreDNS |