53e9681a39
Enable protogetter in golangci config and update all protobuf field access to use getter methods instead of direct field access. Getter methods provide safer nil pointer handling and return appropriate default values, following protobuf best practices. Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
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.
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] [writebuffer] [queue] {
[identity IDENTITY]
[version VERSION]
[extra EXTRA]
[skipverify]
}
- SOCKET is the socket (path) supplied to the dnstap command line tool.
fullto include the wire-format DNS message.- IDENTITY to override the identity of the server. Defaults to the hostname.
- VERSION to override the version field. Defaults to the CoreDNS version.
- EXTRA to define "extra" field in dnstap payload, metadata replacement available here.
skipverifyto skip tls verification during connection. Default to be secure
Examples
Log information about client requests and responses to /tmp/dnstap.sock.
dnstap /tmp/dnstap.sock
Log information about client requests and responses and tcp write buffer is 1024Mb and queue is 204810000.
dnstap /tmp/dnstap.sock full 1024 2048
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
Log to a remote endpoint by FQDN.
dnstap tcp://example.com:6000 full
Log to a socket, overriding the default identity and version.
dnstap /tmp/dnstap.sock {
identity my-dns-server1
version MyDNSServer-1.2.3
}
Log to a socket, customize the "extra" field in dnstap payload. You may use metadata provided by other plugins in the extra field.
forward . 8.8.8.8
metadata
dnstap /tmp/dnstap.sock {
extra "upstream: {/forward/upstream}"
}
Log to a remote TLS endpoint.
dnstap tls://127.0.0.1:6000 full {
skipverify
}
You can use dnstap more than once to define multiple taps. The following logs information including the wire-format DNS message about client requests and responses to /tmp/dnstap.sock, and also sends client requests and responses without wire-format DNS messages to a remote FQDN.
dnstap /tmp/dnstap.sock full
dnstap tcp://example.com:6000
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
In your setup function, collect and store a list of all dnstap plugins loaded in the config:
x := &ExamplePlugin{}
c.OnStartup(func() error {
if taph := dnsserver.GetConfig(c).Handler("dnstap"); taph != nil {
for tapPlugin, ok := taph.(*dnstap.Dnstap); ok; tapPlugin, ok = tapPlugin.Next.(*dnstap.Dnstap) {
x.tapPlugins = append(x.tapPlugins, tapPlugin)
}
}
return nil
})
And then in your plugin:
import (
"github.com/coredns/coredns/plugin/dnstap/msg"
"github.com/coredns/coredns/request"
tap "github.com/dnstap/golang-dnstap"
)
func (x ExamplePlugin) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
for _, tapPlugin := range x.tapPlugins {
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)
// if no metadata interpretation is needed, just send the message
tapPlugin.TapMessage(q)
// OR: to interpret the metadata in "extra" field, give more context info
tapPlugin.TapMessageWithMetadata(ctx, q, request.Request{W: w, Req: query})
}
// ...
}
See Also
The website dnstap.info has info on the dnstap protocol. The forward
plugin's dnstap.go uses dnstap to tap messages sent to an upstream.