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package dnstap
import (
"fmt"
"io"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/dnstap/msg"
"github.com/coredns/coredns/plugin/dnstap/taprw"
tap "github.com/dnstap/golang-dnstap"
"github.com/miekg/dns"
"golang.org/x/net/context"
)
// Dnstap is the dnstap handler.
type Dnstap struct {
Next plugin.Handler
IO IORoutine
Pack bool
}
type (
// IORoutine is the dnstap I/O thread as defined by: <http://dnstap.info/Architecture>.
IORoutine interface {
Dnstap(tap.Dnstap)
}
// Tapper is implemented by the Context passed by the dnstap handler.
Tapper interface {
TapMessage(*tap.Message) error
TapBuilder() msg.Builder
}
tapContext struct {
context.Context
Dnstap
}
)
// ContextKey defines the type of key that is used to save data into the context
type ContextKey string
const (
// DnstapSendOption specifies the Dnstap message to be send. Default is sent all.
DnstapSendOption ContextKey = "dnstap-send-option"
)
// TapperFromContext will return a Tapper if the dnstap plugin is enabled.
func TapperFromContext(ctx context.Context) (t Tapper) {
t, _ = ctx.(Tapper)
return
}
func tapMessageTo(w io.Writer, m *tap.Message) error {
frame, err := msg.Marshal(m)
if err != nil {
return fmt.Errorf("marshal: %s", err)
}
_, err = w.Write(frame)
return err
}
// TapMessage implements Tapper.
func (h Dnstap) TapMessage(m *tap.Message) error {
h.IO.Dnstap(msg.Wrap(m))
return nil
}
// TapBuilder implements Tapper.
func (h Dnstap) TapBuilder() msg.Builder {
return msg.Builder{Full: h.Pack}
}
// ServeDNS logs the client query and response to dnstap and passes the dnstap Context.
func (h Dnstap) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
// Add send option into context so other plugin can decide on which DNSTap
// message to be sent out
sendOption := taprw.SendOption{Cq: true, Cr: true}
newCtx := context.WithValue(ctx, DnstapSendOption, &sendOption)
rw := &taprw.ResponseWriter{ResponseWriter: w, Tapper: &h, Query: r, Send: &sendOption}
rw.SetQueryEpoch()
code, err := plugin.NextOrFailure(h.Name(), h.Next, tapContext{newCtx, h}, rw, r)
if err != nil {
// ignore dnstap errors
return code, err
}
if err := rw.DnstapError(); err != nil {
return code, plugin.Error("dnstap", err)
}
return code, nil
}
// Name returns dnstap.
func (h Dnstap) Name() string { return "dnstap" }
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