fix(forward): make dnstap FORWARDER_* describe the socket from CoreDNS to upstream (#8184)

Signed-off-by: Jaime Hablutzel <hablutzel1@gmail.com>

plugin/forward/dnstap.go

@@ -7,7 +7,6 @@ import (
 	"time"
 
 	"github.com/coredns/coredns/plugin/dnstap/msg"
-	"github.com/coredns/coredns/plugin/pkg/proxy"
 	"github.com/coredns/coredns/request"
 
 	tap "github.com/dnstap/golang-dnstap"
@@ -15,7 +14,7 @@ import (
 )
 
 // toDnstap will send the forward and received message to the dnstap plugin.
-func toDnstap(ctx context.Context, f *Forward, host string, state request.Request, opts proxy.Options, reply *dns.Msg, start time.Time) {
+func toDnstap(ctx context.Context, f *Forward, host string, localAddr net.Addr, proto string, state request.Request, reply *dns.Msg, start time.Time) {
 	ap, _ := netip.ParseAddrPort(host) // this is preparsed and can't err here
 	ip := net.IP(ap.Addr().AsSlice())
 	port := int(ap.Port())
@@ -24,15 +23,7 @@ func toDnstap(ctx context.Context, f *Forward, host string, state request.Reques
 		IP:   ip,
 		Port: port,
 	}
-	t := state.Proto()
-	switch {
-	case opts.ForceTCP:
-		t = "tcp"
-	case opts.PreferUDP:
-		t = "udp"
-	}
-
-	if t == "tcp" {
+	if proto == "tcp" {
 		ta = &net.TCPAddr{IP: ip, Port: port}
 	}
 
@@ -40,9 +31,12 @@ func toDnstap(ctx context.Context, f *Forward, host string, state request.Reques
 		// Query
 		q := new(tap.Message)
 		msg.SetQueryTime(q, start)
-		// Forwarder dnstap messages are from the perspective of the downstream server
-		// (upstream is the forward server)
-		msg.SetQueryAddress(q, state.W.RemoteAddr())
+		// Forwarder dnstap messages are from the perspective of the
+		// downstream DNS server (current CoreDNS) to an upstream DNS
+		// server.
+		if localAddr != nil {
+			msg.SetQueryAddress(q, localAddr)
+		}
 		msg.SetResponseAddress(q, ta)
 		if t.IncludeRawMessage {
 			buf, _ := state.Req.Pack()
@@ -59,7 +53,9 @@ func toDnstap(ctx context.Context, f *Forward, host string, state request.Reques
 				r.ResponseMessage = buf
 			}
 			msg.SetQueryTime(r, start)
-			msg.SetQueryAddress(r, state.W.RemoteAddr())
+			if localAddr != nil {
+				msg.SetQueryAddress(r, localAddr)
+			}
 			msg.SetResponseAddress(r, ta)
 			msg.SetResponseTime(r, time.Now())
 			msg.SetType(r, tap.Message_FORWARDER_RESPONSE)

plugin/forward/forward.go

@@ -8,6 +8,7 @@ import (
 	"context"
 	"crypto/tls"
 	"errors"
+	"net"
 	"net/http"
 	"sync/atomic"
 	"time"
@@ -168,13 +169,15 @@ func (f *Forward) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
 		})
 
 		var (
-			ret *dns.Msg
-			err error
+			ret           *dns.Msg
+			localAddr     net.Addr
+			upstreamProto string
+			err           error
 		)
 		opts := f.opts
 
 		for {
-			ret, err = proxy.Connect(ctx, state, opts)
+			ret, localAddr, upstreamProto, err = proxy.Connect(ctx, state, opts)
 
 			if err == proxyPkg.ErrCachedClosed { // Remote side closed conn, can only happen with TCP.
 				continue
@@ -192,7 +195,7 @@ func (f *Forward) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
 		}
 
 		if len(f.tapPlugins) != 0 {
-			toDnstap(ctx, f, proxy.Addr(), state, opts, ret, start)
+			toDnstap(ctx, f, proxy.Addr(), localAddr, upstreamProto, state, ret, start)
 		}
 
 		upstreamErr = err