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

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

plugin/pkg/proxy/connect_test.go

@@ -1,8 +1,18 @@
 package proxy
 
 import (
+	"context"
+	"net/http"
+	"net/http/httptest"
 	"testing"
 	"time"
+
+	"github.com/coredns/coredns/plugin/pkg/doh"
+	"github.com/coredns/coredns/plugin/pkg/transport"
+	"github.com/coredns/coredns/plugin/test"
+	"github.com/coredns/coredns/request"
+
+	"github.com/miekg/dns"
 )
 
 const (
@@ -49,3 +59,50 @@ func TestDial_MultipleCallsAfterStop(t *testing.T) {
 		}
 	}
 }
+
+// TestConnectHTTPSReportsTCP verifies that Connect reports the transport it
+// actually used to reach the upstream. For an HTTPS upstream that is always
+// "tcp", even when the downstream client connected over UDP.
+func TestConnectHTTPSReportsTCP(t *testing.T) {
+	s := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		msg, err := doh.RequestToMsg(r)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+
+		ret := new(dns.Msg)
+		reply := ret.SetReply(msg)
+		reply.Answer = append(reply.Answer, test.A("example.org. IN A 127.0.0.1"))
+
+		buf, err := reply.Pack()
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		w.Header().Set("Content-Type", doh.MimeType)
+		w.Write(buf)
+	}))
+	defer s.Close()
+
+	p := NewProxy("TestConnectHTTPSReportsTCP", s.URL, transport.HTTPS)
+	p.SetHTTPClient(s.Client())
+
+	m := new(dns.Msg)
+	m.SetQuestion("example.org.", dns.TypeA)
+
+	// The downstream client connected over UDP.
+	req := request.Request{W: &test.ResponseWriter{TCP: false}, Req: m}
+
+	resp, _, proto, err := p.Connect(context.Background(), req, Options{})
+	if err != nil {
+		t.Fatalf("Connect failed: %v", err)
+	}
+	if resp == nil {
+		t.Fatal("Expected response, got nil")
+	}
+	if proto != "tcp" {
+		t.Errorf("HTTPS upstream with a UDP downstream client: expected reported proto %q, got %q", "tcp", proto)
+	}
+}