Add native protocol service plugins

plugins/services/dnstcp_test.go

@@ -0,0 +1,19 @@
+//go:build plugin_dnstcp || !plugin_selective
+
+package services
+
+import (
+	"encoding/binary"
+	"testing"
+)
+
+func TestDNSTCPFrame(t *testing.T) {
+	query := buildDNSRootNSQuery(0x4321)
+	frame := make([]byte, 2, len(query)+2)
+	binary.BigEndian.PutUint16(frame, uint16(len(query)))
+	frame = append(frame, query...)
+
+	if binary.BigEndian.Uint16(frame[:2]) != uint16(len(query)) {
+		t.Fatalf("unexpected dns tcp length prefix: %#v", frame[:2])
+	}
+}