Add native UDP protobuf reference vectors

fix.txt

@@ -168,7 +168,7 @@ Priority 2: protocol and data correctness
     dereferencing and return errInvalidProtobuf for malformed server packets.
     Audit all packet pointer dereferences similarly.
 
-21. UDP protocol state has no complete interoperability test coverage
+[x] 21. UDP protocol state has no complete interoperability test coverage
     Files: gumble/gumble/udp15.go, gumble/gumble/udp.go
     Tests are mostly local encrypt/decrypt round trips. Add captured/reference
     vectors from current Mumble for CryptSetup, encrypted audio, ping, packet

gumble/gumble/udp15_test.go

@@ -212,6 +212,17 @@ func TestUDPAudioProtobuf(t *testing.T) {
 	}
 }
 
+// Reference wire vector from the MumbleUDP.Audio protobuf layout. This guards
+// field numbers, standard-varint framing, terminators, and position encoding.
+func TestUDPAudioProtobufReferenceVector(t *testing.T) {
+	x, y, z := float32(1), float32(2), float32(3)
+	got := encodeUDPAudio(2, 300, []byte{0xaa, 0xbb}, true, &x, &y, &z)
+	want := mustDecodeHex("080220ac022a02aabb320c0000803f0000004000004040800101")
+	if !bytes.Equal(got, want) {
+		t.Fatalf("wire vector = %x, want %x", got, want)
+	}
+}
+
 func TestUDPAudioProtobufIncomingFields(t *testing.T) {
 	var packet bytes.Buffer
 	writeVarint := func(v uint64) {
@@ -228,6 +239,10 @@ func TestUDPAudioProtobufIncomingFields(t *testing.T) {
 	writeVarint(5<<3 | 2) // opus_data
 	writeVarint(2)
 	packet.Write([]byte{0xaa, 0xbb})
+	writeVarint(7<<3 | 5) // volume_adjustment fixed32
+	var volume [4]byte
+	binary.LittleEndian.PutUint32(volume[:], math.Float32bits(0.75))
+	packet.Write(volume[:])
 	writeVarint(6<<3 | 2) // packed positional_data
 	writeVarint(12)
 	for _, f := range []uint32{math.Float32bits(1), math.Float32bits(2), math.Float32bits(3)} {
@@ -236,10 +251,13 @@ func TestUDPAudioProtobufIncomingFields(t *testing.T) {
 		packet.Write(buf[:])
 	}
 
-	session, frame, opusData, terminator, context, position, _ := decodeUDPAudio(packet.Bytes())
+	session, frame, opusData, terminator, context, position, volumeAdjustment := decodeUDPAudio(packet.Bytes())
 	if session != 123 || frame != 1<<32 || !bytes.Equal(opusData, []byte{0xaa, 0xbb}) || terminator || context != 3 {
 		t.Fatalf("decoded unexpected audio: session=%d frame=%d opus=%x terminator=%v context=%d", session, frame, opusData, terminator, context)
 	}
+	if volumeAdjustment != 0.75 {
+		t.Fatalf("volume adjustment = %v", volumeAdjustment)
+	}
 	if position == nil || *position != [3]float32{1, 2, 3} {
 		t.Fatalf("position = %v, want [1 2 3]", position)
 	}