Function TestDeliverLoopback

wgengine/netstack/netstack_test.go:1556–1633

TestDeliverLoopback verifies that DeliverLoopback correctly re-serializes an outbound packet and delivers it back into gVisor's inbound path.

(t *testing.T)

// TestDeliverLoopback verifies that DeliverLoopback correctly re-serializes an
// outbound packet and delivers it back into gVisor's inbound path.
func TestDeliverLoopback(t *testing.T) {
	ep := newLinkEndpoint(64, 1280, "", groNotSupported)

	// Track delivered packets via a mock dispatcher.
	type delivered struct {
		proto tcpip.NetworkProtocolNumber
		data  []byte
	}
	deliveredCh := make(chan delivered, 4)
	ep.Attach(&mockDispatcher{
		onDeliverNetworkPacket: func(proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
			// Capture the raw bytes from the delivered packet. At this
			// point the packet is unparsed — everything is in the
			// payload, no headers have been consumed yet.
			buf := pkt.ToBuffer()
			raw := buf.Flatten()
			deliveredCh <- delivered{proto: proto, data: raw}
		},
	})

	t.Run("ipv4", func(t *testing.T) {
		selfAddr := netip.MustParseAddrPort("100.64.1.2:8081")
		pkt := makeUDP4PacketBuffer(selfAddr, selfAddr)
		// Capture what the outbound bytes look like before loopback.
		wantLen := pkt.Size()
		wantProto := pkt.NetworkProtocolNumber

		if !ep.DeliverLoopback(pkt) {
			t.Fatal("DeliverLoopback returned false")
		}

		select {
		case got := <-deliveredCh:
			if got.proto != wantProto {
				t.Errorf("proto = %d, want %d", got.proto, wantProto)
			}
			if len(got.data) != wantLen {
				t.Errorf("data length = %d, want %d", len(got.data), wantLen)
			}
		case <-time.After(time.Second):
			t.Fatal("timeout waiting for loopback delivery")
		}
	})

	t.Run("ipv6", func(t *testing.T) {
		selfAddr := netip.MustParseAddrPort("[fd7a:115c:a1e0::123]:8081")
		pkt := makeUDP6PacketBuffer(selfAddr, selfAddr)
		wantLen := pkt.Size()
		wantProto := pkt.NetworkProtocolNumber

		if !ep.DeliverLoopback(pkt) {
			t.Fatal("DeliverLoopback returned false")
		}

		select {
		case got := <-deliveredCh:
			if got.proto != wantProto {
				t.Errorf("proto = %d, want %d", got.proto, wantProto)