tstest/natlab: allow sensible default construction of networks.

Add a test for LAN->LAN traffic.

Signed-off-by: David Anderson <danderson@tailscale.com>

tstest/natlab/natlab.go

@@ -34,8 +34,9 @@ func mustPrefix(s string) netaddr.IPPrefix {
 // NewInternet returns a network that simulates the internet.
 func NewInternet() *Network {
 	return &Network{
-		v4Pool: mustPrefix("203.0.113.0/24"), // documentation netblock that looks Internet-y
-		v6Pool: mustPrefix("fc00:52::/64"),
+		Name:    "internet",
+		Prefix4: mustPrefix("203.0.113.0/24"), // documentation netblock that looks Internet-y
+		Prefix6: mustPrefix("fc00:52::/64"),
 		pushRoutes: []netaddr.IPPrefix{
 			mustPrefix("0.0.0.0/0"),
 			mustPrefix("::/0"),
@@ -44,9 +45,9 @@ func NewInternet() *Network {
 }
 
 type Network struct {
-	name   string
-	v4Pool netaddr.IPPrefix
-	v6Pool netaddr.IPPrefix
+	Name    string
+	Prefix4 netaddr.IPPrefix
+	Prefix6 netaddr.IPPrefix
 
 	pushRoutes []netaddr.IPPrefix
 
@@ -69,13 +70,16 @@ func (n *Network) addMachineLocked(ip netaddr.IP, m *Machine) {
 func (n *Network) allocIPv4(m *Machine) netaddr.IP {
 	n.mu.Lock()
 	defer n.mu.Unlock()
+	if n.Prefix4.IsZero() {
+		return netaddr.IP{}
+	}
 	if n.lastV4.IsZero() {
-		n.lastV4 = n.v4Pool.IP
+		n.lastV4 = n.Prefix4.IP
 	}
 	a := n.lastV4.As16()
 	addOne(&a, 15)
 	n.lastV4 = netaddr.IPFrom16(a)
-	if !n.v4Pool.Contains(n.lastV4) {
+	if !n.Prefix4.Contains(n.lastV4) {
 		panic("pool exhausted")
 	}
 	n.addMachineLocked(n.lastV4, m)
@@ -85,13 +89,16 @@ func (n *Network) allocIPv4(m *Machine) netaddr.IP {
 func (n *Network) allocIPv6(m *Machine) netaddr.IP {
 	n.mu.Lock()
 	defer n.mu.Unlock()
+	if n.Prefix6.IsZero() {
+		return netaddr.IP{}
+	}
 	if n.lastV6.IsZero() {
-		n.lastV6 = n.v6Pool.IP
+		n.lastV6 = n.Prefix6.IP
 	}
 	a := n.lastV6.As16()
 	addOne(&a, 15)
 	n.lastV6 = netaddr.IPFrom16(a)
-	if !n.v6Pool.Contains(n.lastV6) {
+	if !n.Prefix6.Contains(n.lastV6) {
 		panic("pool exhausted")
 	}
 	n.addMachineLocked(n.lastV6, m)
@@ -235,6 +242,15 @@ func (m *Machine) Attach(interfaceName string, n *Network) *Interface {
 
 	m.interfaces = append(m.interfaces, f)
 
+	if n.pushRoutes == nil {
+		if !n.Prefix4.IsZero() {
+			n.pushRoutes = append(n.pushRoutes, n.Prefix4)
+		}
+		if !n.Prefix6.IsZero() {
+			n.pushRoutes = append(n.pushRoutes, n.Prefix6)
+		}
+	}
+
 	for _, pfx := range n.pushRoutes {
 		m.routes = append(m.routes, routeEntry{
 			prefix: pfx,

tstest/natlab/natlab_test.go

@@ -46,9 +46,6 @@ func TestSendPacket(t *testing.T) {
 	ifFoo := foo.Attach("eth0", internet)
 	ifBar := bar.Attach("enp0s1", internet)
 
-	t.Logf("foo IP: %v, %v", ifFoo.V4(), ifFoo.V6())
-	t.Logf("bar IP: %v, %v", ifBar.V4(), ifBar.V6())
-
 	fooAddr := netaddr.IPPort{IP: ifFoo.V4(), Port: 123}
 	barAddr := netaddr.IPPort{IP: ifBar.V4(), Port: 456}
 
@@ -79,3 +76,46 @@ func TestSendPacket(t *testing.T) {
 		t.Errorf("addr = %q; want %q", addr, fooAddr)
 	}
 }
+
+func TestLAN(t *testing.T) {
+	// TODO: very duplicate-ey with the previous test, but important
+	// right now to test explicit construction of Networks.
+	lan := Network{
+		Name:    "lan1",
+		Prefix4: mustPrefix("192.168.0.0/24"),
+	}
+
+	foo := NewMachine("foo")
+	bar := NewMachine("bar")
+	ifFoo := foo.Attach("eth0", &lan)
+	ifBar := bar.Attach("eth0", &lan)
+
+	fooPC, err := foo.ListenPacket("udp4", ":123")
+	if err != nil {
+		t.Fatal(err)
+	}
+	barPC, err := bar.ListenPacket("udp4", ":456")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	const msg = "message"
+	barAddr := netaddr.IPPort{IP: ifBar.V4(), Port: 456}
+	if _, err := fooPC.WriteTo([]byte(msg), barAddr.UDPAddr()); err != nil {
+		t.Fatal(err)
+	}
+
+	buf := make([]byte, 1500)
+	n, addr, err := barPC.ReadFrom(buf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	buf = buf[:n]
+	if string(buf) != msg {
+		t.Errorf("read %q; want %q", buf, msg)
+	}
+	fooAddr := netaddr.IPPort{IP: ifFoo.V4(), Port: 123}
+	if addr.String() != fooAddr.String() {
+		t.Errorf("addr = %q; want %q", addr, fooAddr)
+	}
+}