Use tcpip.Subnet in tcpip.Route

This is the first step in replacing some of the redundant types with the
standard library equivalents.

PiperOrigin-RevId: 264706552

pkg/sentry/socket/epsocket/stack.go

@@ -20,7 +20,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/sentry/socket/netfilter"
 	"gvisor.dev/gvisor/pkg/syserr"
-	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/iptables"
 	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
@@ -154,7 +153,7 @@ func (s *Stack) RouteTable() []inet.Route {
 
 	for _, rt := range s.Stack.GetRouteTable() {
 		var family uint8
-		switch len(rt.Destination) {
+		switch len(rt.Destination.ID()) {
 		case header.IPv4AddressSize:
 			family = linux.AF_INET
 		case header.IPv6AddressSize:
@@ -164,14 +163,9 @@ func (s *Stack) RouteTable() []inet.Route {
 			continue
 		}
 
-		dstSubnet, err := tcpip.NewSubnet(rt.Destination, rt.Mask)
-		if err != nil {
-			log.Warningf("Invalid destination & mask in route: %s(%s): %v", rt.Destination, rt.Mask, err)
-			continue
-		}
 		routeTable = append(routeTable, inet.Route{
 			Family: family,
-			DstLen: uint8(dstSubnet.Prefix()), // The CIDR prefix for the destination.
+			DstLen: uint8(rt.Destination.Prefix()), // The CIDR prefix for the destination.
 
 			// Always return unspecified protocol since we have no notion of
 			// protocol for routes.
@@ -182,7 +176,7 @@ func (s *Stack) RouteTable() []inet.Route {
 			Scope: linux.RT_SCOPE_LINK,
 			Type:  linux.RTN_UNICAST,
 
-			DstAddr:         []byte(rt.Destination),
+			DstAddr:         []byte(rt.Destination.ID()),
 			OutputInterface: int32(rt.NIC),
 			GatewayAddr:     []byte(rt.Gateway),
 		})

pkg/tcpip/adapters/gonet/BUILD

@@ -24,6 +24,7 @@ go_test(
     embed = [":gonet"],
     deps = [
         "//pkg/tcpip",
+        "//pkg/tcpip/header",
         "//pkg/tcpip/link/loopback",
         "//pkg/tcpip/network/ipv4",
         "//pkg/tcpip/network/ipv6",

pkg/tcpip/adapters/gonet/gonet_test.go

@@ -26,6 +26,7 @@ import (
 
 	"golang.org/x/net/nettest"
 	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/link/loopback"
 	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
 	"gvisor.dev/gvisor/pkg/tcpip/network/ipv6"
@@ -69,17 +70,13 @@ func newLoopbackStack() (*stack.Stack, *tcpip.Error) {
 	s.SetRouteTable([]tcpip.Route{
 		// IPv4
 		{
-			Destination: tcpip.Address(strings.Repeat("\x00", 4)),
-			Mask:        tcpip.AddressMask(strings.Repeat("\x00", 4)),
-			Gateway:     "",
+			Destination: header.IPv4EmptySubnet,
 			NIC:         NICID,
 		},
 
 		// IPv6
 		{
-			Destination: tcpip.Address(strings.Repeat("\x00", 16)),
-			Mask:        tcpip.AddressMask(strings.Repeat("\x00", 16)),
-			Gateway:     "",
+			Destination: header.IPv6EmptySubnet,
 			NIC:         NICID,
 		},
 	})

pkg/tcpip/header/ipv4.go

@@ -111,6 +111,15 @@ const (
 	IPv4FlagDontFragment
 )
 
+// IPv4EmptySubnet is the empty IPv4 subnet.
+var IPv4EmptySubnet = func() tcpip.Subnet {
+	subnet, err := tcpip.NewSubnet(IPv4Any, tcpip.AddressMask(IPv4Any))
+	if err != nil {
+		panic(err)
+	}
+	return subnet
+}()
+
 // IPVersion returns the version of IP used in the given packet. It returns -1
 // if the packet is not large enough to contain the version field.
 func IPVersion(b []byte) int {

pkg/tcpip/header/ipv6.go

@@ -82,6 +82,15 @@ const (
 	IPv6Any tcpip.Address = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
 )
 
+// IPv6EmptySubnet is the empty IPv6 subnet.
+var IPv6EmptySubnet = func() tcpip.Subnet {
+	subnet, err := tcpip.NewSubnet(IPv6Any, tcpip.AddressMask(IPv6Any))
+	if err != nil {
+		panic(err)
+	}
+	return subnet
+}()
+
 // PayloadLength returns the value of the "payload length" field of the ipv6
 // header.
 func (b IPv6) PayloadLength() uint16 {

pkg/tcpip/network/arp/arp_test.go

@@ -66,9 +66,7 @@ func newTestContext(t *testing.T) *testContext {
 	}
 
 	s.SetRouteTable([]tcpip.Route{{
-		Destination: "\x00\x00\x00\x00",
-		Mask:        "\x00\x00\x00\x00",
-		Gateway:     "",
+		Destination: header.IPv4EmptySubnet,
 		NIC:         1,
 	}})
 

pkg/tcpip/network/ip_test.go

@@ -173,8 +173,7 @@ func buildIPv4Route(local, remote tcpip.Address) (stack.Route, *tcpip.Error) {
 	s.CreateNIC(1, loopback.New())
 	s.AddAddress(1, ipv4.ProtocolNumber, local)
 	s.SetRouteTable([]tcpip.Route{{
-		Destination: ipv4SubnetAddr,
-		Mask:        ipv4SubnetMask,
+		Destination: header.IPv4EmptySubnet,
 		Gateway:     ipv4Gateway,
 		NIC:         1,
 	}})
@@ -187,8 +186,7 @@ func buildIPv6Route(local, remote tcpip.Address) (stack.Route, *tcpip.Error) {
 	s.CreateNIC(1, loopback.New())
 	s.AddAddress(1, ipv6.ProtocolNumber, local)
 	s.SetRouteTable([]tcpip.Route{{
-		Destination: ipv6SubnetAddr,
-		Mask:        ipv6SubnetMask,
+		Destination: header.IPv6EmptySubnet,
 		Gateway:     ipv6Gateway,
 		NIC:         1,
 	}})

pkg/tcpip/network/ipv4/ipv4_test.go

@@ -52,9 +52,7 @@ func TestExcludeBroadcast(t *testing.T) {
 	}
 
 	s.SetRouteTable([]tcpip.Route{{
-		Destination: "\x00\x00\x00\x00",
-		Mask:        "\x00\x00\x00\x00",
-		Gateway:     "",
+		Destination: header.IPv4EmptySubnet,
 		NIC:         1,
 	}})
 
@@ -247,14 +245,22 @@ func buildContext(t *testing.T, packetCollectorErrors []*tcpip.Error, mtu uint32
 	_, linkEP := newErrorChannel(100 /* Enough for all tests. */, mtu, "", packetCollectorErrors)
 	linkEPId := stack.RegisterLinkEndpoint(linkEP)
 	s.CreateNIC(1, linkEPId)
-	s.AddAddress(1, ipv4.ProtocolNumber, "\x10\x00\x00\x01")
-	s.SetRouteTable([]tcpip.Route{{
-		Destination: "\x10\x00\x00\x02",
-		Mask:        "\xff\xff\xff\xff",
-		Gateway:     "",
-		NIC:         1,
-	}})
-	r, err := s.FindRoute(0, "\x10\x00\x00\x01", "\x10\x00\x00\x02", ipv4.ProtocolNumber, false /* multicastLoop */)
+	const (
+		src = "\x10\x00\x00\x01"
+		dst = "\x10\x00\x00\x02"
+	)
+	s.AddAddress(1, ipv4.ProtocolNumber, src)
+	{
+		subnet, err := tcpip.NewSubnet(dst, tcpip.AddressMask(header.IPv4Broadcast))
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{
+			Destination: subnet,
+			NIC:         1,
+		}})
+	}
+	r, err := s.FindRoute(0, src, dst, ipv4.ProtocolNumber, false /* multicastLoop */)
 	if err != nil {
 		t.Fatalf("s.FindRoute got %v, want %v", err, nil)
 	}

pkg/tcpip/network/ipv6/icmp_test.go

@@ -91,13 +91,18 @@ func TestICMPCounts(t *testing.T) {
 			t.Fatalf("AddAddress(_, %d, %s) = %s", ProtocolNumber, lladdr0, err)
 		}
 	}
-	s.SetRouteTable(
-		[]tcpip.Route{{
-			Destination: lladdr1,
-			Mask:        tcpip.AddressMask(strings.Repeat("\xff", 16)),
-			NIC:         1,
-		}},
-	)
+	{
+		subnet, err := tcpip.NewSubnet(lladdr1, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr1))))
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable(
+			[]tcpip.Route{{
+				Destination: subnet,
+				NIC:         1,
+			}},
+		)
+	}
 
 	netProto := s.NetworkProtocolInstance(ProtocolNumber)
 	if netProto == nil {
@@ -237,17 +242,23 @@ func newTestContext(t *testing.T) *testContext {
 		t.Fatalf("AddAddress sn lladdr1: %v", err)
 	}
 
+	subnet0, err := tcpip.NewSubnet(lladdr1, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr1))))
+	if err != nil {
+		t.Fatal(err)
+	}
 	c.s0.SetRouteTable(
 		[]tcpip.Route{{
-			Destination: lladdr1,
-			Mask:        tcpip.AddressMask(strings.Repeat("\xff", 16)),
+			Destination: subnet0,
 			NIC:         1,
 		}},
 	)
+	subnet1, err := tcpip.NewSubnet(lladdr0, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr0))))
+	if err != nil {
+		t.Fatal(err)
+	}
 	c.s1.SetRouteTable(
 		[]tcpip.Route{{
-			Destination: lladdr0,
-			Mask:        tcpip.AddressMask(strings.Repeat("\xff", 16)),
+			Destination: subnet1,
 			NIC:         1,
 		}},
 	)

pkg/tcpip/sample/tun_tcp_connect/BUILD

@@ -8,6 +8,7 @@ go_binary(
     deps = [
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
+        "//pkg/tcpip/header",
         "//pkg/tcpip/link/fdbased",
         "//pkg/tcpip/link/rawfile",
         "//pkg/tcpip/link/sniffer",

pkg/tcpip/sample/tun_tcp_connect/main.go

@@ -52,6 +52,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/link/fdbased"
 	"gvisor.dev/gvisor/pkg/tcpip/link/rawfile"
 	"gvisor.dev/gvisor/pkg/tcpip/link/sniffer"
@@ -152,9 +153,7 @@ func main() {
 	// Add default route.
 	s.SetRouteTable([]tcpip.Route{
 		{
-			Destination: "\x00\x00\x00\x00",
-			Mask:        "\x00\x00\x00\x00",
-			Gateway:     "",
+			Destination: header.IPv4EmptySubnet,
 			NIC:         1,
 		},
 	})

pkg/tcpip/sample/tun_tcp_echo/main.go

@@ -149,12 +149,15 @@ func main() {
 		log.Fatal(err)
 	}
 
+	subnet, err := tcpip.NewSubnet(tcpip.Address(strings.Repeat("\x00", len(addr))), tcpip.AddressMask(strings.Repeat("\x00", len(addr))))
+	if err != nil {
+		log.Fatal(err)
+	}
+
 	// Add default route.
 	s.SetRouteTable([]tcpip.Route{
 		{
-			Destination: tcpip.Address(strings.Repeat("\x00", len(addr))),
-			Mask:        tcpip.AddressMask(strings.Repeat("\x00", len(addr))),
-			Gateway:     "",
+			Destination: subnet,
 			NIC:         1,
 		},
 	})

pkg/tcpip/stack/stack.go

@@ -895,7 +895,7 @@ func (s *Stack) FindRoute(id tcpip.NICID, localAddr, remoteAddr tcpip.Address, n
 		}
 	} else {
 		for _, route := range s.routeTable {
-			if (id != 0 && id != route.NIC) || (len(remoteAddr) != 0 && !route.Match(remoteAddr)) {
+			if (id != 0 && id != route.NIC) || (len(remoteAddr) != 0 && !isBroadcast && !route.Destination.Contains(remoteAddr)) {
 				continue
 			}
 			if nic, ok := s.nics[route.NIC]; ok {

pkg/tcpip/stack/stack_test.go

@@ -312,7 +312,13 @@ func TestNetworkSend(t *testing.T) {
 		t.Fatal("NewNIC failed:", err)
 	}
 
-	s.SetRouteTable([]tcpip.Route{{"\x00", "\x00", "\x00", 1}})
+	{
+		subnet, err := tcpip.NewSubnet("\x00", "\x00")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 1}})
+	}
 
 	if err := s.AddAddress(1, fakeNetNumber, "\x01"); err != nil {
 		t.Fatal("AddAddress failed:", err)
@@ -360,10 +366,20 @@ func TestNetworkSendMultiRoute(t *testing.T) {
 	// Set a route table that sends all packets with odd destination
 	// addresses through the first NIC, and all even destination address
 	// through the second one.
-	s.SetRouteTable([]tcpip.Route{
-		{"\x01", "\x01", "\x00", 1},
-		{"\x00", "\x01", "\x00", 2},
-	})
+	{
+		subnet0, err := tcpip.NewSubnet("\x00", "\x01")
+		if err != nil {
+			t.Fatal(err)
+		}
+		subnet1, err := tcpip.NewSubnet("\x01", "\x01")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{
+			{Destination: subnet1, Gateway: "\x00", NIC: 1},
+			{Destination: subnet0, Gateway: "\x00", NIC: 2},
+		})
+	}
 
 	// Send a packet to an odd destination.
 	sendTo(t, s, "\x05", nil)
@@ -439,10 +455,20 @@ func TestRoutes(t *testing.T) {
 	// Set a route table that sends all packets with odd destination
 	// addresses through the first NIC, and all even destination address
 	// through the second one.
-	s.SetRouteTable([]tcpip.Route{
-		{"\x01", "\x01", "\x00", 1},
-		{"\x00", "\x01", "\x00", 2},
-	})
+	{
+		subnet0, err := tcpip.NewSubnet("\x00", "\x01")
+		if err != nil {
+			t.Fatal(err)
+		}
+		subnet1, err := tcpip.NewSubnet("\x01", "\x01")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{
+			{Destination: subnet1, Gateway: "\x00", NIC: 1},
+			{Destination: subnet0, Gateway: "\x00", NIC: 2},
+		})
+	}
 
 	// Test routes to odd address.
 	testRoute(t, s, 0, "", "\x05", "\x01")
@@ -524,9 +550,13 @@ func TestDelayedRemovalDueToRoute(t *testing.T) {
 		t.Fatal("AddAddress failed:", err)
 	}
 
-	s.SetRouteTable([]tcpip.Route{
-		{"\x00", "\x00", "\x00", 1},
-	})
+	{
+		subnet, err := tcpip.NewSubnet("\x00", "\x00")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 1}})
+	}
 
 	fakeNet := s.NetworkProtocolInstance(fakeNetNumber).(*fakeNetworkProtocol)
 
@@ -583,9 +613,13 @@ func TestPromiscuousMode(t *testing.T) {
 		t.Fatal("CreateNIC failed:", err)
 	}
 
-	s.SetRouteTable([]tcpip.Route{
-		{"\x00", "\x00", "\x00", 1},
-	})
+	{
+		subnet, err := tcpip.NewSubnet("\x00", "\x00")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 1}})
+	}
 
 	fakeNet := s.NetworkProtocolInstance(fakeNetNumber).(*fakeNetworkProtocol)
 
@@ -643,9 +677,13 @@ func TestAddressSpoofing(t *testing.T) {
 		t.Fatal("AddAddress failed:", err)
 	}
 
-	s.SetRouteTable([]tcpip.Route{
-		{"\x00", "\x00", "\x00", 1},
-	})
+	{
+		subnet, err := tcpip.NewSubnet("\x00", "\x00")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 1}})
+	}
 
 	// With address spoofing disabled, FindRoute does not permit an address
 	// that was not added to the NIC to be used as the source.
@@ -806,9 +844,13 @@ func TestSubnetAcceptsMatchingPacket(t *testing.T) {
 		t.Fatal("CreateNIC failed:", err)
 	}
 
-	s.SetRouteTable([]tcpip.Route{
-		{"\x00", "\x00", "\x00", 1},
-	})
+	{
+		subnet, err := tcpip.NewSubnet("\x00", "\x00")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 1}})
+	}
 
 	fakeNet := s.NetworkProtocolInstance(fakeNetNumber).(*fakeNetworkProtocol)
 
@@ -840,9 +882,13 @@ func TestCheckLocalAddressForSubnet(t *testing.T) {
 		t.Fatal("CreateNIC failed:", err)
 	}
 
-	s.SetRouteTable([]tcpip.Route{
-		{"\x00", "\x00", "\x00", nicID}, // default route
-	})
+	{
+		subnet, err := tcpip.NewSubnet("\x00", "\x00")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: nicID}})
+	}
 
 	subnet, err := tcpip.NewSubnet(tcpip.Address("\xa0"), tcpip.AddressMask("\xf0"))
 
@@ -854,7 +900,7 @@ func TestCheckLocalAddressForSubnet(t *testing.T) {
 	}
 
 	// Loop over all subnet addresses and check them.
-	numOfAddresses := (1 << uint((8 - subnet.Prefix())))
+	numOfAddresses := 1 << uint(8-subnet.Prefix())
 	if numOfAddresses < 1 || numOfAddresses > 255 {
 		t.Fatalf("got numOfAddresses = %d, want = [1 .. 255] (subnet=%s)", numOfAddresses, subnet)
 	}
@@ -881,9 +927,13 @@ func TestSubnetRejectsNonmatchingPacket(t *testing.T) {
 		t.Fatal("CreateNIC failed:", err)
 	}
 
-	s.SetRouteTable([]tcpip.Route{
-		{"\x00", "\x00", "\x00", 1},
-	})
+	{
+		subnet, err := tcpip.NewSubnet("\x00", "\x00")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 1}})
+	}
 
 	fakeNet := s.NetworkProtocolInstance(fakeNetNumber).(*fakeNetworkProtocol)
 
@@ -1261,9 +1311,13 @@ func TestNICStats(t *testing.T) {
 		t.Fatal("AddAddress failed:", err)
 	}
 	// Route all packets for address \x01 to NIC 1.
-	s.SetRouteTable([]tcpip.Route{
-		{"\x01", "\xff", "\x00", 1},
-	})
+	{
+		subnet, err := tcpip.NewSubnet("\x01", "\xff")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 1}})
+	}
 
 	// Send a packet to address 1.
 	buf := buffer.NewView(30)
@@ -1312,9 +1366,13 @@ func TestNICForwarding(t *testing.T) {
 	}
 
 	// Route all packets to address 3 to NIC 2.
-	s.SetRouteTable([]tcpip.Route{
-		{"\x03", "\xff", "\x00", 2},
-	})
+	{
+		subnet, err := tcpip.NewSubnet("\x03", "\xff")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 2}})
+	}
 
 	// Send a packet to address 3.
 	buf := buffer.NewView(30)

pkg/tcpip/stack/transport_test.go

@@ -284,7 +284,13 @@ func TestTransportReceive(t *testing.T) {
 		t.Fatalf("CreateNIC failed: %v", err)
 	}
 
-	s.SetRouteTable([]tcpip.Route{{"\x00", "\x00", "\x00", 1}})
+	{
+		subnet, err := tcpip.NewSubnet("\x00", "\x00")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 1}})
+	}
 
 	if err := s.AddAddress(1, fakeNetNumber, "\x01"); err != nil {
 		t.Fatalf("AddAddress failed: %v", err)
@@ -340,7 +346,13 @@ func TestTransportControlReceive(t *testing.T) {
 		t.Fatalf("CreateNIC failed: %v", err)
 	}
 
-	s.SetRouteTable([]tcpip.Route{{"\x00", "\x00", "\x00", 1}})
+	{
+		subnet, err := tcpip.NewSubnet("\x00", "\x00")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 1}})
+	}
 
 	if err := s.AddAddress(1, fakeNetNumber, "\x01"); err != nil {
 		t.Fatalf("AddAddress failed: %v", err)
@@ -406,7 +418,13 @@ func TestTransportSend(t *testing.T) {
 		t.Fatalf("AddAddress failed: %v", err)
 	}
 
-	s.SetRouteTable([]tcpip.Route{{"\x00", "\x00", "\x00", 1}})
+	{
+		subnet, err := tcpip.NewSubnet("\x00", "\x00")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{{Destination: subnet, Gateway: "\x00", NIC: 1}})
+	}
 
 	// Create endpoint and bind it.
 	wq := waiter.Queue{}
@@ -497,10 +515,20 @@ func TestTransportForwarding(t *testing.T) {
 
 	// Route all packets to address 3 to NIC 2 and all packets to address
 	// 1 to NIC 1.
-	s.SetRouteTable([]tcpip.Route{
-		{"\x03", "\xff", "\x00", 2},
-		{"\x01", "\xff", "\x00", 1},
-	})
+	{
+		subnet0, err := tcpip.NewSubnet("\x03", "\xff")
+		if err != nil {
+			t.Fatal(err)
+		}
+		subnet1, err := tcpip.NewSubnet("\x01", "\xff")
+		if err != nil {
+			t.Fatal(err)
+		}
+		s.SetRouteTable([]tcpip.Route{
+			{Destination: subnet0, Gateway: "\x00", NIC: 2},
+			{Destination: subnet1, Gateway: "\x00", NIC: 1},
+		})
+	}
 
 	wq := waiter.Queue{}
 	ep, err := s.NewEndpoint(fakeTransNumber, fakeNetNumber, &wq)

pkg/tcpip/tcpip.go

@@ -205,16 +205,8 @@ func (s *Subnet) ID() Address {
 // Bits returns the number of ones (network bits) and zeros (host bits) in the
 // subnet mask.
 func (s *Subnet) Bits() (ones int, zeros int) {
-	for _, b := range []byte(s.mask) {
-		for i := uint(0); i < 8; i++ {
-			if b&(1<<i) == 0 {
-				zeros++
-			} else {
-				ones++
-			}
-		}
-	}
-	return
+	ones = s.mask.Prefix()
+	return ones, len(s.mask)*8 - ones
 }
 
 // Prefix returns the number of bits before the first host bit.
@@ -578,13 +570,8 @@ type BroadcastOption int
 // gateway) sets of packets should be routed. A row is considered viable if the
 // masked target address matches the destination address in the row.
 type Route struct {
-	// Destination is the address that must be matched against the masked
-	// target address to check if this row is viable.
-	Destination Address
-
-	// Mask specifies which bits of the Destination and the target address
-	// must match for this row to be viable.
-	Mask AddressMask
+	// Destination must contain the target address for this row to be viable.
+	Destination Subnet
 
 	// Gateway is the gateway to be used if this row is viable.
 	Gateway Address
@@ -596,7 +583,7 @@ type Route struct {
 // String implements the fmt.Stringer interface.
 func (r *Route) String() string {
 	var out strings.Builder
-	fmt.Fprintf(&out, "%s/%d", r.Destination, r.Mask.Prefix())
+	fmt.Fprintf(&out, "%s", r.Destination)
 	if len(r.Gateway) > 0 {
 		fmt.Fprintf(&out, " via %s", r.Gateway)
 	}
@@ -604,27 +591,6 @@ func (r *Route) String() string {
 	return out.String()
 }
 
-// Match determines if r is viable for the given destination address.
-func (r *Route) Match(addr Address) bool {
-	if len(addr) != len(r.Destination) {
-		return false
-	}
-
-	// Using header.Ipv4Broadcast would introduce an import cycle, so
-	// we'll use a literal instead.
-	if addr == "\xff\xff\xff\xff" {
-		return true
-	}
-
-	for i := 0; i < len(r.Destination); i++ {
-		if (addr[i] & r.Mask[i]) != r.Destination[i] {
-			return false
-		}
-	}
-
-	return true
-}
-
 // LinkEndpointID represents a data link layer endpoint.
 type LinkEndpointID uint64
 

pkg/tcpip/tcpip_test.go

@@ -60,12 +60,12 @@ func TestSubnetBits(t *testing.T) {
 	}{
 		{"\x00", 0, 8},
 		{"\x00\x00", 0, 16},
-		{"\x36", 4, 4},
-		{"\x5c", 4, 4},
-		{"\x5c\x5c", 8, 8},
-		{"\x5c\x36", 8, 8},
-		{"\x36\x5c", 8, 8},
-		{"\x36\x36", 8, 8},
+		{"\x36", 0, 8},
+		{"\x5c", 0, 8},
+		{"\x5c\x5c", 0, 16},
+		{"\x5c\x36", 0, 16},
+		{"\x36\x5c", 0, 16},
+		{"\x36\x36", 0, 16},
 		{"\xff", 8, 0},
 		{"\xff\xff", 16, 0},
 	}
@@ -122,26 +122,6 @@ func TestSubnetCreation(t *testing.T) {
 	}
 }
 
-func TestRouteMatch(t *testing.T) {
-	tests := []struct {
-		d    Address
-		m    AddressMask
-		a    Address
-		want bool
-	}{
-		{"\xc2\x80", "\xff\xf0", "\xc2\x80", true},
-		{"\xc2\x80", "\xff\xf0", "\xc2\x00", false},
-		{"\xc2\x00", "\xff\xf0", "\xc2\x00", true},
-		{"\xc2\x00", "\xff\xf0", "\xc2\x80", false},
-	}
-	for _, tt := range tests {
-		r := Route{Destination: tt.d, Mask: tt.m}
-		if got := r.Match(tt.a); got != tt.want {
-			t.Errorf("Route(%v).Match(%v) = %v, want %v", r, tt.a, got, tt.want)
-		}
-	}
-}
-
 func TestAddressString(t *testing.T) {
 	for _, want := range []string{
 		// Taken from stdlib.

pkg/tcpip/transport/tcp/endpoint.go

@@ -1348,7 +1348,7 @@ func (e *endpoint) checkV4Mapped(addr *tcpip.FullAddress) (tcpip.NetworkProtocol
 
 		netProto = header.IPv4ProtocolNumber
 		addr.Addr = addr.Addr[header.IPv6AddressSize-header.IPv4AddressSize:]
-		if addr.Addr == "\x00\x00\x00\x00" {
+		if addr.Addr == header.IPv4Any {
 			addr.Addr = ""
 		}
 	}

pkg/tcpip/transport/tcp/tcp_test.go

@@ -2874,15 +2874,11 @@ func makeStack() (*stack.Stack, *tcpip.Error) {
 
 	s.SetRouteTable([]tcpip.Route{
 		{
-			Destination: "\x00\x00\x00\x00",
-			Mask:        "\x00\x00\x00\x00",
-			Gateway:     "",
+			Destination: header.IPv4EmptySubnet,
 			NIC:         1,
 		},
 		{
-			Destination: "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
-			Mask:        "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
-			Gateway:     "",
+			Destination: header.IPv6EmptySubnet,
 			NIC:         1,
 		},
 	})

pkg/tcpip/transport/tcp/testing/context/context.go

@@ -168,15 +168,11 @@ func New(t *testing.T, mtu uint32) *Context {
 
 	s.SetRouteTable([]tcpip.Route{
 		{
-			Destination: "\x00\x00\x00\x00",
-			Mask:        "\x00\x00\x00\x00",
-			Gateway:     "",
+			Destination: header.IPv4EmptySubnet,
 			NIC:         1,
 		},
 		{
-			Destination: "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
-			Mask:        "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
-			Gateway:     "",
+			Destination: header.IPv6EmptySubnet,
 			NIC:         1,
 		},
 	})