Add POLLRDNORM/POLLWRNORM support.

On Linux these are meant to be equivalent to POLLIN/POLLOUT. Rather
than hack these on in sys_poll etc it felt cleaner to just cleanup
the call sites to notify for both events. This is what linux does
as well.

Fixes #5544

PiperOrigin-RevId: 364859977

26 files changed, 122 insertions, 122 deletions

diff --git a/pkg/tcpip/adapters/gonet/gonet.go b/pkg/tcpip/adapters/gonet/gonet.go
index c188aaa18..010e2e833 100644
--- a/pkg/tcpip/adapters/gonet/gonet.go
+++ b/pkg/tcpip/adapters/gonet/gonet.go
@@ -251,7 +251,7 @@ func (l *TCPListener) Accept() (net.Conn, error) {
 	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Create wait queue entry that notifies a channel.
 		waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-		l.wq.EventRegister(&waitEntry, waiter.EventIn)
+		l.wq.EventRegister(&waitEntry, waiter.ReadableEvents)
 		defer l.wq.EventUnregister(&waitEntry)
 
 		for {
@@ -301,7 +301,7 @@ func commonRead(b []byte, ep tcpip.Endpoint, wq *waiter.Queue, deadline <-chan s
 	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Create wait queue entry that notifies a channel.
 		waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-		wq.EventRegister(&waitEntry, waiter.EventIn)
+		wq.EventRegister(&waitEntry, waiter.ReadableEvents)
 		defer wq.EventUnregister(&waitEntry)
 		for {
 			res, err = ep.Read(&w, opts)
@@ -382,7 +382,7 @@ func (c *TCPConn) Write(b []byte) (int, error) {
 			if ch == nil {
 				entry, ch = waiter.NewChannelEntry(nil)
 
-				c.wq.EventRegister(&entry, waiter.EventOut)
+				c.wq.EventRegister(&entry, waiter.WritableEvents)
 				defer c.wq.EventUnregister(&entry)
 			} else {
 				// Don't wait immediately after registration in case more data
@@ -485,7 +485,7 @@ func DialContextTCP(ctx context.Context, s *stack.Stack, addr tcpip.FullAddress,
 	//
 	// We do this unconditionally as Connect will always return an error.
 	waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&waitEntry, waiter.EventOut)
+	wq.EventRegister(&waitEntry, waiter.WritableEvents)
 	defer wq.EventUnregister(&waitEntry)
 
 	select {
@@ -652,7 +652,7 @@ func (c *UDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
 	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Create wait queue entry that notifies a channel.
 		waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-		c.wq.EventRegister(&waitEntry, waiter.EventOut)
+		c.wq.EventRegister(&waitEntry, waiter.WritableEvents)
 		defer c.wq.EventUnregister(&waitEntry)
 		for {
 			select {
diff --git a/pkg/tcpip/adapters/gonet/gonet_test.go b/pkg/tcpip/adapters/gonet/gonet_test.go
index 2b3ea4bdf..48b24692b 100644
--- a/pkg/tcpip/adapters/gonet/gonet_test.go
+++ b/pkg/tcpip/adapters/gonet/gonet_test.go
@@ -102,7 +102,7 @@ func connect(s *stack.Stack, addr tcpip.FullAddress) (*testConnection, tcpip.Err
 	}
 
 	entry, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&entry, waiter.EventOut)
+	wq.EventRegister(&entry, waiter.WritableEvents)
 
 	err = ep.Connect(addr)
 	if _, ok := err.(*tcpip.ErrConnectStarted); ok {
@@ -114,7 +114,7 @@ func connect(s *stack.Stack, addr tcpip.FullAddress) (*testConnection, tcpip.Err
 	}
 
 	wq.EventUnregister(&entry)
-	wq.EventRegister(&entry, waiter.EventIn)
+	wq.EventRegister(&entry, waiter.ReadableEvents)
 
 	return &testConnection{wq, &entry, ch, ep}, nil
 }
diff --git a/pkg/tcpip/link/tun/device.go b/pkg/tcpip/link/tun/device.go
index 80fb343c5..36af2a029 100644
--- a/pkg/tcpip/link/tun/device.go
+++ b/pkg/tcpip/link/tun/device.go
@@ -309,20 +309,20 @@ func (d *Device) Flags() Flags {
 
 // Readiness implements watier.Waitable.Readiness.
 func (d *Device) Readiness(mask waiter.EventMask) waiter.EventMask {
-	if mask&waiter.EventIn != 0 {
+	if mask&waiter.ReadableEvents != 0 {
 		d.mu.RLock()
 		endpoint := d.endpoint
 		d.mu.RUnlock()
 		if endpoint != nil && endpoint.NumQueued() == 0 {
-			mask &= ^waiter.EventIn
+			mask &= ^waiter.ReadableEvents
 		}
 	}
-	return mask & (waiter.EventIn | waiter.EventOut)
+	return mask & (waiter.ReadableEvents | waiter.WritableEvents)
 }
 
 // WriteNotify implements channel.Notification.WriteNotify.
 func (d *Device) WriteNotify() {
-	d.Notify(waiter.EventIn)
+	d.Notify(waiter.ReadableEvents)
 }
 
 // tunEndpoint is the link endpoint for the NIC created by the tun device.
diff --git a/pkg/tcpip/network/ipv4/ipv4_test.go b/pkg/tcpip/network/ipv4/ipv4_test.go
index cfed241bf..eba91c68c 100644
--- a/pkg/tcpip/network/ipv4/ipv4_test.go
+++ b/pkg/tcpip/network/ipv4/ipv4_test.go
@@ -2514,7 +2514,7 @@ func TestReceiveFragments(t *testing.T) {
 
 			wq := waiter.Queue{}
 			we, ch := waiter.NewChannelEntry(nil)
-			wq.EventRegister(&we, waiter.EventIn)
+			wq.EventRegister(&we, waiter.ReadableEvents)
 			defer wq.EventUnregister(&we)
 			defer close(ch)
 			ep, err := s.NewEndpoint(udp.ProtocolNumber, header.IPv4ProtocolNumber, &wq)
diff --git a/pkg/tcpip/network/ipv6/ipv6_test.go b/pkg/tcpip/network/ipv6/ipv6_test.go
index 81f5f23c3..c206cebeb 100644
--- a/pkg/tcpip/network/ipv6/ipv6_test.go
+++ b/pkg/tcpip/network/ipv6/ipv6_test.go
@@ -101,7 +101,7 @@ func testReceiveUDP(t *testing.T, s *stack.Stack, e *channel.Endpoint, src, dst
 
 	wq := waiter.Queue{}
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 	defer close(ch)
 
@@ -912,7 +912,7 @@ func TestReceiveIPv6ExtHdrs(t *testing.T) {
 
 			wq := waiter.Queue{}
 			we, ch := waiter.NewChannelEntry(nil)
-			wq.EventRegister(&we, waiter.EventIn)
+			wq.EventRegister(&we, waiter.WritableEvents)
 			defer wq.EventUnregister(&we)
 			defer close(ch)
 			ep, err := s.NewEndpoint(udp.ProtocolNumber, ProtocolNumber, &wq)
@@ -1998,7 +1998,7 @@ func TestReceiveIPv6Fragments(t *testing.T) {
 
 			wq := waiter.Queue{}
 			we, ch := waiter.NewChannelEntry(nil)
-			wq.EventRegister(&we, waiter.EventIn)
+			wq.EventRegister(&we, waiter.ReadableEvents)
 			defer wq.EventUnregister(&we)
 			defer close(ch)
 			ep, err := s.NewEndpoint(udp.ProtocolNumber, ProtocolNumber, &wq)
diff --git a/pkg/tcpip/sample/tun_tcp_connect/main.go b/pkg/tcpip/sample/tun_tcp_connect/main.go
index 856ea998d..b9a24ff56 100644
--- a/pkg/tcpip/sample/tun_tcp_connect/main.go
+++ b/pkg/tcpip/sample/tun_tcp_connect/main.go
@@ -173,7 +173,7 @@ func main() {
 
 	// Issue connect request and wait for it to complete.
 	waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&waitEntry, waiter.EventOut)
+	wq.EventRegister(&waitEntry, waiter.WritableEvents)
 	terr := ep.Connect(remote)
 	if _, ok := terr.(*tcpip.ErrConnectStarted); ok {
 		fmt.Println("Connect is pending...")
@@ -194,7 +194,7 @@ func main() {
 
 	// Read data and write to standard output until the peer closes the
 	// connection from its side.
-	wq.EventRegister(&waitEntry, waiter.EventIn)
+	wq.EventRegister(&waitEntry, waiter.ReadableEvents)
 	for {
 		_, err := ep.Read(os.Stdout, tcpip.ReadOptions{})
 		if err != nil {
diff --git a/pkg/tcpip/sample/tun_tcp_echo/main.go b/pkg/tcpip/sample/tun_tcp_echo/main.go
index 9b23df3a9..ef1bfc186 100644
--- a/pkg/tcpip/sample/tun_tcp_echo/main.go
+++ b/pkg/tcpip/sample/tun_tcp_echo/main.go
@@ -79,7 +79,7 @@ func echo(wq *waiter.Queue, ep tcpip.Endpoint) {
 	// Create wait queue entry that notifies a channel.
 	waitEntry, notifyCh := waiter.NewChannelEntry(nil)
 
-	wq.EventRegister(&waitEntry, waiter.EventIn)
+	wq.EventRegister(&waitEntry, waiter.ReadableEvents)
 	defer wq.EventUnregister(&waitEntry)
 
 	w := endpointWriter{
@@ -211,7 +211,7 @@ func main() {
 
 	// Wait for connections to appear.
 	waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&waitEntry, waiter.EventIn)
+	wq.EventRegister(&waitEntry, waiter.ReadableEvents)
 	defer wq.EventUnregister(&waitEntry)
 
 	for {
diff --git a/pkg/tcpip/stack/ndp_test.go b/pkg/tcpip/stack/ndp_test.go
index 0725e028b..14124ae66 100644
--- a/pkg/tcpip/stack/ndp_test.go
+++ b/pkg/tcpip/stack/ndp_test.go
@@ -2909,7 +2909,7 @@ func addrForNewConnectionTo(t *testing.T, s *stack.Stack, addr tcpip.FullAddress
 
 	wq := waiter.Queue{}
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 	defer close(ch)
 	ep, err := s.NewEndpoint(header.UDPProtocolNumber, header.IPv6ProtocolNumber, &wq)
@@ -2943,7 +2943,7 @@ func addrForNewConnectionWithAddr(t *testing.T, s *stack.Stack, addr tcpip.FullA
 
 	wq := waiter.Queue{}
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 	defer close(ch)
 	ep, err := s.NewEndpoint(header.UDPProtocolNumber, header.IPv6ProtocolNumber, &wq)
@@ -3272,7 +3272,7 @@ func TestAutoGenAddrJobDeprecation(t *testing.T) {
 	}
 	wq := waiter.Queue{}
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 	defer close(ch)
 	ep, err := s.NewEndpoint(header.UDPProtocolNumber, header.IPv6ProtocolNumber, &wq)
diff --git a/pkg/tcpip/stack/transport_demuxer_test.go b/pkg/tcpip/stack/transport_demuxer_test.go
index c1c6cbccd..4848495c9 100644
--- a/pkg/tcpip/stack/transport_demuxer_test.go
+++ b/pkg/tcpip/stack/transport_demuxer_test.go
@@ -290,7 +290,7 @@ func TestBindToDeviceDistribution(t *testing.T) {
 						// Try to receive the data.
 						wq := waiter.Queue{}
 						we, ch := waiter.NewChannelEntry(nil)
-						wq.EventRegister(&we, waiter.EventIn)
+						wq.EventRegister(&we, waiter.ReadableEvents)
 						defer wq.EventUnregister(&we)
 						defer close(ch)
 
diff --git a/pkg/tcpip/tests/integration/forward_test.go b/pkg/tcpip/tests/integration/forward_test.go
index 38c2f321b..d10ae05c2 100644
--- a/pkg/tcpip/tests/integration/forward_test.go
+++ b/pkg/tcpip/tests/integration/forward_test.go
@@ -48,7 +48,7 @@ func TestForwarding(t *testing.T) {
 		t.Helper()
 		var wq waiter.Queue
 		we, ch := waiter.NewChannelEntry(nil)
-		wq.EventRegister(&we, waiter.EventIn)
+		wq.EventRegister(&we, waiter.ReadableEvents)
 		ep, err := s.NewEndpoint(transProto, netProto, &wq)
 		if err != nil {
 			t.Fatalf("s.NewEndpoint(%d, %d, _): %s", transProto, netProto, err)
@@ -184,7 +184,7 @@ func TestForwarding(t *testing.T) {
 					}
 
 					we, newCH := waiter.NewChannelEntry(nil)
-					wq.EventRegister(&we, waiter.EventIn)
+					wq.EventRegister(&we, waiter.ReadableEvents)
 					return newEP, newCH
 				}
 			},
diff --git a/pkg/tcpip/tests/integration/link_resolution_test.go b/pkg/tcpip/tests/integration/link_resolution_test.go
index 095623789..d39809e1c 100644
--- a/pkg/tcpip/tests/integration/link_resolution_test.go
+++ b/pkg/tcpip/tests/integration/link_resolution_test.go
@@ -151,7 +151,7 @@ func TestPing(t *testing.T) {
 
 			var wq waiter.Queue
 			we, waiterCH := waiter.NewChannelEntry(nil)
-			wq.EventRegister(&we, waiter.EventIn)
+			wq.EventRegister(&we, waiter.ReadableEvents)
 			ep, err := host1Stack.NewEndpoint(test.transProto, test.netProto, &wq)
 			if err != nil {
 				t.Fatalf("host1Stack.NewEndpoint(%d, %d, _): %s", test.transProto, test.netProto, err)
@@ -308,7 +308,7 @@ func TestTCPLinkResolutionFailure(t *testing.T) {
 
 			var clientWQ waiter.Queue
 			we, ch := waiter.NewChannelEntry(nil)
-			clientWQ.EventRegister(&we, waiter.EventOut|waiter.EventErr)
+			clientWQ.EventRegister(&we, waiter.WritableEvents|waiter.EventErr)
 			clientEP, err := host1Stack.NewEndpoint(tcp.ProtocolNumber, test.netProto, &clientWQ)
 			if err != nil {
 				t.Fatalf("host1Stack.NewEndpoint(%d, %d, _): %s", tcp.ProtocolNumber, test.netProto, err)
@@ -641,7 +641,7 @@ func TestWritePacketsLinkResolution(t *testing.T) {
 
 			var serverWQ waiter.Queue
 			serverWE, serverCH := waiter.NewChannelEntry(nil)
-			serverWQ.EventRegister(&serverWE, waiter.EventIn)
+			serverWQ.EventRegister(&serverWE, waiter.ReadableEvents)
 			serverEP, err := host2Stack.NewEndpoint(udp.ProtocolNumber, test.netProto, &serverWQ)
 			if err != nil {
 				t.Fatalf("host2Stack.NewEndpoint(%d, %d, _): %s", udp.ProtocolNumber, test.netProto, err)
@@ -821,7 +821,7 @@ func TestTCPConfirmNeighborReachability(t *testing.T) {
 
 				var clientWQ waiter.Queue
 				clientWE, clientCH := waiter.NewChannelEntry(nil)
-				clientWQ.EventRegister(&clientWE, waiter.EventOut)
+				clientWQ.EventRegister(&clientWE, waiter.WritableEvents)
 				clientEP, err := host1Stack.NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &clientWQ)
 				if err != nil {
 					listenerEP.Close()
@@ -845,7 +845,7 @@ func TestTCPConfirmNeighborReachability(t *testing.T) {
 
 				var clientWQ waiter.Queue
 				clientWE, clientCH := waiter.NewChannelEntry(nil)
-				clientWQ.EventRegister(&clientWE, waiter.EventOut)
+				clientWQ.EventRegister(&clientWE, waiter.WritableEvents)
 				clientEP, err := host1Stack.NewEndpoint(tcp.ProtocolNumber, ipv6.ProtocolNumber, &clientWQ)
 				if err != nil {
 					listenerEP.Close()
@@ -869,7 +869,7 @@ func TestTCPConfirmNeighborReachability(t *testing.T) {
 
 				var clientWQ waiter.Queue
 				clientWE, clientCH := waiter.NewChannelEntry(nil)
-				clientWQ.EventRegister(&clientWE, waiter.EventOut)
+				clientWQ.EventRegister(&clientWE, waiter.WritableEvents)
 				clientEP, err := host1Stack.NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &clientWQ)
 				if err != nil {
 					listenerEP.Close()
@@ -893,7 +893,7 @@ func TestTCPConfirmNeighborReachability(t *testing.T) {
 
 				var clientWQ waiter.Queue
 				clientWE, clientCH := waiter.NewChannelEntry(nil)
-				clientWQ.EventRegister(&clientWE, waiter.EventOut)
+				clientWQ.EventRegister(&clientWE, waiter.WritableEvents)
 				clientEP, err := host1Stack.NewEndpoint(tcp.ProtocolNumber, ipv6.ProtocolNumber, &clientWQ)
 				if err != nil {
 					listenerEP.Close()
@@ -917,7 +917,7 @@ func TestTCPConfirmNeighborReachability(t *testing.T) {
 
 				var clientWQ waiter.Queue
 				clientWE, clientCH := waiter.NewChannelEntry(nil)
-				clientWQ.EventRegister(&clientWE, waiter.EventOut)
+				clientWQ.EventRegister(&clientWE, waiter.WritableEvents)
 				clientEP, err := routerStack.NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &clientWQ)
 				if err != nil {
 					listenerEP.Close()
@@ -942,7 +942,7 @@ func TestTCPConfirmNeighborReachability(t *testing.T) {
 
 				var clientWQ waiter.Queue
 				clientWE, clientCH := waiter.NewChannelEntry(nil)
-				clientWQ.EventRegister(&clientWE, waiter.EventOut)
+				clientWQ.EventRegister(&clientWE, waiter.WritableEvents)
 				clientEP, err := routerStack.NewEndpoint(tcp.ProtocolNumber, ipv6.ProtocolNumber, &clientWQ)
 				if err != nil {
 					listenerEP.Close()
@@ -967,7 +967,7 @@ func TestTCPConfirmNeighborReachability(t *testing.T) {
 
 				var clientWQ waiter.Queue
 				clientWE, clientCH := waiter.NewChannelEntry(nil)
-				clientWQ.EventRegister(&clientWE, waiter.EventOut)
+				clientWQ.EventRegister(&clientWE, waiter.WritableEvents)
 				clientEP, err := host2Stack.NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &clientWQ)
 				if err != nil {
 					listenerEP.Close()
@@ -992,7 +992,7 @@ func TestTCPConfirmNeighborReachability(t *testing.T) {
 
 				var clientWQ waiter.Queue
 				clientWE, clientCH := waiter.NewChannelEntry(nil)
-				clientWQ.EventRegister(&clientWE, waiter.EventOut)
+				clientWQ.EventRegister(&clientWE, waiter.WritableEvents)
 				clientEP, err := host2Stack.NewEndpoint(tcp.ProtocolNumber, ipv6.ProtocolNumber, &clientWQ)
 				if err != nil {
 					listenerEP.Close()
diff --git a/pkg/tcpip/tests/integration/loopback_test.go b/pkg/tcpip/tests/integration/loopback_test.go
index 6462e9d42..2c538a43e 100644
--- a/pkg/tcpip/tests/integration/loopback_test.go
+++ b/pkg/tcpip/tests/integration/loopback_test.go
@@ -449,7 +449,7 @@ func TestLoopbackAcceptAllInSubnetTCP(t *testing.T) {
 
 			var wq waiter.Queue
 			we, ch := waiter.NewChannelEntry(nil)
-			wq.EventRegister(&we, waiter.EventIn)
+			wq.EventRegister(&we, waiter.ReadableEvents)
 			defer wq.EventUnregister(&we)
 			listeningEndpoint, err := s.NewEndpoint(tcp.ProtocolNumber, test.addAddress.Protocol, &wq)
 			if err != nil {
diff --git a/pkg/tcpip/tests/integration/multicast_broadcast_test.go b/pkg/tcpip/tests/integration/multicast_broadcast_test.go
index 77f4a88ec..c6a9c2393 100644
--- a/pkg/tcpip/tests/integration/multicast_broadcast_test.go
+++ b/pkg/tcpip/tests/integration/multicast_broadcast_test.go
@@ -498,7 +498,7 @@ func TestReuseAddrAndBroadcast(t *testing.T) {
 				for i := 0; i < 2; i++ {
 					var wq waiter.Queue
 					we, ch := waiter.NewChannelEntry(nil)
-					wq.EventRegister(&we, waiter.EventIn)
+					wq.EventRegister(&we, waiter.ReadableEvents)
 					ep, err := s.NewEndpoint(udp.ProtocolNumber, ipv4.ProtocolNumber, &wq)
 					if err != nil {
 						t.Fatalf("(eps[%d]) NewEndpoint(%d, %d, _): %s", len(eps), udp.ProtocolNumber, ipv4.ProtocolNumber, err)
diff --git a/pkg/tcpip/tests/integration/route_test.go b/pkg/tcpip/tests/integration/route_test.go
index ed499179f..78244f4eb 100644
--- a/pkg/tcpip/tests/integration/route_test.go
+++ b/pkg/tcpip/tests/integration/route_test.go
@@ -189,7 +189,7 @@ func TestLocalPing(t *testing.T) {
 
 					var wq waiter.Queue
 					we, ch := waiter.NewChannelEntry(nil)
-					wq.EventRegister(&we, waiter.EventIn)
+					wq.EventRegister(&we, waiter.ReadableEvents)
 					ep, err := s.NewEndpoint(test.transProto, test.netProto, &wq)
 					if err != nil {
 						t.Fatalf("s.NewEndpoint(%d, %d, _): %s", test.transProto, test.netProto, err)
@@ -311,7 +311,7 @@ func TestLocalUDP(t *testing.T) {
 
 					var serverWQ waiter.Queue
 					serverWE, serverCH := waiter.NewChannelEntry(nil)
-					serverWQ.EventRegister(&serverWE, waiter.EventIn)
+					serverWQ.EventRegister(&serverWE, waiter.ReadableEvents)
 					server, err := s.NewEndpoint(udp.ProtocolNumber, test.firstPrimaryAddr.Protocol, &serverWQ)
 					if err != nil {
 						t.Fatalf("s.NewEndpoint(%d, %d): %s", udp.ProtocolNumber, test.firstPrimaryAddr.Protocol, err)
@@ -325,7 +325,7 @@ func TestLocalUDP(t *testing.T) {
 
 					var clientWQ waiter.Queue
 					clientWE, clientCH := waiter.NewChannelEntry(nil)
-					clientWQ.EventRegister(&clientWE, waiter.EventIn)
+					clientWQ.EventRegister(&clientWE, waiter.ReadableEvents)
 					client, err := s.NewEndpoint(udp.ProtocolNumber, test.firstPrimaryAddr.Protocol, &clientWQ)
 					if err != nil {
 						t.Fatalf("s.NewEndpoint(%d, %d): %s", udp.ProtocolNumber, test.firstPrimaryAddr.Protocol, err)
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index 1dce35c63..50991c3c0 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -149,7 +149,7 @@ func (e *endpoint) Close() {
 
 	e.mu.Unlock()
 
-	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.ReadableEvents | waiter.WritableEvents)
 }
 
 // ModerateRecvBuf implements tcpip.Endpoint.ModerateRecvBuf.
@@ -588,7 +588,7 @@ func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
 		e.rcvMu.Unlock()
 
 		if !wasClosed {
-			e.waiterQueue.Notify(waiter.EventIn)
+			e.waiterQueue.Notify(waiter.ReadableEvents)
 		}
 	}
 
@@ -725,13 +725,13 @@ func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 // waiter.EventIn is set, the endpoint is immediately readable.
 func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 	// The endpoint is always writable.
-	result := waiter.EventOut & mask
+	result := waiter.WritableEvents & mask
 
 	// Determine if the endpoint is readable if requested.
-	if (mask & waiter.EventIn) != 0 {
+	if (mask & waiter.ReadableEvents) != 0 {
 		e.rcvMu.Lock()
 		if !e.rcvList.Empty() || e.rcvClosed {
-			result |= waiter.EventIn
+			result |= waiter.ReadableEvents
 		}
 		e.rcvMu.Unlock()
 	}
@@ -804,7 +804,7 @@ func (e *endpoint) HandlePacket(id stack.TransportEndpointID, pkt *stack.PacketB
 	e.stats.PacketsReceived.Increment()
 	// Notify any waiters that there's data to be read now.
 	if wasEmpty {
-		e.waiterQueue.Notify(waiter.EventIn)
+		e.waiterQueue.Notify(waiter.ReadableEvents)
 	}
 }
 
diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
index 367757d3b..52ed9560c 100644
--- a/pkg/tcpip/transport/packet/endpoint.go
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -152,7 +152,7 @@ func (ep *endpoint) Close() {
 
 	ep.closed = true
 	ep.bound = false
-	ep.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+	ep.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.ReadableEvents | waiter.WritableEvents)
 }
 
 // ModerateRecvBuf implements tcpip.Endpoint.ModerateRecvBuf.
@@ -287,13 +287,13 @@ func (*endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 // Readiness implements tcpip.Endpoint.Readiness.
 func (ep *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 	// The endpoint is always writable.
-	result := waiter.EventOut & mask
+	result := waiter.WritableEvents & mask
 
 	// Determine whether the endpoint is readable.
-	if (mask & waiter.EventIn) != 0 {
+	if (mask & waiter.ReadableEvents) != 0 {
 		ep.rcvMu.Lock()
 		if !ep.rcvList.Empty() || ep.rcvClosed {
-			result |= waiter.EventIn
+			result |= waiter.ReadableEvents
 		}
 		ep.rcvMu.Unlock()
 	}
@@ -483,7 +483,7 @@ func (ep *endpoint) HandlePacket(nicID tcpip.NICID, localAddr tcpip.LinkAddress,
 	ep.stats.PacketsReceived.Increment()
 	// Notify waiters that there's data to be read.
 	if wasEmpty {
-		ep.waiterQueue.Notify(waiter.EventIn)
+		ep.waiterQueue.Notify(waiter.ReadableEvents)
 	}
 }
 
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index 4b2f08379..e27a249cd 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -177,7 +177,7 @@ func (e *endpoint) Close() {
 
 	e.closed = true
 
-	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.ReadableEvents | waiter.WritableEvents)
 }
 
 // ModerateRecvBuf implements tcpip.Endpoint.ModerateRecvBuf.
@@ -486,13 +486,13 @@ func (*endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 // Readiness implements tcpip.Endpoint.Readiness.
 func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 	// The endpoint is always writable.
-	result := waiter.EventOut & mask
+	result := waiter.WritableEvents & mask
 
 	// Determine whether the endpoint is readable.
-	if (mask & waiter.EventIn) != 0 {
+	if (mask & waiter.ReadableEvents) != 0 {
 		e.rcvMu.Lock()
 		if !e.rcvList.Empty() || e.rcvClosed {
-			result |= waiter.EventIn
+			result |= waiter.ReadableEvents
 		}
 		e.rcvMu.Unlock()
 	}
@@ -655,7 +655,7 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 	e.stats.PacketsReceived.Increment()
 	// Notify waiters that there's data to be read.
 	if wasEmpty {
-		e.waiterQueue.Notify(waiter.EventIn)
+		e.waiterQueue.Notify(waiter.ReadableEvents)
 	}
 }
 
diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go
index 0a2f3291c..025b134e2 100644
--- a/pkg/tcpip/transport/tcp/accept.go
+++ b/pkg/tcpip/transport/tcp/accept.go
@@ -410,7 +410,7 @@ func (e *endpoint) deliverAccepted(n *endpoint, withSynCookie bool) {
 				atomic.AddInt32(&e.synRcvdCount, -1)
 			}
 			e.acceptMu.Unlock()
-			e.waiterQueue.Notify(waiter.EventIn)
+			e.waiterQueue.Notify(waiter.ReadableEvents)
 			return
 		default:
 			e.acceptCond.Wait()
@@ -462,7 +462,7 @@ func (e *endpoint) reserveTupleLocked() bool {
 // can't really have any registered waiters except when stack.Wait() is called
 // which waits for all registered endpoints to stop and expects an EventHUp.
 func (e *endpoint) notifyAborted() {
-	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.ReadableEvents | waiter.WritableEvents)
 }
 
 // handleSynSegment is called in its own goroutine once the listening endpoint
@@ -771,7 +771,7 @@ func (e *endpoint) protocolListenLoop(rcvWnd seqnum.Size) {
 		e.drainClosingSegmentQueue()
 
 		// Notify waiters that the endpoint is shutdown.
-		e.waiterQueue.Notify(waiter.EventIn | waiter.EventOut | waiter.EventHUp | waiter.EventErr)
+		e.waiterQueue.Notify(waiter.ReadableEvents | waiter.WritableEvents | waiter.EventHUp | waiter.EventErr)
 	}()
 
 	var s sleep.Sleeper
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index b32fe2fb1..a9e978cf6 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -1320,7 +1320,7 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 		e.drainClosingSegmentQueue()
 
 		// When the protocol loop exits we should wake up our waiters.
-		e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+		e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.ReadableEvents | waiter.WritableEvents)
 	}
 
 	if handshake {
@@ -1495,7 +1495,7 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 	}
 
 	// Tell waiters that the endpoint is connected and writable.
-	e.waiterQueue.Notify(waiter.EventOut)
+	e.waiterQueue.Notify(waiter.WritableEvents)
 
 	// The following assertions and notifications are needed for restored
 	// endpoints. Fresh newly created endpoints have empty states and should
@@ -1506,7 +1506,7 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 
 	e.rcvListMu.Lock()
 	if !e.rcvList.Empty() {
-		e.waiterQueue.Notify(waiter.EventIn)
+		e.waiterQueue.Notify(waiter.ReadableEvents)
 	}
 	e.rcvListMu.Unlock()
 
@@ -1570,7 +1570,7 @@ loop:
 		// wakers.
 		s.Done()
 		// Wake up any waiters before we enter TIME_WAIT.
-		e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+		e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.ReadableEvents | waiter.WritableEvents)
 		e.workerCleanup = true
 		reuseTW = e.doTimeWait()
 	}
diff --git a/pkg/tcpip/transport/tcp/dual_stack_test.go b/pkg/tcpip/transport/tcp/dual_stack_test.go
index 2d90246e4..f6a16f96e 100644
--- a/pkg/tcpip/transport/tcp/dual_stack_test.go
+++ b/pkg/tcpip/transport/tcp/dual_stack_test.go
@@ -45,7 +45,7 @@ func TestV4MappedConnectOnV6Only(t *testing.T) {
 func testV4Connect(t *testing.T, c *context.Context, checkers ...checker.NetworkChecker) {
 	// Start connection attempt.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventOut)
+	c.WQ.EventRegister(&we, waiter.WritableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestV4MappedAddr, Port: context.TestPort})
@@ -152,7 +152,7 @@ func TestV4ConnectWhenBoundToV4Mapped(t *testing.T) {
 func testV6Connect(t *testing.T, c *context.Context, checkers ...checker.NetworkChecker) {
 	// Start connection attempt to IPv6 address.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventOut)
+	c.WQ.EventRegister(&we, waiter.WritableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestV6Addr, Port: context.TestPort})
@@ -387,7 +387,7 @@ func testV4Accept(t *testing.T, c *context.Context) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	nep, _, err := c.EP.Accept(nil)
@@ -521,7 +521,7 @@ func TestV6AcceptOnV6(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 	var addr tcpip.FullAddress
 	_, _, err := c.EP.Accept(&addr)
@@ -610,7 +610,7 @@ func testV4ListenClose(t *testing.T, c *context.Context) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 	nep, _, err := c.EP.Accept(nil)
 	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 0a5e9cbb4..c5daba232 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -960,30 +960,30 @@ func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 
 	case StateListen:
 		// Check if there's anything in the accepted channel.
-		if (mask & waiter.EventIn) != 0 {
+		if (mask & waiter.ReadableEvents) != 0 {
 			e.acceptMu.Lock()
 			if len(e.acceptedChan) > 0 {
-				result |= waiter.EventIn
+				result |= waiter.ReadableEvents
 			}
 			e.acceptMu.Unlock()
 		}
 	}
 	if e.EndpointState().connected() {
 		// Determine if the endpoint is writable if requested.
-		if (mask & waiter.EventOut) != 0 {
+		if (mask & waiter.WritableEvents) != 0 {
 			e.sndBufMu.Lock()
 			sndBufSize := e.getSendBufferSize()
 			if e.sndClosed || e.sndBufUsed < sndBufSize {
-				result |= waiter.EventOut
+				result |= waiter.WritableEvents
 			}
 			e.sndBufMu.Unlock()
 		}
 
 		// Determine if the endpoint is readable if requested.
-		if (mask & waiter.EventIn) != 0 {
+		if (mask & waiter.ReadableEvents) != 0 {
 			e.rcvListMu.Lock()
 			if e.rcvBufUsed > 0 || e.rcvClosed {
-				result |= waiter.EventIn
+				result |= waiter.ReadableEvents
 			}
 			e.rcvListMu.Unlock()
 		}
@@ -1121,7 +1121,7 @@ func (e *endpoint) closeNoShutdownLocked() {
 		return
 	}
 
-	eventMask := waiter.EventIn | waiter.EventOut
+	eventMask := waiter.ReadableEvents | waiter.WritableEvents
 	// Either perform the local cleanup or kick the worker to make sure it
 	// knows it needs to cleanup.
 	if e.workerRunning {
@@ -2133,7 +2133,7 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) tcpip.Error {
 	if err != nil {
 		if !err.IgnoreStats() {
 			// Connect failed. Let's wake up any waiters.
-			e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+			e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.ReadableEvents | waiter.WritableEvents)
 			e.stack.Stats().TCP.FailedConnectionAttempts.Increment()
 			e.stats.FailedConnectionAttempts.Increment()
 		}
@@ -2463,7 +2463,7 @@ func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) tcpip.Error {
 			e.rcvListMu.Unlock()
 			e.closePendingAcceptableConnectionsLocked()
 			// Notify waiters that the endpoint is shutdown.
-			e.waiterQueue.Notify(waiter.EventIn | waiter.EventOut | waiter.EventHUp | waiter.EventErr)
+			e.waiterQueue.Notify(waiter.ReadableEvents | waiter.WritableEvents | waiter.EventHUp | waiter.EventErr)
 		}
 		return nil
 	default:
@@ -2811,7 +2811,7 @@ func (e *endpoint) updateSndBufferUsage(v int) {
 	e.sndBufMu.Unlock()
 
 	if notify {
-		e.waiterQueue.Notify(waiter.EventOut)
+		e.waiterQueue.Notify(waiter.WritableEvents)
 	}
 }
 
@@ -2828,7 +2828,7 @@ func (e *endpoint) readyToRead(s *segment) {
 		e.rcvClosed = true
 	}
 	e.rcvListMu.Unlock()
-	e.waiterQueue.Notify(waiter.EventIn)
+	e.waiterQueue.Notify(waiter.ReadableEvents)
 }
 
 // receiveBufferAvailableLocked calculates how many bytes are still available
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index 6c86ae1ae..9c23469f2 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -388,7 +388,7 @@ func TestTCPResetSentForACKWhenNotUsingSynCookies(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
@@ -809,7 +809,7 @@ func TestSimpleReceive(t *testing.T) {
 	c.CreateConnected(context.TestInitialSequenceNumber, 30000, -1 /* epRcvBuf */)
 
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
@@ -1315,7 +1315,7 @@ func TestListenCloseWhileConnect(t *testing.T) {
 	}
 
 	waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&waitEntry, waiter.EventIn)
+	c.WQ.EventRegister(&waitEntry, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&waitEntry)
 
 	executeHandshake(t, c, context.TestPort, false /* synCookiesInUse */)
@@ -1455,7 +1455,7 @@ func TestConnectBindToDevice(t *testing.T) {
 			}
 			// Start connection attempt.
 			waitEntry, _ := waiter.NewChannelEntry(nil)
-			c.WQ.EventRegister(&waitEntry, waiter.EventOut)
+			c.WQ.EventRegister(&waitEntry, waiter.WritableEvents)
 			defer c.WQ.EventUnregister(&waitEntry)
 
 			err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort})
@@ -1590,7 +1590,7 @@ func TestOutOfOrderReceive(t *testing.T) {
 	c.CreateConnected(context.TestInitialSequenceNumber, 30000, -1 /* epRcvBuf */)
 
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
@@ -1732,7 +1732,7 @@ func TestRstOnCloseWithUnreadData(t *testing.T) {
 	c.CreateConnected(context.TestInitialSequenceNumber, 30000, -1 /* epRcvBuf */)
 
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
@@ -1801,7 +1801,7 @@ func TestRstOnCloseWithUnreadDataFinConvertRst(t *testing.T) {
 	c.CreateConnected(context.TestInitialSequenceNumber, 30000, -1 /* epRcvBuf */)
 
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
@@ -1909,7 +1909,7 @@ func TestFullWindowReceive(t *testing.T) {
 	c.CreateConnected(context.TestInitialSequenceNumber, 30000, rcvBufSz)
 
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
@@ -2069,7 +2069,7 @@ func TestNoWindowShrinking(t *testing.T) {
 	})
 
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
@@ -2391,7 +2391,7 @@ func TestScaledWindowAccept(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
@@ -2465,7 +2465,7 @@ func TestNonScaledWindowAccept(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
@@ -3059,7 +3059,7 @@ func TestPassiveSendMSSLessThanMTU(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
@@ -3115,7 +3115,7 @@ func TestSynCookiePassiveSendMSSLessThanMTU(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
@@ -3191,7 +3191,7 @@ func TestSynOptionsOnActiveConnect(t *testing.T) {
 
 	// Start connection attempt.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventOut)
+	c.WQ.EventRegister(&we, waiter.WritableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	{
@@ -3304,7 +3304,7 @@ func TestReceiveOnResetConnection(t *testing.T) {
 
 	// Try to read.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 loop:
@@ -4232,7 +4232,7 @@ func TestReadAfterClosedState(t *testing.T) {
 	c.CreateConnected(context.TestInitialSequenceNumber, 30000, -1 /* epRcvBuf */)
 
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
@@ -4660,7 +4660,7 @@ func TestSelfConnect(t *testing.T) {
 
 	// Register for notification, then start connection attempt.
 	waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&waitEntry, waiter.EventOut)
+	wq.EventRegister(&waitEntry, waiter.WritableEvents)
 	defer wq.EventUnregister(&waitEntry)
 
 	{
@@ -4685,7 +4685,7 @@ func TestSelfConnect(t *testing.T) {
 
 	// Read back what was written.
 	wq.EventUnregister(&waitEntry)
-	wq.EventRegister(&waitEntry, waiter.EventIn)
+	wq.EventRegister(&waitEntry, waiter.ReadableEvents)
 	ept := endpointTester{ep}
 	rd := ept.CheckReadFull(t, len(data), notifyCh, 5*time.Second)
 
@@ -5382,7 +5382,7 @@ func TestListenBacklogFull(t *testing.T) {
 
 	// Try to accept the connections in the backlog.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	for i := 0; i < listenBacklog; i++ {
@@ -5730,7 +5730,7 @@ func TestListenSynRcvdQueueFull(t *testing.T) {
 
 	// Try to accept the connections in the backlog.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	newEP, _, err := c.EP.Accept(nil)
@@ -5807,7 +5807,7 @@ func TestListenBacklogFullSynCookieInUse(t *testing.T) {
 
 	// Verify that there is only one acceptable connection at this point.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	_, _, err = c.EP.Accept(nil)
@@ -5969,7 +5969,7 @@ func TestSynRcvdBadSeqNumber(t *testing.T) {
 	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Try to accept the connections in the backlog.
 		we, ch := waiter.NewChannelEntry(nil)
-		c.WQ.EventRegister(&we, waiter.EventIn)
+		c.WQ.EventRegister(&we, waiter.ReadableEvents)
 		defer c.WQ.EventUnregister(&we)
 
 		// Wait for connection to be established.
@@ -6029,7 +6029,7 @@ func TestPassiveConnectionAttemptIncrement(t *testing.T) {
 	executeHandshake(t, c, srcPort+1, false)
 
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	// Verify that there is only one acceptable connection at this point.
@@ -6099,7 +6099,7 @@ func TestPassiveFailedConnectionAttemptIncrement(t *testing.T) {
 	}
 
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	// Now check that there is one acceptable connections.
@@ -6152,7 +6152,7 @@ func TestEndpointBindListenAcceptState(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	aep, _, err := ep.Accept(nil)
@@ -6614,7 +6614,7 @@ func TestTCPTimeWaitRSTIgnored(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
@@ -6733,7 +6733,7 @@ func TestTCPTimeWaitOutOfOrder(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
@@ -6840,7 +6840,7 @@ func TestTCPTimeWaitNewSyn(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
@@ -7004,7 +7004,7 @@ func TestTCPTimeWaitDuplicateFINExtendsTimeWait(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
@@ -7154,7 +7154,7 @@ func TestTCPCloseWithData(t *testing.T) {
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
diff --git a/pkg/tcpip/transport/tcp/tcp_timestamp_test.go b/pkg/tcpip/transport/tcp/tcp_timestamp_test.go
index cb4f82903..2949588ce 100644
--- a/pkg/tcpip/transport/tcp/tcp_timestamp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_timestamp_test.go
@@ -46,7 +46,7 @@ func TestTimeStampEnabledConnect(t *testing.T) {
 
 	// Register for read and validate that we have data to read.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	// The following tests ensure that TS option once enabled behaves
@@ -273,7 +273,7 @@ func TestSegmentNotDroppedWhenTimestampMissing(t *testing.T) {
 
 	// Register for read.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&we, waiter.EventIn)
+	c.WQ.EventRegister(&we, waiter.ReadableEvents)
 	defer c.WQ.EventUnregister(&we)
 
 	droppedPacketsStat := c.Stack().Stats().DroppedPackets
diff --git a/pkg/tcpip/transport/tcp/testing/context/context.go b/pkg/tcpip/transport/tcp/testing/context/context.go
index 2f1c1011d..e73f90bb0 100644
--- a/pkg/tcpip/transport/tcp/testing/context/context.go
+++ b/pkg/tcpip/transport/tcp/testing/context/context.go
@@ -686,7 +686,7 @@ func (c *Context) Connect(iss seqnum.Value, rcvWnd seqnum.Size, options []byte)
 
 	// Start connection attempt.
 	waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&waitEntry, waiter.EventOut)
+	c.WQ.EventRegister(&waitEntry, waiter.WritableEvents)
 	defer c.WQ.EventUnregister(&waitEntry)
 
 	err := c.EP.Connect(tcpip.FullAddress{Addr: TestAddr, Port: TestPort})
@@ -899,7 +899,7 @@ func (c *Context) CreateConnectedWithOptions(wantOptions header.TCPSynOptions) *
 
 	// Start connection attempt.
 	waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-	c.WQ.EventRegister(&waitEntry, waiter.EventOut)
+	c.WQ.EventRegister(&waitEntry, waiter.WritableEvents)
 	defer c.WQ.EventUnregister(&waitEntry)
 
 	testFullAddr := tcpip.FullAddress{Addr: TestAddr, Port: TestPort}
@@ -1051,7 +1051,7 @@ func (c *Context) AcceptWithOptions(wndScale int, synOptions header.TCPSynOption
 
 	// Try to accept the connection.
 	we, ch := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&we, waiter.EventIn)
+	wq.EventRegister(&we, waiter.ReadableEvents)
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 0f59181bb..956da0e0c 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -284,7 +284,7 @@ func (e *endpoint) Close() {
 
 	e.mu.Unlock()
 
-	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+	e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.ReadableEvents | waiter.WritableEvents)
 }
 
 // ModerateRecvBuf implements tcpip.Endpoint.ModerateRecvBuf.
@@ -1070,7 +1070,7 @@ func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
 		e.rcvMu.Unlock()
 
 		if !wasClosed {
-			e.waiterQueue.Notify(waiter.EventIn)
+			e.waiterQueue.Notify(waiter.ReadableEvents)
 		}
 	}
 
@@ -1234,13 +1234,13 @@ func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 // waiter.EventIn is set, the endpoint is immediately readable.
 func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 	// The endpoint is always writable.
-	result := waiter.EventOut & mask
+	result := waiter.WritableEvents & mask
 
 	// Determine if the endpoint is readable if requested.
-	if (mask & waiter.EventIn) != 0 {
+	if mask&waiter.ReadableEvents != 0 {
 		e.rcvMu.Lock()
 		if !e.rcvList.Empty() || e.rcvClosed {
-			result |= waiter.EventIn
+			result |= waiter.ReadableEvents
 		}
 		e.rcvMu.Unlock()
 	}
@@ -1349,7 +1349,7 @@ func (e *endpoint) HandlePacket(id stack.TransportEndpointID, pkt *stack.PacketB
 
 	// Notify any waiters that there's data to be read now.
 	if wasEmpty {
-		e.waiterQueue.Notify(waiter.EventIn)
+		e.waiterQueue.Notify(waiter.ReadableEvents)
 	}
 }
 
diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go
index c8126b51b..77ca70a04 100644
--- a/pkg/tcpip/transport/udp/udp_test.go
+++ b/pkg/tcpip/transport/udp/udp_test.go
@@ -591,7 +591,7 @@ func testReadInternal(c *testContext, flow testFlow, packetShouldBeDropped, expe
 
 	// Try to receive the data.
 	we, ch := waiter.NewChannelEntry(nil)
-	c.wq.EventRegister(&we, waiter.EventIn)
+	c.wq.EventRegister(&we, waiter.ReadableEvents)
 	defer c.wq.EventUnregister(&we)
 
 	// Take a snapshot of the stats to validate them at the end of the test.