[netstack] Move SO_REUSEPORT and SO_REUSEADDR option to SocketOptions.

This changes also introduces:
- `SocketOptionsHandler` interface which can be implemented by endpoints to
  handle endpoint specific behavior on SetSockOpt. This is analogous to what
  Linux does.
- `DefaultSocketOptionsHandler` which is a default implementation of the above.
  This is embedded in all endpoints so that we don't have to uselessly
  implement empty functions. Endpoints with specific behavior can override the
  embedded method by manually defining its own implementation.

PiperOrigin-RevId: 343158301

2 files changed, 22 insertions, 42 deletions

diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 36b915510..f893324c2 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -362,6 +362,7 @@ func (*EndpointInfo) IsEndpointInfo() {}
 // +stateify savable
 type endpoint struct {
 	EndpointInfo
+	tcpip.DefaultSocketOptionsHandler
 
 	// endpointEntry is used to queue endpoints for processing to the
 	// a given tcp processor goroutine.
@@ -884,6 +885,7 @@ func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQue
 		windowClamp:   DefaultReceiveBufferSize,
 		maxSynRetries: DefaultSynRetries,
 	}
+	e.ops.InitHandler(e)
 
 	var ss tcpip.TCPSendBufferSizeRangeOption
 	if err := s.TransportProtocolOption(ProtocolNumber, &ss); err == nil {
@@ -1627,6 +1629,20 @@ func (e *endpoint) windowCrossedACKThresholdLocked(deltaBefore int) (crossed boo
 	return false, false
 }
 
+// OnReuseAddressSet implements tcpip.SocketOptionsHandler.OnReuseAddressSet.
+func (e *endpoint) OnReuseAddressSet(v bool) {
+	e.LockUser()
+	e.portFlags.TupleOnly = v
+	e.UnlockUser()
+}
+
+// OnReusePortSet implements tcpip.SocketOptionsHandler.OnReusePortSet.
+func (e *endpoint) OnReusePortSet(v bool) {
+	e.LockUser()
+	e.portFlags.LoadBalanced = v
+	e.UnlockUser()
+}
+
 // SetSockOptBool sets a socket option.
 func (e *endpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error {
 	switch opt {
@@ -1666,16 +1682,6 @@ func (e *endpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error {
 		}
 		atomic.StoreUint32(&e.slowAck, o)
 
-	case tcpip.ReuseAddressOption:
-		e.LockUser()
-		e.portFlags.TupleOnly = v
-		e.UnlockUser()
-
-	case tcpip.ReusePortOption:
-		e.LockUser()
-		e.portFlags.LoadBalanced = v
-		e.UnlockUser()
-
 	case tcpip.V6OnlyOption:
 		// We only recognize this option on v6 endpoints.
 		if e.NetProto != header.IPv6ProtocolNumber {
@@ -1995,20 +2001,6 @@ func (e *endpoint) GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error) {
 		v := atomic.LoadUint32(&e.slowAck) == 0
 		return v, nil
 
-	case tcpip.ReuseAddressOption:
-		e.LockUser()
-		v := e.portFlags.TupleOnly
-		e.UnlockUser()
-
-		return v, nil
-
-	case tcpip.ReusePortOption:
-		e.LockUser()
-		v := e.portFlags.LoadBalanced
-		e.UnlockUser()
-
-		return v, nil
-
 	case tcpip.V6OnlyOption:
 		// We only recognize this option on v6 endpoints.
 		if e.NetProto != header.IPv6ProtocolNumber {
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index c366a4cbc..9fa3aa740 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -4191,9 +4191,7 @@ func TestReusePort(t *testing.T) {
 	if err != nil {
 		t.Fatalf("NewEndpoint failed; %s", err)
 	}
-	if err := c.EP.SetSockOptBool(tcpip.ReuseAddressOption, true); err != nil {
-		t.Fatalf("SetSockOptBool ReuseAddressOption failed: %s", err)
-	}
+	c.EP.SocketOptions().SetReuseAddress(true)
 	if err := c.EP.Bind(tcpip.FullAddress{Port: context.StackPort}); err != nil {
 		t.Fatalf("Bind failed: %s", err)
 	}
@@ -4203,9 +4201,7 @@ func TestReusePort(t *testing.T) {
 	if err != nil {
 		t.Fatalf("NewEndpoint failed; %s", err)
 	}
-	if err := c.EP.SetSockOptBool(tcpip.ReuseAddressOption, true); err != nil {
-		t.Fatalf("SetSockOptBool ReuseAddressOption failed: %s", err)
-	}
+	c.EP.SocketOptions().SetReuseAddress(true)
 	if err := c.EP.Bind(tcpip.FullAddress{Port: context.StackPort}); err != nil {
 		t.Fatalf("Bind failed: %s", err)
 	}
@@ -4216,9 +4212,7 @@ func TestReusePort(t *testing.T) {
 	if err != nil {
 		t.Fatalf("NewEndpoint failed; %s", err)
 	}
-	if err := c.EP.SetSockOptBool(tcpip.ReuseAddressOption, true); err != nil {
-		t.Fatalf("SetSockOptBool ReuseAddressOption failed: %s", err)
-	}
+	c.EP.SocketOptions().SetReuseAddress(true)
 	if err := c.EP.Bind(tcpip.FullAddress{Port: context.StackPort}); err != nil {
 		t.Fatalf("Bind failed: %s", err)
 	}
@@ -4231,9 +4225,7 @@ func TestReusePort(t *testing.T) {
 	if err != nil {
 		t.Fatalf("NewEndpoint failed; %s", err)
 	}
-	if err := c.EP.SetSockOptBool(tcpip.ReuseAddressOption, true); err != nil {
-		t.Fatalf("SetSockOptBool ReuseAddressOption failed: %s", err)
-	}
+	c.EP.SocketOptions().SetReuseAddress(true)
 	if err := c.EP.Bind(tcpip.FullAddress{Port: context.StackPort}); err != nil {
 		t.Fatalf("Bind failed: %s", err)
 	}
@@ -4244,9 +4236,7 @@ func TestReusePort(t *testing.T) {
 	if err != nil {
 		t.Fatalf("NewEndpoint failed; %s", err)
 	}
-	if err := c.EP.SetSockOptBool(tcpip.ReuseAddressOption, true); err != nil {
-		t.Fatalf("SetSockOptBool ReuseAddressOption failed: %s", err)
-	}
+	c.EP.SocketOptions().SetReuseAddress(true)
 	if err := c.EP.Bind(tcpip.FullAddress{Port: context.StackPort}); err != nil {
 		t.Fatalf("Bind failed: %s", err)
 	}
@@ -4259,9 +4249,7 @@ func TestReusePort(t *testing.T) {
 	if err != nil {
 		t.Fatalf("NewEndpoint failed; %s", err)
 	}
-	if err := c.EP.SetSockOptBool(tcpip.ReuseAddressOption, true); err != nil {
-		t.Fatalf("SetSockOptBool ReuseAddressOption failed: %s", err)
-	}
+	c.EP.SocketOptions().SetReuseAddress(true)
 	if err := c.EP.Bind(tcpip.FullAddress{Port: context.StackPort}); err != nil {
 		t.Fatalf("Bind failed: %s", err)
 	}