[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

1 files changed, 16 insertions, 24 deletions

diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 5aa16bf35..e57833644 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -77,6 +77,7 @@ func (s EndpointState) String() string {
 // +stateify savable
 type endpoint struct {
 	stack.TransportEndpointInfo
+	tcpip.DefaultSocketOptionsHandler
 
 	// The following fields are initialized at creation time and do not
 	// change throughout the lifetime of the endpoint.
@@ -194,6 +195,7 @@ func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQue
 		state:                StateInitial,
 		uniqueID:             s.UniqueID(),
 	}
+	e.ops.InitHandler(e)
 
 	// Override with stack defaults.
 	var ss stack.SendBufferSizeOption
@@ -574,6 +576,20 @@ func (e *endpoint) Peek([][]byte) (int64, tcpip.ControlMessages, *tcpip.Error) {
 	return 0, tcpip.ControlMessages{}, nil
 }
 
+// OnReuseAddressSet implements tcpip.SocketOptionsHandler.OnReuseAddressSet.
+func (e *endpoint) OnReuseAddressSet(v bool) {
+	e.mu.Lock()
+	e.portFlags.MostRecent = v
+	e.mu.Unlock()
+}
+
+// OnReusePortSet implements tcpip.SocketOptionsHandler.OnReusePortSet.
+func (e *endpoint) OnReusePortSet(v bool) {
+	e.mu.Lock()
+	e.portFlags.LoadBalanced = v
+	e.mu.Unlock()
+}
+
 // SetSockOptBool implements tcpip.Endpoint.SetSockOptBool.
 func (e *endpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error {
 	switch opt {
@@ -602,16 +618,6 @@ func (e *endpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error {
 		e.receiveIPPacketInfo = v
 		e.mu.Unlock()
 
-	case tcpip.ReuseAddressOption:
-		e.mu.Lock()
-		e.portFlags.MostRecent = v
-		e.mu.Unlock()
-
-	case tcpip.ReusePortOption:
-		e.mu.Lock()
-		e.portFlags.LoadBalanced = v
-		e.mu.Unlock()
-
 	case tcpip.V6OnlyOption:
 		// We only recognize this option on v6 endpoints.
 		if e.NetProto != header.IPv6ProtocolNumber {
@@ -875,20 +881,6 @@ func (e *endpoint) GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error) {
 		e.mu.RUnlock()
 		return v, nil
 
-	case tcpip.ReuseAddressOption:
-		e.mu.RLock()
-		v := e.portFlags.MostRecent
-		e.mu.RUnlock()
-
-		return v, nil
-
-	case tcpip.ReusePortOption:
-		e.mu.RLock()
-		v := e.portFlags.LoadBalanced
-		e.mu.RUnlock()
-
-		return v, nil
-
 	case tcpip.V6OnlyOption:
 		// We only recognize this option on v6 endpoints.
 		if e.NetProto != header.IPv6ProtocolNumber {