[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, 3 insertions, 0 deletions

diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
index 3bff3755a..35d1be792 100644
--- a/pkg/tcpip/transport/packet/endpoint.go
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -60,6 +60,8 @@ type packet struct {
 // +stateify savable
 type endpoint struct {
 	stack.TransportEndpointInfo
+	tcpip.DefaultSocketOptionsHandler
+
 	// The following fields are initialized at creation time and are
 	// immutable.
 	stack       *stack.Stack `state:"manual"`
@@ -107,6 +109,7 @@ func NewEndpoint(s *stack.Stack, cooked bool, netProto tcpip.NetworkProtocolNumb
 		rcvBufSizeMax: 32 * 1024,
 		sndBufSize:    32 * 1024,
 	}
+	ep.ops.InitHandler(ep)
 
 	// Override with stack defaults.
 	var ss stack.SendBufferSizeOption