[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, 12 insertions, 9 deletions

diff --git a/pkg/tcpip/stack/transport_demuxer_test.go b/pkg/tcpip/stack/transport_demuxer_test.go
index 41a8e5ad0..2cdb5ca79 100644
--- a/pkg/tcpip/stack/transport_demuxer_test.go
+++ b/pkg/tcpip/stack/transport_demuxer_test.go
@@ -307,9 +307,7 @@ func TestBindToDeviceDistribution(t *testing.T) {
 						}(ep)
 
 						defer ep.Close()
-						if err := ep.SetSockOptBool(tcpip.ReusePortOption, endpoint.reuse); err != nil {
-							t.Fatalf("SetSockOptBool(ReusePortOption, %t) on endpoint %d failed: %s", endpoint.reuse, i, err)
-						}
+						ep.SocketOptions().SetReusePort(endpoint.reuse)
 						bindToDeviceOption := tcpip.BindToDeviceOption(endpoint.bindToDevice)
 						if err := ep.SetSockOpt(&bindToDeviceOption); err != nil {
 							t.Fatalf("SetSockOpt(&%T(%d)) on endpoint %d failed: %s", bindToDeviceOption, bindToDeviceOption, i, err)
diff --git a/pkg/tcpip/stack/transport_test.go b/pkg/tcpip/stack/transport_test.go
index 5b9043d85..fbac66993 100644
--- a/pkg/tcpip/stack/transport_test.go
+++ b/pkg/tcpip/stack/transport_test.go
@@ -38,6 +38,7 @@ const (
 // use it.
 type fakeTransportEndpoint struct {
 	stack.TransportEndpointInfo
+	tcpip.DefaultSocketOptionsHandler
 
 	proto    *fakeTransportProtocol
 	peerAddr tcpip.Address
@@ -45,7 +46,7 @@ type fakeTransportEndpoint struct {
 	uniqueID uint64
 
 	// acceptQueue is non-nil iff bound.
-	acceptQueue []fakeTransportEndpoint
+	acceptQueue []*fakeTransportEndpoint
 
 	// ops is used to set and get socket options.
 	ops tcpip.SocketOptions
@@ -65,7 +66,9 @@ func (f *fakeTransportEndpoint) SocketOptions() *tcpip.SocketOptions {
 	return &f.ops
 }
 func newFakeTransportEndpoint(proto *fakeTransportProtocol, netProto tcpip.NetworkProtocolNumber, uniqueID uint64) tcpip.Endpoint {
-	return &fakeTransportEndpoint{TransportEndpointInfo: stack.TransportEndpointInfo{NetProto: netProto}, proto: proto, uniqueID: uniqueID}
+	ep := &fakeTransportEndpoint{TransportEndpointInfo: stack.TransportEndpointInfo{NetProto: netProto}, proto: proto, uniqueID: uniqueID}
+	ep.ops.InitHandler(ep)
+	return ep
 }
 
 func (f *fakeTransportEndpoint) Abort() {
@@ -189,7 +192,7 @@ func (f *fakeTransportEndpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *wai
 	if len(f.acceptQueue) == 0 {
 		return nil, nil, nil
 	}
-	a := &f.acceptQueue[0]
+	a := f.acceptQueue[0]
 	f.acceptQueue = f.acceptQueue[1:]
 	return a, nil, nil
 }
@@ -206,7 +209,7 @@ func (f *fakeTransportEndpoint) Bind(a tcpip.FullAddress) *tcpip.Error {
 	); err != nil {
 		return err
 	}
-	f.acceptQueue = []fakeTransportEndpoint{}
+	f.acceptQueue = []*fakeTransportEndpoint{}
 	return nil
 }
 
@@ -232,7 +235,7 @@ func (f *fakeTransportEndpoint) HandlePacket(id stack.TransportEndpointID, pkt *
 	}
 	route.ResolveWith(pkt.SourceLinkAddress())
 
-	f.acceptQueue = append(f.acceptQueue, fakeTransportEndpoint{
+	ep := &fakeTransportEndpoint{
 		TransportEndpointInfo: stack.TransportEndpointInfo{
 			ID:       f.ID,
 			NetProto: f.NetProto,
@@ -240,7 +243,9 @@ func (f *fakeTransportEndpoint) HandlePacket(id stack.TransportEndpointID, pkt *
 		proto:    f.proto,
 		peerAddr: route.RemoteAddress,
 		route:    route,
-	})
+	}
+	ep.ops.InitHandler(ep)
+	f.acceptQueue = append(f.acceptQueue, ep)
 }
 
 func (f *fakeTransportEndpoint) HandleControlPacket(stack.TransportEndpointID, stack.ControlType, uint32, *stack.PacketBuffer) {