Improve type safety for socket options

The existing implementation for {G,S}etSockOpt take arguments of an
empty interface type which all types (implicitly) implement; any
type may be passed to the functions.

This change introduces marker interfaces for socket options that may be
set or queried which socket option types implement to ensure that invalid
types are caught at compile time. Different interfaces are used to allow
the compiler to enforce read-only or set-only socket options.

Fixes #3714.

RELNOTES: n/a
PiperOrigin-RevId: 328832161

2 files changed, 4 insertions, 4 deletions

diff --git a/pkg/tcpip/stack/transport_demuxer_test.go b/pkg/tcpip/stack/transport_demuxer_test.go
index 1339edc2d..4d6d62eec 100644
--- a/pkg/tcpip/stack/transport_demuxer_test.go
+++ b/pkg/tcpip/stack/transport_demuxer_test.go
@@ -312,8 +312,8 @@ func TestBindToDeviceDistribution(t *testing.T) {
 							t.Fatalf("SetSockOptBool(ReusePortOption, %t) on endpoint %d failed: %s", endpoint.reuse, i, err)
 						}
 						bindToDeviceOption := tcpip.BindToDeviceOption(endpoint.bindToDevice)
-						if err := ep.SetSockOpt(bindToDeviceOption); err != nil {
-							t.Fatalf("SetSockOpt(%#v) on endpoint %d failed: %s", bindToDeviceOption, i, err)
+						if err := ep.SetSockOpt(&bindToDeviceOption); err != nil {
+							t.Fatalf("SetSockOpt(&%T(%d)) on endpoint %d failed: %s", bindToDeviceOption, bindToDeviceOption, i, err)
 						}
 
 						var dstAddr tcpip.Address
diff --git a/pkg/tcpip/stack/transport_test.go b/pkg/tcpip/stack/transport_test.go
index 7869bb98b..a1458c899 100644
--- a/pkg/tcpip/stack/transport_test.go
+++ b/pkg/tcpip/stack/transport_test.go
@@ -105,7 +105,7 @@ func (*fakeTransportEndpoint) Peek([][]byte) (int64, tcpip.ControlMessages, *tcp
 }
 
 // SetSockOpt sets a socket option. Currently not supported.
-func (*fakeTransportEndpoint) SetSockOpt(interface{}) *tcpip.Error {
+func (*fakeTransportEndpoint) SetSockOpt(tcpip.SettableSocketOption) *tcpip.Error {
 	return tcpip.ErrInvalidEndpointState
 }
 
@@ -130,7 +130,7 @@ func (*fakeTransportEndpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.E
 }
 
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
-func (*fakeTransportEndpoint) GetSockOpt(opt interface{}) *tcpip.Error {
+func (*fakeTransportEndpoint) GetSockOpt(tcpip.GettableSocketOption) *tcpip.Error {
 	return tcpip.ErrInvalidEndpointState
 }