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

1 files changed, 6 insertions, 8 deletions

diff --git a/pkg/sentry/socket/unix/transport/unix.go b/pkg/sentry/socket/unix/transport/unix.go
index 4bf06d4dc..cc9d650fb 100644
--- a/pkg/sentry/socket/unix/transport/unix.go
+++ b/pkg/sentry/socket/unix/transport/unix.go
@@ -172,9 +172,8 @@ type Endpoint interface {
 	// connected.
 	GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error)
 
-	// SetSockOpt sets a socket option. opt should be one of the tcpip.*Option
-	// types.
-	SetSockOpt(opt interface{}) *tcpip.Error
+	// SetSockOpt sets a socket option.
+	SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error
 
 	// SetSockOptBool sets a socket option for simple cases when a value has
 	// the int type.
@@ -184,9 +183,8 @@ type Endpoint interface {
 	// the int type.
 	SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error
 
-	// GetSockOpt gets a socket option. opt should be a pointer to one of the
-	// tcpip.*Option types.
-	GetSockOpt(opt interface{}) *tcpip.Error
+	// GetSockOpt gets a socket option.
+	GetSockOpt(opt tcpip.GettableSocketOption) *tcpip.Error
 
 	// GetSockOptBool gets a socket option for simple cases when a return
 	// value has the int type.
@@ -841,7 +839,7 @@ func (e *baseEndpoint) SendMsg(ctx context.Context, data [][]byte, c ControlMess
 }
 
 // SetSockOpt sets a socket option. Currently not supported.
-func (e *baseEndpoint) SetSockOpt(opt interface{}) *tcpip.Error {
+func (e *baseEndpoint) SetSockOpt(tcpip.SettableSocketOption) *tcpip.Error {
 	return nil
 }
 
@@ -943,7 +941,7 @@ func (e *baseEndpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 }
 
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
-func (e *baseEndpoint) GetSockOpt(opt interface{}) *tcpip.Error {
+func (e *baseEndpoint) GetSockOpt(opt tcpip.GettableSocketOption) *tcpip.Error {
 	switch opt.(type) {
 	case *tcpip.LingerOption:
 		return nil