Improve type safety for transport protocol options

The existing implementation for TransportProtocol.{Set}Option 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 transport protocol options
that may be set or queried which transport protocol 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.

RELNOTES: n/a
PiperOrigin-RevId: 330559811

1 files changed, 2 insertions, 2 deletions

diff --git a/pkg/tcpip/transport/udp/protocol.go b/pkg/tcpip/transport/udp/protocol.go
index f65751dd4..3f87e8057 100644
--- a/pkg/tcpip/transport/udp/protocol.go
+++ b/pkg/tcpip/transport/udp/protocol.go
@@ -202,12 +202,12 @@ func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.Trans
 }
 
 // SetOption implements stack.TransportProtocol.SetOption.
-func (p *protocol) SetOption(option interface{}) *tcpip.Error {
+func (*protocol) SetOption(tcpip.SettableTransportProtocolOption) *tcpip.Error {
 	return tcpip.ErrUnknownProtocolOption
 }
 
 // Option implements stack.TransportProtocol.Option.
-func (p *protocol) Option(option interface{}) *tcpip.Error {
+func (*protocol) Option(tcpip.GettableTransportProtocolOption) *tcpip.Error {
 	return tcpip.ErrUnknownProtocolOption
 }