Improve type safety for network protocol options

The existing implementation for NetworkProtocol.{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 network protocol options
that may be set or queried which network 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.

PiperOrigin-RevId: 328980359

3 files changed, 10 insertions, 10 deletions

diff --git a/pkg/tcpip/network/arp/arp.go b/pkg/tcpip/network/arp/arp.go
index cbbe5b77f..7aaee08c4 100644
--- a/pkg/tcpip/network/arp/arp.go
+++ b/pkg/tcpip/network/arp/arp.go
@@ -217,12 +217,12 @@ func (*protocol) ResolveStaticAddress(addr tcpip.Address) (tcpip.LinkAddress, bo
 }
 
 // SetOption implements stack.NetworkProtocol.SetOption.
-func (*protocol) SetOption(option interface{}) *tcpip.Error {
+func (*protocol) SetOption(tcpip.SettableNetworkProtocolOption) *tcpip.Error {
 	return tcpip.ErrUnknownProtocolOption
 }
 
 // Option implements stack.NetworkProtocol.Option.
-func (*protocol) Option(option interface{}) *tcpip.Error {
+func (*protocol) Option(tcpip.GettableNetworkProtocolOption) *tcpip.Error {
 	return tcpip.ErrUnknownProtocolOption
 }
 
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index 55ca94268..fa4ae2012 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -486,10 +486,10 @@ func (*protocol) ParseAddresses(v buffer.View) (src, dst tcpip.Address) {
 }
 
 // SetOption implements NetworkProtocol.SetOption.
-func (p *protocol) SetOption(option interface{}) *tcpip.Error {
+func (p *protocol) SetOption(option tcpip.SettableNetworkProtocolOption) *tcpip.Error {
 	switch v := option.(type) {
-	case tcpip.DefaultTTLOption:
-		p.SetDefaultTTL(uint8(v))
+	case *tcpip.DefaultTTLOption:
+		p.SetDefaultTTL(uint8(*v))
 		return nil
 	default:
 		return tcpip.ErrUnknownProtocolOption
@@ -497,7 +497,7 @@ func (p *protocol) SetOption(option interface{}) *tcpip.Error {
 }
 
 // Option implements NetworkProtocol.Option.
-func (p *protocol) Option(option interface{}) *tcpip.Error {
+func (p *protocol) Option(option tcpip.GettableNetworkProtocolOption) *tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.DefaultTTLOption:
 		*v = tcpip.DefaultTTLOption(p.DefaultTTL())
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 36fbbebf0..af3cd91c6 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -469,10 +469,10 @@ func (p *protocol) NewEndpoint(nicID tcpip.NICID, linkAddrCache stack.LinkAddres
 }
 
 // SetOption implements NetworkProtocol.SetOption.
-func (p *protocol) SetOption(option interface{}) *tcpip.Error {
+func (p *protocol) SetOption(option tcpip.SettableNetworkProtocolOption) *tcpip.Error {
 	switch v := option.(type) {
-	case tcpip.DefaultTTLOption:
-		p.SetDefaultTTL(uint8(v))
+	case *tcpip.DefaultTTLOption:
+		p.SetDefaultTTL(uint8(*v))
 		return nil
 	default:
 		return tcpip.ErrUnknownProtocolOption
@@ -480,7 +480,7 @@ func (p *protocol) SetOption(option interface{}) *tcpip.Error {
 }
 
 // Option implements NetworkProtocol.Option.
-func (p *protocol) Option(option interface{}) *tcpip.Error {
+func (p *protocol) Option(option tcpip.GettableNetworkProtocolOption) *tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.DefaultTTLOption:
 		*v = tcpip.DefaultTTLOption(p.DefaultTTL())