Support creating protocol instances with Stack ref

Network or transport protocols may want to reach the stack. Support this
by letting the stack create the protocol instances so it can pass a
reference to itself at protocol creation time.

Note, protocols do not yet use the stack in this CL but later CLs will
make use of the stack from protocols.

PiperOrigin-RevId: 334260210

1 files changed, 18 insertions, 4 deletions

diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index e7b7e95d4..c22633f6b 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -517,13 +517,25 @@ type UniqueID interface {
 	UniqueID() uint64
 }
 
+// NetworkProtocolFactory instantiates a network protocol.
+//
+// NetworkProtocolFactory must not attempt to modify the stack, it may only
+// query the stack.
+type NetworkProtocolFactory func(*Stack) NetworkProtocol
+
+// TransportProtocolFactory instantiates a transport protocol.
+//
+// TransportProtocolFactory must not attempt to modify the stack, it may only
+// query the stack.
+type TransportProtocolFactory func(*Stack) TransportProtocol
+
 // Options contains optional Stack configuration.
 type Options struct {
 	// NetworkProtocols lists the network protocols to enable.
-	NetworkProtocols []NetworkProtocol
+	NetworkProtocols []NetworkProtocolFactory
 
 	// TransportProtocols lists the transport protocols to enable.
-	TransportProtocols []TransportProtocol
+	TransportProtocols []TransportProtocolFactory
 
 	// Clock is an optional clock source used for timestampping packets.
 	//
@@ -755,7 +767,8 @@ func New(opts Options) *Stack {
 	s.forwarding.protocols = make(map[tcpip.NetworkProtocolNumber]bool)
 
 	// Add specified network protocols.
-	for _, netProto := range opts.NetworkProtocols {
+	for _, netProtoFactory := range opts.NetworkProtocols {
+		netProto := netProtoFactory(s)
 		s.networkProtocols[netProto.Number()] = netProto
 		if r, ok := netProto.(LinkAddressResolver); ok {
 			s.linkAddrResolvers[r.LinkAddressProtocol()] = r
@@ -763,7 +776,8 @@ func New(opts Options) *Stack {
 	}
 
 	// Add specified transport protocols.
-	for _, transProto := range opts.TransportProtocols {
+	for _, transProtoFactory := range opts.TransportProtocols {
+		transProto := transProtoFactory(s)
 		s.transportProtocols[transProto.Number()] = &transportProtocolState{
 			proto: transProto,
 		}