Inform NDPDispatcher when Stack learns about available configurations via DHCPv6

Inform the Stack's NDPDispatcher when it receives an NDP Router Advertisement
that updates the available configurations via DHCPv6. The Stack makes sure that
its NDPDispatcher isn't informed unless the avaiable configurations via DHCPv6
for a NIC is updated.

Tests: Test that a Stack's NDPDispatcher is informed when it receives an NDP
Router Advertisement that informs it of new configurations available via DHCPv6.
PiperOrigin-RevId: 289001283

1 files changed, 62 insertions, 0 deletions

diff --git a/pkg/tcpip/stack/ndp.go b/pkg/tcpip/stack/ndp.go
index 35825ebf7..a9dd322db 100644
--- a/pkg/tcpip/stack/ndp.go
+++ b/pkg/tcpip/stack/ndp.go
@@ -115,6 +115,30 @@ var (
 	MinPrefixInformationValidLifetimeForUpdate = 2 * time.Hour
 )
 
+// DHCPv6ConfigurationFromNDPRA is a configuration available via DHCPv6 that an
+// NDP Router Advertisement informed the Stack about.
+type DHCPv6ConfigurationFromNDPRA int
+
+const (
+	// DHCPv6NoConfiguration indicates that no configurations are available via
+	// DHCPv6.
+	DHCPv6NoConfiguration DHCPv6ConfigurationFromNDPRA = iota
+
+	// DHCPv6ManagedAddress indicates that addresses are available via DHCPv6.
+	//
+	// DHCPv6ManagedAddress also implies DHCPv6OtherConfigurations because DHCPv6
+	// will return all available configuration information.
+	DHCPv6ManagedAddress
+
+	// DHCPv6OtherConfigurations indicates that other configuration information is
+	// available via DHCPv6.
+	//
+	// Other configurations are configurations other than addresses. Examples of
+	// other configurations are recursive DNS server list, DNS search lists and
+	// default gateway.
+	DHCPv6OtherConfigurations
+)
+
 // NDPDispatcher is the interface integrators of netstack must implement to
 // receive and handle NDP related events.
 type NDPDispatcher interface {
@@ -194,7 +218,20 @@ type NDPDispatcher interface {
 	// already known DNS servers. If called with known DNS servers, their
 	// valid lifetimes must be refreshed to lifetime (it may be increased,
 	// decreased, or completely invalidated when lifetime = 0).
+	//
+	// This function is not permitted to block indefinitely. It must not
+	// call functions on the stack itself.
 	OnRecursiveDNSServerOption(nicID tcpip.NICID, addrs []tcpip.Address, lifetime time.Duration)
+
+	// OnDHCPv6Configuration will be called with an updated configuration that is
+	// available via DHCPv6 for a specified NIC.
+	//
+	// NDPDispatcher assumes that the initial configuration available by DHCPv6 is
+	// DHCPv6NoConfiguration.
+	//
+	// This function is not permitted to block indefinitely. It must not
+	// call functions on the stack itself.
+	OnDHCPv6Configuration(tcpip.NICID, DHCPv6ConfigurationFromNDPRA)
 }
 
 // NDPConfigurations is the NDP configurations for the netstack.
@@ -281,6 +318,9 @@ type ndpState struct {
 
 	// The addresses generated by SLAAC.
 	autoGenAddresses map[tcpip.Address]autoGenAddressState
+
+	// The last learned DHCPv6 configuration from an NDP RA.
+	dhcpv6Configuration DHCPv6ConfigurationFromNDPRA
 }
 
 // dadState holds the Duplicate Address Detection timer and channel to signal
@@ -533,6 +573,28 @@ func (ndp *ndpState) handleRA(ip tcpip.Address, ra header.NDPRouterAdvert) {
 		return
 	}
 
+	// Only worry about the DHCPv6 configuration if we have an NDPDispatcher as we
+	// only inform the dispatcher on configuration changes. We do nothing else
+	// with the information.
+	if ndpDisp := ndp.nic.stack.ndpDisp; ndpDisp != nil {
+		var configuration DHCPv6ConfigurationFromNDPRA
+		switch {
+		case ra.ManagedAddrConfFlag():
+			configuration = DHCPv6ManagedAddress
+
+		case ra.OtherConfFlag():
+			configuration = DHCPv6OtherConfigurations
+
+		default:
+			configuration = DHCPv6NoConfiguration
+		}
+
+		if ndp.dhcpv6Configuration != configuration {
+			ndp.dhcpv6Configuration = configuration
+			ndpDisp.OnDHCPv6Configuration(ndp.nic.ID(), configuration)
+		}
+	}
+
 	// Is the NIC configured to discover default routers?
 	if ndp.configs.DiscoverDefaultRouters {
 		rtr, ok := ndp.defaultRouters[ip]