Refactor SLAAC address state into SLAAC prefix state

Previously, SLAAC related state was stored on a per-address basis. This was
sufficient for the simple case of a single SLAAC address per prefix, but
future CLs will introduce temporary addresses which will result in multiple
SLAAC addresses for a prefix. This refactor allows storing multiple addresses
for a prefix in a single SLAAC prefix state.

No behaviour changes - existing tests continue to pass.

PiperOrigin-RevId: 300832812

2 files changed, 167 insertions, 149 deletions

diff --git a/pkg/tcpip/stack/ndp.go b/pkg/tcpip/stack/ndp.go
index a9f4d5dad..d689a006d 100644
--- a/pkg/tcpip/stack/ndp.go
+++ b/pkg/tcpip/stack/ndp.go
@@ -361,16 +361,16 @@ type ndpState struct {
 	// The default routers discovered through Router Advertisements.
 	defaultRouters map[tcpip.Address]defaultRouterState
 
+	// The timer used to send the next router solicitation message.
+	rtrSolicitTimer *time.Timer
+
 	// The on-link prefixes discovered through Router Advertisements' Prefix
 	// Information option.
 	onLinkPrefixes map[tcpip.Subnet]onLinkPrefixState
 
-	// The timer used to send the next router solicitation message.
-	// If routers are being solicited, rtrSolicitTimer MUST NOT be nil.
-	rtrSolicitTimer *time.Timer
-
-	// The addresses generated by SLAAC.
-	autoGenAddresses map[tcpip.Address]autoGenAddressState
+	// The SLAAC prefixes discovered through Router Advertisements' Prefix
+	// Information option.
+	slaacPrefixes map[tcpip.Subnet]slaacPrefixState
 
 	// The last learned DHCPv6 configuration from an NDP RA.
 	dhcpv6Configuration DHCPv6ConfigurationFromNDPRA
@@ -402,18 +402,16 @@ type onLinkPrefixState struct {
 	invalidationTimer tcpip.CancellableTimer
 }
 
-// autoGenAddressState holds data associated with an address generated via
-// SLAAC.
-type autoGenAddressState struct {
-	// A reference to the referencedNetworkEndpoint that this autoGenAddressState
-	// is holding state for.
-	ref *referencedNetworkEndpoint
-
+// slaacPrefixState holds state associated with a SLAAC prefix.
+type slaacPrefixState struct {
 	deprecationTimer  tcpip.CancellableTimer
 	invalidationTimer tcpip.CancellableTimer
 
 	// Nonzero only when the address is not valid forever.
 	validUntil time.Time
+
+	// The prefix's permanent address endpoint.
+	ref *referencedNetworkEndpoint
 }
 
 // startDuplicateAddressDetection performs Duplicate Address Detection.
@@ -899,23 +897,15 @@ func (ndp *ndpState) handleAutonomousPrefixInformation(pi header.NDPPrefixInform
 
 	prefix := pi.Subnet()
 
-	// Check if we already have an auto-generated address for prefix.
-	for addr, addrState := range ndp.autoGenAddresses {
-		refAddrWithPrefix := tcpip.AddressWithPrefix{Address: addr, PrefixLen: addrState.ref.ep.PrefixLen()}
-		if refAddrWithPrefix.Subnet() != prefix {
-			continue
-		}
-
-		// At this point, we know we are refreshing a SLAAC generated IPv6 address
-		// with the prefix prefix. Do the work as outlined by RFC 4862 section
-		// 5.5.3.e.
-		ndp.refreshAutoGenAddressLifetimes(addr, pl, vl)
+	// Check if we already maintain SLAAC state for prefix.
+	if _, ok := ndp.slaacPrefixes[prefix]; ok {
+		// As per RFC 4862 section 5.5.3.e, refresh prefix's SLAAC lifetimes.
+		ndp.refreshSLAACPrefixLifetimes(prefix, pl, vl)
 		return
 	}
 
-	// We do not already have an address with the prefix prefix. Do the
-	// work as outlined by RFC 4862 section 5.5.3.d if n is configured
-	// to auto-generate global addresses by SLAAC.
+	// prefix is a new SLAAC prefix. Do the work as outlined by RFC 4862 section
+	// 5.5.3.d if ndp is configured to auto-generate new addresses via SLAAC.
 	if !ndp.configs.AutoGenGlobalAddresses {
 		return
 	}
@@ -927,6 +917,8 @@ func (ndp *ndpState) handleAutonomousPrefixInformation(pi header.NDPPrefixInform
 // for prefix.
 //
 // pl is the new preferred lifetime. vl is the new valid lifetime.
+//
+// The NIC that ndp belongs to MUST be locked.
 func (ndp *ndpState) doSLAAC(prefix tcpip.Subnet, pl, vl time.Duration) {
 	// If we do not already have an address for this prefix and the valid
 	// lifetime is 0, no need to do anything further, as per RFC 4862
@@ -942,9 +934,59 @@ func (ndp *ndpState) doSLAAC(prefix tcpip.Subnet, pl, vl time.Duration) {
 		return
 	}
 
+	// If the preferred lifetime is zero, then the prefix should be considered
+	// deprecated.
+	deprecated := pl == 0
+	ref := ndp.addSLAACAddr(prefix, deprecated)
+	if ref == nil {
+		// We were unable to generate a permanent address for prefix so do nothing
+		// further as there is no reason to maintain state for a SLAAC prefix we
+		// cannot generate a permanent address for.
+		return
+	}
+
+	state := slaacPrefixState{
+		deprecationTimer: tcpip.MakeCancellableTimer(&ndp.nic.mu, func() {
+			prefixState, ok := ndp.slaacPrefixes[prefix]
+			if !ok {
+				log.Fatalf("ndp: must have a slaacPrefixes entry for the SLAAC prefix %s", prefix)
+			}
+
+			ndp.deprecateSLAACAddress(prefixState.ref)
+		}),
+		invalidationTimer: tcpip.MakeCancellableTimer(&ndp.nic.mu, func() {
+			ndp.invalidateSLAACPrefix(prefix, true)
+		}),
+		ref: ref,
+	}
+
+	// Setup the initial timers to deprecate and invalidate prefix.
+
+	if !deprecated && pl < header.NDPInfiniteLifetime {
+		state.deprecationTimer.Reset(pl)
+	}
+
+	if vl < header.NDPInfiniteLifetime {
+		state.invalidationTimer.Reset(vl)
+		state.validUntil = time.Now().Add(vl)
+	}
+
+	ndp.slaacPrefixes[prefix] = state
+}
+
+// addSLAACAddr adds a SLAAC address for prefix.
+//
+// The NIC that ndp belongs to MUST be locked.
+func (ndp *ndpState) addSLAACAddr(prefix tcpip.Subnet, deprecated bool) *referencedNetworkEndpoint {
 	addrBytes := []byte(prefix.ID())
 	if oIID := ndp.nic.stack.opaqueIIDOpts; oIID.NICNameFromID != nil {
-		addrBytes = header.AppendOpaqueInterfaceIdentifier(addrBytes[:header.IIDOffsetInIPv6Address], prefix, oIID.NICNameFromID(ndp.nic.ID(), ndp.nic.name), 0 /* dadCounter */, oIID.SecretKey)
+		addrBytes = header.AppendOpaqueInterfaceIdentifier(
+			addrBytes[:header.IIDOffsetInIPv6Address],
+			prefix,
+			oIID.NICNameFromID(ndp.nic.ID(), ndp.nic.name),
+			0, /* dadCounter */
+			oIID.SecretKey,
+		)
 	} else {
 		// Only attempt to generate an interface-specific IID if we have a valid
 		// link address.
@@ -953,137 +995,103 @@ func (ndp *ndpState) doSLAAC(prefix tcpip.Subnet, pl, vl time.Duration) {
 		// LinkEndpoint.LinkAddress) before reaching this point.
 		linkAddr := ndp.nic.linkEP.LinkAddress()
 		if !header.IsValidUnicastEthernetAddress(linkAddr) {
-			return
+			return nil
 		}
 
 		// Generate an address within prefix from the modified EUI-64 of ndp's NIC's
 		// Ethernet MAC address.
 		header.EthernetAdddressToModifiedEUI64IntoBuf(linkAddr, addrBytes[header.IIDOffsetInIPv6Address:])
 	}
-	addr := tcpip.Address(addrBytes)
-	addrWithPrefix := tcpip.AddressWithPrefix{
-		Address:   addr,
-		PrefixLen: validPrefixLenForAutoGen,
+
+	generatedAddr := tcpip.ProtocolAddress{
+		Protocol: header.IPv6ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(addrBytes),
+			PrefixLen: validPrefixLenForAutoGen,
+		},
 	}
 
 	// If the nic already has this address, do nothing further.
-	if ndp.nic.hasPermanentAddrLocked(addr) {
-		return
+	if ndp.nic.hasPermanentAddrLocked(generatedAddr.AddressWithPrefix.Address) {
+		return nil
 	}
 
 	// Inform the integrator that we have a new SLAAC address.
 	ndpDisp := ndp.nic.stack.ndpDisp
 	if ndpDisp == nil {
-		return
+		return nil
 	}
-	if !ndpDisp.OnAutoGenAddress(ndp.nic.ID(), addrWithPrefix) {
+
+	if !ndpDisp.OnAutoGenAddress(ndp.nic.ID(), generatedAddr.AddressWithPrefix) {
 		// Informed by the integrator not to add the address.
-		return
+		return nil
 	}
 
-	protocolAddr := tcpip.ProtocolAddress{
-		Protocol:          header.IPv6ProtocolNumber,
-		AddressWithPrefix: addrWithPrefix,
-	}
-	// If the preferred lifetime is zero, then the address should be considered
-	// deprecated.
-	deprecated := pl == 0
-	ref, err := ndp.nic.addAddressLocked(protocolAddr, FirstPrimaryEndpoint, permanent, slaac, deprecated)
+	ref, err := ndp.nic.addAddressLocked(generatedAddr, FirstPrimaryEndpoint, permanent, slaac, deprecated)
 	if err != nil {
-		log.Fatalf("ndp: error when adding address %s: %s", protocolAddr, err)
-	}
-
-	state := autoGenAddressState{
-		ref: ref,
-		deprecationTimer: tcpip.MakeCancellableTimer(&ndp.nic.mu, func() {
-			addrState, ok := ndp.autoGenAddresses[addr]
-			if !ok {
-				log.Fatalf("ndp: must have an autoGenAddressess entry for the SLAAC generated IPv6 address %s", addr)
-			}
-			addrState.ref.deprecated = true
-			ndp.notifyAutoGenAddressDeprecated(addr)
-		}),
-		invalidationTimer: tcpip.MakeCancellableTimer(&ndp.nic.mu, func() {
-			ndp.invalidateAutoGenAddress(addr)
-		}),
+		log.Fatalf("ndp: error when adding address %+v: %s", generatedAddr, err)
 	}
 
-	// Setup the initial timers to deprecate and invalidate this newly generated
-	// address.
-
-	if !deprecated && pl < header.NDPInfiniteLifetime {
-		state.deprecationTimer.Reset(pl)
-	}
-
-	if vl < header.NDPInfiniteLifetime {
-		state.invalidationTimer.Reset(vl)
-		state.validUntil = time.Now().Add(vl)
-	}
-
-	ndp.autoGenAddresses[addr] = state
+	return ref
 }
 
-// refreshAutoGenAddressLifetimes refreshes the lifetime of a SLAAC generated
-// address addr.
+// refreshSLAACPrefixLifetimes refreshes the lifetimes of a SLAAC prefix.
 //
 // pl is the new preferred lifetime. vl is the new valid lifetime.
-func (ndp *ndpState) refreshAutoGenAddressLifetimes(addr tcpip.Address, pl, vl time.Duration) {
-	addrState, ok := ndp.autoGenAddresses[addr]
+//
+// The NIC that ndp belongs to MUST be locked.
+func (ndp *ndpState) refreshSLAACPrefixLifetimes(prefix tcpip.Subnet, pl, vl time.Duration) {
+	prefixState, ok := ndp.slaacPrefixes[prefix]
 	if !ok {
-		log.Fatalf("ndp: SLAAC state not found to refresh lifetimes for %s", addr)
+		log.Fatalf("ndp: SLAAC prefix state not found to refresh lifetimes for %s", prefix)
 	}
-	defer func() { ndp.autoGenAddresses[addr] = addrState }()
+	defer func() { ndp.slaacPrefixes[prefix] = prefixState }()
 
-	// If the preferred lifetime is zero, then the address should be considered
-	// deprecated.
+	// If the preferred lifetime is zero, then the prefix should be deprecated.
 	deprecated := pl == 0
-	wasDeprecated := addrState.ref.deprecated
-	addrState.ref.deprecated = deprecated
-
-	// Only send the deprecation event if the deprecated status for addr just
-	// changed from non-deprecated to deprecated.
-	if !wasDeprecated && deprecated {
-		ndp.notifyAutoGenAddressDeprecated(addr)
+	if deprecated {
+		ndp.deprecateSLAACAddress(prefixState.ref)
+	} else {
+		prefixState.ref.deprecated = false
 	}
 
-	// If addr was preferred for some finite lifetime before, stop the deprecation
-	// timer so it can be reset.
-	addrState.deprecationTimer.StopLocked()
+	// If prefix was preferred for some finite lifetime before, stop the
+	// deprecation timer so it can be reset.
+	prefixState.deprecationTimer.StopLocked()
 
-	// Reset the deprecation timer if addr has a finite preferred lifetime.
+	// Reset the deprecation timer if prefix has a finite preferred lifetime.
 	if !deprecated && pl < header.NDPInfiniteLifetime {
-		addrState.deprecationTimer.Reset(pl)
+		prefixState.deprecationTimer.Reset(pl)
 	}
 
-	// As per RFC 4862 section 5.5.3.e, the valid lifetime of the address
-	//
+	// As per RFC 4862 section 5.5.3.e, update the valid lifetime for prefix:
 	//
 	// 1) If the received Valid Lifetime is greater than 2 hours or greater than
-	//    RemainingLifetime, set the valid lifetime of the address to the
+	//    RemainingLifetime, set the valid lifetime of the prefix to the
 	//    advertised Valid Lifetime.
 	//
 	// 2) If RemainingLifetime is less than or equal to 2 hours, ignore the
 	//    advertised Valid Lifetime.
 	//
-	// 3) Otherwise, reset the valid lifetime of the address to 2 hours.
+	// 3) Otherwise, reset the valid lifetime of the prefix to 2 hours.
 
 	// Handle the infinite valid lifetime separately as we do not keep a timer in
 	// this case.
 	if vl >= header.NDPInfiniteLifetime {
-		addrState.invalidationTimer.StopLocked()
-		addrState.validUntil = time.Time{}
+		prefixState.invalidationTimer.StopLocked()
+		prefixState.validUntil = time.Time{}
 		return
 	}
 
 	var effectiveVl time.Duration
 	var rl time.Duration
 
-	// If the address was originally set to be valid forever, assume the remaining
+	// If the prefix was originally set to be valid forever, assume the remaining
 	// time to be the maximum possible value.
-	if addrState.validUntil == (time.Time{}) {
+	if prefixState.validUntil == (time.Time{}) {
 		rl = header.NDPInfiniteLifetime
 	} else {
-		rl = time.Until(addrState.validUntil)
+		rl = time.Until(prefixState.validUntil)
 	}
 
 	if vl > MinPrefixInformationValidLifetimeForUpdate || vl > rl {
@@ -1094,58 +1102,66 @@ func (ndp *ndpState) refreshAutoGenAddressLifetimes(addr tcpip.Address, pl, vl t
 		effectiveVl = MinPrefixInformationValidLifetimeForUpdate
 	}
 
-	addrState.invalidationTimer.StopLocked()
-	addrState.invalidationTimer.Reset(effectiveVl)
-	addrState.validUntil = time.Now().Add(effectiveVl)
-}
-
-// notifyAutoGenAddressDeprecated notifies the stack's NDP dispatcher that addr
-// has been deprecated.
-func (ndp *ndpState) notifyAutoGenAddressDeprecated(addr tcpip.Address) {
-	if ndpDisp := ndp.nic.stack.ndpDisp; ndpDisp != nil {
-		ndpDisp.OnAutoGenAddressDeprecated(ndp.nic.ID(), tcpip.AddressWithPrefix{
-			Address:   addr,
-			PrefixLen: validPrefixLenForAutoGen,
-		})
-	}
+	prefixState.invalidationTimer.StopLocked()
+	prefixState.invalidationTimer.Reset(effectiveVl)
+	prefixState.validUntil = time.Now().Add(effectiveVl)
 }
 
-// invalidateAutoGenAddress invalidates an auto-generated address.
+// deprecateSLAACAddress marks ref as deprecated and notifies the stack's NDP
+// dispatcher that ref has been deprecated.
+//
+// deprecateSLAACAddress does nothing if ref is already deprecated.
 //
 // The NIC that ndp belongs to MUST be locked.
-func (ndp *ndpState) invalidateAutoGenAddress(addr tcpip.Address) {
-	if !ndp.cleanupAutoGenAddrResourcesAndNotify(addr) {
+func (ndp *ndpState) deprecateSLAACAddress(ref *referencedNetworkEndpoint) {
+	if ref.deprecated {
 		return
 	}
 
-	ndp.nic.removePermanentAddressLocked(addr)
+	ref.deprecated = true
+	if ndpDisp := ndp.nic.stack.ndpDisp; ndpDisp != nil {
+		ndpDisp.OnAutoGenAddressDeprecated(ndp.nic.ID(), tcpip.AddressWithPrefix{
+			Address:   ref.ep.ID().LocalAddress,
+			PrefixLen: ref.ep.PrefixLen(),
+		})
+	}
 }
 
-// cleanupAutoGenAddrResourcesAndNotify cleans up an invalidated auto-generated
-// address's resources from ndp. If the stack has an NDP dispatcher, it will
-// be notified that addr has been invalidated.
-//
-// Returns true if ndp had resources for addr to cleanup.
+// invalidateSLAACPrefix invalidates a SLAAC prefix.
 //
 // The NIC that ndp belongs to MUST be locked.
-func (ndp *ndpState) cleanupAutoGenAddrResourcesAndNotify(addr tcpip.Address) bool {
-	state, ok := ndp.autoGenAddresses[addr]
+func (ndp *ndpState) invalidateSLAACPrefix(prefix tcpip.Subnet, removeAddr bool) {
+	state, ok := ndp.slaacPrefixes[prefix]
 	if !ok {
-		return false
+		return
 	}
 
 	state.deprecationTimer.StopLocked()
 	state.invalidationTimer.StopLocked()
-	delete(ndp.autoGenAddresses, addr)
+	delete(ndp.slaacPrefixes, prefix)
+
+	addr := state.ref.ep.ID().LocalAddress
+
+	if removeAddr {
+		if err := ndp.nic.removePermanentAddressLocked(addr); err != nil {
+			log.Fatalf("ndp: removePermanentAddressLocked(%s): %s", addr, err)
+		}
+	}
 
 	if ndpDisp := ndp.nic.stack.ndpDisp; ndpDisp != nil {
 		ndpDisp.OnAutoGenAddressInvalidated(ndp.nic.ID(), tcpip.AddressWithPrefix{
 			Address:   addr,
-			PrefixLen: validPrefixLenForAutoGen,
+			PrefixLen: state.ref.ep.PrefixLen(),
 		})
 	}
+}
 
-	return true
+// cleanupSLAACAddrResourcesAndNotify cleans up an invalidated SLAAC
+// address's resources from ndp.
+//
+// The NIC that ndp belongs to MUST be locked.
+func (ndp *ndpState) cleanupSLAACAddrResourcesAndNotify(addr tcpip.AddressWithPrefix) {
+	ndp.invalidateSLAACPrefix(addr.Subnet(), false)
 }
 
 // cleanupState cleans up ndp's state.
@@ -1163,21 +1179,21 @@ func (ndp *ndpState) cleanupAutoGenAddrResourcesAndNotify(addr tcpip.Address) bo
 // The NIC that ndp belongs to MUST be locked.
 func (ndp *ndpState) cleanupState(hostOnly bool) {
 	linkLocalSubnet := header.IPv6LinkLocalPrefix.Subnet()
-	linkLocalAddrs := 0
-	for addr := range ndp.autoGenAddresses {
+	linkLocalPrefixes := 0
+	for prefix := range ndp.slaacPrefixes {
 		// RFC 4862 section 5 states that routers are also expected to generate a
 		// link-local address so we do not invalidate them if we are cleaning up
 		// host-only state.
-		if hostOnly && linkLocalSubnet.Contains(addr) {
-			linkLocalAddrs++
+		if hostOnly && prefix == linkLocalSubnet {
+			linkLocalPrefixes++
 			continue
 		}
 
-		ndp.invalidateAutoGenAddress(addr)
+		ndp.invalidateSLAACPrefix(prefix, true)
 	}
 
-	if got := len(ndp.autoGenAddresses); got != linkLocalAddrs {
-		log.Fatalf("ndp: still have non-linklocal auto-generated addresses after cleaning up; found = %d prefixes, of which %d are link-local", got, linkLocalAddrs)
+	if got := len(ndp.slaacPrefixes); got != linkLocalPrefixes {
+		log.Fatalf("ndp: still have non-linklocal SLAAC prefixes after cleaning up; found = %d prefixes, of which %d are link-local", got, linkLocalPrefixes)
 	}
 
 	for prefix := range ndp.onLinkPrefixes {
diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index 11eaa6a2c..9dcb1d52c 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -126,12 +126,12 @@ func newNIC(stack *Stack, id tcpip.NICID, name string, ep LinkEndpoint, ctx NICC
 	nic.mu.mcastJoins = make(map[NetworkEndpointID]uint32)
 	nic.mu.packetEPs = make(map[tcpip.NetworkProtocolNumber][]PacketEndpoint)
 	nic.mu.ndp = ndpState{
-		nic:              nic,
-		configs:          stack.ndpConfigs,
-		dad:              make(map[tcpip.Address]dadState),
-		defaultRouters:   make(map[tcpip.Address]defaultRouterState),
-		onLinkPrefixes:   make(map[tcpip.Subnet]onLinkPrefixState),
-		autoGenAddresses: make(map[tcpip.Address]autoGenAddressState),
+		nic:            nic,
+		configs:        stack.ndpConfigs,
+		dad:            make(map[tcpip.Address]dadState),
+		defaultRouters: make(map[tcpip.Address]defaultRouterState),
+		onLinkPrefixes: make(map[tcpip.Subnet]onLinkPrefixState),
+		slaacPrefixes:  make(map[tcpip.Subnet]slaacPrefixState),
 	}
 
 	// Register supported packet endpoint protocols.
@@ -1017,8 +1017,7 @@ func (n *NIC) removePermanentAddressLocked(addr tcpip.Address) *tcpip.Error {
 	isIPv6Unicast := r.protocol == header.IPv6ProtocolNumber && header.IsV6UnicastAddress(addr)
 
 	if isIPv6Unicast {
-		// If we are removing a tentative IPv6 unicast address, stop
-		// DAD.
+		// If we are removing a tentative IPv6 unicast address, stop DAD.
 		if kind == permanentTentative {
 			n.mu.ndp.stopDuplicateAddressDetection(addr)
 		}
@@ -1026,7 +1025,10 @@ func (n *NIC) removePermanentAddressLocked(addr tcpip.Address) *tcpip.Error {
 		// If we are removing an address generated via SLAAC, cleanup
 		// its SLAAC resources and notify the integrator.
 		if r.configType == slaac {
-			n.mu.ndp.cleanupAutoGenAddrResourcesAndNotify(addr)
+			n.mu.ndp.cleanupSLAACAddrResourcesAndNotify(tcpip.AddressWithPrefix{
+				Address:   addr,
+				PrefixLen: r.ep.PrefixLen(),
+			})
 		}
 	}