Support performing DAD for any address

...as long as the network protocol supports duplicate address detection.

This CL provides the facilities for a netstack integrator to perform
DAD.

DHCP recommends that clients effectively perform DAD before accepting an
offer. As per RFC 2131 section 4.4.1 pg 38,

  The client SHOULD perform a check on the suggested address to ensure
  that the address is not already in use.  For example, if the client
  is on a network that supports ARP, the client may issue an ARP request
  for the suggested request.

The implementation of ARP-based IPv4 DAD effectively operates the same
as IPv6's NDP DAD - using ARP requests and responses in place of
NDP neighbour solicitations and advertisements, respectively.

DAD performed by calls to (*Stack).CheckDuplicateAddress don't interfere
with DAD performed when a new IPv6 address is added. This is so that
integrator requests to check for duplicate addresses aren't unexpectedly
aborted when addresses are removed.

A network package internal package provides protocol agnostic DAD state
management that specific protocols that provide DAD can use.

Fixes #4550.

Tests:
  - internal/ip_test.*
  - integration_test.TestDAD
  - arp_test.TestDADARPRequestPacket
  - ipv6.TestCheckDuplicateAddress
PiperOrigin-RevId: 356405593

6 files changed, 250 insertions, 211 deletions

diff --git a/pkg/tcpip/network/ipv6/BUILD b/pkg/tcpip/network/ipv6/BUILD
index 0c5f8d683..d75b0b8de 100644
--- a/pkg/tcpip/network/ipv6/BUILD
+++ b/pkg/tcpip/network/ipv6/BUILD
@@ -21,6 +21,7 @@ go_library(
         "//pkg/tcpip/header/parse",
         "//pkg/tcpip/network/fragmentation",
         "//pkg/tcpip/network/hash",
+        "//pkg/tcpip/network/internal/ip",
         "//pkg/tcpip/network/ip",
         "//pkg/tcpip/stack",
     ],
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index edf4ef4e5..2690644d6 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -537,6 +537,11 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer, hasFragmentHeader bool) {
 		// NDP datagrams are very small and ToView() will not incur allocations.
 		na := header.NDPNeighborAdvert(payload.ToView())
 		targetAddr := na.TargetAddress()
+
+		e.dad.mu.Lock()
+		e.dad.mu.dad.StopLocked(targetAddr, false /* aborted */)
+		e.dad.mu.Unlock()
+
 		if e.hasTentativeAddr(targetAddr) {
 			// We just got an NA from a node that owns an address we are performing
 			// DAD on, implying the address is not unique. In this case we let the
@@ -866,37 +871,9 @@ func (e *endpoint) LinkAddressRequest(targetAddr, localAddr tcpip.Address, remot
 		return &tcpip.ErrBadLocalAddress{}
 	}
 
-	optsSerializer := header.NDPOptionsSerializer{
+	return e.sendNDPNS(localAddr, remoteAddr, targetAddr, remoteLinkAddr, header.NDPOptionsSerializer{
 		header.NDPSourceLinkLayerAddressOption(e.nic.LinkAddress()),
-	}
-	neighborSolicitSize := header.ICMPv6NeighborSolicitMinimumSize + optsSerializer.Length()
-	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
-		ReserveHeaderBytes: int(e.nic.MaxHeaderLength()) + header.IPv6FixedHeaderSize + neighborSolicitSize,
 	})
-	pkt.TransportProtocolNumber = header.ICMPv6ProtocolNumber
-	packet := header.ICMPv6(pkt.TransportHeader().Push(neighborSolicitSize))
-	packet.SetType(header.ICMPv6NeighborSolicit)
-	ns := header.NDPNeighborSolicit(packet.MessageBody())
-	ns.SetTargetAddress(targetAddr)
-	ns.Options().Serialize(optsSerializer)
-	packet.SetChecksum(header.ICMPv6Checksum(packet, localAddr, remoteAddr, buffer.VectorisedView{}))
-
-	if err := addIPHeader(localAddr, remoteAddr, pkt, stack.NetworkHeaderParams{
-		Protocol: header.ICMPv6ProtocolNumber,
-		TTL:      header.NDPHopLimit,
-	}, header.IPv6ExtHdrSerializer{}); err != nil {
-		panic(fmt.Sprintf("failed to add IP header: %s", err))
-	}
-
-	stat := e.stats.icmp.packetsSent
-
-	if err := e.nic.WritePacketToRemote(remoteLinkAddr, nil /* gso */, ProtocolNumber, pkt); err != nil {
-		stat.dropped.Increment()
-		return err
-	}
-
-	stat.neighborSolicit.Increment()
-	return nil
 }
 
 // ResolveStaticAddress implements stack.LinkAddressResolver.
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 5856c9d3c..56bbf1cc3 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -32,6 +32,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip/header/parse"
 	"gvisor.dev/gvisor/pkg/tcpip/network/fragmentation"
 	"gvisor.dev/gvisor/pkg/tcpip/network/hash"
+	"gvisor.dev/gvisor/pkg/tcpip/network/internal/ip"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
@@ -164,6 +165,7 @@ func getLabel(addr tcpip.Address) uint8 {
 	panic(fmt.Sprintf("should have a label for address = %s", addr))
 }
 
+var _ stack.DuplicateAddressDetector = (*endpoint)(nil)
 var _ stack.LinkAddressResolver = (*endpoint)(nil)
 var _ stack.LinkResolvableNetworkEndpoint = (*endpoint)(nil)
 var _ stack.GroupAddressableEndpoint = (*endpoint)(nil)
@@ -192,6 +194,23 @@ type endpoint struct {
 		ndp                      ndpState
 		mld                      mldState
 	}
+
+	// dad is used to check if an arbitrary address is already assigned to some
+	// neighbor.
+	//
+	// Note: this is different from mu.ndp.dad which is used to perform DAD for
+	// addresses that are assigned to the interface. Removing an address aborts
+	// DAD; if we had used the same state, handlers for a removed address would
+	// not be called with the actual DAD result.
+	//
+	// LOCK ORDERING: mu > dad.mu.
+	dad struct {
+		mu struct {
+			sync.Mutex
+
+			dad ip.DAD
+		}
+	}
 }
 
 // NICNameFromID is a function that returns a stable name for the specified NIC,
@@ -226,6 +245,29 @@ type OpaqueInterfaceIdentifierOptions struct {
 	SecretKey []byte
 }
 
+// CheckDuplicateAddress implements stack.DuplicateAddressDetector.
+func (e *endpoint) CheckDuplicateAddress(addr tcpip.Address, h stack.DADCompletionHandler) stack.DADCheckAddressDisposition {
+	e.dad.mu.Lock()
+	defer e.dad.mu.Unlock()
+	return e.dad.mu.dad.CheckDuplicateAddressLocked(addr, h)
+}
+
+// SetDADConfigurations implements stack.DuplicateAddressDetector.
+func (e *endpoint) SetDADConfigurations(c stack.DADConfigurations) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	e.dad.mu.Lock()
+	defer e.dad.mu.Unlock()
+
+	e.mu.ndp.dad.SetConfigsLocked(c)
+	e.dad.mu.dad.SetConfigsLocked(c)
+}
+
+// DuplicateAddressProtocol implements stack.DuplicateAddressDetector.
+func (*endpoint) DuplicateAddressProtocol() tcpip.NetworkProtocolNumber {
+	return ProtocolNumber
+}
+
 // HandleLinkResolutionFailure implements stack.LinkResolvableNetworkEndpoint.
 func (e *endpoint) HandleLinkResolutionFailure(pkt *stack.PacketBuffer) {
 	// handleControl expects the entire offending packet to be in the packet
@@ -321,7 +363,7 @@ func (e *endpoint) dupTentativeAddrDetected(addr tcpip.Address) tcpip.Error {
 
 	// If the address is a SLAAC address, do not invalidate its SLAAC prefix as an
 	// attempt will be made to generate a new address for it.
-	if err := e.removePermanentEndpointLocked(addressEndpoint, false /* allowSLAACInvalidation */); err != nil {
+	if err := e.removePermanentEndpointLocked(addressEndpoint, false /* allowSLAACInvalidation */, true /* dadFailure */); err != nil {
 		return err
 	}
 
@@ -525,7 +567,7 @@ func (e *endpoint) stopDADForPermanentAddressesLocked() {
 
 		addr := addressEndpoint.AddressWithPrefix().Address
 		if header.IsV6UnicastAddress(addr) {
-			e.mu.ndp.stopDuplicateAddressDetection(addr)
+			e.mu.ndp.stopDuplicateAddressDetection(addr, false /* failed */)
 		}
 
 		return true
@@ -1390,18 +1432,18 @@ func (e *endpoint) RemovePermanentAddress(addr tcpip.Address) tcpip.Error {
 		return &tcpip.ErrBadLocalAddress{}
 	}
 
-	return e.removePermanentEndpointLocked(addressEndpoint, true)
+	return e.removePermanentEndpointLocked(addressEndpoint, true /* allowSLAACInvalidation */, false /* dadFailure */)
 }
 
 // removePermanentEndpointLocked is like removePermanentAddressLocked except
 // it works with a stack.AddressEndpoint.
 //
 // Precondition: e.mu must be write locked.
-func (e *endpoint) removePermanentEndpointLocked(addressEndpoint stack.AddressEndpoint, allowSLAACInvalidation bool) tcpip.Error {
+func (e *endpoint) removePermanentEndpointLocked(addressEndpoint stack.AddressEndpoint, allowSLAACInvalidation, dadFailure bool) tcpip.Error {
 	addr := addressEndpoint.AddressWithPrefix()
 	unicast := header.IsV6UnicastAddress(addr.Address)
 	if unicast {
-		e.mu.ndp.stopDuplicateAddressDetection(addr.Address)
+		e.mu.ndp.stopDuplicateAddressDetection(addr.Address, dadFailure)
 
 		// If we are removing an address generated via SLAAC, cleanup
 		// its SLAAC resources and notify the integrator.
@@ -1747,6 +1789,13 @@ func (p *protocol) NewEndpoint(nic stack.NetworkInterface, dispatcher stack.Tran
 	e.mu.addressableEndpointState.Init(e)
 	e.mu.ndp.init(e)
 	e.mu.mld.init(e)
+	e.dad.mu.Lock()
+	e.dad.mu.dad.Init(&e.dad.mu, p.options.DADConfigs, ip.DADOptions{
+		Clock:    p.stack.Clock(),
+		Protocol: &e.mu.ndp,
+		NICID:    nic.ID(),
+	})
+	e.dad.mu.Unlock()
 	e.mu.Unlock()
 
 	stackStats := p.stack.Stats()
@@ -1949,6 +1998,9 @@ type Options struct {
 
 	// MLD holds options for MLD.
 	MLD MLDOptions
+
+	// DADConfigs holds the default DAD configurations used by IPv6 endpoints.
+	DADConfigs stack.DADConfigurations
 }
 
 // NewProtocolWithOptions returns an IPv6 network protocol.
diff --git a/pkg/tcpip/network/ipv6/mld_test.go b/pkg/tcpip/network/ipv6/mld_test.go
index f6ffa7133..fe39555e0 100644
--- a/pkg/tcpip/network/ipv6/mld_test.go
+++ b/pkg/tcpip/network/ipv6/mld_test.go
@@ -126,7 +126,7 @@ func TestSendQueuedMLDReports(t *testing.T) {
 			clock := faketime.NewManualClock()
 			s := stack.New(stack.Options{
 				NetworkProtocols: []stack.NetworkProtocolFactory{ipv6.NewProtocolWithOptions(ipv6.Options{
-					NDPConfigs: ipv6.NDPConfigurations{
+					DADConfigs: stack.DADConfigurations{
 						DupAddrDetectTransmits: test.dadTransmits,
 						RetransmitTimer:        test.retransmitTimer,
 					},
diff --git a/pkg/tcpip/network/ipv6/ndp.go b/pkg/tcpip/network/ipv6/ndp.go
index 411a6c862..a55330b7e 100644
--- a/pkg/tcpip/network/ipv6/ndp.go
+++ b/pkg/tcpip/network/ipv6/ndp.go
@@ -23,34 +23,11 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/network/internal/ip"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
 const (
-	// defaultRetransmitTimer is the default amount of time to wait between
-	// sending reachability probes.
-	//
-	// Default taken from RETRANS_TIMER of RFC 4861 section 10.
-	defaultRetransmitTimer = time.Second
-
-	// minimumRetransmitTimer is the minimum amount of time to wait between
-	// sending reachability probes.
-	//
-	// Note, RFC 4861 does not impose a minimum Retransmit Timer, but we do here
-	// to make sure the messages are not sent all at once. We also come to this
-	// value because in the RetransmitTimer field of a Router Advertisement, a
-	// value of 0 means unspecified, so the smallest valid value is 1. Note, the
-	// unit of the RetransmitTimer field in the Router Advertisement is
-	// milliseconds.
-	minimumRetransmitTimer = time.Millisecond
-
-	// defaultDupAddrDetectTransmits is the default number of NDP Neighbor
-	// Solicitation messages to send when doing Duplicate Address Detection
-	// for a tentative address.
-	//
-	// Default = 1 (from RFC 4862 section 5.1)
-	defaultDupAddrDetectTransmits = 1
-
 	// defaultMaxRtrSolicitations is the default number of Router
 	// Solicitation messages to send when an IPv6 endpoint becomes enabled.
 	//
@@ -330,18 +307,6 @@ type NDPDispatcher interface {
 
 // NDPConfigurations is the NDP configurations for the netstack.
 type NDPConfigurations struct {
-	// The number of Neighbor Solicitation messages to send when doing
-	// Duplicate Address Detection for a tentative address.
-	//
-	// Note, a value of zero effectively disables DAD.
-	DupAddrDetectTransmits uint8
-
-	// The amount of time to wait between sending Neighbor solicitation
-	// messages.
-	//
-	// Must be greater than or equal to 1ms.
-	RetransmitTimer time.Duration
-
 	// The number of Router Solicitation messages to send when the IPv6 endpoint
 	// becomes enabled.
 	MaxRtrSolicitations uint8
@@ -413,8 +378,6 @@ type NDPConfigurations struct {
 // default values.
 func DefaultNDPConfigurations() NDPConfigurations {
 	return NDPConfigurations{
-		DupAddrDetectTransmits:       defaultDupAddrDetectTransmits,
-		RetransmitTimer:              defaultRetransmitTimer,
 		MaxRtrSolicitations:          defaultMaxRtrSolicitations,
 		RtrSolicitationInterval:      defaultRtrSolicitationInterval,
 		MaxRtrSolicitationDelay:      defaultMaxRtrSolicitationDelay,
@@ -432,10 +395,6 @@ func DefaultNDPConfigurations() NDPConfigurations {
 // validate modifies an NDPConfigurations with valid values. If invalid values
 // are present in c, the corresponding default values are used instead.
 func (c *NDPConfigurations) validate() {
-	if c.RetransmitTimer < minimumRetransmitTimer {
-		c.RetransmitTimer = defaultRetransmitTimer
-	}
-
 	if c.RtrSolicitationInterval < minimumRtrSolicitationInterval {
 		c.RtrSolicitationInterval = defaultRtrSolicitationInterval
 	}
@@ -476,7 +435,7 @@ type ndpState struct {
 	configs NDPConfigurations
 
 	// The DAD timers to send the next NS message, or resolve the address.
-	dad map[tcpip.Address]timer
+	dad ip.DAD
 
 	// The default routers discovered through Router Advertisements.
 	defaultRouters map[tcpip.Address]defaultRouterState
@@ -635,130 +594,46 @@ func (ndp *ndpState) startDuplicateAddressDetection(addr tcpip.Address, addressE
 		panic(fmt.Sprintf("ndpdad: addr %s is not tentative on NIC(%d)", addr, ndp.ep.nic.ID()))
 	}
 
-	// Should not attempt to perform DAD on an address that is currently in the
-	// DAD process.
-	if _, ok := ndp.dad[addr]; ok {
-		// Should never happen because we should only ever call this function for
-		// newly created addresses. If we attemped to "add" an address that already
-		// existed, we would get an error since we attempted to add a duplicate
-		// address, or its reference count would have been increased without doing
-		// the work that would have been done for an address that was brand new.
-		// See endpoint.addAddressLocked.
-		panic(fmt.Sprintf("ndpdad: already performing DAD for addr %s on NIC(%d)", addr, ndp.ep.nic.ID()))
-	}
+	ret := ndp.dad.CheckDuplicateAddressLocked(addr, func(r stack.DADResult) {
+		if addressEndpoint.GetKind() != stack.PermanentTentative {
+			// The endpoint should still be marked as tentative since we are still
+			// performing DAD on it.
+			panic(fmt.Sprintf("ndpdad: addr %s is no longer tentative on NIC(%d)", addr, ndp.ep.nic.ID()))
+		}
 
-	if ndp.configs.DupAddrDetectTransmits == 0 {
-		addressEndpoint.SetKind(stack.Permanent)
+		if r.Resolved {
+			addressEndpoint.SetKind(stack.Permanent)
+		}
 
-		// Consider DAD to have resolved even if no DAD messages were actually
-		// transmitted.
 		if ndpDisp := ndp.ep.protocol.options.NDPDisp; ndpDisp != nil {
-			ndpDisp.OnDuplicateAddressDetectionStatus(ndp.ep.nic.ID(), addr, true, nil)
+			ndpDisp.OnDuplicateAddressDetectionStatus(ndp.ep.nic.ID(), addr, r.Resolved, r.Err)
 		}
 
-		ndp.ep.onAddressAssignedLocked(addr)
-		return nil
-	}
-
-	var remaining remainingCounter
-	remaining.init(ndp.configs.DupAddrDetectTransmits)
-	// We initially start a timer to fire immediately because some of the DAD work
-	// cannot be done while holding the IPv6 endpoint's lock. This is effectively
-	// the same as starting a goroutine but we use a timer that fires immediately
-	// so we can reset it for the next DAD iteration.
-
-	// Protected by ndp.ep.mu.
-	done := false
-
-	ndp.dad[addr] = timer{
-		done: &done,
-		timer: ndp.ep.protocol.stack.Clock().AfterFunc(0, func() {
-			// Okay to hold this lock while writing packets since we use a different
-			// lock per DAD timer so there will not be any lock contention.
-			remaining.mu.Lock()
-			defer remaining.mu.Unlock()
-
-			var err tcpip.Error
-			dadDone := remaining.mu.remaining == 0
-			if !dadDone {
-				snmc := header.SolicitedNodeAddr(addr)
-
-				icmp := header.ICMPv6(buffer.NewView(header.ICMPv6NeighborSolicitMinimumSize))
-				icmp.SetType(header.ICMPv6NeighborSolicit)
-				ns := header.NDPNeighborSolicit(icmp.MessageBody())
-				ns.SetTargetAddress(addr)
-				icmp.SetChecksum(header.ICMPv6Checksum(icmp, header.IPv6Any, snmc, buffer.VectorisedView{}))
-
-				pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
-					ReserveHeaderBytes: int(ndp.ep.MaxHeaderLength()),
-					Data:               buffer.View(icmp).ToVectorisedView(),
-				})
-
-				sent := ndp.ep.stats.icmp.packetsSent
-				if err := addIPHeader(header.IPv6Any, snmc, pkt, stack.NetworkHeaderParams{
-					Protocol: header.ICMPv6ProtocolNumber,
-					TTL:      header.NDPHopLimit,
-				}, nil /* extensionHeaders */); err != nil {
-					panic(fmt.Sprintf("failed to add IP header: %s", err))
-				}
-
-				err = ndp.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv6Address(snmc), nil /* gso */, ProtocolNumber, pkt)
-				if err != nil {
-					sent.dropped.Increment()
-				} else {
-					sent.neighborSolicit.Increment()
-				}
+		if r.Resolved {
+			if addressEndpoint.ConfigType() == stack.AddressConfigSlaac {
+				// Reset the generation attempts counter as we are starting the
+				// generation of a new address for the SLAAC prefix.
+				ndp.regenerateTempSLAACAddr(addressEndpoint.AddressWithPrefix().Subnet(), true /* resetGenAttempts */)
 			}
 
-			ndp.ep.mu.Lock()
-			defer ndp.ep.mu.Unlock()
-
-			if done {
-				// DAD was stopped.
-				return
-			}
-
-			timer, ok := ndp.dad[addr]
-			if !ok {
-				panic(fmt.Sprintf("ndpdad: DAD timer fired but missing state for %s on NIC(%d)", addr, ndp.ep.nic.ID()))
-			}
-
-			if addressEndpoint.GetKind() != stack.PermanentTentative {
-				// The endpoint should still be marked as tentative since we are still
-				// performing DAD on it.
-				panic(fmt.Sprintf("ndpdad: addr %s is no longer tentative on NIC(%d)", addr, ndp.ep.nic.ID()))
-			}
-
-			if dadDone {
-				// DAD has resolved.
-				addressEndpoint.SetKind(stack.Permanent)
-			} else if err == nil {
-				// DAD is not done and we had no errors when sending the last NDP NS,
-				// schedule the next DAD timer.
-				remaining.mu.remaining--
-				timer.timer.Reset(ndp.configs.RetransmitTimer)
-				return
-			}
-
-			// At this point we know that either DAD is done or we hit an error
-			// sending the last NDP NS. Either way, clean up addr's DAD state and let
-			// the integrator know DAD has completed.
-			delete(ndp.dad, addr)
+			ndp.ep.onAddressAssignedLocked(addr)
+		}
+	})
 
-			if ndpDisp := ndp.ep.protocol.options.NDPDisp; ndpDisp != nil {
-				ndpDisp.OnDuplicateAddressDetectionStatus(ndp.ep.nic.ID(), addr, dadDone, err)
-			}
+	switch ret {
+	case stack.DADStarting:
+	case stack.DADAlreadyRunning:
+		panic(fmt.Sprintf("ndpdad: already performing DAD for addr %s on NIC(%d)", addr, ndp.ep.nic.ID()))
+	case stack.DADDisabled:
+		addressEndpoint.SetKind(stack.Permanent)
 
-			if dadDone {
-				if addressEndpoint.ConfigType() == stack.AddressConfigSlaac {
-					// Reset the generation attempts counter as we are starting the
-					// generation of a new address for the SLAAC prefix.
-					ndp.regenerateTempSLAACAddr(addressEndpoint.AddressWithPrefix().Subnet(), true /* resetGenAttempts */)
-				}
+		// Consider DAD to have resolved even if no DAD messages were actually
+		// transmitted.
+		if ndpDisp := ndp.ep.protocol.options.NDPDisp; ndpDisp != nil {
+			ndpDisp.OnDuplicateAddressDetectionStatus(ndp.ep.nic.ID(), addr, true, nil)
+		}
 
-				ndp.ep.onAddressAssignedLocked(addr)
-			}
-		}),
+		ndp.ep.onAddressAssignedLocked(addr)
 	}
 
 	return nil
@@ -772,21 +647,8 @@ func (ndp *ndpState) startDuplicateAddressDetection(addr tcpip.Address, addressE
 // of this function to handle such a scenario.
 //
 // The IPv6 endpoint that ndp belongs to MUST be locked.
-func (ndp *ndpState) stopDuplicateAddressDetection(addr tcpip.Address) {
-	timer, ok := ndp.dad[addr]
-	if !ok {
-		// Not currently performing DAD on addr, just return.
-		return
-	}
-
-	timer.timer.Stop()
-	*timer.done = true
-	delete(ndp.dad, addr)
-
-	// Let the integrator know DAD did not resolve.
-	if ndpDisp := ndp.ep.protocol.options.NDPDisp; ndpDisp != nil {
-		ndpDisp.OnDuplicateAddressDetectionStatus(ndp.ep.nic.ID(), addr, false, nil)
-	}
+func (ndp *ndpState) stopDuplicateAddressDetection(addr tcpip.Address, failed bool) {
+	ndp.dad.StopLocked(addr, !failed)
 }
 
 // handleRA handles a Router Advertisement message that arrived on the NIC
@@ -1651,7 +1513,7 @@ func (ndp *ndpState) invalidateSLAACPrefix(prefix tcpip.Subnet, state slaacPrefi
 	if addressEndpoint := state.stableAddr.addressEndpoint; addressEndpoint != nil {
 		// Since we are already invalidating the prefix, do not invalidate the
 		// prefix when removing the address.
-		if err := ndp.ep.removePermanentEndpointLocked(addressEndpoint, false /* allowSLAACInvalidation */); err != nil {
+		if err := ndp.ep.removePermanentEndpointLocked(addressEndpoint, false /* allowSLAACInvalidation */, false /* dadFailure */); err != nil {
 			panic(fmt.Sprintf("ndp: error removing stable SLAAC address %s: %s", addressEndpoint.AddressWithPrefix(), err))
 		}
 	}
@@ -1710,7 +1572,7 @@ func (ndp *ndpState) cleanupSLAACPrefixResources(prefix tcpip.Subnet, state slaa
 func (ndp *ndpState) invalidateTempSLAACAddr(tempAddrs map[tcpip.Address]tempSLAACAddrState, tempAddr tcpip.Address, tempAddrState tempSLAACAddrState) {
 	// Since we are already invalidating the address, do not invalidate the
 	// address when removing the address.
-	if err := ndp.ep.removePermanentEndpointLocked(tempAddrState.addressEndpoint, false /* allowSLAACInvalidation */); err != nil {
+	if err := ndp.ep.removePermanentEndpointLocked(tempAddrState.addressEndpoint, false /* allowSLAACInvalidation */, false /* dadFailure */); err != nil {
 		panic(fmt.Sprintf("error removing temporary SLAAC address %s: %s", tempAddrState.addressEndpoint.AddressWithPrefix(), err))
 	}
 
@@ -1942,13 +1804,17 @@ func (ndp *ndpState) stopSolicitingRouters() {
 }
 
 func (ndp *ndpState) init(ep *endpoint) {
-	if ndp.dad != nil {
+	if ndp.defaultRouters != nil {
 		panic("attempted to initialize NDP state twice")
 	}
 
 	ndp.ep = ep
 	ndp.configs = ep.protocol.options.NDPConfigs
-	ndp.dad = make(map[tcpip.Address]timer)
+	ndp.dad.Init(&ndp.ep.mu, ep.protocol.options.DADConfigs, ip.DADOptions{
+		Clock:    ep.protocol.stack.Clock(),
+		Protocol: ndp,
+		NICID:    ep.nic.ID(),
+	})
 	ndp.defaultRouters = make(map[tcpip.Address]defaultRouterState)
 	ndp.onLinkPrefixes = make(map[tcpip.Subnet]onLinkPrefixState)
 	ndp.slaacPrefixes = make(map[tcpip.Subnet]slaacPrefixState)
@@ -1958,3 +1824,38 @@ func (ndp *ndpState) init(ep *endpoint) {
 		ndp.temporaryAddressDesyncFactor = time.Duration(rand.Int63n(int64(MaxDesyncFactor)))
 	}
 }
+
+func (ndp *ndpState) SendDADMessage(addr tcpip.Address) tcpip.Error {
+	snmc := header.SolicitedNodeAddr(addr)
+	return ndp.ep.sendNDPNS(header.IPv6Any, snmc, addr, header.EthernetAddressFromMulticastIPv6Address(snmc), nil /* opts */)
+}
+
+func (e *endpoint) sendNDPNS(srcAddr, dstAddr, targetAddr tcpip.Address, remoteLinkAddr tcpip.LinkAddress, opts header.NDPOptionsSerializer) tcpip.Error {
+	icmp := header.ICMPv6(buffer.NewView(header.ICMPv6NeighborSolicitMinimumSize + opts.Length()))
+	icmp.SetType(header.ICMPv6NeighborSolicit)
+	ns := header.NDPNeighborSolicit(icmp.MessageBody())
+	ns.SetTargetAddress(targetAddr)
+	ns.Options().Serialize(opts)
+	icmp.SetChecksum(header.ICMPv6Checksum(icmp, srcAddr, dstAddr, buffer.VectorisedView{}))
+
+	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
+		ReserveHeaderBytes: int(e.MaxHeaderLength()),
+		Data:               buffer.View(icmp).ToVectorisedView(),
+	})
+
+	if err := addIPHeader(srcAddr, dstAddr, pkt, stack.NetworkHeaderParams{
+		Protocol: header.ICMPv6ProtocolNumber,
+		TTL:      header.NDPHopLimit,
+	}, nil /* extensionHeaders */); err != nil {
+		panic(fmt.Sprintf("failed to add IP header: %s", err))
+	}
+
+	sent := e.stats.icmp.packetsSent
+	err := e.nic.WritePacketToRemote(remoteLinkAddr, nil /* gso */, ProtocolNumber, pkt)
+	if err != nil {
+		sent.dropped.Increment()
+	} else {
+		sent.neighborSolicit.Increment()
+	}
+	return err
+}
diff --git a/pkg/tcpip/network/ipv6/ndp_test.go b/pkg/tcpip/network/ipv6/ndp_test.go
index 5ff247653..ce20af0e3 100644
--- a/pkg/tcpip/network/ipv6/ndp_test.go
+++ b/pkg/tcpip/network/ipv6/ndp_test.go
@@ -24,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/checker"
+	"gvisor.dev/gvisor/pkg/tcpip/faketime"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/link/channel"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
@@ -1222,3 +1223,110 @@ func TestRouterAdvertValidation(t *testing.T) {
 		})
 	}
 }
+
+// TestCheckDuplicateAddress checks that calls to CheckDuplicateAddress and DAD
+// performed when adding new addresses do not interfere with each other.
+func TestCheckDuplicateAddress(t *testing.T) {
+	const nicID = 1
+
+	clock := faketime.NewManualClock()
+	dadConfigs := stack.DADConfigurations{
+		DupAddrDetectTransmits: 1,
+		RetransmitTimer:        time.Second,
+	}
+	s := stack.New(stack.Options{
+		Clock: clock,
+		NetworkProtocols: []stack.NetworkProtocolFactory{NewProtocolWithOptions(Options{
+			DADConfigs: dadConfigs,
+		})},
+	})
+	// This test is expected to send at max 2 DAD messages. We allow an extra
+	// packet to be stored to catch unexpected packets.
+	e := channel.New(3, header.IPv6MinimumMTU, linkAddr0)
+	e.LinkEPCapabilities |= stack.CapabilityResolutionRequired
+	if err := s.CreateNIC(nicID, e); err != nil {
+		t.Fatalf("CreateNIC(%d, _) = %s", nicID, err)
+	}
+
+	dadPacketsSent := 1
+	if err := s.AddAddress(nicID, ProtocolNumber, lladdr0); err != nil {
+		t.Fatalf("AddAddress(%d, %d, %s) = %s", nicID, ProtocolNumber, lladdr0, err)
+	}
+
+	// Start DAD for the address we just added.
+	//
+	// Even though the stack will perform DAD before the added address transitions
+	// from tentative to assigned, this DAD request should be independent of that.
+	ch := make(chan stack.DADResult, 3)
+	dadRequestsMade := 1
+	dadPacketsSent++
+	if res, err := s.CheckDuplicateAddress(nicID, ProtocolNumber, lladdr0, func(r stack.DADResult) {
+		ch <- r
+	}); err != nil {
+		t.Fatalf("s.CheckDuplicateAddress(%d, %d, %s, _): %s", nicID, ProtocolNumber, lladdr0, err)
+	} else if res != stack.DADStarting {
+		t.Fatalf("got s.CheckDuplicateAddress(%d, %d, %s, _) = %d, want = %d", nicID, ProtocolNumber, lladdr0, res, stack.DADStarting)
+	}
+
+	// Remove the address and make sure our DAD request was not stopped.
+	if err := s.RemoveAddress(nicID, lladdr0); err != nil {
+		t.Fatalf("RemoveAddress(%d, %s): %s", nicID, lladdr0, err)
+	}
+	// Should not restart DAD since we already requested DAD above - the handler
+	// should be called when the original request compeletes so we should not send
+	// an extra DAD message here.
+	dadRequestsMade++
+	if res, err := s.CheckDuplicateAddress(nicID, ProtocolNumber, lladdr0, func(r stack.DADResult) {
+		ch <- r
+	}); err != nil {
+		t.Fatalf("s.CheckDuplicateAddress(%d, %d, %s, _): %s", nicID, ProtocolNumber, lladdr0, err)
+	} else if res != stack.DADAlreadyRunning {
+		t.Fatalf("got s.CheckDuplicateAddress(%d, %d, %s, _) = %d, want = %d", nicID, ProtocolNumber, lladdr0, res, stack.DADAlreadyRunning)
+	}
+
+	// Wait for DAD to resolve.
+	clock.Advance(time.Duration(dadConfigs.DupAddrDetectTransmits) * dadConfigs.RetransmitTimer)
+	for i := 0; i < dadRequestsMade; i++ {
+		if diff := cmp.Diff(stack.DADResult{Resolved: true}, <-ch); diff != "" {
+			t.Errorf("(i=%d) DAD result mismatch (-want +got):\n%s", i, diff)
+		}
+	}
+	// Should have no more results.
+	select {
+	case r := <-ch:
+		t.Errorf("unexpectedly got an extra DAD result; r = %#v", r)
+	default:
+	}
+
+	snmc := header.SolicitedNodeAddr(lladdr0)
+	remoteLinkAddr := header.EthernetAddressFromMulticastIPv6Address(snmc)
+
+	for i := 0; i < dadPacketsSent; i++ {
+		p, ok := e.Read()
+		if !ok {
+			t.Fatalf("expected %d-th DAD message", i)
+		}
+
+		if p.Proto != header.IPv6ProtocolNumber {
+			t.Errorf("(i=%d) got p.Proto = %d, want = %d", i, p.Proto, header.IPv6ProtocolNumber)
+		}
+
+		if p.Route.RemoteLinkAddress != remoteLinkAddr {
+			t.Errorf("(i=%d) got p.Route.RemoteLinkAddress = %s, want = %s", i, p.Route.RemoteLinkAddress, remoteLinkAddr)
+		}
+
+		checker.IPv6(t, stack.PayloadSince(p.Pkt.NetworkHeader()),
+			checker.SrcAddr(header.IPv6Any),
+			checker.DstAddr(snmc),
+			checker.TTL(header.NDPHopLimit),
+			checker.NDPNS(
+				checker.NDPNSTargetAddress(lladdr0),
+				checker.NDPNSOptions(nil),
+			))
+	}
+
+	// Should have no more packets.
+	if p, ok := e.Read(); ok {
+		t.Errorf("got unexpected packet = %#v", p)
+	}
+}