Make stack.DADResult an interface

While I'm here, update NDPDispatcher.OnDuplicateAddressDetectionStatus to
take a DADResult and rename it to OnDuplicateAddressDetectionResult.

Fixes #5606.

PiperOrigin-RevId: 360965416

pkg/tcpip/network/arp/arp.go

@@ -232,7 +232,7 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 		linkAddr := tcpip.LinkAddress(h.HardwareAddressSender())
 
 		e.mu.Lock()
-		e.mu.dad.StopLocked(addr, false /* aborted */)
+		e.mu.dad.StopLocked(addr, &stack.DADDupAddrDetected{})
 		e.mu.Unlock()
 
 		// The solicited, override, and isRouter flags are not available for ARP;

pkg/tcpip/network/internal/ip/duplicate_address_detection.go

@@ -126,9 +126,12 @@ func (d *DAD) CheckDuplicateAddressLocked(addr tcpip.Address, h stack.DADComplet
 				s.timer.Stop()
 				delete(d.addresses, addr)
 
-				r := stack.DADResult{Resolved: dadDone, Err: err}
+				var res stack.DADResult = &stack.DADSucceeded{}
+				if err != nil {
+					res = &stack.DADError{Err: err}
+				}
 				for _, h := range s.completionHandlers {
-					h(r)
+					h(res)
 				}
 			}),
 		}
@@ -142,7 +145,7 @@ func (d *DAD) CheckDuplicateAddressLocked(addr tcpip.Address, h stack.DADComplet
 // StopLocked stops a currently running DAD process.
 //
 // Precondition: d.protocolMU must be locked.
-func (d *DAD) StopLocked(addr tcpip.Address, aborted bool) {
+func (d *DAD) StopLocked(addr tcpip.Address, reason stack.DADResult) {
 	s, ok := d.addresses[addr]
 	if !ok {
 		return
@@ -152,14 +155,8 @@ func (d *DAD) StopLocked(addr tcpip.Address, aborted bool) {
 	s.timer.Stop()
 	delete(d.addresses, addr)
 
-	var err tcpip.Error
-	if aborted {
-		err = &tcpip.ErrAborted{}
-	}
-
-	r := stack.DADResult{Resolved: false, Err: err}
 	for _, h := range s.completionHandlers {
-		h(r)
+		h(reason)
 	}
 }
 

pkg/tcpip/network/internal/ip/duplicate_address_detection_test.go

@@ -78,10 +78,10 @@ func (m *mockDADProtocol) checkDuplicateAddress(addr tcpip.Address, h stack.DADC
 	return m.mu.dad.CheckDuplicateAddressLocked(addr, h)
 }
 
-func (m *mockDADProtocol) stop(addr tcpip.Address, aborted bool) {
+func (m *mockDADProtocol) stop(addr tcpip.Address, reason stack.DADResult) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
-	m.mu.dad.StopLocked(addr, aborted)
+	m.mu.dad.StopLocked(addr, reason)
 }
 
 func (m *mockDADProtocol) setConfigs(c stack.DADConfigurations) {
@@ -175,7 +175,7 @@ func TestDADCheckDuplicateAddress(t *testing.T) {
 	}
 	clock.Advance(delta)
 	for i := 0; i < 2; i++ {
-		if diff := cmp.Diff(dadResult{Addr: addr1, R: stack.DADResult{Resolved: true, Err: nil}}, <-ch); diff != "" {
+		if diff := cmp.Diff(dadResult{Addr: addr1, R: &stack.DADSucceeded{}}, <-ch); diff != "" {
 			t.Errorf("(i=%d) dad result mismatch (-want +got):\n%s", i, diff)
 		}
 	}
@@ -189,7 +189,7 @@ func TestDADCheckDuplicateAddress(t *testing.T) {
 	default:
 	}
 	clock.Advance(delta)
-	if diff := cmp.Diff(dadResult{Addr: addr2, R: stack.DADResult{Resolved: true, Err: nil}}, <-ch); diff != "" {
+	if diff := cmp.Diff(dadResult{Addr: addr2, R: &stack.DADSucceeded{}}, <-ch); diff != "" {
 		t.Errorf("dad result mismatch (-want +got):\n%s", diff)
 	}
 
@@ -202,7 +202,7 @@ func TestDADCheckDuplicateAddress(t *testing.T) {
 		t.Errorf("dad check mismatch (-want +got):\n%s", diff)
 	}
 	clock.Advance(dadConfig2Duration)
-	if diff := cmp.Diff(dadResult{Addr: addr2, R: stack.DADResult{Resolved: true, Err: nil}}, <-ch); diff != "" {
+	if diff := cmp.Diff(dadResult{Addr: addr2, R: &stack.DADSucceeded{}}, <-ch); diff != "" {
 		t.Errorf("dad result mismatch (-want +got):\n%s", diff)
 	}
 
@@ -241,19 +241,19 @@ func TestDADStop(t *testing.T) {
 		t.Errorf("dad check mismatch (-want +got):\n%s", diff)
 	}
 
-	dad.stop(addr1, true /* aborted */)
-	if diff := cmp.Diff(dadResult{Addr: addr1, R: stack.DADResult{Resolved: false, Err: &tcpip.ErrAborted{}}}, <-ch); diff != "" {
+	dad.stop(addr1, &stack.DADAborted{})
+	if diff := cmp.Diff(dadResult{Addr: addr1, R: &stack.DADAborted{}}, <-ch); diff != "" {
 		t.Errorf("dad result mismatch (-want +got):\n%s", diff)
 	}
 
-	dad.stop(addr2, false /* aborted */)
-	if diff := cmp.Diff(dadResult{Addr: addr2, R: stack.DADResult{Resolved: false, Err: nil}}, <-ch); diff != "" {
+	dad.stop(addr2, &stack.DADDupAddrDetected{})
+	if diff := cmp.Diff(dadResult{Addr: addr2, R: &stack.DADDupAddrDetected{}}, <-ch); diff != "" {
 		t.Errorf("dad result mismatch (-want +got):\n%s", diff)
 	}
 
 	dadResolutionDuration := time.Duration(dadConfigs.DupAddrDetectTransmits) * dadConfigs.RetransmitTimer
 	clock.Advance(dadResolutionDuration)
-	if diff := cmp.Diff(dadResult{Addr: addr3, R: stack.DADResult{Resolved: true, Err: nil}}, <-ch); diff != "" {
+	if diff := cmp.Diff(dadResult{Addr: addr3, R: &stack.DADSucceeded{}}, <-ch); diff != "" {
 		t.Errorf("dad result mismatch (-want +got):\n%s", diff)
 	}
 
@@ -266,7 +266,7 @@ func TestDADStop(t *testing.T) {
 		t.Errorf("dad check mismatch (-want +got):\n%s", diff)
 	}
 	clock.Advance(dadResolutionDuration)
-	if diff := cmp.Diff(dadResult{Addr: addr1, R: stack.DADResult{Resolved: true, Err: nil}}, <-ch); diff != "" {
+	if diff := cmp.Diff(dadResult{Addr: addr1, R: &stack.DADSucceeded{}}, <-ch); diff != "" {
 		t.Errorf("dad result mismatch (-want +got):\n%s", diff)
 	}
 

pkg/tcpip/network/ipv6/icmp.go

@@ -564,7 +564,7 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer, hasFragmentHeader bool, r
 		targetAddr := na.TargetAddress()
 
 		e.dad.mu.Lock()
-		e.dad.mu.dad.StopLocked(targetAddr, false /* aborted */)
+		e.dad.mu.dad.StopLocked(targetAddr, &stack.DADDupAddrDetected{})
 		e.dad.mu.Unlock()
 
 		if e.hasTentativeAddr(targetAddr) {

pkg/tcpip/network/ipv6/ipv6.go

@@ -363,7 +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 */, true /* dadFailure */); err != nil {
+	if err := e.removePermanentEndpointLocked(addressEndpoint, false /* allowSLAACInvalidation */, &stack.DADDupAddrDetected{}); err != nil {
 		return err
 	}
 
@@ -536,8 +536,20 @@ func (e *endpoint) disableLocked() {
 	}
 
 	e.mu.ndp.stopSolicitingRouters()
+	// Stop DAD for all the tentative unicast addresses.
+	e.mu.addressableEndpointState.ForEachEndpoint(func(addressEndpoint stack.AddressEndpoint) bool {
+		if addressEndpoint.GetKind() != stack.PermanentTentative {
+			return true
+		}
+
+		addr := addressEndpoint.AddressWithPrefix().Address
+		if header.IsV6UnicastAddress(addr) {
+			e.mu.ndp.stopDuplicateAddressDetection(addr, &stack.DADAborted{})
+		}
+
+		return true
+	})
 	e.mu.ndp.cleanupState(false /* hostOnly */)
-	e.stopDADForPermanentAddressesLocked()
 
 	// The endpoint may have already left the multicast group.
 	switch err := e.leaveGroupLocked(header.IPv6AllNodesMulticastAddress); err.(type) {
@@ -555,25 +567,6 @@ func (e *endpoint) disableLocked() {
 	}
 }
 
-// stopDADForPermanentAddressesLocked stops DAD for all permaneent addresses.
-//
-// Precondition: e.mu must be write locked.
-func (e *endpoint) stopDADForPermanentAddressesLocked() {
-	// Stop DAD for all the tentative unicast addresses.
-	e.mu.addressableEndpointState.ForEachEndpoint(func(addressEndpoint stack.AddressEndpoint) bool {
-		if addressEndpoint.GetKind() != stack.PermanentTentative {
-			return true
-		}
-
-		addr := addressEndpoint.AddressWithPrefix().Address
-		if header.IsV6UnicastAddress(addr) {
-			e.mu.ndp.stopDuplicateAddressDetection(addr, false /* failed */)
-		}
-
-		return true
-	})
-}
-
 // DefaultTTL is the default hop limit for this endpoint.
 func (e *endpoint) DefaultTTL() uint8 {
 	return e.protocol.DefaultTTL()
@@ -1384,8 +1377,6 @@ func (e *endpoint) handlePacket(pkt *stack.PacketBuffer) {
 func (e *endpoint) Close() {
 	e.mu.Lock()
 	e.disableLocked()
-	e.mu.ndp.removeSLAACAddresses(false /* keepLinkLocal */)
-	e.stopDADForPermanentAddressesLocked()
 	e.mu.addressableEndpointState.Cleanup()
 	e.mu.Unlock()
 
@@ -1451,14 +1442,14 @@ func (e *endpoint) RemovePermanentAddress(addr tcpip.Address) tcpip.Error {
 		return &tcpip.ErrBadLocalAddress{}
 	}
 
-	return e.removePermanentEndpointLocked(addressEndpoint, true /* allowSLAACInvalidation */, false /* dadFailure */)
+	return e.removePermanentEndpointLocked(addressEndpoint, true /* allowSLAACInvalidation */, &stack.DADAborted{})
 }
 
 // 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, dadFailure bool) tcpip.Error {
+func (e *endpoint) removePermanentEndpointLocked(addressEndpoint stack.AddressEndpoint, allowSLAACInvalidation bool, dadResult stack.DADResult) tcpip.Error {
 	addr := addressEndpoint.AddressWithPrefix()
 	// If we are removing an address generated via SLAAC, cleanup
 	// its SLAAC resources and notify the integrator.
@@ -1469,16 +1460,16 @@ func (e *endpoint) removePermanentEndpointLocked(addressEndpoint stack.AddressEn
 		e.mu.ndp.cleanupTempSLAACAddrResourcesAndNotify(addr)
 	}
 
-	return e.removePermanentEndpointInnerLocked(addressEndpoint, dadFailure)
+	return e.removePermanentEndpointInnerLocked(addressEndpoint, dadResult)
 }
 
 // removePermanentEndpointInnerLocked is like removePermanentEndpointLocked
 // except it does not cleanup SLAAC address state.
 //
 // Precondition: e.mu must be write locked.
-func (e *endpoint) removePermanentEndpointInnerLocked(addressEndpoint stack.AddressEndpoint, dadFailure bool) tcpip.Error {
+func (e *endpoint) removePermanentEndpointInnerLocked(addressEndpoint stack.AddressEndpoint, dadResult stack.DADResult) tcpip.Error {
 	addr := addressEndpoint.AddressWithPrefix()
-	e.mu.ndp.stopDuplicateAddressDetection(addr.Address, dadFailure)
+	e.mu.ndp.stopDuplicateAddressDetection(addr.Address, dadResult)
 
 	if err := e.mu.addressableEndpointState.RemovePermanentEndpoint(addressEndpoint); err != nil {
 		return err

pkg/tcpip/network/ipv6/ndp.go

@@ -208,16 +208,12 @@ const (
 // NDPDispatcher is the interface integrators of netstack must implement to
 // receive and handle NDP related events.
 type NDPDispatcher interface {
-	// OnDuplicateAddressDetectionStatus is called when the DAD process for an
-	// address (addr) on a NIC (with ID nicID) completes. resolved is set to true
-	// if DAD completed successfully (no duplicate addr detected); false otherwise
-	// (addr was detected to be a duplicate on the link the NIC is a part of, or
-	// it was stopped for some other reason, such as the address being removed).
-	// If an error occured during DAD, err is set and resolved must be ignored.
+	// OnDuplicateAddressDetectionResult is called when the DAD process for an
+	// address on a NIC completes.
 	//
 	// This function is not permitted to block indefinitely. This function
 	// is also not permitted to call into the stack.
-	OnDuplicateAddressDetectionStatus(nicID tcpip.NICID, addr tcpip.Address, resolved bool, err tcpip.Error)
+	OnDuplicateAddressDetectionResult(tcpip.NICID, tcpip.Address, stack.DADResult)
 
 	// OnDefaultRouterDiscovered is called when a new default router is
 	// discovered. Implementations must return true if the newly discovered
@@ -225,14 +221,14 @@ type NDPDispatcher interface {
 	//
 	// This function is not permitted to block indefinitely. This function
 	// is also not permitted to call into the stack.
-	OnDefaultRouterDiscovered(nicID tcpip.NICID, addr tcpip.Address) bool
+	OnDefaultRouterDiscovered(tcpip.NICID, tcpip.Address) bool
 
 	// OnDefaultRouterInvalidated is called when a discovered default router that
 	// was remembered is invalidated.
 	//
 	// This function is not permitted to block indefinitely. This function
 	// is also not permitted to call into the stack.
-	OnDefaultRouterInvalidated(nicID tcpip.NICID, addr tcpip.Address)
+	OnDefaultRouterInvalidated(tcpip.NICID, tcpip.Address)
 
 	// OnOnLinkPrefixDiscovered is called when a new on-link prefix is discovered.
 	// Implementations must return true if the newly discovered on-link prefix
@@ -240,14 +236,14 @@ type NDPDispatcher interface {
 	//
 	// This function is not permitted to block indefinitely. This function
 	// is also not permitted to call into the stack.
-	OnOnLinkPrefixDiscovered(nicID tcpip.NICID, prefix tcpip.Subnet) bool
+	OnOnLinkPrefixDiscovered(tcpip.NICID, tcpip.Subnet) bool
 
 	// OnOnLinkPrefixInvalidated is called when a discovered on-link prefix that
 	// was remembered is invalidated.
 	//
 	// This function is not permitted to block indefinitely. This function
 	// is also not permitted to call into the stack.
-	OnOnLinkPrefixInvalidated(nicID tcpip.NICID, prefix tcpip.Subnet)
+	OnOnLinkPrefixInvalidated(tcpip.NICID, tcpip.Subnet)
 
 	// OnAutoGenAddress is called when a new prefix with its autonomous address-
 	// configuration flag set is received and SLAAC was performed. Implementations
@@ -280,12 +276,12 @@ type NDPDispatcher interface {
 	// It is up to the caller to use the DNS Servers only for their valid
 	// lifetime. OnRecursiveDNSServerOption may be called for new or
 	// 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).
+	// valid lifetimes must be refreshed to the lifetime (it may be increased,
+	// decreased, or completely invalidated when the 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)
+	OnRecursiveDNSServerOption(tcpip.NICID, []tcpip.Address, time.Duration)
 
 	// OnDNSSearchListOption is called when the stack learns of DNS search lists
 	// through NDP.
@@ -293,9 +289,9 @@ type NDPDispatcher interface {
 	// It is up to the caller to use the domain names in the search list
 	// for only their valid lifetime. OnDNSSearchListOption may be called
 	// with new or already known domain names. If called with known domain
-	// names, their valid lifetimes must be refreshed to lifetime (it may
-	// be increased, decreased or completely invalidated when lifetime = 0.
-	OnDNSSearchListOption(nicID tcpip.NICID, domainNames []string, lifetime time.Duration)
+	// names, their valid lifetimes must be refreshed to the lifetime (it may
+	// be increased, decreased or completely invalidated when the lifetime = 0.
+	OnDNSSearchListOption(tcpip.NICID, []string, time.Duration)
 
 	// OnDHCPv6Configuration is called with an updated configuration that is
 	// available via DHCPv6 for the passed NIC.
@@ -587,15 +583,25 @@ func (ndp *ndpState) startDuplicateAddressDetection(addr tcpip.Address, addressE
 			panic(fmt.Sprintf("ndpdad: addr %s is no longer tentative on NIC(%d)", addr, ndp.ep.nic.ID()))
 		}
 
-		if r.Resolved {
+		var dadSucceeded bool
+		switch r.(type) {
+		case *stack.DADAborted, *stack.DADError, *stack.DADDupAddrDetected:
+			dadSucceeded = false
+		case *stack.DADSucceeded:
+			dadSucceeded = true
+		default:
+			panic(fmt.Sprintf("unrecognized DAD result = %T", r))
+		}
+
+		if dadSucceeded {
 			addressEndpoint.SetKind(stack.Permanent)
 		}
 
 		if ndpDisp := ndp.ep.protocol.options.NDPDisp; ndpDisp != nil {
-			ndpDisp.OnDuplicateAddressDetectionStatus(ndp.ep.nic.ID(), addr, r.Resolved, r.Err)
+			ndpDisp.OnDuplicateAddressDetectionResult(ndp.ep.nic.ID(), addr, r)
 		}
 
-		if r.Resolved {
+		if dadSucceeded {
 			if addressEndpoint.ConfigType() == stack.AddressConfigSlaac {
 				// Reset the generation attempts counter as we are starting the
 				// generation of a new address for the SLAAC prefix.
@@ -616,7 +622,7 @@ func (ndp *ndpState) startDuplicateAddressDetection(addr tcpip.Address, addressE
 		// 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.OnDuplicateAddressDetectionResult(ndp.ep.nic.ID(), addr, &stack.DADSucceeded{})
 		}
 
 		ndp.ep.onAddressAssignedLocked(addr)
@@ -633,8 +639,8 @@ 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, failed bool) {
-	ndp.dad.StopLocked(addr, !failed)
+func (ndp *ndpState) stopDuplicateAddressDetection(addr tcpip.Address, reason stack.DADResult) {
+	ndp.dad.StopLocked(addr, reason)
 }
 
 // handleRA handles a Router Advertisement message that arrived on the NIC
@@ -1501,7 +1507,7 @@ func (ndp *ndpState) invalidateSLAACPrefix(prefix tcpip.Subnet, state slaacPrefi
 			ndpDisp.OnAutoGenAddressInvalidated(ndp.ep.nic.ID(), addressEndpoint.AddressWithPrefix())
 		}
 
-		if err := ndp.ep.removePermanentEndpointInnerLocked(addressEndpoint, false /* dadFailure */); err != nil {
+		if err := ndp.ep.removePermanentEndpointInnerLocked(addressEndpoint, &stack.DADAborted{}); err != nil {
 			panic(fmt.Sprintf("ndp: error removing stable SLAAC address %s: %s", addressEndpoint.AddressWithPrefix(), err))
 		}
 	}
@@ -1560,7 +1566,7 @@ func (ndp *ndpState) cleanupSLAACPrefixResources(prefix tcpip.Subnet, state slaa
 func (ndp *ndpState) invalidateTempSLAACAddr(tempAddrs map[tcpip.Address]tempSLAACAddrState, tempAddr tcpip.Address, tempAddrState tempSLAACAddrState) {
 	ndp.cleanupTempSLAACAddrResourcesAndNotifyInner(tempAddrs, tempAddr, tempAddrState)
 
-	if err := ndp.ep.removePermanentEndpointInnerLocked(tempAddrState.addressEndpoint, false /* dadFailure */); err != nil {
+	if err := ndp.ep.removePermanentEndpointInnerLocked(tempAddrState.addressEndpoint, &stack.DADAborted{}); err != nil {
 		panic(fmt.Sprintf("error removing temporary SLAAC address %s: %s", tempAddrState.addressEndpoint.AddressWithPrefix(), err))
 	}
 }

pkg/tcpip/network/ipv6/ndp_test.go

@@ -90,7 +90,7 @@ type testNDPDispatcher struct {
 	addr tcpip.Address
 }
 
-func (*testNDPDispatcher) OnDuplicateAddressDetectionStatus(tcpip.NICID, tcpip.Address, bool, tcpip.Error) {
+func (*testNDPDispatcher) OnDuplicateAddressDetectionResult(tcpip.NICID, tcpip.Address, stack.DADResult) {
 }
 
 func (t *testNDPDispatcher) OnDefaultRouterDiscovered(_ tcpip.NICID, addr tcpip.Address) bool {
@@ -1314,10 +1314,10 @@ func TestCheckDuplicateAddress(t *testing.T) {
 		t.Fatalf("got s.CheckDuplicateAddress(%d, %d, %s, _) = %d, want = %d", nicID, ProtocolNumber, lladdr0, res, stack.DADAlreadyRunning)
 	}
 
-	// Wait for DAD to resolve.
+	// Wait for DAD to complete.
 	clock.Advance(time.Duration(dadConfigs.DupAddrDetectTransmits) * dadConfigs.RetransmitTimer)
 	for i := 0; i < dadRequestsMade; i++ {
-		if diff := cmp.Diff(stack.DADResult{Resolved: true}, <-ch); diff != "" {
+		if diff := cmp.Diff(&stack.DADSucceeded{}, <-ch); diff != "" {
 			t.Errorf("(i=%d) DAD result mismatch (-want +got):\n%s", i, diff)
 		}
 	}

pkg/tcpip/stack/ndp_test.go

@@ -99,12 +99,11 @@ func prefixSubnetAddr(offset uint8, linkAddr tcpip.LinkAddress) (tcpip.AddressWi
 }
 
 // ndpDADEvent is a set of parameters that was passed to
-// ndpDispatcher.OnDuplicateAddressDetectionStatus.
+// ndpDispatcher.OnDuplicateAddressDetectionResult.
 type ndpDADEvent struct {
-	nicID    tcpip.NICID
-	addr     tcpip.Address
-	resolved bool
-	err      tcpip.Error
+	nicID tcpip.NICID
+	addr  tcpip.Address
+	res   stack.DADResult
 }
 
 type ndpRouterEvent struct {
@@ -173,14 +172,13 @@ type ndpDispatcher struct {
 	dhcpv6ConfigurationC chan ndpDHCPv6Event
 }
 
-// Implements ipv6.NDPDispatcher.OnDuplicateAddressDetectionStatus.
-func (n *ndpDispatcher) OnDuplicateAddressDetectionStatus(nicID tcpip.NICID, addr tcpip.Address, resolved bool, err tcpip.Error) {
+// Implements ipv6.NDPDispatcher.OnDuplicateAddressDetectionResult.
+func (n *ndpDispatcher) OnDuplicateAddressDetectionResult(nicID tcpip.NICID, addr tcpip.Address, res stack.DADResult) {
 	if n.dadC != nil {
 		n.dadC <- ndpDADEvent{
 			nicID,
 			addr,
-			resolved,
-			err,
+			res,
 		}
 	}
 }
@@ -311,8 +309,8 @@ func (l *channelLinkWithHeaderLength) MaxHeaderLength() uint16 {
 
 // Check e to make sure that the event is for addr on nic with ID 1, and the
 // resolved flag set to resolved with the specified err.
-func checkDADEvent(e ndpDADEvent, nicID tcpip.NICID, addr tcpip.Address, resolved bool, err tcpip.Error) string {
-	return cmp.Diff(ndpDADEvent{nicID: nicID, addr: addr, resolved: resolved, err: err}, e, cmp.AllowUnexported(e))
+func checkDADEvent(e ndpDADEvent, nicID tcpip.NICID, addr tcpip.Address, res stack.DADResult) string {
+	return cmp.Diff(ndpDADEvent{nicID: nicID, addr: addr, res: res}, e, cmp.AllowUnexported(e))
 }
 
 // TestDADDisabled tests that an address successfully resolves immediately
@@ -344,7 +342,7 @@ func TestDADDisabled(t *testing.T) {
 	// DAD on it.
 	select {
 	case e := <-ndpDisp.dadC:
-		if diff := checkDADEvent(e, nicID, addr1, true, nil); diff != "" {
+		if diff := checkDADEvent(e, nicID, addr1, &stack.DADSucceeded{}); diff != "" {
 			t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 		}
 	default:
@@ -491,7 +489,7 @@ func TestDADResolve(t *testing.T) {
 			case <-time.After(defaultAsyncPositiveEventTimeout):
 				t.Fatal("timed out waiting for DAD resolution")
 			case e := <-ndpDisp.dadC:
-				if diff := checkDADEvent(e, nicID, addr1, true, nil); diff != "" {
+				if diff := checkDADEvent(e, nicID, addr1, &stack.DADSucceeded{}); diff != "" {
 					t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 				}
 			}
@@ -691,7 +689,7 @@ func TestDADFail(t *testing.T) {
 				// something is wrong.
 				t.Fatal("timed out waiting for DAD failure")
 			case e := <-ndpDisp.dadC:
-				if diff := checkDADEvent(e, nicID, addr1, false, nil); diff != "" {
+				if diff := checkDADEvent(e, nicID, addr1, &stack.DADDupAddrDetected{}); diff != "" {
 					t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 				}
 			}
@@ -790,7 +788,7 @@ func TestDADStop(t *testing.T) {
 				// time + extra 1s buffer, something is wrong.
 				t.Fatal("timed out waiting for DAD failure")
 			case e := <-ndpDisp.dadC:
-				if diff := checkDADEvent(e, nicID, addr1, false, &tcpip.ErrAborted{}); diff != "" {
+				if diff := checkDADEvent(e, nicID, addr1, &stack.DADAborted{}); diff != "" {
 					t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 				}
 			}
@@ -852,7 +850,7 @@ func TestSetNDPConfigurations(t *testing.T) {
 			expectDADEvent := func(nicID tcpip.NICID, addr tcpip.Address) {
 				select {
 				case e := <-ndpDisp.dadC:
-					if diff := checkDADEvent(e, nicID, addr, true, nil); diff != "" {
+					if diff := checkDADEvent(e, nicID, addr, &stack.DADSucceeded{}); diff != "" {
 						t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 					}
 				default:
@@ -944,7 +942,7 @@ func TestSetNDPConfigurations(t *testing.T) {
 				// means something is wrong.
 				t.Fatal("timed out waiting for DAD resolution")
 			case e := <-ndpDisp.dadC:
-				if diff := checkDADEvent(e, nicID1, addr1, true, nil); diff != "" {
+				if diff := checkDADEvent(e, nicID1, addr1, &stack.DADSucceeded{}); diff != "" {
 					t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 				}
 			}
@@ -1963,7 +1961,7 @@ func TestAutoGenTempAddr(t *testing.T) {
 
 					select {
 					case e := <-ndpDisp.dadC:
-						if diff := checkDADEvent(e, nicID, addr, true, nil); diff != "" {
+						if diff := checkDADEvent(e, nicID, addr, &stack.DADSucceeded{}); diff != "" {
 							t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 						}
 					case <-time.After(time.Duration(test.dupAddrTransmits)*test.retransmitTimer + defaultAsyncPositiveEventTimeout):
@@ -2169,7 +2167,7 @@ func TestNoAutoGenTempAddrForLinkLocal(t *testing.T) {
 				}
 				select {
 				case e := <-ndpDisp.dadC:
-					if diff := checkDADEvent(e, nicID, llAddr1, true, nil); diff != "" {
+					if diff := checkDADEvent(e, nicID, llAddr1, &stack.DADSucceeded{}); diff != "" {
 						t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 					}
 				case <-time.After(time.Duration(test.dupAddrTransmits)*test.retransmitTimer + defaultAsyncPositiveEventTimeout):
@@ -2257,7 +2255,7 @@ func TestNoAutoGenTempAddrWithoutStableAddr(t *testing.T) {
 	// address to be generated.
 	select {
 	case e := <-ndpDisp.dadC:
-		if diff := checkDADEvent(e, nicID, addr.Address, true, nil); diff != "" {
+		if diff := checkDADEvent(e, nicID, addr.Address, &stack.DADSucceeded{}); diff != "" {
 			t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 		}
 	case <-time.After(dadTransmits*retransmitTimer + defaultAsyncPositiveEventTimeout):
@@ -2723,7 +2721,7 @@ func TestMixedSLAACAddrConflictRegen(t *testing.T) {
 				t.Helper()
 
 				clock.Advance(dupAddrTransmits * retransmitTimer)
-				if diff := checkDADEvent(<-ndpDisp.dadC, nicID, addr, true, nil); diff != "" {
+				if diff := checkDADEvent(<-ndpDisp.dadC, nicID, addr, &stack.DADSucceeded{}); diff != "" {
 					t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 				}
 			}
@@ -2754,7 +2752,7 @@ func TestMixedSLAACAddrConflictRegen(t *testing.T) {
 			rxNDPSolicit(e, addr.Address)
 			select {
 			case e := <-ndpDisp.dadC:
-				if diff := checkDADEvent(e, nicID, addr.Address, false, nil); diff != "" {
+				if diff := checkDADEvent(e, nicID, addr.Address, &stack.DADDupAddrDetected{}); diff != "" {
 					t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 				}
 			default:
@@ -3853,12 +3851,12 @@ func TestAutoGenAddrInResponseToDADConflicts(t *testing.T) {
 		}
 	}
 
-	expectDADEvent := func(t *testing.T, ndpDisp *ndpDispatcher, addr tcpip.Address, resolved bool, err tcpip.Error) {
+	expectDADEvent := func(t *testing.T, ndpDisp *ndpDispatcher, addr tcpip.Address, res stack.DADResult) {
 		t.Helper()
 
 		select {
 		case e := <-ndpDisp.dadC:
-			if diff := checkDADEvent(e, nicID, addr, resolved, err); diff != "" {
+			if diff := checkDADEvent(e, nicID, addr, res); diff != "" {
 				t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 			}
 		default:
@@ -3866,12 +3864,12 @@ func TestAutoGenAddrInResponseToDADConflicts(t *testing.T) {
 		}
 	}
 
-	expectDADEventAsync := func(t *testing.T, ndpDisp *ndpDispatcher, addr tcpip.Address, resolved bool) {
+	expectDADEventAsync := func(t *testing.T, ndpDisp *ndpDispatcher, addr tcpip.Address, res stack.DADResult) {
 		t.Helper()
 
 		select {
 		case e := <-ndpDisp.dadC:
-			if diff := checkDADEvent(e, nicID, addr, resolved, nil); diff != "" {
+			if diff := checkDADEvent(e, nicID, addr, res); diff != "" {
 				t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 			}
 		case <-time.After(dadTransmits*retransmitTimer + defaultAsyncPositiveEventTimeout):
@@ -3929,7 +3927,7 @@ func TestAutoGenAddrInResponseToDADConflicts(t *testing.T) {
 				// generated.
 				e.InjectInbound(header.IPv6ProtocolNumber, raBufWithPI(llAddr2, 0, prefix, true, true, 100, 100))
 				expectAutoGenAddrEvent(t, ndpDisp, stableAddrForTempAddrTest, newAddr)
-				expectDADEventAsync(t, ndpDisp, stableAddrForTempAddrTest.Address, true)
+				expectDADEventAsync(t, ndpDisp, stableAddrForTempAddrTest.Address, &stack.DADSucceeded{})
 
 				// The stable address will be assigned throughout the test.
 				return []tcpip.AddressWithPrefix{stableAddrForTempAddrTest}
@@ -4004,7 +4002,7 @@ func TestAutoGenAddrInResponseToDADConflicts(t *testing.T) {
 							// Simulate a DAD conflict.
 							rxNDPSolicit(e, addr.Address)
 							expectAutoGenAddrEvent(t, &ndpDisp, addr, invalidatedAddr)
-							expectDADEvent(t, &ndpDisp, addr.Address, false, nil)
+							expectDADEvent(t, &ndpDisp, addr.Address, &stack.DADDupAddrDetected{})
 
 							// Attempting to add the address manually should not fail if the
 							// address's state was cleaned up when DAD failed.
@@ -4014,7 +4012,7 @@ func TestAutoGenAddrInResponseToDADConflicts(t *testing.T) {
 							if err := s.RemoveAddress(nicID, addr.Address); err != nil {
 								t.Fatalf("RemoveAddress(%d, %s) = %s", nicID, addr.Address, err)
 							}
-							expectDADEvent(t, &ndpDisp, addr.Address, false, &tcpip.ErrAborted{})
+							expectDADEvent(t, &ndpDisp, addr.Address, &stack.DADAborted{})
 						}
 
 						// Should not have any new addresses assigned to the NIC.
@@ -4027,7 +4025,7 @@ func TestAutoGenAddrInResponseToDADConflicts(t *testing.T) {
 						if maxRetries+1 > numFailures {
 							addr := addrType.addrGenFn(numFailures, tempIIDHistory[:])
 							expectAutoGenAddrEventAsync(t, &ndpDisp, addr, newAddr)
-							expectDADEventAsync(t, &ndpDisp, addr.Address, true)
+							expectDADEventAsync(t, &ndpDisp, addr.Address, &stack.DADSucceeded{})
 							if mismatch := addressCheck(s.NICInfo()[nicID].ProtocolAddresses, append(stableAddrs, addr), nil); mismatch != "" {
 								t.Fatal(mismatch)
 							}
@@ -4144,7 +4142,7 @@ func TestAutoGenAddrWithEUI64IIDNoDADRetries(t *testing.T) {
 			expectAutoGenAddrEvent(addr, invalidatedAddr)
 			select {
 			case e := <-ndpDisp.dadC:
-				if diff := checkDADEvent(e, nicID, addr.Address, false, nil); diff != "" {
+				if diff := checkDADEvent(e, nicID, addr.Address, &stack.DADDupAddrDetected{}); diff != "" {
 					t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 				}
 			default:
@@ -4243,7 +4241,7 @@ func TestAutoGenAddrContinuesLifetimesAfterRetry(t *testing.T) {
 	expectAutoGenAddrEvent(addr, invalidatedAddr)
 	select {
 	case e := <-ndpDisp.dadC:
-		if diff := checkDADEvent(e, nicID, addr.Address, false, nil); diff != "" {
+		if diff := checkDADEvent(e, nicID, addr.Address, &stack.DADDupAddrDetected{}); diff != "" {
 			t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 		}
 	default:
@@ -4255,7 +4253,7 @@ func TestAutoGenAddrContinuesLifetimesAfterRetry(t *testing.T) {
 	expectAutoGenAddrEvent(addr, newAddr)
 	select {
 	case e := <-ndpDisp.dadC:
-		if diff := checkDADEvent(e, nicID, addr.Address, true, nil); diff != "" {
+		if diff := checkDADEvent(e, nicID, addr.Address, &stack.DADSucceeded{}); diff != "" {
 			t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 		}
 	case <-time.After(dadTransmits*retransmitTimer + defaultAsyncPositiveEventTimeout):

pkg/tcpip/stack/registration.go

@@ -852,18 +852,42 @@ type InjectableLinkEndpoint interface {
 	InjectOutbound(dest tcpip.Address, packet []byte) tcpip.Error
 }
 
-// DADResult is the result of a duplicate address detection process.
-type DADResult struct {
-	// Resolved is true when DAD completed without detecting a duplicate address
-	// on the link.
-	//
-	// Ignored when Err is non-nil.
-	Resolved bool
+// DADResult is a marker interface for the result of a duplicate address
+// detection process.
+type DADResult interface {
+	isDADResult()
+}
 
-	// Err is an error encountered while performing DAD.
+var _ DADResult = (*DADSucceeded)(nil)
+
+// DADSucceeded indicates DAD completed without finding any duplicate addresses.
+type DADSucceeded struct{}
+
+func (*DADSucceeded) isDADResult() {}
+
+var _ DADResult = (*DADError)(nil)
+
+// DADError indicates DAD hit an error.
+type DADError struct {
 	Err tcpip.Error
 }
 
+func (*DADError) isDADResult() {}
+
+var _ DADResult = (*DADAborted)(nil)
+
+// DADAborted indicates DAD was aborted.
+type DADAborted struct{}
+
+func (*DADAborted) isDADResult() {}
+
+var _ DADResult = (*DADDupAddrDetected)(nil)
+
+// DADDupAddrDetected indicates DAD detected a duplicate address.
+type DADDupAddrDetected struct{}
+
+func (*DADDupAddrDetected) isDADResult() {}
+
 // DADCompletionHandler is a handler for DAD completion.
 type DADCompletionHandler func(DADResult)
 

pkg/tcpip/stack/stack_test.go

@@ -2605,7 +2605,7 @@ func TestNICAutoGenAddrDoesDAD(t *testing.T) {
 		// means something is wrong.
 		t.Fatal("timed out waiting for DAD resolution")
 	case e := <-ndpDisp.dadC:
-		if diff := checkDADEvent(e, nicID, linkLocalAddr, true, nil); diff != "" {
+		if diff := checkDADEvent(e, nicID, linkLocalAddr, &stack.DADSucceeded{}); diff != "" {
 			t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 		}
 	}
@@ -3289,7 +3289,7 @@ func TestDoDADWhenNICEnabled(t *testing.T) {
 	case <-time.After(dadTransmits*retransmitTimer + defaultAsyncPositiveEventTimeout):
 		t.Fatal("timed out waiting for DAD resolution")
 	case e := <-ndpDisp.dadC:
-		if diff := checkDADEvent(e, nicID, addr.AddressWithPrefix.Address, true, nil); diff != "" {
+		if diff := checkDADEvent(e, nicID, addr.AddressWithPrefix.Address, &stack.DADSucceeded{}); diff != "" {
 			t.Errorf("dad event mismatch (-want +got):\n%s", diff)
 		}
 	}

pkg/tcpip/tests/integration/link_resolution_test.go

@@ -1167,53 +1167,53 @@ func TestDAD(t *testing.T) {
 	}
 
 	tests := []struct {
-		name             string
-		netProto         tcpip.NetworkProtocolNumber
-		dadNetProto      tcpip.NetworkProtocolNumber
-		remoteAddr       tcpip.Address
-		expectedResolved bool
+		name           string
+		netProto       tcpip.NetworkProtocolNumber
+		dadNetProto    tcpip.NetworkProtocolNumber
+		remoteAddr     tcpip.Address
+		expectedResult stack.DADResult
 	}{
 		{
-			name:             "IPv4 own address",
-			netProto:         ipv4.ProtocolNumber,
-			dadNetProto:      arp.ProtocolNumber,
-			remoteAddr:       utils.Ipv4Addr1.AddressWithPrefix.Address,
-			expectedResolved: true,
+			name:           "IPv4 own address",
+			netProto:       ipv4.ProtocolNumber,
+			dadNetProto:    arp.ProtocolNumber,
+			remoteAddr:     utils.Ipv4Addr1.AddressWithPrefix.Address,
+			expectedResult: &stack.DADSucceeded{},
 		},
 		{
-			name:             "IPv6 own address",
-			netProto:         ipv6.ProtocolNumber,
-			dadNetProto:      ipv6.ProtocolNumber,
-			remoteAddr:       utils.Ipv6Addr1.AddressWithPrefix.Address,
-			expectedResolved: true,
+			name:           "IPv6 own address",
+			netProto:       ipv6.ProtocolNumber,
+			dadNetProto:    ipv6.ProtocolNumber,
+			remoteAddr:     utils.Ipv6Addr1.AddressWithPrefix.Address,
+			expectedResult: &stack.DADSucceeded{},
 		},
 		{
-			name:             "IPv4 duplicate address",
-			netProto:         ipv4.ProtocolNumber,
-			dadNetProto:      arp.ProtocolNumber,
-			remoteAddr:       utils.Ipv4Addr2.AddressWithPrefix.Address,
-			expectedResolved: false,
+			name:           "IPv4 duplicate address",
+			netProto:       ipv4.ProtocolNumber,
+			dadNetProto:    arp.ProtocolNumber,
+			remoteAddr:     utils.Ipv4Addr2.AddressWithPrefix.Address,
+			expectedResult: &stack.DADDupAddrDetected{},
 		},
 		{
-			name:             "IPv6 duplicate address",
-			netProto:         ipv6.ProtocolNumber,
-			dadNetProto:      ipv6.ProtocolNumber,
-			remoteAddr:       utils.Ipv6Addr2.AddressWithPrefix.Address,
-			expectedResolved: false,
+			name:           "IPv6 duplicate address",
+			netProto:       ipv6.ProtocolNumber,
+			dadNetProto:    ipv6.ProtocolNumber,
+			remoteAddr:     utils.Ipv6Addr2.AddressWithPrefix.Address,
+			expectedResult: &stack.DADDupAddrDetected{},
 		},
 		{
-			name:             "IPv4 no duplicate address",
-			netProto:         ipv4.ProtocolNumber,
-			dadNetProto:      arp.ProtocolNumber,
-			remoteAddr:       utils.Ipv4Addr3.AddressWithPrefix.Address,
-			expectedResolved: true,
+			name:           "IPv4 no duplicate address",
+			netProto:       ipv4.ProtocolNumber,
+			dadNetProto:    arp.ProtocolNumber,
+			remoteAddr:     utils.Ipv4Addr3.AddressWithPrefix.Address,
+			expectedResult: &stack.DADSucceeded{},
 		},
 		{
-			name:             "IPv6 no duplicate address",
-			netProto:         ipv6.ProtocolNumber,
-			dadNetProto:      ipv6.ProtocolNumber,
-			remoteAddr:       utils.Ipv6Addr3.AddressWithPrefix.Address,
-			expectedResolved: true,
+			name:           "IPv6 no duplicate address",
+			netProto:       ipv6.ProtocolNumber,
+			dadNetProto:    ipv6.ProtocolNumber,
+			remoteAddr:     utils.Ipv6Addr3.AddressWithPrefix.Address,
+			expectedResult: &stack.DADSucceeded{},
 		},
 	}
 
@@ -1260,7 +1260,7 @@ func TestDAD(t *testing.T) {
 			}
 
 			expectResults := 1
-			if test.expectedResolved {
+			if _, ok := test.expectedResult.(*stack.DADSucceeded); ok {
 				const delta = time.Nanosecond
 				clock.Advance(time.Duration(dadConfigs.DupAddrDetectTransmits)*dadConfigs.RetransmitTimer - delta)
 				select {
@@ -1285,7 +1285,7 @@ func TestDAD(t *testing.T) {
 			}
 
 			for i := 0; i < expectResults; i++ {
-				if diff := cmp.Diff(stack.DADResult{Resolved: test.expectedResolved}, <-ch); diff != "" {
+				if diff := cmp.Diff(test.expectedResult, <-ch); diff != "" {
 					t.Errorf("(i=%d) DAD result mismatch (-want +got):\n%s", i, diff)
 				}
 			}

pkg/tcpip/tests/integration/loopback_test.go

@@ -38,7 +38,7 @@ var _ ipv6.NDPDispatcher = (*ndpDispatcher)(nil)
 
 type ndpDispatcher struct{}
 
-func (*ndpDispatcher) OnDuplicateAddressDetectionStatus(tcpip.NICID, tcpip.Address, bool, tcpip.Error) {
+func (*ndpDispatcher) OnDuplicateAddressDetectionResult(tcpip.NICID, tcpip.Address, stack.DADResult) {
 }
 
 func (*ndpDispatcher) OnDefaultRouterDiscovered(tcpip.NICID, tcpip.Address) bool {