// Copyright 2019 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package stack_test

import (
	"testing"
	"time"

	"gvisor.dev/gvisor/pkg/tcpip"
	"gvisor.dev/gvisor/pkg/tcpip/buffer"
	"gvisor.dev/gvisor/pkg/tcpip/checker"
	"gvisor.dev/gvisor/pkg/tcpip/header"
	"gvisor.dev/gvisor/pkg/tcpip/link/channel"
	"gvisor.dev/gvisor/pkg/tcpip/network/ipv6"
	"gvisor.dev/gvisor/pkg/tcpip/stack"
	"gvisor.dev/gvisor/pkg/tcpip/transport/icmp"
)

const (
	addr1     = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01"
	addr2     = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02"
	addr3     = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x03"
	linkAddr1 = "\x02\x02\x03\x04\x05\x06"
)

// TestDADDisabled tests that an address successfully resolves immediately
// when DAD is not enabled (the default for an empty stack.Options).
func TestDADDisabled(t *testing.T) {
	opts := stack.Options{
		NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
	}

	e := channel.New(10, 1280, linkAddr1)
	s := stack.New(opts)
	if err := s.CreateNIC(1, e); err != nil {
		t.Fatalf("CreateNIC(_) = %s", err)
	}

	if err := s.AddAddress(1, header.IPv6ProtocolNumber, addr1); err != nil {
		t.Fatalf("AddAddress(_, %d, %s) = %s", header.IPv6ProtocolNumber, addr1, err)
	}

	// Should get the address immediately since we should not have performed
	// DAD on it.
	addr, err := s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
	if err != nil {
		t.Fatalf("stack.GetMainNICAddress(_, _) err = %s", err)
	}
	if addr.Address != addr1 {
		t.Fatalf("got stack.GetMainNICAddress(_, _) = %s, want = %s", addr, addr1)
	}

	// We should not have sent any NDP NS messages.
	if got := s.Stats().ICMP.V6PacketsSent.NeighborSolicit.Value(); got != 0 {
		t.Fatalf("got NeighborSolicit = %d, want = 0", got)
	}
}

// ndpDADEvent is a set of parameters that was passed to
// ndpDispatcher.OnDuplicateAddressDetectionStatus.
type ndpDADEvent struct {
	nicid    tcpip.NICID
	addr     tcpip.Address
	resolved bool
	err      *tcpip.Error
}

var _ stack.NDPDispatcher = (*ndpDispatcher)(nil)

// ndpDispatcher implements NDPDispatcher so tests can know when various NDP
// related events happen for test purposes.
type ndpDispatcher struct {
	dadC chan ndpDADEvent
}

// Implements stack.NDPDispatcher.OnDuplicateAddressDetectionStatus.
//
// If the DAD event matches what we are expecting, send signal on n.dadC.
func (n *ndpDispatcher) OnDuplicateAddressDetectionStatus(nicid tcpip.NICID, addr tcpip.Address, resolved bool, err *tcpip.Error) {
	n.dadC <- ndpDADEvent{
		nicid,
		addr,
		resolved,
		err,
	}
}

// TestDADResolve tests that an address successfully resolves after performing
// DAD for various values of DupAddrDetectTransmits and RetransmitTimer.
// Included in the subtests is a test to make sure that an invalid
// RetransmitTimer (<1ms) values get fixed to the default RetransmitTimer of 1s.
func TestDADResolve(t *testing.T) {
	tests := []struct {
		name                    string
		dupAddrDetectTransmits  uint8
		retransTimer            time.Duration
		expectedRetransmitTimer time.Duration
	}{
		{"1:1s:1s", 1, time.Second, time.Second},
		{"2:1s:1s", 2, time.Second, time.Second},
		{"1:2s:2s", 1, 2 * time.Second, 2 * time.Second},
		// 0s is an invalid RetransmitTimer timer and will be fixed to
		// the default RetransmitTimer value of 1s.
		{"1:0s:1s", 1, 0, time.Second},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			ndpDisp := ndpDispatcher{
				dadC: make(chan ndpDADEvent),
			}
			opts := stack.Options{
				NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
				NDPDisp:          &ndpDisp,
			}
			opts.NDPConfigs.RetransmitTimer = test.retransTimer
			opts.NDPConfigs.DupAddrDetectTransmits = test.dupAddrDetectTransmits

			e := channel.New(10, 1280, linkAddr1)
			s := stack.New(opts)
			if err := s.CreateNIC(1, e); err != nil {
				t.Fatalf("CreateNIC(_) = %s", err)
			}

			if err := s.AddAddress(1, header.IPv6ProtocolNumber, addr1); err != nil {
				t.Fatalf("AddAddress(_, %d, %s) = %s", header.IPv6ProtocolNumber, addr1, err)
			}

			stat := s.Stats().ICMP.V6PacketsSent.NeighborSolicit

			// Should have sent an NDP NS immediately.
			if got := stat.Value(); got != 1 {
				t.Fatalf("got NeighborSolicit = %d, want = 1", got)

			}

			// Address should not be considered bound to the NIC yet
			// (DAD ongoing).
			addr, err := s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
			if err != nil {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (_, %v), want = (_, nil)", err)
			}
			if want := (tcpip.AddressWithPrefix{}); addr != want {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (%s, nil), want = (%s, nil)", addr, want)
			}

			// Wait for the remaining time - some delta (500ms), to
			// make sure the address is still not resolved.
			const delta = 500 * time.Millisecond
			time.Sleep(test.expectedRetransmitTimer*time.Duration(test.dupAddrDetectTransmits) - delta)
			addr, err = s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
			if err != nil {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (_, %v), want = (_, nil)", err)
			}
			if want := (tcpip.AddressWithPrefix{}); addr != want {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (%s, nil), want = (%s, nil)", addr, want)
			}

			// Wait for DAD to resolve.
			select {
			case <-time.After(2 * delta):
				// We should get a resolution event after 500ms
				// (delta) since we wait for 500ms less than the
				// expected resolution time above to make sure
				// that the address did not yet resolve. Waiting
				// for 1s (2x delta) without a resolution event
				// means something is wrong.
				t.Fatal("timed out waiting for DAD resolution")
			case e := <-ndpDisp.dadC:
				if e.err != nil {
					t.Fatal("got DAD error: ", e.err)
				}
				if e.nicid != 1 {
					t.Fatalf("got DAD event w/ nicid = %d, want = 1", e.nicid)
				}
				if e.addr != addr1 {
					t.Fatalf("got DAD event w/ addr = %s, want = %s", addr, addr1)
				}
				if !e.resolved {
					t.Fatal("got DAD event w/ resolved = false, want = true")
				}
			}
			addr, err = s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
			if err != nil {
				t.Fatalf("stack.GetMainNICAddress(_, _) err = %s", err)
			}
			if addr.Address != addr1 {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = %s, want = %s", addr, addr1)
			}

			// Should not have sent any more NS messages.
			if got := stat.Value(); got != uint64(test.dupAddrDetectTransmits) {
				t.Fatalf("got NeighborSolicit = %d, want = %d", got, test.dupAddrDetectTransmits)
			}

			// Validate the sent Neighbor Solicitation messages.
			for i := uint8(0); i < test.dupAddrDetectTransmits; i++ {
				p := <-e.C

				// Make sure its an IPv6 packet.
				if p.Proto != header.IPv6ProtocolNumber {
					t.Fatalf("got Proto = %d, want = %d", p.Proto, header.IPv6ProtocolNumber)
				}

				// Check NDP packet.
				checker.IPv6(t, p.Header.ToVectorisedView().First(),
					checker.TTL(header.NDPHopLimit),
					checker.NDPNS(
						checker.NDPNSTargetAddress(addr1)))
			}
		})
	}

}

// TestDADFail tests to make sure that the DAD process fails if another node is
// detected to be performing DAD on the same address (receive an NS message from
// a node doing DAD for the same address), or if another node is detected to own
// the address already (receive an NA message for the tentative address).
func TestDADFail(t *testing.T) {
	tests := []struct {
		name    string
		makeBuf func(tgt tcpip.Address) buffer.Prependable
		getStat func(s tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter
	}{
		{
			"RxSolicit",
			func(tgt tcpip.Address) buffer.Prependable {
				hdr := buffer.NewPrependable(header.IPv6MinimumSize + header.ICMPv6NeighborSolicitMinimumSize)
				pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborSolicitMinimumSize))
				pkt.SetType(header.ICMPv6NeighborSolicit)
				ns := header.NDPNeighborSolicit(pkt.NDPPayload())
				ns.SetTargetAddress(tgt)
				snmc := header.SolicitedNodeAddr(tgt)
				pkt.SetChecksum(header.ICMPv6Checksum(pkt, header.IPv6Any, snmc, buffer.VectorisedView{}))
				payloadLength := hdr.UsedLength()
				ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
				ip.Encode(&header.IPv6Fields{
					PayloadLength: uint16(payloadLength),
					NextHeader:    uint8(icmp.ProtocolNumber6),
					HopLimit:      255,
					SrcAddr:       header.IPv6Any,
					DstAddr:       snmc,
				})

				return hdr

			},
			func(s tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
				return s.NeighborSolicit
			},
		},
		{
			"RxAdvert",
			func(tgt tcpip.Address) buffer.Prependable {
				hdr := buffer.NewPrependable(header.IPv6MinimumSize + header.ICMPv6NeighborAdvertSize)
				pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborAdvertSize))
				pkt.SetType(header.ICMPv6NeighborAdvert)
				na := header.NDPNeighborAdvert(pkt.NDPPayload())
				na.SetSolicitedFlag(true)
				na.SetOverrideFlag(true)
				na.SetTargetAddress(tgt)
				pkt.SetChecksum(header.ICMPv6Checksum(pkt, tgt, header.IPv6AllNodesMulticastAddress, buffer.VectorisedView{}))
				payloadLength := hdr.UsedLength()
				ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
				ip.Encode(&header.IPv6Fields{
					PayloadLength: uint16(payloadLength),
					NextHeader:    uint8(icmp.ProtocolNumber6),
					HopLimit:      255,
					SrcAddr:       tgt,
					DstAddr:       header.IPv6AllNodesMulticastAddress,
				})

				return hdr

			},
			func(s tcpip.ICMPv6ReceivedPacketStats) *tcpip.StatCounter {
				return s.NeighborAdvert
			},
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			ndpDisp := ndpDispatcher{
				dadC: make(chan ndpDADEvent),
			}
			ndpConfigs := stack.DefaultNDPConfigurations()
			opts := stack.Options{
				NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
				NDPConfigs:       ndpConfigs,
				NDPDisp:          &ndpDisp,
			}
			opts.NDPConfigs.RetransmitTimer = time.Second * 2

			e := channel.New(10, 1280, linkAddr1)
			s := stack.New(opts)
			if err := s.CreateNIC(1, e); err != nil {
				t.Fatalf("CreateNIC(_) = %s", err)
			}

			if err := s.AddAddress(1, header.IPv6ProtocolNumber, addr1); err != nil {
				t.Fatalf("AddAddress(_, %d, %s) = %s", header.IPv6ProtocolNumber, addr1, err)
			}

			// Address should not be considered bound to the NIC yet
			// (DAD ongoing).
			addr, err := s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
			if err != nil {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (_, %v), want = (_, nil)", err)
			}
			if want := (tcpip.AddressWithPrefix{}); addr != want {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (%s, nil), want = (%s, nil)", addr, want)
			}

			// Receive a packet to simulate multiple nodes owning or
			// attempting to own the same address.
			hdr := test.makeBuf(addr1)
			e.InjectInbound(header.IPv6ProtocolNumber, tcpip.PacketBuffer{
				Data: hdr.View().ToVectorisedView(),
			})

			stat := test.getStat(s.Stats().ICMP.V6PacketsReceived)
			if got := stat.Value(); got != 1 {
				t.Fatalf("got stat = %d, want = 1", got)
			}

			// Wait for DAD to fail and make sure the address did
			// not get resolved.
			select {
			case <-time.After(time.Duration(ndpConfigs.DupAddrDetectTransmits)*ndpConfigs.RetransmitTimer + time.Second):
				// If we don't get a failure event after the
				// expected resolution time + extra 1s buffer,
				// something is wrong.
				t.Fatal("timed out waiting for DAD failure")
			case e := <-ndpDisp.dadC:
				if e.err != nil {
					t.Fatal("got DAD error: ", e.err)
				}
				if e.nicid != 1 {
					t.Fatalf("got DAD event w/ nicid = %d, want = 1", e.nicid)
				}
				if e.addr != addr1 {
					t.Fatalf("got DAD event w/ addr = %s, want = %s", addr, addr1)
				}
				if e.resolved {
					t.Fatal("got DAD event w/ resolved = true, want = false")
				}
			}
			addr, err = s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
			if err != nil {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (_, %v), want = (_, nil)", err)
			}
			if want := (tcpip.AddressWithPrefix{}); addr != want {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (%s, nil), want = (%s, nil)", addr, want)
			}
		})
	}
}

// TestDADStop tests to make sure that the DAD process stops when an address is
// removed.
func TestDADStop(t *testing.T) {
	ndpDisp := ndpDispatcher{
		dadC: make(chan ndpDADEvent),
	}
	ndpConfigs := stack.NDPConfigurations{
		RetransmitTimer:        time.Second,
		DupAddrDetectTransmits: 2,
	}
	opts := stack.Options{
		NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
		NDPDisp:          &ndpDisp,
		NDPConfigs:       ndpConfigs,
	}

	e := channel.New(10, 1280, linkAddr1)
	s := stack.New(opts)
	if err := s.CreateNIC(1, e); err != nil {
		t.Fatalf("CreateNIC(_) = %s", err)
	}

	if err := s.AddAddress(1, header.IPv6ProtocolNumber, addr1); err != nil {
		t.Fatalf("AddAddress(_, %d, %s) = %s", header.IPv6ProtocolNumber, addr1, err)
	}

	// Address should not be considered bound to the NIC yet (DAD ongoing).
	addr, err := s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
	if err != nil {
		t.Fatalf("got stack.GetMainNICAddress(_, _) = (_, %v), want = (_, nil)", err)
	}
	if want := (tcpip.AddressWithPrefix{}); addr != want {
		t.Fatalf("got stack.GetMainNICAddress(_, _) = (%s, nil), want = (%s, nil)", addr, want)
	}

	// Remove the address. This should stop DAD.
	if err := s.RemoveAddress(1, addr1); err != nil {
		t.Fatalf("RemoveAddress(_, %s) = %s", addr1, err)
	}

	// Wait for DAD to fail (since the address was removed during DAD).
	select {
	case <-time.After(time.Duration(ndpConfigs.DupAddrDetectTransmits)*ndpConfigs.RetransmitTimer + time.Second):
		// If we don't get a failure event after the expected resolution
		// time + extra 1s buffer, something is wrong.
		t.Fatal("timed out waiting for DAD failure")
	case e := <-ndpDisp.dadC:
		if e.err != nil {
			t.Fatal("got DAD error: ", e.err)
		}
		if e.nicid != 1 {
			t.Fatalf("got DAD event w/ nicid = %d, want = 1", e.nicid)
		}
		if e.addr != addr1 {
			t.Fatalf("got DAD event w/ addr = %s, want = %s", addr, addr1)
		}
		if e.resolved {
			t.Fatal("got DAD event w/ resolved = true, want = false")
		}

	}
	addr, err = s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
	if err != nil {
		t.Fatalf("got stack.GetMainNICAddress(_, _) = (_, %v), want = (_, nil)", err)
	}
	if want := (tcpip.AddressWithPrefix{}); addr != want {
		t.Fatalf("got stack.GetMainNICAddress(_, _) = (%s, nil), want = (%s, nil)", addr, want)
	}

	// Should not have sent more than 1 NS message.
	if got := s.Stats().ICMP.V6PacketsSent.NeighborSolicit.Value(); got > 1 {
		t.Fatalf("got NeighborSolicit = %d, want <= 1", got)
	}
}

// TestSetNDPConfigurationFailsForBadNICID tests to make sure we get an error if
// we attempt to update NDP configurations using an invalid NICID.
func TestSetNDPConfigurationFailsForBadNICID(t *testing.T) {
	s := stack.New(stack.Options{
		NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
	})

	// No NIC with ID 1 yet.
	if got := s.SetNDPConfigurations(1, stack.NDPConfigurations{}); got != tcpip.ErrUnknownNICID {
		t.Fatalf("got s.SetNDPConfigurations = %v, want = %s", got, tcpip.ErrUnknownNICID)
	}
}

// TestSetNDPConfigurations tests that we can update and use per-interface NDP
// configurations without affecting the default NDP configurations or other
// interfaces' configurations.
func TestSetNDPConfigurations(t *testing.T) {
	tests := []struct {
		name                    string
		dupAddrDetectTransmits  uint8
		retransmitTimer         time.Duration
		expectedRetransmitTimer time.Duration
	}{
		{
			"OK",
			1,
			time.Second,
			time.Second,
		},
		{
			"Invalid Retransmit Timer",
			1,
			0,
			time.Second,
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			ndpDisp := ndpDispatcher{
				dadC: make(chan ndpDADEvent),
			}
			e := channel.New(10, 1280, linkAddr1)
			s := stack.New(stack.Options{
				NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
				NDPDisp:          &ndpDisp,
			})

			// This NIC(1)'s NDP configurations will be updated to
			// be different from the default.
			if err := s.CreateNIC(1, e); err != nil {
				t.Fatalf("CreateNIC(1) = %s", err)
			}

			// Created before updating NIC(1)'s NDP configurations
			// but updating NIC(1)'s NDP configurations should not
			// affect other existing NICs.
			if err := s.CreateNIC(2, e); err != nil {
				t.Fatalf("CreateNIC(2) = %s", err)
			}

			// Update the NDP configurations on NIC(1) to use DAD.
			configs := stack.NDPConfigurations{
				DupAddrDetectTransmits: test.dupAddrDetectTransmits,
				RetransmitTimer:        test.retransmitTimer,
			}
			if err := s.SetNDPConfigurations(1, configs); err != nil {
				t.Fatalf("got SetNDPConfigurations(1, _) = %s", err)
			}

			// Created after updating NIC(1)'s NDP configurations
			// but the stack's default NDP configurations should not
			// have been updated.
			if err := s.CreateNIC(3, e); err != nil {
				t.Fatalf("CreateNIC(3) = %s", err)
			}

			// Add addresses for each NIC.
			if err := s.AddAddress(1, header.IPv6ProtocolNumber, addr1); err != nil {
				t.Fatalf("AddAddress(1, %d, %s) = %s", header.IPv6ProtocolNumber, addr1, err)
			}
			if err := s.AddAddress(2, header.IPv6ProtocolNumber, addr2); err != nil {
				t.Fatalf("AddAddress(2, %d, %s) = %s", header.IPv6ProtocolNumber, addr2, err)
			}
			if err := s.AddAddress(3, header.IPv6ProtocolNumber, addr3); err != nil {
				t.Fatalf("AddAddress(3, %d, %s) = %s", header.IPv6ProtocolNumber, addr3, err)
			}

			// Address should not be considered bound to NIC(1) yet
			// (DAD ongoing).
			addr, err := s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
			if err != nil {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (_, %v), want = (_, nil)", err)
			}
			if want := (tcpip.AddressWithPrefix{}); addr != want {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (%s, nil), want = (%s, nil)", addr, want)
			}

			// Should get the address on NIC(2) and NIC(3)
			// immediately since we should not have performed DAD on
			// it as the stack was configured to not do DAD by
			// default and we only updated the NDP configurations on
			// NIC(1).
			addr, err = s.GetMainNICAddress(2, header.IPv6ProtocolNumber)
			if err != nil {
				t.Fatalf("stack.GetMainNICAddress(2, _) err = %s", err)
			}
			if addr.Address != addr2 {
				t.Fatalf("got stack.GetMainNICAddress(2, _) = %s, want = %s", addr, addr2)
			}
			addr, err = s.GetMainNICAddress(3, header.IPv6ProtocolNumber)
			if err != nil {
				t.Fatalf("stack.GetMainNICAddress(3, _) err = %s", err)
			}
			if addr.Address != addr3 {
				t.Fatalf("got stack.GetMainNICAddress(3, _) = %s, want = %s", addr, addr3)
			}

			// Sleep until right (500ms before) before resolution to
			// make sure the address didn't resolve on NIC(1) yet.
			const delta = 500 * time.Millisecond
			time.Sleep(time.Duration(test.dupAddrDetectTransmits)*test.expectedRetransmitTimer - delta)
			addr, err = s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
			if err != nil {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (_, %v), want = (_, nil)", err)
			}
			if want := (tcpip.AddressWithPrefix{}); addr != want {
				t.Fatalf("got stack.GetMainNICAddress(_, _) = (%s, nil), want = (%s, nil)", addr, want)
			}

			// Wait for DAD to resolve.
			select {
			case <-time.After(2 * delta):
				// We should get a resolution event after 500ms
				// (delta) since we wait for 500ms less than the
				// expected resolution time above to make sure
				// that the address did not yet resolve. Waiting
				// for 1s (2x delta) without a resolution event
				// means something is wrong.
				t.Fatal("timed out waiting for DAD resolution")
			case e := <-ndpDisp.dadC:
				if e.err != nil {
					t.Fatal("got DAD error: ", e.err)
				}
				if e.nicid != 1 {
					t.Fatalf("got DAD event w/ nicid = %d, want = 1", e.nicid)
				}
				if e.addr != addr1 {
					t.Fatalf("got DAD event w/ addr = %s, want = %s", addr, addr1)
				}
				if !e.resolved {
					t.Fatal("got DAD event w/ resolved = false, want = true")
				}
			}
			addr, err = s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
			if err != nil {
				t.Fatalf("stack.GetMainNICAddress(1, _) err = %s", err)
			}
			if addr.Address != addr1 {
				t.Fatalf("got stack.GetMainNICAddress(1, _) = %s, want = %s", addr, addr1)
			}
		})
	}
}