// 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"

	"github.com/google/netstack/tcpip"
	"github.com/google/netstack/tcpip/buffer"
	"github.com/google/netstack/tcpip/checker"
	"github.com/google/netstack/tcpip/header"
	"github.com/google/netstack/tcpip/link/channel"
	"github.com/google/netstack/tcpip/network/ipv6"
	"github.com/google/netstack/tcpip/stack"
	"github.com/google/netstack/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"
	linkAddr1 = "\x01\x02\x03\x04\x05\x06"
	linkAddr2 = "\x01\x02\x03\x04\x05\x07"
)

// 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)
	}
}

// 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) {
			opts := stack.Options{
				NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
			}
			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 almost immediately.
			time.Sleep(100 * time.Millisecond)
			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 - 500ms, to make sure
			// the address is still not resolved. Note, we subtract
			// 600ms because we already waited for 100ms earlier,
			// so our remaining time is 100ms less than the expected
			// time.
			// (X - 100ms) - 500ms = X - 600ms
			//
			// TODO(b/140896005): Use events from the netstack to
			// be signalled before DAD resolves.
			time.Sleep(test.expectedRetransmitTimer*time.Duration(test.dupAddrDetectTransmits) - 600*time.Millisecond)
			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 + 250ms, at which point
			// the address should be resolved. Note, the remaining
			// time is 500ms. See above comments.
			//
			// TODO(b/140896005): Use events from the netstack to
			// know immediately when DAD completes.
			time.Sleep(750 * time.Millisecond)
			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) {
			opts := stack.Options{
				NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
				NDPConfigs:       stack.DefaultNDPConfigurations(),
			}
			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.Inject(header.IPv6ProtocolNumber, 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 3 seconds to make sure that DAD did not resolve
			time.Sleep(3 * time.Second)
			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) {
	opts := stack.Options{
		NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
	}
	opts.NDPConfigs.RetransmitTimer = time.Second
	opts.NDPConfigs.DupAddrDetectTransmits = 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)
	}

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

	// Wait for the time to normally resolve
	// DupAddrDetectTransmits(2) * RetransmitTimer(1s) = 2s.
	// An extra 250ms is added to make sure that if DAD was still running
	// it resolves and the check below fails.
	time.Sleep(2*time.Second + 250*time.Millisecond)
	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)
	}
}