// 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 ipv6

import (
	"testing"

	"gvisor.dev/gvisor/pkg/tcpip"
	"gvisor.dev/gvisor/pkg/tcpip/buffer"
	"gvisor.dev/gvisor/pkg/tcpip/header"
	"gvisor.dev/gvisor/pkg/tcpip/link/channel"
	"gvisor.dev/gvisor/pkg/tcpip/stack"
	"gvisor.dev/gvisor/pkg/tcpip/transport/icmp"
	"gvisor.dev/gvisor/pkg/tcpip/transport/udp"
	"gvisor.dev/gvisor/pkg/waiter"
)

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"
	// The least significant 3 bytes are the same as addr2 so both addr2 and
	// addr3 will have the same solicited-node address.
	addr3 = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x02"
)

// testReceiveICMP tests receiving an ICMP packet from src to dst. want is the
// expected Neighbor Advertisement received count after receiving the packet.
func testReceiveICMP(t *testing.T, s *stack.Stack, e *channel.Endpoint, src, dst tcpip.Address, want uint64) {
	t.Helper()

	// Receive ICMP packet.
	hdr := buffer.NewPrependable(header.IPv6MinimumSize + header.ICMPv6NeighborAdvertSize)
	pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborAdvertSize))
	pkt.SetType(header.ICMPv6NeighborAdvert)
	pkt.SetChecksum(header.ICMPv6Checksum(pkt, src, dst, buffer.VectorisedView{}))
	payloadLength := hdr.UsedLength()
	ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
	ip.Encode(&header.IPv6Fields{
		PayloadLength: uint16(payloadLength),
		NextHeader:    uint8(header.ICMPv6ProtocolNumber),
		HopLimit:      255,
		SrcAddr:       src,
		DstAddr:       dst,
	})

	e.Inject(ProtocolNumber, hdr.View().ToVectorisedView())

	stats := s.Stats().ICMP.V6PacketsReceived

	if got := stats.NeighborAdvert.Value(); got != want {
		t.Fatalf("got NeighborAdvert = %d, want = %d", got, want)
	}
}

// testReceiveICMP tests receiving a UDP packet from src to dst. want is the
// expected UDP received count after receiving the packet.
func testReceiveUDP(t *testing.T, s *stack.Stack, e *channel.Endpoint, src, dst tcpip.Address, want uint64) {
	t.Helper()

	wq := waiter.Queue{}
	we, ch := waiter.NewChannelEntry(nil)
	wq.EventRegister(&we, waiter.EventIn)
	defer wq.EventUnregister(&we)
	defer close(ch)

	ep, err := s.NewEndpoint(udp.ProtocolNumber, ProtocolNumber, &wq)
	if err != nil {
		t.Fatalf("NewEndpoint failed: %v", err)
	}
	defer ep.Close()

	if err := ep.Bind(tcpip.FullAddress{Addr: dst, Port: 80}); err != nil {
		t.Fatalf("ep.Bind(...) failed: %v", err)
	}

	// Receive UDP Packet.
	hdr := buffer.NewPrependable(header.IPv6MinimumSize + header.UDPMinimumSize)
	u := header.UDP(hdr.Prepend(header.UDPMinimumSize))
	u.Encode(&header.UDPFields{
		SrcPort: 5555,
		DstPort: 80,
		Length:  header.UDPMinimumSize,
	})

	// UDP pseudo-header checksum.
	sum := header.PseudoHeaderChecksum(udp.ProtocolNumber, src, dst, header.UDPMinimumSize)

	// UDP checksum
	sum = header.Checksum(header.UDP([]byte{}), sum)
	u.SetChecksum(^u.CalculateChecksum(sum))

	payloadLength := hdr.UsedLength()
	ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
	ip.Encode(&header.IPv6Fields{
		PayloadLength: uint16(payloadLength),
		NextHeader:    uint8(udp.ProtocolNumber),
		HopLimit:      255,
		SrcAddr:       src,
		DstAddr:       dst,
	})

	e.Inject(ProtocolNumber, hdr.View().ToVectorisedView())

	stat := s.Stats().UDP.PacketsReceived

	if got := stat.Value(); got != want {
		t.Fatalf("got UDPPacketsReceived = %d, want = %d", got, want)
	}
}

// TestReceiveOnAllNodesMulticastAddr tests that IPv6 endpoints receive ICMP and
// UDP packets destined to the IPv6 link-local all-nodes multicast address.
func TestReceiveOnAllNodesMulticastAddr(t *testing.T) {
	tests := []struct {
		name         string
		protocolName string
		rxf          func(t *testing.T, s *stack.Stack, e *channel.Endpoint, src, dst tcpip.Address, want uint64)
	}{
		{"ICMP", icmp.ProtocolName6, testReceiveICMP},
		{"UDP", udp.ProtocolName, testReceiveUDP},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			s := stack.New([]string{ProtocolName}, []string{test.protocolName}, stack.Options{})
			e := channel.New(10, 1280, linkAddr1)
			if err := s.CreateNIC(1, e); err != nil {
				t.Fatalf("CreateNIC(_) = %s", err)
			}

			// Should receive a packet destined to the all-nodes
			// multicast address.
			test.rxf(t, s, e, addr1, header.IPv6AllNodesMulticastAddress, 1)
		})
	}
}

// TestReceiveOnSolicitedNodeAddr tests that IPv6 endpoints receive ICMP and UDP
// packets destined to the IPv6 solicited-node address of an assigned IPv6
// address.
func TestReceiveOnSolicitedNodeAddr(t *testing.T) {
	tests := []struct {
		name         string
		protocolName string
		rxf          func(t *testing.T, s *stack.Stack, e *channel.Endpoint, src, dst tcpip.Address, want uint64)
	}{
		{"ICMP", icmp.ProtocolName6, testReceiveICMP},
		{"UDP", udp.ProtocolName, testReceiveUDP},
	}

	snmc := header.SolicitedNodeAddr(addr2)

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			s := stack.New([]string{ProtocolName}, []string{test.protocolName}, stack.Options{})
			e := channel.New(10, 1280, linkAddr1)
			if err := s.CreateNIC(1, e); err != nil {
				t.Fatalf("CreateNIC(_) = %s", err)
			}

			// Should not receive a packet destined to the solicited
			// node address of addr2/addr3 yet as we haven't added
			// those addresses.
			test.rxf(t, s, e, addr1, snmc, 0)

			if err := s.AddAddress(1, ProtocolNumber, addr2); err != nil {
				t.Fatalf("AddAddress(_, %d, %s) = %s", ProtocolNumber, addr2, err)
			}

			// Should receive a packet destined to the solicited
			// node address of addr2/addr3 now that we have added
			// added addr2.
			test.rxf(t, s, e, addr1, snmc, 1)

			if err := s.AddAddress(1, ProtocolNumber, addr3); err != nil {
				t.Fatalf("AddAddress(_, %d, %s) = %s", ProtocolNumber, addr3, err)
			}

			// Should still receive a packet destined to the
			// solicited node address of addr2/addr3 now that we
			// have added addr3.
			test.rxf(t, s, e, addr1, snmc, 2)

			if err := s.RemoveAddress(1, addr2); err != nil {
				t.Fatalf("RemoveAddress(_, %s) = %s", addr2, err)
			}

			// Should still receive a packet destined to the
			// solicited node address of addr2/addr3 now that we
			// have removed addr2.
			test.rxf(t, s, e, addr1, snmc, 3)

			if err := s.RemoveAddress(1, addr3); err != nil {
				t.Fatalf("RemoveAddress(_, %s) = %s", addr3, err)
			}

			// Should not receive a packet destined to the solicited
			// node address of addr2/addr3 yet as both of them got
			// removed.
			test.rxf(t, s, e, addr1, snmc, 3)
		})
	}
}

// TestAddIpv6Address tests adding IPv6 addresses.
func TestAddIpv6Address(t *testing.T) {
	tests := []struct {
		name string
		addr tcpip.Address
	}{
		// This test is in response to b/140943433.
		{
			"Nil",
			tcpip.Address([]byte(nil)),
		},
		{
			"ValidUnicast",
			addr1,
		},
		{
			"ValidLinkLocalUnicast",
			lladdr0,
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			s := stack.New([]string{ProtocolName}, nil, stack.Options{})
			if err := s.CreateNIC(1, &stubLinkEndpoint{}); err != nil {
				t.Fatalf("CreateNIC(_) = %s", err)
			}

			if err := s.AddAddress(1, ProtocolNumber, test.addr); err != nil {
				t.Fatalf("AddAddress(_, %d, nil) = %s", ProtocolNumber, err)
			}

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