// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT

package vnet

import (
	"net"
	"testing"
	"time"

	"github.com/pion/logging"
	"github.com/stretchr/testify/assert"
)

// oic: outbound internal chunk
// oec: outbound external chunk
// iic: inbound internal chunk
// iec: inbound external chunk

const demoIP = "1.2.3.4"

func TestNATTypeDefaults(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()
	nat, err := newNAT(&natConfig{
		natType:       NATType{},
		mappedIPs:     []net.IP{net.ParseIP(demoIP)},
		loggerFactory: loggerFactory,
	})
	assert.NoError(t, err, "should succeed")

	assert.Equal(t, EndpointIndependent, nat.natType.MappingBehavior, "should match")
	assert.Equal(t, EndpointIndependent, nat.natType.FilteringBehavior, "should match")
	assert.False(t, nat.natType.Hairpinning, "should be false")
	assert.False(t, nat.natType.PortPreservation, "should be false")
	assert.Equal(t, defaultNATMappingLifeTime, nat.natType.MappingLifeTime, "should be false")
}

func TestNATMappingBehavior(t *testing.T) { //nolint:maintidx
	loggerFactory := logging.NewDefaultLoggerFactory()
	log := loggerFactory.NewLogger("test")

	t.Run("full-cone NAT", func(t *testing.T) {
		nat, err := newNAT(&natConfig{
			natType: NATType{
				MappingBehavior:   EndpointIndependent,
				FilteringBehavior: EndpointIndependent,
				Hairpinning:       false,
				MappingLifeTime:   30 * time.Second,
			},
			mappedIPs:     []net.IP{net.ParseIP(demoIP)},
			loggerFactory: loggerFactory,
		})
		assert.NoError(t, err, "should succeed")

		src := &net.UDPAddr{
			IP:   net.ParseIP("192.168.0.2"),
			Port: 1234,
		}
		dst := &net.UDPAddr{
			IP:   net.ParseIP("5.6.7.8"),
			Port: 5678,
		}

		oic := newChunkUDP(src, dst)

		oec, err := nat.translateOutbound(oic)
		assert.Nil(t, err, "should succeed")
		assert.Equal(t, 1, len(nat.outboundMap), "should match")
		assert.Equal(t, 1, len(nat.inboundMap), "should match")

		log.Debugf("o-original  : %s", oic.String())
		log.Debugf("o-translated: %s", oec.String())

		//nolint:forcetypeassert
		iec := newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: dst.Port,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort,
			},
		)

		log.Debugf("i-original  : %s", iec.String())

		iic, err := nat.translateInbound(iec)
		assert.Nil(t, err, "should succeed")

		log.Debugf("i-translated: %s", iic.String())

		//nolint:forcetypeassert
		assert.Equal(t,
			oic.SourceAddr().String(),
			iic.(*chunkUDP).DestinationAddr().String(),
			"should match")

		// packet with dest addr that does not exist in the mapping table
		// will be dropped
		//nolint:forcetypeassert
		iec = newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: dst.Port,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort + 1,
			},
		)

		_, err = nat.translateInbound(iec)
		log.Debug(err.Error())
		assert.NotNil(t, err, "should fail (dropped)")

		// packet from any addr will be accepted (full-cone)
		//nolint:forcetypeassert
		iec = newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: 7777,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort,
			},
		)

		_, err = nat.translateInbound(iec)
		assert.Nil(t, err, "should succeed")
	})

	t.Run("addr-restricted-cone NAT", func(t *testing.T) {
		nat, err := newNAT(&natConfig{
			natType: NATType{
				MappingBehavior:   EndpointIndependent,
				FilteringBehavior: EndpointAddrDependent,
				Hairpinning:       false,
				MappingLifeTime:   30 * time.Second,
			},
			mappedIPs:     []net.IP{net.ParseIP(demoIP)},
			loggerFactory: loggerFactory,
		})
		assert.NoError(t, err, "should succeed")

		src := &net.UDPAddr{
			IP:   net.ParseIP("192.168.0.2"),
			Port: 1234,
		}
		dst := &net.UDPAddr{
			IP:   net.ParseIP("5.6.7.8"),
			Port: 5678,
		}

		oic := newChunkUDP(src, dst)
		log.Debugf("o-original  : %s", oic.String())

		oec, err := nat.translateOutbound(oic)
		assert.Nil(t, err, "should succeed")
		assert.Equal(t, 1, len(nat.outboundMap), "should match")
		assert.Equal(t, 1, len(nat.inboundMap), "should match")
		log.Debugf("o-translated: %s", oec.String())

		// sending different (IP: 5.6.7.9) won't create a new mapping
		oic2 := newChunkUDP(&net.UDPAddr{
			IP:   net.ParseIP("192.168.0.2"),
			Port: 1234,
		}, &net.UDPAddr{
			IP:   net.ParseIP("5.6.7.9"),
			Port: 9000,
		})
		oec2, err := nat.translateOutbound(oic2)
		assert.Nil(t, err, "should succeed")
		assert.Equal(t, 1, len(nat.outboundMap), "should match")
		assert.Equal(t, 1, len(nat.inboundMap), "should match")
		log.Debugf("o-translated: %s", oec2.String())

		//nolint:forcetypeassert
		iec := newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: dst.Port,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort,
			},
		)

		log.Debugf("i-original  : %s", iec.String())

		iic, err := nat.translateInbound(iec)
		if !assert.NoError(t, err, "should succeed") {
			return
		}

		log.Debugf("i-translated: %s", iic.String())

		//nolint:forcetypeassert
		assert.Equal(t,
			oic.SourceAddr().String(),
			iic.(*chunkUDP).DestinationAddr().String(),
			"should match")

		// packet with dest addr that does not exist in the mapping table
		// will be dropped
		//nolint:forcetypeassert
		iec = newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: dst.Port,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort + 1,
			},
		)

		_, err = nat.translateInbound(iec)
		log.Debug(err.Error())
		assert.NotNil(t, err, "should fail (dropped)")

		// packet from any port will be accepted (restricted-cone)
		//nolint:forcetypeassert
		iec = newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: 7777,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort,
			},
		)

		_, err = nat.translateInbound(iec)
		assert.Nil(t, err, "should succeed")

		// packet from different addr will be dropped (restricted-cone)
		//nolint:forcetypeassert
		iec = newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("6.6.6.6"),
				Port: dst.Port,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort,
			},
		)

		_, err = nat.translateInbound(iec)
		log.Debug(err.Error())
		assert.NotNil(t, err, "should fail (dropped)")
	})

	t.Run("port-restricted-cone NAT", func(t *testing.T) {
		nat, err := newNAT(&natConfig{
			natType: NATType{
				MappingBehavior:   EndpointIndependent,
				FilteringBehavior: EndpointAddrPortDependent,
				Hairpinning:       false,
				MappingLifeTime:   30 * time.Second,
			},
			mappedIPs:     []net.IP{net.ParseIP(demoIP)},
			loggerFactory: loggerFactory,
		})
		assert.NoError(t, err, "should succeed")

		src := &net.UDPAddr{
			IP:   net.ParseIP("192.168.0.2"),
			Port: 1234,
		}
		dst := &net.UDPAddr{
			IP:   net.ParseIP("5.6.7.8"),
			Port: 5678,
		}

		oic := newChunkUDP(src, dst)
		log.Debugf("o-original  : %s", oic.String())

		oec, err := nat.translateOutbound(oic)
		assert.Nil(t, err, "should succeed")
		assert.Equal(t, 1, len(nat.outboundMap), "should match")
		assert.Equal(t, 1, len(nat.inboundMap), "should match")

		log.Debugf("o-translated: %s", oec.String())

		// sending different (IP: 5.6.7.9) won't create a new mapping
		oic2 := newChunkUDP(&net.UDPAddr{
			IP:   net.ParseIP("192.168.0.2"),
			Port: 1234,
		}, &net.UDPAddr{
			IP:   net.ParseIP("5.6.7.9"),
			Port: 9000,
		})
		oec2, err := nat.translateOutbound(oic2)
		assert.Nil(t, err, "should succeed")
		assert.Equal(t, 1, len(nat.outboundMap), "should match")
		assert.Equal(t, 1, len(nat.inboundMap), "should match")
		log.Debugf("o-translated: %s", oec2.String())

		//nolint:forcetypeassert
		iec := newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: dst.Port,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort,
			},
		)

		log.Debugf("i-original  : %s", iec.String())

		iic, err := nat.translateInbound(iec)
		assert.Nil(t, err, "should succeed")

		log.Debugf("i-translated: %s", iic.String())

		//nolint:forcetypeassert
		assert.Equal(t,
			oic.SourceAddr().String(),
			iic.(*chunkUDP).DestinationAddr().String(),
			"should match")

		// packet with dest addr that does not exist in the mapping table
		// will be dropped
		//nolint:forcetypeassert
		iec = newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: dst.Port,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort + 1,
			},
		)

		_, err = nat.translateInbound(iec)
		assert.NotNil(t, err, "should fail (dropped)")

		// packet from different port will be dropped (port-restricted-cone)
		//nolint:forcetypeassert
		iec = newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: 7777,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort,
			},
		)

		_, err = nat.translateInbound(iec)
		assert.NotNil(t, err, "should fail (dropped)")

		// packet from different addr will be dropped (restricted-cone)
		//nolint:forcetypeassert
		iec = newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("6.6.6.6"),
				Port: dst.Port,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort,
			},
		)

		_, err = nat.translateInbound(iec)
		assert.NotNil(t, err, "should fail (dropped)")
	})

	t.Run("symmetric NAT addr dependent mapping", func(t *testing.T) { //nolint:dupl
		nat, err := newNAT(&natConfig{
			natType: NATType{
				MappingBehavior:   EndpointAddrDependent,
				FilteringBehavior: EndpointAddrDependent,
				Hairpinning:       false,
				MappingLifeTime:   30 * time.Second,
			},
			mappedIPs:     []net.IP{net.ParseIP(demoIP)},
			loggerFactory: loggerFactory,
		})
		assert.NoError(t, err, "should succeed")

		oic1 := newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("192.168.0.2"),
				Port: 1234,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.8"),
				Port: 5678,
			},
		)

		oic2 := newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("192.168.0.2"),
				Port: 1234,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.100"),
				Port: 5678,
			},
		)

		oic3 := newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("192.168.0.2"),
				Port: 1234,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.8"),
				Port: 6000,
			},
		)

		log.Debugf("o-original  : %s", oic1.String())
		log.Debugf("o-original  : %s", oic2.String())
		log.Debugf("o-original  : %s", oic3.String())

		oec1, err := nat.translateOutbound(oic1)
		assert.Nil(t, err, "should succeed")

		oec2, err := nat.translateOutbound(oic2)
		assert.Nil(t, err, "should succeed")

		oec3, err := nat.translateOutbound(oic3)
		assert.Nil(t, err, "should succeed")

		assert.Equal(t, 2, len(nat.outboundMap), "should match")
		assert.Equal(t, 2, len(nat.inboundMap), "should match")

		log.Debugf("o-translated: %s", oec1.String())
		log.Debugf("o-translated: %s", oec2.String())
		log.Debugf("o-translated: %s", oec3.String())

		assert.NotEqual(
			t,
			oec1.(*chunkUDP).sourcePort, //nolint:forcetypeassert
			oec2.(*chunkUDP).sourcePort, //nolint:forcetypeassert
			"should not match",
		)
		assert.Equal(
			t,
			oec1.(*chunkUDP).sourcePort, //nolint:forcetypeassert
			oec3.(*chunkUDP).sourcePort, //nolint:forcetypeassert
			"should match",
		)
	})

	t.Run("symmetric NAT port dependent mapping", func(t *testing.T) { //nolint:dupl
		nat, err := newNAT(&natConfig{
			natType: NATType{
				MappingBehavior:   EndpointAddrPortDependent,
				FilteringBehavior: EndpointAddrPortDependent,
				Hairpinning:       false,
				MappingLifeTime:   30 * time.Second,
			},
			mappedIPs:     []net.IP{net.ParseIP(demoIP)},
			loggerFactory: loggerFactory,
		})
		assert.NoError(t, err, "should succeed")

		oic1 := newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("192.168.0.2"),
				Port: 1234,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.8"),
				Port: 5678,
			},
		)

		oic2 := newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("192.168.0.2"),
				Port: 1234,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.100"),
				Port: 5678,
			},
		)

		oic3 := newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("192.168.0.2"),
				Port: 1234,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.8"),
				Port: 6000,
			},
		)

		log.Debugf("o-original  : %s", oic1.String())
		log.Debugf("o-original  : %s", oic2.String())
		log.Debugf("o-original  : %s", oic3.String())

		oec1, err := nat.translateOutbound(oic1)
		assert.Nil(t, err, "should succeed")

		oec2, err := nat.translateOutbound(oic2)
		assert.Nil(t, err, "should succeed")

		oec3, err := nat.translateOutbound(oic3)
		assert.Nil(t, err, "should succeed")

		assert.Equal(t, 3, len(nat.outboundMap), "should match")
		assert.Equal(t, 3, len(nat.inboundMap), "should match")

		log.Debugf("o-translated: %s", oec1.String())
		log.Debugf("o-translated: %s", oec2.String())
		log.Debugf("o-translated: %s", oec3.String())

		assert.NotEqual(
			t,
			oec1.(*chunkUDP).sourcePort, //nolint:forcetypeassert
			oec2.(*chunkUDP).sourcePort, //nolint:forcetypeassert
			"should not match",
		)
		assert.NotEqual(
			t,
			oec1.(*chunkUDP).sourcePort, //nolint:forcetypeassert
			oec3.(*chunkUDP).sourcePort, //nolint:forcetypeassert
			"should match",
		)
	})
}

func TestNATMappingTimeout(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()
	log := loggerFactory.NewLogger("test")

	t.Run("refresh on outbound", func(t *testing.T) {
		nat, err := newNAT(&natConfig{
			natType: NATType{
				MappingBehavior:   EndpointIndependent,
				FilteringBehavior: EndpointIndependent,
				Hairpinning:       false,
				MappingLifeTime:   100 * time.Millisecond,
			},
			mappedIPs:     []net.IP{net.ParseIP(demoIP)},
			loggerFactory: loggerFactory,
		})
		assert.NoError(t, err, "should succeed")

		src := &net.UDPAddr{
			IP:   net.ParseIP("192.168.0.2"),
			Port: 1234,
		}
		dst := &net.UDPAddr{
			IP:   net.ParseIP("5.6.7.8"),
			Port: 5678,
		}

		oic := newChunkUDP(src, dst)

		oec, err := nat.translateOutbound(oic)
		assert.Nil(t, err, "should succeed")
		assert.Equal(t, 1, len(nat.outboundMap), "should match")
		assert.Equal(t, 1, len(nat.inboundMap), "should match")

		log.Debugf("o-original  : %s", oic.String())
		log.Debugf("o-translated: %s", oec.String())

		// record mapped addr
		mapped := oec.(*chunkUDP).SourceAddr().String() //nolint:forcetypeassert

		time.Sleep(75 * time.Millisecond)

		// refresh
		oec, err = nat.translateOutbound(oic)
		assert.Nil(t, err, "should succeed")
		assert.Equal(t, 1, len(nat.outboundMap), "should match")
		assert.Equal(t, 1, len(nat.inboundMap), "should match")

		log.Debugf("o-original  : %s", oic.String())
		log.Debugf("o-translated: %s", oec.String())

		assert.Equal(t, mapped, oec.(*chunkUDP).SourceAddr().String(), "mapped addr should match") //nolint:forcetypeassert

		// sleep long enough for the mapping to expire
		time.Sleep(125 * time.Millisecond)

		// refresh after expiration
		oec, err = nat.translateOutbound(oic)
		assert.Nil(t, err, "should succeed")
		assert.Equal(t, 1, len(nat.outboundMap), "should match")
		assert.Equal(t, 1, len(nat.inboundMap), "should match")

		log.Debugf("o-original  : %s", oic.String())
		log.Debugf("o-translated: %s", oec.String())

		assert.NotEqual(
			t,
			mapped,
			oec.(*chunkUDP).SourceAddr().String(), //nolint:forcetypeassert
			"mapped addr should not match",
		)
	})

	t.Run("outbound detects timeout", func(t *testing.T) {
		nat, err := newNAT(&natConfig{
			natType: NATType{
				MappingBehavior:   EndpointIndependent,
				FilteringBehavior: EndpointIndependent,
				Hairpinning:       false,
				MappingLifeTime:   100 * time.Millisecond,
			},
			mappedIPs:     []net.IP{net.ParseIP(demoIP)},
			loggerFactory: loggerFactory,
		})
		assert.NoError(t, err, "should succeed")

		src := &net.UDPAddr{
			IP:   net.ParseIP("192.168.0.2"),
			Port: 1234,
		}
		dst := &net.UDPAddr{
			IP:   net.ParseIP("5.6.7.8"),
			Port: 5678,
		}

		oic := newChunkUDP(src, dst)

		oec, err := nat.translateOutbound(oic)
		assert.Nil(t, err, "should succeed")
		assert.Equal(t, 1, len(nat.outboundMap), "should match")
		assert.Equal(t, 1, len(nat.inboundMap), "should match")

		log.Debugf("o-original  : %s", oic.String())
		log.Debugf("o-translated: %s", oec.String())

		// sleep long enough for the mapping to expire
		time.Sleep(125 * time.Millisecond)

		//nolint:forcetypeassert
		iec := newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: dst.Port,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort,
			},
		)

		log.Debugf("i-original  : %s", iec.String())

		_, err = nat.translateInbound(iec)
		assert.NotNil(t, err, "should drop")
		assert.Empty(t, nat.outboundMap, "should have no binding")
		assert.Empty(t, nat.inboundMap, "should have no binding")
	})
}

func TestNAT1To1Behavior(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()
	log := loggerFactory.NewLogger("test")

	t.Run("1:1 NAT with one mapping", func(t *testing.T) {
		nat, err := newNAT(&natConfig{
			natType: NATType{
				Mode: NATModeNAT1To1,
			},
			mappedIPs:     []net.IP{net.ParseIP(demoIP)},
			localIPs:      []net.IP{net.ParseIP("10.0.0.1")},
			loggerFactory: loggerFactory,
		})
		if !assert.NoError(t, err, "should succeed") {
			return
		}

		src := &net.UDPAddr{
			IP:   net.ParseIP("10.0.0.1"),
			Port: 1234,
		}
		dst := &net.UDPAddr{
			IP:   net.ParseIP("5.6.7.8"),
			Port: 5678,
		}

		oic := newChunkUDP(src, dst)

		oec, err := nat.translateOutbound(oic)
		assert.Nil(t, err, "should succeed")
		assert.Empty(t, nat.outboundMap, "should match")
		assert.Empty(t, nat.inboundMap, "should match")

		log.Debugf("o-original  : %s", oic.String())
		log.Debugf("o-translated: %s", oec.String())

		assert.Equal(t, "1.2.3.4:1234", oec.SourceAddr().String(), "should match")

		//nolint:forcetypeassert
		iec := newChunkUDP(
			&net.UDPAddr{
				IP:   dst.IP,
				Port: dst.Port,
			},
			&net.UDPAddr{
				IP:   oec.(*chunkUDP).sourceIP,
				Port: oec.(*chunkUDP).sourcePort,
			},
		)

		log.Debugf("i-original  : %s", iec.String())

		iic, err := nat.translateInbound(iec)
		assert.Nil(t, err, "should succeed")

		log.Debugf("i-translated: %s", iic.String())

		assert.Equal(t,
			oic.SourceAddr().String(),
			iic.DestinationAddr().String(),
			"should match")
	})

	t.Run("1:1 NAT with more than one mapping", func(t *testing.T) {
		nat, err := newNAT(&natConfig{
			natType: NATType{
				Mode: NATModeNAT1To1,
			},
			mappedIPs: []net.IP{
				net.ParseIP(demoIP),
				net.ParseIP("1.2.3.5"),
			},
			localIPs: []net.IP{
				net.ParseIP("10.0.0.1"),
				net.ParseIP("10.0.0.2"),
			},
			loggerFactory: loggerFactory,
		})
		if !assert.NoError(t, err, "should succeed") {
			return
		}

		// outbound translation

		before := newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("10.0.0.1"),
				Port: 1234,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.8"),
				Port: 5678,
			})

		after, err := nat.translateOutbound(before)
		if !assert.NoError(t, err, "should succeed") {
			return
		}
		assert.Equal(t, "1.2.3.4:1234", after.SourceAddr().String(), "should match")

		before = newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("10.0.0.2"),
				Port: 1234,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.8"),
				Port: 5678,
			})

		after, err = nat.translateOutbound(before)
		if !assert.NoError(t, err, "should succeed") {
			return
		}
		assert.Equal(t, "1.2.3.5:1234", after.SourceAddr().String(), "should match")

		// inbound translation

		before = newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.8"),
				Port: 5678,
			},
			&net.UDPAddr{
				IP:   net.ParseIP(demoIP),
				Port: 2525,
			})

		after, err = nat.translateInbound(before)
		if !assert.NoError(t, err, "should succeed") {
			return
		}
		assert.Equal(t, "10.0.0.1:2525", after.DestinationAddr().String(), "should match")

		before = newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.8"),
				Port: 5678,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("1.2.3.5"),
				Port: 9847,
			})

		after, err = nat.translateInbound(before)
		if !assert.NoError(t, err, "should succeed") {
			return
		}
		assert.Equal(t, "10.0.0.2:9847", after.DestinationAddr().String(), "should match")
	})

	t.Run("1:1 NAT failure", func(t *testing.T) {
		// 1:1 NAT requires more than one mapping
		_, err := newNAT(&natConfig{
			natType: NATType{
				Mode: NATModeNAT1To1,
			},
			loggerFactory: loggerFactory,
		})
		assert.Error(t, err, "should fail")

		// 1:1 NAT requires the same number of mappedIPs and localIPs
		_, err = newNAT(&natConfig{
			natType: NATType{
				Mode: NATModeNAT1To1,
			},
			mappedIPs: []net.IP{
				net.ParseIP(demoIP),
				net.ParseIP("1.2.3.5"),
			},
			localIPs: []net.IP{
				net.ParseIP("10.0.0.1"),
			},
			loggerFactory: loggerFactory,
		})
		assert.Error(t, err, "should fail")

		// drop outbound or inbound chunk with no route in 1:1 NAT

		nat, err := newNAT(&natConfig{
			natType: NATType{
				Mode: NATModeNAT1To1,
			},
			mappedIPs: []net.IP{
				net.ParseIP(demoIP),
			},
			localIPs: []net.IP{
				net.ParseIP("10.0.0.1"),
			},
			loggerFactory: loggerFactory,
		})
		assert.NoError(t, err, "should succeed")

		before := newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("10.0.0.2"), // no external mapping for this
				Port: 1234,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.8"),
				Port: 5678,
			})

		after, err := nat.translateOutbound(before)
		if !assert.NoError(t, err, "should succeed") {
			return
		}
		if !assert.Nil(t, after, "should be nil") {
			return
		}

		before = newChunkUDP(
			&net.UDPAddr{
				IP:   net.ParseIP("5.6.7.8"),
				Port: 5678,
			},
			&net.UDPAddr{
				IP:   net.ParseIP("10.0.0.2"), // no local mapping for this
				Port: 1234,
			})

		_, err = nat.translateInbound(before)
		assert.Error(t, err, "should fail")
	})
}