association_test.go

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

//go:build !js
// +build !js

package sctp

import (
	"context"
	cryptoRand "crypto/rand"
	"encoding/binary"
	"errors"
	"io"
	"math"
	"math/rand"
	"net"
	"os"
	"runtime"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/pion/logging"
	"github.com/pion/transport/v3/test"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

var (
	errHandshakeFailed       = errors.New("handshake failed")
	errSINotMatch            = errors.New("SI should match")
	errReadData              = errors.New("failed to read data")
	errReceivedDataNot3Bytes = errors.New("received data must by 3 bytes")
	errPPIUnexpected         = errors.New("unexpected ppi")
	errReceivedDataMismatch  = errors.New("received data mismatch")
)

func TestAssocStressDuplex(t *testing.T) {
	// Limit runtime in case of deadlocks
	lim := test.TimeOut(time.Second * 20)
	defer lim.Stop()

	// Check for leaking routines
	report := test.CheckRoutines(t)
	defer report()

	stressDuplex(t)
}

func stressDuplex(t *testing.T) {
	ca, cb, stop, err := pipe(pipeDump)
	if err != nil {
		t.Fatal(err)
	}

	defer stop(t)

	// Need to Increase once SCTP is more reliable in case of slow reader
	opt := test.Options{
		MsgSize:  2048, // 65535,
		MsgCount: 10,   // 1000,
	}

	err = test.StressDuplex(ca, cb, opt)
	if err != nil {
		t.Fatal(err)
	}
}

func pipe(piper piperFunc) (*Stream, *Stream, func(*testing.T), error) {
	var err error

	var aa, ab *Association
	aa, ab, err = association(piper)
	if err != nil {
		return nil, nil, nil, err
	}

	var sa, sb *Stream
	sa, err = aa.OpenStream(0, 0)
	if err != nil {
		return nil, nil, nil, err
	}

	sb, err = ab.OpenStream(0, 0)
	if err != nil {
		return nil, nil, nil, err
	}

	stop := func(t *testing.T) {
		err = sa.Close()
		if err != nil {
			t.Error(err)
		}
		err = sb.Close()
		if err != nil {
			t.Error(err)
		}
		err = aa.Close()
		if err != nil {
			t.Error(err)
		}
		err = ab.Close()
		if err != nil {
			t.Error(err)
		}
	}

	return sa, sb, stop, nil
}

func association(piper piperFunc) (*Association, *Association, error) {
	ca, cb := piper()

	type result struct {
		a   *Association
		err error
	}

	c := make(chan result)
	loggerFactory := logging.NewDefaultLoggerFactory()

	// Setup client
	go func() {
		client, err := Client(Config{
			NetConn:       ca,
			LoggerFactory: loggerFactory,
		})
		c <- result{client, err}
	}()

	// Setup server
	server, err := Server(Config{
		NetConn:       cb,
		LoggerFactory: loggerFactory,
	})
	if err != nil {
		return nil, nil, err
	}

	// Receive client
	res := <-c
	if res.err != nil {
		return nil, nil, res.err
	}

	return res.a, server, nil
}

type piperFunc func() (net.Conn, net.Conn)

func check(err error) {
	if err != nil {
		panic(err)
	}
}

func pipeDump() (net.Conn, net.Conn) {
	aConn := acceptDumbConn()

	bConn, err := net.DialUDP("udp4", nil, aConn.LocalAddr().(*net.UDPAddr))
	check(err)

	// Dumb handshake
	mgs := "Test"
	_, err = bConn.Write([]byte(mgs))
	check(err)

	b := make([]byte, 4)
	_, err = aConn.Read(b)
	check(err)

	if string(b) != mgs {
		panic("Dumb handshake failed")
	}

	return aConn, bConn
}

type dumbConn struct {
	mu    sync.RWMutex
	rAddr net.Addr
	pConn net.PacketConn
}

func acceptDumbConn() *dumbConn {
	pConn, err := net.ListenUDP("udp4", nil)
	check(err)
	return &dumbConn{
		pConn: pConn,
	}
}

// Read
func (c *dumbConn) Read(p []byte) (int, error) {
	i, rAddr, err := c.pConn.ReadFrom(p)
	if err != nil {
		return 0, err
	}

	c.mu.Lock()
	c.rAddr = rAddr
	c.mu.Unlock()

	return i, err
}

// Write writes len(p) bytes from p to the DTLS connection
func (c *dumbConn) Write(p []byte) (n int, err error) {
	return c.pConn.WriteTo(p, c.RemoteAddr())
}

// Close closes the conn and releases any Read calls
func (c *dumbConn) Close() error {
	return c.pConn.Close()
}

// LocalAddr is a stub
func (c *dumbConn) LocalAddr() net.Addr {
	if c.pConn != nil {
		return c.pConn.LocalAddr()
	}
	return nil
}

// RemoteAddr is a stub
func (c *dumbConn) RemoteAddr() net.Addr {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return c.rAddr
}

// SetDeadline is a stub
func (c *dumbConn) SetDeadline(time.Time) error {
	return nil
}

// SetReadDeadline is a stub
func (c *dumbConn) SetReadDeadline(time.Time) error {
	return nil
}

// SetWriteDeadline is a stub
func (c *dumbConn) SetWriteDeadline(time.Time) error {
	return nil
}

func createNewAssociationPair(br *test.Bridge, ackMode int, recvBufSize uint32) (*Association, *Association, error) {
	var a0, a1 *Association
	var err0, err1 error
	loggerFactory := logging.NewDefaultLoggerFactory()

	handshake0Ch := make(chan bool)
	handshake1Ch := make(chan bool)

	go func() {
		a0, err0 = Client(Config{
			Name:                 "a0",
			NetConn:              br.GetConn0(),
			MaxReceiveBufferSize: recvBufSize,
			LoggerFactory:        loggerFactory,
		})
		handshake0Ch <- true
	}()
	go func() {
		// we could have two "client"s here but it's more
		// standard to have one peer starting initialization and
		// another waiting for the initialization to be requested (INIT).
		a1, err1 = Server(Config{
			Name:                 "a1",
			NetConn:              br.GetConn1(),
			MaxReceiveBufferSize: recvBufSize,
			LoggerFactory:        loggerFactory,
		})
		handshake1Ch <- true
	}()

	a0handshakeDone := false
	a1handshakeDone := false

loop1:
	for i := 0; i < 100; i++ {
		time.Sleep(10 * time.Millisecond)
		br.Tick()

		select {
		case a0handshakeDone = <-handshake0Ch:
			if a1handshakeDone {
				break loop1
			}
		case a1handshakeDone = <-handshake1Ch:
			if a0handshakeDone {
				break loop1
			}
		default:
		}
	}

	if !a0handshakeDone || !a1handshakeDone {
		return nil, nil, errHandshakeFailed
	}

	if err0 != nil {
		return nil, nil, err0
	}
	if err1 != nil {
		return nil, nil, err1
	}

	a0.ackMode = ackMode
	a1.ackMode = ackMode

	return a0, a1, nil
}

func closeAssociationPair(br *test.Bridge, a0, a1 *Association) {
	close0Ch := make(chan bool)
	close1Ch := make(chan bool)

	go func() {
		// nolint:errcheck,gosec
		a0.Close()
		close0Ch <- true
	}()
	go func() {
		// nolint:errcheck,gosec
		a1.Close()
		close1Ch <- true
	}()

	a0closed := false
	a1closed := false
loop1:
	for i := 0; i < 100; i++ {
		time.Sleep(10 * time.Millisecond)
		br.Tick()

		select {
		case a0closed = <-close0Ch:
			if a1closed {
				break loop1
			}
		case a1closed = <-close1Ch:
			if a0closed {
				break loop1
			}
		default:
		}
	}
}

func flushBuffers(br *test.Bridge, a0, a1 *Association) {
	for {
		for {
			n := br.Tick()
			if n == 0 {
				break
			}
		}

		if a0.bufferedAmount() == 0 && a1.bufferedAmount() == 0 {
			break
		}
		time.Sleep(10 * time.Millisecond)
	}
}

func establishSessionPair(br *test.Bridge, a0, a1 *Association, si uint16) (*Stream, *Stream, error) {
	helloMsg := "Hello" // mimic datachannel.channelOpen
	s0, err := a0.OpenStream(si, PayloadTypeWebRTCBinary)
	if err != nil {
		return nil, nil, err
	}

	_, err = s0.WriteSCTP([]byte(helloMsg), PayloadTypeWebRTCDCEP)
	if err != nil {
		return nil, nil, err
	}

	flushBuffers(br, a0, a1)

	s1, err := a1.AcceptStream()
	if err != nil {
		return nil, nil, err
	}

	if s0.streamIdentifier != s1.streamIdentifier {
		return nil, nil, errSINotMatch
	}

	br.Process()

	buf := make([]byte, 1024)
	n, ppi, err := s1.ReadSCTP(buf)
	if err != nil {
		return nil, nil, errReadData
	}

	if n != len(helloMsg) {
		return nil, nil, errReceivedDataNot3Bytes
	}

	if ppi != PayloadTypeWebRTCDCEP {
		return nil, nil, errPPIUnexpected
	}

	if string(buf[:n]) != helloMsg {
		return nil, nil, errReceivedDataMismatch
	}

	flushBuffers(br, a0, a1)

	return s0, s1, nil
}

func TestAssocReliable(t *testing.T) {
	// sbuf - small enough not to be fragmented
	//        large enough not to be bundled
	sbuf := make([]byte, 1000)
	for i := 0; i < len(sbuf); i++ {
		sbuf[i] = byte(i & 0xff)
	}
	rand.Seed(time.Now().UnixNano())
	rand.Shuffle(len(sbuf), func(i, j int) { sbuf[i], sbuf[j] = sbuf[j], sbuf[i] })

	// sbufL - large enough to be fragmented into two chunks and each chunks are
	//        large enough not to be bundled
	sbufL := make([]byte, 2000)
	for i := 0; i < len(sbufL); i++ {
		sbufL[i] = byte(i & 0xff)
	}
	rand.Seed(time.Now().UnixNano())
	rand.Shuffle(len(sbufL), func(i, j int) { sbufL[i], sbufL[j] = sbufL[j], sbufL[i] })

	t.Run("Simple", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 1
		const msg = "ABC"
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		assert.Equal(t, 0, a0.bufferedAmount(), "incorrect bufferedAmount")

		n, err := s0.WriteSCTP([]byte(msg), PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(msg), n, "unexpected length of received data")
		assert.Equal(t, len(msg), a0.bufferedAmount(), "incorrect bufferedAmount")

		flushBuffers(br, a0, a1)

		buf := make([]byte, 32)
		n, ppi, err := s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, n, len(msg), "unexpected length of received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		assert.Equal(t, 0, a0.bufferedAmount(), "incorrect bufferedAmount")

		closeAssociationPair(br, a0, a1)
	})

	t.Run("ReadDeadline", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 1
		const msg = "ABC"
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		assert.Equal(t, 0, a0.bufferedAmount(), "incorrect bufferedAmount")

		assert.NoError(t, s1.SetReadDeadline(time.Now().Add(time.Millisecond)), "failed to set read deadline")
		buf := make([]byte, 32)
		// First fails
		n, ppi, err := s1.ReadSCTP(buf)
		assert.Equal(t, 0, n)
		assert.Equal(t, PayloadProtocolIdentifier(0), ppi)
		assert.True(t, errors.Is(err, os.ErrDeadlineExceeded))
		// Second too
		n, ppi, err = s1.ReadSCTP(buf)
		assert.Equal(t, 0, n)
		assert.Equal(t, PayloadProtocolIdentifier(0), ppi)
		assert.True(t, errors.Is(err, os.ErrDeadlineExceeded))
		assert.NoError(t, s1.SetReadDeadline(time.Time{}), "failed to disable read deadline")

		n, err = s0.WriteSCTP([]byte(msg), PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(msg), n, "unexpected length of received data")
		assert.Equal(t, len(msg), a0.bufferedAmount(), "incorrect bufferedAmount")

		flushBuffers(br, a0, a1)

		n, ppi, err = s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, n, len(msg), "unexpected length of received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		closeAssociationPair(br, a0, a1)
	})

	t.Run("ordered reordered", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 2
		var n int
		var ppi PayloadProtocolIdentifier
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		binary.BigEndian.PutUint32(sbuf, 0)
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		assert.Nil(t, err, "WriteSCTP failed")
		assert.Equal(t, n, len(sbuf), "unexpected length of received data")

		binary.BigEndian.PutUint32(sbuf, 1)
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		assert.Nil(t, err, "WriteSCTP failed")
		assert.Equal(t, n, len(sbuf), "unexpected length of received data")

		time.Sleep(10 * time.Millisecond)
		err = br.Reorder(0)
		assert.Nil(t, err, "reorder failed")
		br.Process()

		buf := make([]byte, 2000)

		n, ppi, err = s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, n, len(sbuf), "unexpected length of received data")
		assert.Equal(t, uint32(0), binary.BigEndian.Uint32(buf[:n]),
			"unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		n, ppi, err = s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, n, len(sbuf), "unexpected length of received data")
		assert.Equal(t, uint32(1), binary.BigEndian.Uint32(buf[:n]),
			"unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()
		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		closeAssociationPair(br, a0, a1)
	})

	t.Run("ordered fragmented then defragmented", func(t *testing.T) { // nolint:dupl
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 3
		var n int
		var ppi PayloadProtocolIdentifier
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		s0.SetReliabilityParams(false, ReliabilityTypeReliable, 0)
		s1.SetReliabilityParams(false, ReliabilityTypeReliable, 0)

		n, err = s0.WriteSCTP(sbufL, PayloadTypeWebRTCBinary)
		assert.Nil(t, err, "WriteSCTP failed")
		assert.Equal(t, n, len(sbufL), "unexpected length of received data")

		rbuf := make([]byte, 2000)
		flushBuffers(br, a0, a1)

		n, ppi, err = s1.ReadSCTP(rbuf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}

		assert.Equal(t, n, len(sbufL), "unexpected length of received data")
		assert.Equal(t, sbufL, rbuf[:n], "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()
		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		closeAssociationPair(br, a0, a1)
	})

	t.Run("unordered fragmented then defragmented", func(t *testing.T) { // nolint:dupl
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 4
		var n int
		var ppi PayloadProtocolIdentifier
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		s0.SetReliabilityParams(true, ReliabilityTypeReliable, 0)
		s1.SetReliabilityParams(true, ReliabilityTypeReliable, 0)

		n, err = s0.WriteSCTP(sbufL, PayloadTypeWebRTCBinary)
		assert.Nil(t, err, "WriteSCTP failed")
		assert.Equal(t, n, len(sbufL), "unexpected length of received data")

		rbuf := make([]byte, 2000)
		flushBuffers(br, a0, a1)

		n, ppi, err = s1.ReadSCTP(rbuf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}

		assert.Equal(t, n, len(sbufL), "unexpected length of received data")
		assert.Equal(t, sbufL, rbuf[:n], "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()
		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		closeAssociationPair(br, a0, a1)
	})

	t.Run("unordered reordered", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 5
		var n int
		var ppi PayloadProtocolIdentifier
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		s0.SetReliabilityParams(true, ReliabilityTypeReliable, 0)
		s1.SetReliabilityParams(true, ReliabilityTypeReliable, 0)

		br.ReorderNextNWrites(0, 2)

		binary.BigEndian.PutUint32(sbuf, 0)
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		assert.Nil(t, err, "WriteSCTP failed")
		assert.Equal(t, n, len(sbuf), "unexpected length of received data")

		binary.BigEndian.PutUint32(sbuf, 1)
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		assert.Nil(t, err, "WriteSCTP failed")
		assert.Equal(t, n, len(sbuf), "unexpected length of received data")

		buf := make([]byte, 2000)
		flushBuffers(br, a0, a1)

		n, ppi, err = s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, n, len(sbuf), "unexpected length of received data")
		assert.Equal(t, uint32(1), binary.BigEndian.Uint32(buf[:n]), "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()

		n, ppi, err = s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}

		assert.Equal(t, n, len(sbuf), "unexpected length of received data")
		assert.Equal(t, uint32(0), binary.BigEndian.Uint32(buf[:n]), "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()
		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		closeAssociationPair(br, a0, a1)
	})

	t.Run("retransmission", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 6
		const msg1 = "ABC"
		const msg2 = "DEFG"
		var n int
		var ppi PayloadProtocolIdentifier
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		// lock RTO value at 100 [msec]
		a0.rtoMgr.setRTO(100.0, true)

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		n, err = s0.WriteSCTP([]byte(msg1), PayloadTypeWebRTCBinary)
		assert.Nil(t, err, "WriteSCTP failed")
		assert.Equal(t, n, len(msg1), "unexpected length of received data")
		n, err = s0.WriteSCTP([]byte(msg2), PayloadTypeWebRTCBinary)
		assert.Nil(t, err, "WriteSCTP failed")
		assert.Equal(t, n, len(msg2), "unexpected length of received data")

		br.Drop(0, 0, 1) // drop the first packet (second one should be sacked)

		// process packets for 200 msec
		for i := 0; i < 20; i++ {
			br.Tick()
			time.Sleep(10 * time.Millisecond)
		}

		buf := make([]byte, 32)

		n, ppi, err = s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, n, len(msg1), "unexpected length of received data")
		assert.Equal(t, msg1, string(buf[:n]), "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		n, ppi, err = s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, n, len(msg2), "unexpected length of received data")
		assert.Equal(t, msg2, string(buf[:n]), "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()
		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		closeAssociationPair(br, a0, a1)
	})

	t.Run("short buffer", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 1
		const msg = "Hello"
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		assert.Equal(t, 0, a0.bufferedAmount(), "incorrect bufferedAmount")

		n, err := s0.WriteSCTP([]byte(msg), PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(msg), n, "unexpected length of received data")
		assert.Equal(t, len(msg), a0.bufferedAmount(), "incorrect bufferedAmount")

		flushBuffers(br, a0, a1)

		buf := make([]byte, 3)
		n, ppi, err := s1.ReadSCTP(buf)
		assert.Equal(t, err, io.ErrShortBuffer, "expected error to be io.ErrShortBuffer")
		assert.Equal(t, n, 0, "unexpected length of received data")
		assert.Equal(t, ppi, PayloadProtocolIdentifier(0), "unexpected ppi")

		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		assert.Equal(t, 0, a0.bufferedAmount(), "incorrect bufferedAmount")

		closeAssociationPair(br, a0, a1)
	})
}

func TestAssocUnreliable(t *testing.T) {
	// sbuf1, sbuf2:
	//    large enough to be fragmented into two chunks and each chunks are
	//    large enough not to be bundled
	sbuf1 := make([]byte, 2000)
	sbuf2 := make([]byte, 2000)
	for i := 0; i < len(sbuf1); i++ {
		sbuf1[i] = byte(i & 0xff)
	}
	rand.Seed(time.Now().UnixNano())
	rand.Shuffle(len(sbuf1), func(i, j int) { sbuf1[i], sbuf1[j] = sbuf1[j], sbuf1[i] })
	for i := 0; i < len(sbuf2); i++ {
		sbuf2[i] = byte(i & 0xff)
	}
	rand.Seed(time.Now().UnixNano())
	rand.Shuffle(len(sbuf2), func(i, j int) { sbuf2[i], sbuf2[j] = sbuf2[j], sbuf2[i] })

	// sbuf - small enough not to be fragmented
	//        large enough not to be bundled
	sbuf := make([]byte, 1000)
	for i := 0; i < len(sbuf); i++ {
		sbuf[i] = byte(i & 0xff)
	}
	rand.Seed(time.Now().UnixNano())
	rand.Shuffle(len(sbuf), func(i, j int) { sbuf[i], sbuf[j] = sbuf[j], sbuf[i] })

	t.Run("Rexmit ordered no fragment", func(t *testing.T) { // nolint:dupl
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 1
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		// When we set the reliability value to 0 [times], then it will cause
		// the chunk to be abandoned immediately after the first transmission.
		s0.SetReliabilityParams(false, ReliabilityTypeRexmit, 0)
		s1.SetReliabilityParams(false, ReliabilityTypeRexmit, 0) // doesn't matter

		br.DropNextNWrites(0, 1) // drop the first packet (second one should be sacked)

		var n int
		binary.BigEndian.PutUint32(sbuf, uint32(0))
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")

		binary.BigEndian.PutUint32(sbuf, uint32(1))
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")

		flushBuffers(br, a0, a1)

		buf := make([]byte, 2000)
		n, ppi, err := s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		// should receive the second one only
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")
		assert.Equal(t, uint32(1), binary.BigEndian.Uint32(buf[:n]), "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()
		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		closeAssociationPair(br, a0, a1)
	})

	t.Run("Rexmit ordered fragments", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 1
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		// lock RTO value at 100 [msec]
		a0.rtoMgr.setRTO(100.0, true)

		// When we set the reliability value to 0 [times], then it will cause
		// the chunk to be abandoned immediately after the first transmission.
		s0.SetReliabilityParams(false, ReliabilityTypeRexmit, 0)
		s1.SetReliabilityParams(false, ReliabilityTypeRexmit, 0) // doesn't matter

		br.DropNextNWrites(0, 1) // drop the first fragment of the first chunk (second chunk should be sacked)

		var n int
		n, err = s0.WriteSCTP(sbuf1, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf1), n, "unexpected length of written data")

		n, err = s0.WriteSCTP(sbuf2, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf2), n, "unexpected length of written data")

		flushBuffers(br, a0, a1)

		rbuf := make([]byte, 2000)
		n, ppi, err := s1.ReadSCTP(rbuf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		// should receive the second one only
		assert.Equal(t, sbuf2, rbuf[:n], "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()

		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		assert.Equal(t, 0, len(s0.reassemblyQueue.ordered), "should be nothing in the ordered queue")
		closeAssociationPair(br, a0, a1)
	})

	t.Run("Rexmit unordered no fragment", func(t *testing.T) { // nolint:dupl
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 2
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		// When we set the reliability value to 0 [times], then it will cause
		// the chunk to be abandoned immediately after the first transmission.
		s0.SetReliabilityParams(true, ReliabilityTypeRexmit, 0)
		s1.SetReliabilityParams(true, ReliabilityTypeRexmit, 0) // doesn't matter

		br.DropNextNWrites(0, 1) // drop the first packet (second one should be sacked)

		var n int
		binary.BigEndian.PutUint32(sbuf, uint32(0))
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")

		binary.BigEndian.PutUint32(sbuf, uint32(1))
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")

		flushBuffers(br, a0, a1)

		buf := make([]byte, 2000)
		n, ppi, err := s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		// should receive the second one only
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")
		assert.Equal(t, uint32(1), binary.BigEndian.Uint32(buf[:n]), "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()
		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		closeAssociationPair(br, a0, a1)
	})

	t.Run("Rexmit unordered fragments", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 1
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		// When we set the reliability value to 0 [times], then it will cause
		// the chunk to be abandoned immediately after the first transmission.
		s0.SetReliabilityParams(true, ReliabilityTypeRexmit, 0)
		s1.SetReliabilityParams(true, ReliabilityTypeRexmit, 0) // doesn't matter

		var n int
		n, err = s0.WriteSCTP(sbuf1, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf1), n, "unexpected length of written data")

		n, err = s0.WriteSCTP(sbuf2, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf2), n, "unexpected length of written data")

		time.Sleep(10 * time.Millisecond)
		br.Drop(0, 0, 2) // drop the second fragment of the first chunk (second chunk should be sacked)
		flushBuffers(br, a0, a1)

		rbuf := make([]byte, 2000)
		n, ppi, err := s1.ReadSCTP(rbuf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		// should receive the second one only
		assert.Equal(t, sbuf2, rbuf[:n], "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()

		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		assert.Equal(t, 0, len(s0.reassemblyQueue.unordered), "should be nothing in the unordered queue")
		assert.Equal(t, 0, len(s0.reassemblyQueue.unorderedChunks), "should be nothing in the unorderedChunks list")
		closeAssociationPair(br, a0, a1)
	})

	t.Run("Timed ordered", func(t *testing.T) { // nolint:dupl
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 3
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		// When we set the reliability value to 0 [msec], then it will cause
		// the chunk to be abandoned immediately after the first transmission.
		s0.SetReliabilityParams(false, ReliabilityTypeTimed, 0)
		s1.SetReliabilityParams(false, ReliabilityTypeTimed, 0) // doesn't matter

		br.DropNextNWrites(0, 1) // drop the first packet (second one should be sacked)

		var n int
		binary.BigEndian.PutUint32(sbuf, uint32(0))
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")

		binary.BigEndian.PutUint32(sbuf, uint32(1))
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")

		// br.Drop(0, 0, 1) // drop the first packet (second one should be sacked)
		flushBuffers(br, a0, a1)

		buf := make([]byte, 2000)
		n, ppi, err := s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		// should receive the second one only
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")
		assert.Equal(t, uint32(1), binary.BigEndian.Uint32(buf[:n]), "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()
		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		closeAssociationPair(br, a0, a1)
	})

	t.Run("Timed unordered", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 3
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		// When we set the reliability value to 0 [msec], then it will cause
		// the chunk to be abandoned immediately after the first transmission.
		s0.SetReliabilityParams(true, ReliabilityTypeTimed, 0)
		s1.SetReliabilityParams(true, ReliabilityTypeTimed, 0) // doesn't matter

		br.DropNextNWrites(0, 1) // drop the first packet (second one should be sacked)

		var n int
		binary.BigEndian.PutUint32(sbuf, uint32(0))
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")

		binary.BigEndian.PutUint32(sbuf, uint32(1))
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")

		flushBuffers(br, a0, a1)

		buf := make([]byte, 2000)
		n, ppi, err := s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		// should receive the second one only
		assert.Equal(t, len(sbuf), n, "unexpected length of written data")
		assert.Equal(t, uint32(1), binary.BigEndian.Uint32(buf[:n]), "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()
		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		assert.Equal(t, 0, len(s0.reassemblyQueue.unordered), "should be nothing in the unordered queue")
		assert.Equal(t, 0, len(s0.reassemblyQueue.unorderedChunks), "should be nothing in the unorderedChunks list")
		closeAssociationPair(br, a0, a1)
	})
}

func TestCreateForwardTSN(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()

	t.Run("forward one abandoned", func(t *testing.T) {
		a := createAssociation(Config{
			NetConn:       &dumbConn{},
			LoggerFactory: loggerFactory,
		})

		a.cumulativeTSNAckPoint = 9
		a.advancedPeerTSNAckPoint = 10
		a.inflightQueue.pushNoCheck(&chunkPayloadData{
			beginningFragment:    true,
			endingFragment:       true,
			tsn:                  10,
			streamIdentifier:     1,
			streamSequenceNumber: 2,
			userData:             []byte("ABC"),
			nSent:                1,
			_abandoned:           true,
		})

		fwdtsn := a.createForwardTSN()

		assert.Equal(t, uint32(10), fwdtsn.newCumulativeTSN, "should be able to serialize")
		assert.Equal(t, 1, len(fwdtsn.streams), "there should be one stream")
		assert.Equal(t, uint16(1), fwdtsn.streams[0].identifier, "si should be 1")
		assert.Equal(t, uint16(2), fwdtsn.streams[0].sequence, "ssn should be 2")
	})

	t.Run("forward two abandoned with the same SI", func(t *testing.T) {
		a := createAssociation(Config{
			NetConn:       &dumbConn{},
			LoggerFactory: loggerFactory,
		})

		a.cumulativeTSNAckPoint = 9
		a.advancedPeerTSNAckPoint = 12
		a.inflightQueue.pushNoCheck(&chunkPayloadData{
			beginningFragment:    true,
			endingFragment:       true,
			tsn:                  10,
			streamIdentifier:     1,
			streamSequenceNumber: 2,
			userData:             []byte("ABC"),
			nSent:                1,
			_abandoned:           true,
		})
		a.inflightQueue.pushNoCheck(&chunkPayloadData{
			beginningFragment:    true,
			endingFragment:       true,
			tsn:                  11,
			streamIdentifier:     1,
			streamSequenceNumber: 3,
			userData:             []byte("DEF"),
			nSent:                1,
			_abandoned:           true,
		})
		a.inflightQueue.pushNoCheck(&chunkPayloadData{
			beginningFragment:    true,
			endingFragment:       true,
			tsn:                  12,
			streamIdentifier:     2,
			streamSequenceNumber: 1,
			userData:             []byte("123"),
			nSent:                1,
			_abandoned:           true,
		})

		fwdtsn := a.createForwardTSN()

		assert.Equal(t, uint32(12), fwdtsn.newCumulativeTSN, "should be able to serialize")
		assert.Equal(t, 2, len(fwdtsn.streams), "there should be two stream")

		si1OK := false
		si2OK := false
		for _, s := range fwdtsn.streams {
			switch s.identifier {
			case 1:
				assert.Equal(t, uint16(3), s.sequence, "ssn should be 3")
				si1OK = true
			case 2:
				assert.Equal(t, uint16(1), s.sequence, "ssn should be 1")
				si2OK = true
			default:
				assert.Fail(t, "unexpected stream indentifier")
			}
		}
		assert.True(t, si1OK, "si=1 should be present")
		assert.True(t, si2OK, "si=2 should be present")
	})
}

func TestHandleForwardTSN(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()

	t.Run("forward 3 unreceived chunks", func(t *testing.T) {
		a := createAssociation(Config{
			NetConn:       &dumbConn{},
			LoggerFactory: loggerFactory,
		})
		a.useForwardTSN = true
		prevTSN := a.peerLastTSN()

		fwdtsn := &chunkForwardTSN{
			newCumulativeTSN: prevTSN + 3,
			streams:          []chunkForwardTSNStream{{identifier: 0, sequence: 0}},
		}

		p := a.handleForwardTSN(fwdtsn)

		a.lock.Lock()
		delayedAckTriggered := a.delayedAckTriggered
		immediateAckTriggered := a.immediateAckTriggered
		a.lock.Unlock()
		assert.Equal(t, a.peerLastTSN(), prevTSN+3, "peerLastTSN should advance by 3 ")
		assert.True(t, delayedAckTriggered, "delayed sack should be triggered")
		assert.False(t, immediateAckTriggered, "immediate sack should NOT be triggered")
		assert.Nil(t, p, "should return nil")
	})

	t.Run("forward 1 for 1 missing", func(t *testing.T) {
		a := createAssociation(Config{
			NetConn:       &dumbConn{},
			LoggerFactory: loggerFactory,
		})
		a.useForwardTSN = true
		prevTSN := a.peerLastTSN()

		// this chunk is blocked by the missing chunk at tsn=1
		a.payloadQueue.push(a.peerLastTSN() + 2)

		fwdtsn := &chunkForwardTSN{
			newCumulativeTSN: a.peerLastTSN() + 1,
			streams: []chunkForwardTSNStream{
				{identifier: 0, sequence: 1},
			},
		}

		p := a.handleForwardTSN(fwdtsn)

		a.lock.Lock()
		delayedAckTriggered := a.delayedAckTriggered
		immediateAckTriggered := a.immediateAckTriggered
		a.lock.Unlock()
		assert.Equal(t, a.peerLastTSN(), prevTSN+2, "peerLastTSN should advance by 3")
		assert.True(t, delayedAckTriggered, "delayed sack should be triggered")
		assert.False(t, immediateAckTriggered, "immediate sack should NOT be triggered")
		assert.Nil(t, p, "should return nil")
	})

	t.Run("forward 1 for 2 missing", func(t *testing.T) {
		a := createAssociation(Config{
			NetConn:       &dumbConn{},
			LoggerFactory: loggerFactory,
		})
		a.useForwardTSN = true
		prevTSN := a.peerLastTSN()

		// this chunk is blocked by the missing chunk at tsn=1
		a.payloadQueue.push(a.peerLastTSN() + 3)

		fwdtsn := &chunkForwardTSN{
			newCumulativeTSN: a.peerLastTSN() + 1,
			streams: []chunkForwardTSNStream{
				{identifier: 0, sequence: 1},
			},
		}

		p := a.handleForwardTSN(fwdtsn)

		a.lock.Lock()
		immediateAckTriggered := a.immediateAckTriggered
		a.lock.Unlock()
		assert.Equal(t, a.peerLastTSN(), prevTSN+1, "peerLastTSN should advance by 1")
		assert.True(t, immediateAckTriggered, "immediate sack should be triggered")

		assert.Nil(t, p, "should return nil")
	})

	t.Run("dup forward TSN chunk should generate sack", func(t *testing.T) {
		a := createAssociation(Config{
			NetConn:       &dumbConn{},
			LoggerFactory: loggerFactory,
		})
		a.useForwardTSN = true
		prevTSN := a.peerLastTSN()

		fwdtsn := &chunkForwardTSN{
			newCumulativeTSN: a.peerLastTSN(), // old TSN
			streams: []chunkForwardTSNStream{
				{identifier: 0, sequence: 1},
			},
		}

		p := a.handleForwardTSN(fwdtsn)

		a.lock.Lock()
		ackState := a.ackState
		a.lock.Unlock()
		assert.Equal(t, a.peerLastTSN(), prevTSN, "peerLastTSN should not advance")
		assert.Equal(t, ackStateImmediate, ackState, "sack should be requested")
		assert.Nil(t, p, "should return nil")
	})
}

func TestAssocT1InitTimer(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()

	t.Run("Retransmission success", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		br := test.NewBridge()
		a0 := createAssociation(Config{
			NetConn:       br.GetConn0(),
			LoggerFactory: loggerFactory,
		})
		a1 := createAssociation(Config{
			NetConn:       br.GetConn1(),
			LoggerFactory: loggerFactory,
		})

		var err0, err1 error
		a0ReadyCh := make(chan bool)
		a1ReadyCh := make(chan bool)

		assert.Equal(t, rtoInitial, a0.rtoMgr.getRTO())
		assert.Equal(t, rtoInitial, a1.rtoMgr.getRTO())

		// modified rto for fast test
		a0.rtoMgr.setRTO(20, false)

		go func() {
			err0 = <-a0.handshakeCompletedCh
			a0ReadyCh <- true
		}()

		go func() {
			err1 = <-a1.handshakeCompletedCh
			a1ReadyCh <- true
		}()

		// Drop the first write
		br.DropNextNWrites(0, 1)

		// Start the handlshake
		a0.init(true)
		a1.init(true)

		a0Ready := false
		a1Ready := false
		for !a0Ready || !a1Ready {
			br.Process()

			select {
			case a0Ready = <-a0ReadyCh:
			case a1Ready = <-a1ReadyCh:
			default:
			}
		}
		flushBuffers(br, a0, a1)

		assert.Nil(t, err0, "should be nil")
		assert.Nil(t, err1, "should be nil")

		closeAssociationPair(br, a0, a1)
	})

	t.Run("Retransmission failure", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		br := test.NewBridge()
		a0 := createAssociation(Config{
			NetConn:       br.GetConn0(),
			LoggerFactory: loggerFactory,
		})
		a1 := createAssociation(Config{
			NetConn:       br.GetConn1(),
			LoggerFactory: loggerFactory,
		})

		var err0, err1 error
		a0ReadyCh := make(chan bool)
		a1ReadyCh := make(chan bool)

		assert.Equal(t, rtoInitial, a0.rtoMgr.getRTO())
		assert.Equal(t, rtoInitial, a1.rtoMgr.getRTO())

		// modified rto for fast test
		a0.rtoMgr.setRTO(20, false)
		a1.rtoMgr.setRTO(20, false)

		// fail after 4 retransmission
		a0.t1Init.maxRetrans = 4
		a1.t1Init.maxRetrans = 4

		go func() {
			err0 = <-a0.handshakeCompletedCh
			a0ReadyCh <- true
		}()

		go func() {
			err1 = <-a1.handshakeCompletedCh
			a1ReadyCh <- true
		}()

		// Drop all INIT
		br.DropNextNWrites(0, 99)
		br.DropNextNWrites(1, 99)

		// Start the handlshake
		a0.init(true)
		a1.init(true)

		a0Ready := false
		a1Ready := false
		for !a0Ready || !a1Ready {
			br.Process()

			select {
			case a0Ready = <-a0ReadyCh:
			case a1Ready = <-a1ReadyCh:
			default:
			}
		}

		assert.NotNil(t, err0, "should NOT be nil")
		assert.NotNil(t, err1, "should NOT be nil")

		closeAssociationPair(br, a0, a1)
	})
}

func TestAssocT1CookieTimer(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()

	t.Run("Retransmission success", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		br := test.NewBridge()
		a0 := createAssociation(Config{
			NetConn:       br.GetConn0(),
			LoggerFactory: loggerFactory,
		})
		a1 := createAssociation(Config{
			NetConn:       br.GetConn1(),
			LoggerFactory: loggerFactory,
		})

		var err0, err1 error
		a0ReadyCh := make(chan bool)
		a1ReadyCh := make(chan bool)

		assert.Equal(t, rtoInitial, a0.rtoMgr.getRTO())
		assert.Equal(t, rtoInitial, a1.rtoMgr.getRTO())

		// modified rto for fast test
		a0.rtoMgr.setRTO(20, false)

		go func() {
			err0 = <-a0.handshakeCompletedCh
			a0ReadyCh <- true
		}()

		go func() {
			err1 = <-a1.handshakeCompletedCh
			a1ReadyCh <- true
		}()

		// Start the handlshake
		a0.init(true)
		a1.init(true)

		// Let the INIT go.
		br.Tick()

		// Drop COOKIE-ECHO
		br.DropNextNWrites(0, 1)

		a0Ready := false
		a1Ready := false
		for !a0Ready || !a1Ready {
			br.Process()

			select {
			case a0Ready = <-a0ReadyCh:
			case a1Ready = <-a1ReadyCh:
			default:
			}
		}

		assert.Nil(t, err0, "should be nil")
		assert.Nil(t, err1, "should be nil")

		closeAssociationPair(br, a0, a1)
	})

	t.Run("Retransmission failure", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		br := test.NewBridge()
		a0 := createAssociation(Config{
			NetConn:       br.GetConn0(),
			LoggerFactory: loggerFactory,
		})
		a1 := createAssociation(Config{
			NetConn:       br.GetConn1(),
			LoggerFactory: loggerFactory,
		})

		var err0 error
		a0ReadyCh := make(chan bool)

		assert.Equal(t, rtoInitial, a0.rtoMgr.getRTO())
		assert.Equal(t, rtoInitial, a1.rtoMgr.getRTO())

		// modified rto for fast test
		a0.rtoMgr.setRTO(20, false)
		// fail after 4 retransmission
		a0.t1Cookie.maxRetrans = 4

		go func() {
			err0 = <-a0.handshakeCompletedCh
			a0ReadyCh <- true
		}()

		// Drop all COOKIE-ECHO
		br.Filter(0, func(raw []byte) bool {
			p := &packet{}
			err := p.unmarshal(true, raw)
			if !assert.Nil(t, err, "failed to parse packet") {
				return false // drop
			}
			for _, c := range p.chunks {
				switch c.(type) {
				case *chunkCookieEcho:
					return false // drop
				default:
					return true
				}
			}
			return true
		})

		// Start the handlshake
		a0.init(true)
		a1.init(false)

		a0Ready := false
		for !a0Ready {
			br.Process()

			select {
			case a0Ready = <-a0ReadyCh:
			default:
			}
		}

		assert.NotNil(t, err0, "should be an error")

		time.Sleep(1000 * time.Millisecond)
		br.Process()

		closeAssociationPair(br, a0, a1)
	})
}

func TestAssocCreateNewStream(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()

	t.Run("acceptChSize", func(t *testing.T) {
		a := createAssociation(Config{
			NetConn:       &dumbConn{},
			LoggerFactory: loggerFactory,
		})

		for i := 0; i < acceptChSize; i++ {
			s := a.createStream(uint16(i), true)
			_, ok := a.streams[s.streamIdentifier]
			assert.True(t, ok, "should be in a.streams map")
		}

		newSI := uint16(acceptChSize)
		s := a.createStream(newSI, true)
		assert.Nil(t, s, "should be nil")
		_, ok := a.streams[newSI]
		assert.False(t, ok, "should NOT be in a.streams map")

		toBeIgnored := &chunkPayloadData{
			beginningFragment: true,
			endingFragment:    true,
			tsn:               a.peerLastTSN() + 1,
			streamIdentifier:  newSI,
			userData:          []byte("ABC"),
		}

		p := a.handleData(toBeIgnored)
		assert.Nil(t, p, "should be nil")
	})
}

func TestAssocT3RtxTimer(t *testing.T) {
	// Send one packet, drop it, then retransmitted successfully.
	t.Run("Retransmission success", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 6
		const msg1 = "ABC"
		var n int
		var ppi PayloadProtocolIdentifier
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		// lock RTO value at 20 [msec]
		a0.rtoMgr.setRTO(20.0, false)
		a0.rtoMgr.noUpdate = true

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		n, err = s0.WriteSCTP([]byte(msg1), PayloadTypeWebRTCBinary)
		assert.Nil(t, err, "WriteSCTP failed")
		assert.Equal(t, n, len(msg1), "unexpected length of received data")

		br.Drop(0, 0, 1) // drop the first packet (second one should be sacked)

		// process packets for 100 msec
		for i := 0; i < 10; i++ {
			br.Tick()
			time.Sleep(10 * time.Millisecond)
		}

		buf := make([]byte, 32)

		n, ppi, err = s1.ReadSCTP(buf)
		if !assert.Nil(t, err, "ReadSCTP failed") {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, n, len(msg1), "unexpected length of received data")
		assert.Equal(t, msg1, string(buf[:n]), "unexpected received data")
		assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

		br.Process()
		assert.False(t, s0.reassemblyQueue.isReadable(), "should no longer be readable")
		a0.lock.RLock()
		assert.Equal(t, 0, a0.pendingQueue.size(), "should be no packet pending")
		assert.Equal(t, 0, a0.inflightQueue.size(), "should be no packet inflight")
		a0.lock.RUnlock()

		closeAssociationPair(br, a0, a1)
	})
}

func TestAssocCongestionControl(t *testing.T) {
	// sbuf - large enough not to be bundled
	sbuf := make([]byte, 1000)
	for i := 0; i < len(sbuf); i++ {
		sbuf[i] = byte(i & 0xcc)
	}

	// 1) Send 4 packets. drop the first one.
	// 2) Last 3 packet will be received, which triggers fast-retransmission
	// 3) The first one is retransmitted, which makes s1 readable
	// Above should be done before RTO occurs (fast recovery)
	t.Run("Fast retransmission", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 6
		var n int
		var ppi PayloadProtocolIdentifier
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNormal, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		br.DropNextNWrites(0, 1) // drop the next write

		for i := 0; i < 4; i++ {
			binary.BigEndian.PutUint32(sbuf, uint32(i)) // uint32 sequence number
			n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
			assert.Nil(t, err, "WriteSCTP failed")
			assert.Equal(t, n, len(sbuf), "unexpected length of received data")
		}

		// process packets for 500 msec, assuming that the fast retrans/recover
		// should complete within 500 msec.
		for i := 0; i < 50; i++ {
			br.Tick()
			time.Sleep(10 * time.Millisecond)
		}

		rbuf := make([]byte, 3000)

		// Try to read all 4 packets
		for i := 0; i < 4; i++ {
			// The receiver (s1) should be readable
			s1.lock.RLock()
			readable := s1.reassemblyQueue.isReadable()
			s1.lock.RUnlock()

			if !assert.True(t, readable, "should be readable") {
				return
			}

			n, ppi, err = s1.ReadSCTP(rbuf)
			if !assert.Nil(t, err, "ReadSCTP failed") {
				return
			}
			assert.Equal(t, len(sbuf), n, "unexpected length of received data")
			assert.Equal(t, i, int(binary.BigEndian.Uint32(rbuf)), "unexpected length of received data")
			assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")
		}

		a0.lock.RLock()
		inFastRecovery := a0.inFastRecovery
		a0.lock.RUnlock()
		assert.False(t, inFastRecovery, "should not be in fast-recovery")

		t.Logf("nDATAs      : %d\n", a1.stats.getNumDATAs())
		t.Logf("nSACKs      : %d\n", a0.stats.getNumSACKsReceived())
		t.Logf("nAckTimeouts: %d\n", a1.stats.getNumAckTimeouts())
		t.Logf("nFastRetrans: %d\n", a0.stats.getNumFastRetrans())

		assert.Equal(t, uint64(1), a0.stats.getNumFastRetrans(), "should be 1")

		closeAssociationPair(br, a0, a1)
	})

	t.Run("Congestion Avoidance", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const maxReceiveBufferSize uint32 = 64 * 1024
		const si uint16 = 6
		const nPacketsToSend = 2000
		var n int
		var nPacketsReceived int
		var ppi PayloadProtocolIdentifier
		rbuf := make([]byte, 3000)

		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNormal, maxReceiveBufferSize)
		a0.cwndCAStep = 2800 // 2 mtu
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		a0.stats.reset()
		a1.stats.reset()

		for i := 0; i < nPacketsToSend; i++ {
			binary.BigEndian.PutUint32(sbuf, uint32(i)) // uint32 sequence number
			n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
			assert.Nil(t, err, "WriteSCTP failed")
			assert.Equal(t, n, len(sbuf), "unexpected length of received data")
		}

		// Repeat calling br.Tick() until the buffered amount becomes 0
		for s0.BufferedAmount() > 0 && nPacketsReceived < nPacketsToSend {
			for {
				n = br.Tick()
				if n == 0 {
					break
				}
			}

			for {
				s1.lock.RLock()
				readable := s1.reassemblyQueue.isReadable()
				s1.lock.RUnlock()
				if !readable {
					break
				}
				n, ppi, err = s1.ReadSCTP(rbuf)
				if !assert.Nil(t, err, "ReadSCTP failed") {
					return
				}
				assert.Equal(t, len(sbuf), n, "unexpected length of received data")
				assert.Equal(t, nPacketsReceived, int(binary.BigEndian.Uint32(rbuf)), "unexpected length of received data")
				assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

				nPacketsReceived++
			}
		}

		br.Process()

		a0.lock.RLock()
		inFastRecovery := a0.inFastRecovery
		cwnd := a0.cwnd
		ssthresh := a0.ssthresh
		a0.lock.RUnlock()
		assert.False(t, inFastRecovery, "should not be in fast-recovery")
		assert.True(t, cwnd > ssthresh, "should be in congestion avoidance mode")
		assert.True(t, ssthresh >= maxReceiveBufferSize, "should not be less than the initial size of 128KB")

		assert.Equal(t, nPacketsReceived, nPacketsToSend, "unexpected num of packets received")
		assert.Equal(t, 0, s1.getNumBytesInReassemblyQueue(), "reassembly queue should be empty")

		t.Logf("nDATAs      : %d\n", a1.stats.getNumDATAs())
		t.Logf("nSACKs      : %d\n", a0.stats.getNumSACKsReceived())
		t.Logf("nT3Timeouts : %d\n", a0.stats.getNumT3Timeouts())

		assert.Equal(t, uint64(nPacketsToSend), a1.stats.getNumDATAs(), "packet count mismatch")
		assert.True(t, a0.stats.getNumSACKsReceived() <= nPacketsToSend/2, "too many sacks")
		assert.Equal(t, uint64(0), a0.stats.getNumT3Timeouts(), "should be no retransmit")

		closeAssociationPair(br, a0, a1)
	})

	// This is to test even rwnd becomes 0, sender should be able to send a zero window probe
	// on T3-rtx retramission timeout to complete receiving all the packets.
	t.Run("Slow reader", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const maxReceiveBufferSize uint32 = 64 * 1024
		const si uint16 = 6
		nPacketsToSend := int(math.Floor(float64(maxReceiveBufferSize)/1000.0)) * 2
		var n int
		var nPacketsReceived int
		var ppi PayloadProtocolIdentifier
		rbuf := make([]byte, 3000)

		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, maxReceiveBufferSize)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		for i := 0; i < nPacketsToSend; i++ {
			binary.BigEndian.PutUint32(sbuf, uint32(i)) // uint32 sequence number
			n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
			assert.Nil(t, err, "WriteSCTP failed")
			assert.Equal(t, n, len(sbuf), "unexpected length of received data")
		}

		// 1. First forward packets to receiver until rwnd becomes 0
		// 2. Wait until the sender's cwnd becomes 1*MTU (RTO occurred)
		// 3. Stat reading a1's data
		var hasRTOed bool
		for s0.BufferedAmount() > 0 && nPacketsReceived < nPacketsToSend {
			for {
				n = br.Tick()
				if n == 0 {
					break
				}
			}

			if !hasRTOed {
				a1.lock.RLock()
				rwnd := a1.getMyReceiverWindowCredit()
				a1.lock.RUnlock()
				a0.lock.RLock()
				cwnd := a0.cwnd
				a0.lock.RUnlock()
				if cwnd > a0.mtu || rwnd > 0 {
					// Do not read until a1.getMyReceiverWindowCredit() becomes zero
					continue
				}

				hasRTOed = true
			}

			for {
				s1.lock.RLock()
				readable := s1.reassemblyQueue.isReadable()
				s1.lock.RUnlock()
				if !readable {
					break
				}
				n, ppi, err = s1.ReadSCTP(rbuf)
				if !assert.Nil(t, err, "ReadSCTP failed") {
					return
				}
				assert.Equal(t, len(sbuf), n, "unexpected length of received data")
				assert.Equal(t, nPacketsReceived, int(binary.BigEndian.Uint32(rbuf)), "unexpected length of received data")
				assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

				nPacketsReceived++
			}

			time.Sleep(4 * time.Millisecond)
		}

		br.Process()

		assert.Equal(t, nPacketsReceived, nPacketsToSend, "unexpected num of packets received")
		assert.Equal(t, 0, s1.getNumBytesInReassemblyQueue(), "reassembly queue should be empty")

		t.Logf("nDATAs      : %d\n", a1.stats.getNumDATAs())
		t.Logf("nSACKs      : %d\n", a0.stats.getNumSACKsReceived())
		t.Logf("nAckTimeouts: %d\n", a1.stats.getNumAckTimeouts())

		closeAssociationPair(br, a0, a1)
	})
}

func TestAssocDelayedAck(t *testing.T) {
	t.Run("First DATA chunk gets acked with delay", func(t *testing.T) {
		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 6
		var n int
		var nPacketsReceived int
		var ppi PayloadProtocolIdentifier
		sbuf := make([]byte, 1000) // size should be less than initial cwnd (4380)
		rbuf := make([]byte, 1500)

		_, err := cryptoRand.Read(sbuf)
		if !assert.Nil(t, err, "failed to create associations") {
			return
		}

		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeAlwaysDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		a0.stats.reset()
		a1.stats.reset()

		// Writes data (will fragmented)
		n, err = s0.WriteSCTP(sbuf, PayloadTypeWebRTCBinary)
		assert.Nil(t, err, "WriteSCTP failed")
		assert.Equal(t, n, len(sbuf), "unexpected length of received data")

		// Repeat calling br.Tick() until the buffered amount becomes 0
		since := time.Now()
		for s0.BufferedAmount() > 0 {
			for {
				n = br.Tick()
				if n == 0 {
					break
				}
			}

			for {
				s1.lock.RLock()
				readable := s1.reassemblyQueue.isReadable()
				s1.lock.RUnlock()
				if !readable {
					break
				}
				n, ppi, err = s1.ReadSCTP(rbuf)
				if !assert.Nil(t, err, "ReadSCTP failed") {
					return
				}
				assert.Equal(t, len(sbuf), n, "unexpected length of received data")
				assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")

				nPacketsReceived++
			}
		}
		delay := time.Since(since).Seconds()
		t.Logf("received in %.03f seconds", delay)
		assert.True(t, delay >= 0.2, "should be >= 200msec")

		br.Process()

		assert.Equal(t, 1, nPacketsReceived, "should be one packet received")
		assert.Equal(t, 0, s1.getNumBytesInReassemblyQueue(), "reassembly queue should be empty")

		t.Logf("nDATAs      : %d\n", a1.stats.getNumDATAs())
		t.Logf("nSACKs      : %d\n", a0.stats.getNumSACKsReceived())
		t.Logf("nAckTimeouts: %d\n", a1.stats.getNumAckTimeouts())

		assert.Equal(t, uint64(1), a1.stats.getNumDATAs(), "DATA chunk count mismatch")
		assert.Equal(t, a0.stats.getNumSACKsReceived(), a1.stats.getNumDATAs(), "sack count should be equal to the number of data chunks")
		assert.Equal(t, uint64(1), a1.stats.getNumAckTimeouts(), "ackTimeout count mismatch")
		assert.Equal(t, uint64(0), a0.stats.getNumT3Timeouts(), "should be no retransmit")

		closeAssociationPair(br, a0, a1)
	})
}

func checkGoroutineLeaks(t *testing.T) {
	// Get the count of goroutines at the start of the test.
	initialGoroutines := runtime.NumGoroutine()
	// Register a cleanup function to run after the test completes.
	t.Cleanup(func() {
		// Allow for up to 1 second for all goroutines to finish.
		for i := 0; i < 10; i++ {
			time.Sleep(100 * time.Millisecond)
			if goroutines := runtime.NumGoroutine(); goroutines <= initialGoroutines {
				return
			}
		}

		// If we've gotten this far, not all goroutines have finished.
		t.Errorf("leaked %d goroutines", runtime.NumGoroutine()-initialGoroutines)
	})
}

func TestAssocReset(t *testing.T) {
	t.Run("Close one way", func(t *testing.T) {
		checkGoroutineLeaks(t)

		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 1
		const msg = "ABC"
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		assert.Equal(t, 0, a0.bufferedAmount(), "incorrect bufferedAmount")

		n, err := s0.WriteSCTP([]byte(msg), PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(msg), n, "unexpected length of received data")
		assert.Equal(t, len(msg), a0.bufferedAmount(), "incorrect bufferedAmount")

		err = s0.Close() // send reset
		if err != nil {
			t.Error(err)
		}

		doneCh := make(chan error)
		buf := make([]byte, 32)

		go func() {
			for {
				var ppi PayloadProtocolIdentifier
				n, ppi, err = s1.ReadSCTP(buf)
				if err != nil {
					doneCh <- err
					return
				}

				assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")
				assert.Equal(t, n, len(msg), "unexpected length of received data")
			}
		}()

	loop:
		for {
			br.Process()
			select {
			case err = <-doneCh:
				assert.Equal(t, io.EOF, err, "should end with EOF")
				break loop
			default:
			}
		}

		closeAssociationPair(br, a0, a1)
	})

	t.Run("Close both ways", func(t *testing.T) {
		checkGoroutineLeaks(t)

		lim := test.TimeOut(time.Second * 10)
		defer lim.Stop()

		const si uint16 = 1
		const msg = "ABC"
		br := test.NewBridge()

		a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
		if !assert.Nil(t, err, "failed to create associations") {
			assert.FailNow(t, "failed due to earlier error")
		}

		s0, s1, err := establishSessionPair(br, a0, a1, si)
		assert.Nil(t, err, "failed to establish session pair")

		assert.Equal(t, 0, a0.bufferedAmount(), "incorrect bufferedAmount")

		// send a message from s0 to s1
		n, err := s0.WriteSCTP([]byte(msg), PayloadTypeWebRTCBinary)
		if err != nil {
			assert.FailNow(t, "failed due to earlier error")
		}
		assert.Equal(t, len(msg), n, "unexpected length of received data")
		assert.Equal(t, len(msg), a0.bufferedAmount(), "incorrect bufferedAmount")

		// close s0 as soon as the message is sent
		err = s0.Close()
		if err != nil {
			t.Error(err)
		}

		doneCh := make(chan error)
		buf := make([]byte, 32)

		go func() {
			for {
				var ppi PayloadProtocolIdentifier
				n, ppi, err = s1.ReadSCTP(buf)
				if err != nil {
					doneCh <- err
					return
				}

				assert.Equal(t, ppi, PayloadTypeWebRTCBinary, "unexpected ppi")
				assert.Equal(t, n, len(msg), "unexpected length of received data")
			}
		}()

	loop0:
		for {
			br.Process()
			select {
			case err = <-doneCh:
				assert.Equal(t, io.EOF, err, "should end with EOF")
				break loop0
			default:
			}
		}

		// send reset from s1
		err = s1.Close()
		if err != nil {
			t.Error(err)
		}

		go func() {
			for {
				_, _, err = s0.ReadSCTP(buf)
				assert.Equal(t, io.EOF, err, "should be EOF")
				if err != nil {
					doneCh <- err
					return
				}
			}
		}()

	loop1:
		for {
			br.Process()
			select {
			case <-doneCh:
				break loop1
			default:
			}
		}

		time.Sleep(2 * time.Second)

		closeAssociationPair(br, a0, a1)
	})
}

func TestAssocAbort(t *testing.T) {
	lim := test.TimeOut(time.Second * 10)
	defer lim.Stop()

	const si uint16 = 1
	br := test.NewBridge()

	a0, a1, err := createNewAssociationPair(br, ackModeNoDelay, 0)
	assert.NoError(t, err)

	abort := &chunkAbort{
		errorCauses: []errorCause{&errorCauseProtocolViolation{
			errorCauseHeader: errorCauseHeader{code: protocolViolation},
		}},
	}
	packet, err := a0.marshalPacket(a0.createPacket([]chunk{abort}))
	assert.NoError(t, err)

	_, _, err = establishSessionPair(br, a0, a1, si)
	assert.NoError(t, err)

	// Both associations are established
	assert.Equal(t, established, a0.getState())
	assert.Equal(t, established, a1.getState())

	_, err = a0.netConn.Write(packet)
	assert.NoError(t, err)
	flushBuffers(br, a0, a1)

	// There is a little delay before changing the state to closed
	time.Sleep(10 * time.Millisecond)

	// The receiving association should be closed because it got an ABORT
	assert.Equal(t, established, a0.getState())
	assert.Equal(t, closed, a1.getState())

	closeAssociationPair(br, a0, a1)
}

type fakeEchoConn struct {
	echo     chan []byte
	done     chan struct{}
	closed   chan struct{}
	once     sync.Once
	errClose error
	mu       sync.Mutex

	bytesSent     uint64
	bytesReceived uint64

	mtu  uint32
	cwnd uint32
	rwnd uint32
	srtt float64
}

func newFakeEchoConn(errClose error) *fakeEchoConn {
	return &fakeEchoConn{
		echo:     make(chan []byte, 1),
		done:     make(chan struct{}),
		closed:   make(chan struct{}),
		mtu:      initialMTU,
		cwnd:     min32(4*initialMTU, max32(2*initialMTU, 4380)),
		rwnd:     initialRecvBufSize,
		errClose: errClose,
	}
}

func (c *fakeEchoConn) Read(b []byte) (int, error) {
	r, ok := <-c.echo
	if ok {
		copy(b, r)
		c.once.Do(func() { close(c.done) })

		c.mu.Lock()
		c.bytesReceived += uint64(len(r))
		c.mu.Unlock()

		return len(r), nil
	}
	return 0, io.EOF
}

func (c *fakeEchoConn) Write(b []byte) (int, error) {
	c.mu.Lock()
	defer c.mu.Unlock()
	select {
	case <-c.closed:
		return 0, io.EOF
	default:
	}
	c.echo <- b
	c.bytesSent += uint64(len(b))
	return len(b), nil
}

func (c *fakeEchoConn) Close() error {
	c.mu.Lock()
	defer c.mu.Unlock()
	close(c.echo)
	close(c.closed)
	return c.errClose
}
func (c *fakeEchoConn) LocalAddr() net.Addr              { return nil }
func (c *fakeEchoConn) RemoteAddr() net.Addr             { return nil }
func (c *fakeEchoConn) SetDeadline(time.Time) error      { return nil }
func (c *fakeEchoConn) SetReadDeadline(time.Time) error  { return nil }
func (c *fakeEchoConn) SetWriteDeadline(time.Time) error { return nil }

func TestRoutineLeak(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()
	t.Run("Close failed", func(t *testing.T) {
		checkGoroutineLeaks(t)

		conn := newFakeEchoConn(io.EOF)
		a, err := Client(Config{NetConn: conn, LoggerFactory: loggerFactory})
		assert.Equal(t, nil, err, "errored to initialize Client")

		<-conn.done

		err = a.Close()
		assert.Equal(t, io.EOF, err, "Close() should fail with EOF")

		select {
		case _, ok := <-a.closeWriteLoopCh:
			if ok {
				t.Errorf("closeWriteLoopCh is expected to be closed, but received signal")
			}
		default:
			t.Errorf("closeWriteLoopCh is expected to be closed, but not")
		}
		_ = a
	})
	t.Run("Connection closed by remote host", func(t *testing.T) {
		checkGoroutineLeaks(t)

		conn := newFakeEchoConn(nil)
		a, err := Client(Config{NetConn: conn, LoggerFactory: loggerFactory})
		assert.Equal(t, nil, err, "errored to initialize Client")

		<-conn.done

		err = conn.Close() // close connection
		assert.Equal(t, nil, err, "fake connection returned unexpected error")
		<-conn.closed
		<-time.After(10 * time.Millisecond) // switch context to make read/write loops finished

		select {
		case _, ok := <-a.closeWriteLoopCh:
			if ok {
				t.Errorf("closeWriteLoopCh is expected to be closed, but received signal")
			}
		default:
			t.Errorf("closeWriteLoopCh is expected to be closed, but not")
		}
	})
}

func TestStats(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()

	conn := newFakeEchoConn(nil)
	a, err := Client(Config{NetConn: conn, LoggerFactory: loggerFactory})
	assert.Equal(t, nil, err, "errored to initialize Client")

	<-conn.done

	assert.NoError(t, conn.Close())

	conn.mu.Lock()
	defer conn.mu.Unlock()
	assert.Equal(t, conn.bytesReceived, a.BytesReceived())
	assert.Equal(t, conn.bytesSent, a.BytesSent())
	assert.Equal(t, conn.mtu, a.MTU())
	assert.Equal(t, conn.cwnd, a.CWND())
	assert.Equal(t, conn.rwnd, a.RWND())
	assert.Equal(t, conn.srtt, a.SRTT())
}

func TestAssocHandleInit(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()

	handleInitTest := func(t *testing.T, initialState uint32, expectErr bool) {
		a := createAssociation(Config{
			NetConn:       &dumbConn{},
			LoggerFactory: loggerFactory,
		})
		a.setState(initialState)
		pkt := &packet{
			sourcePort:      5001,
			destinationPort: 5002,
		}
		init := &chunkInit{}
		init.initialTSN = 1234
		init.numOutboundStreams = 1001
		init.numInboundStreams = 1002
		init.initiateTag = 5678
		init.advertisedReceiverWindowCredit = 512 * 1024
		setSupportedExtensions(&init.chunkInitCommon)

		_, err := a.handleInit(pkt, init)
		if expectErr {
			assert.Error(t, err, "should fail")
			return
		}
		assert.NoError(t, err, "should succeed")
		assert.Equal(t, init.initialTSN-1, a.peerLastTSN(), "should match")
		assert.Equal(t, uint16(1001), a.myMaxNumOutboundStreams, "should match")
		assert.Equal(t, uint16(1002), a.myMaxNumInboundStreams, "should match")
		assert.Equal(t, uint32(5678), a.peerVerificationTag, "should match")
		assert.Equal(t, pkt.sourcePort, a.destinationPort, "should match")
		assert.Equal(t, pkt.destinationPort, a.sourcePort, "should match")
		assert.True(t, a.useForwardTSN, "should be set to true")
	}

	t.Run("normal", func(t *testing.T) {
		handleInitTest(t, closed, false)
	})

	t.Run("unexpected state established", func(t *testing.T) {
		handleInitTest(t, established, true)
	})

	t.Run("unexpected state shutdownAckSent", func(t *testing.T) {
		handleInitTest(t, shutdownAckSent, true)
	})

	t.Run("unexpected state shutdownPending", func(t *testing.T) {
		handleInitTest(t, shutdownPending, true)
	})

	t.Run("unexpected state shutdownReceived", func(t *testing.T) {
		handleInitTest(t, shutdownReceived, true)
	})

	t.Run("unexpected state shutdownSent", func(t *testing.T) {
		handleInitTest(t, shutdownSent, true)
	})
}

func TestAssocMaxMessageSize(t *testing.T) {
	t.Run("default", func(t *testing.T) {
		loggerFactory := logging.NewDefaultLoggerFactory()
		a := createAssociation(Config{
			LoggerFactory: loggerFactory,
		})
		assert.NotNil(t, a, "should succeed")
		assert.Equal(t, uint32(65536), a.MaxMessageSize(), "should match")

		s := a.createStream(1, false)
		assert.NotNil(t, s, "should succeed")

		p := make([]byte, 65537)
		var err error
		_, err = s.WriteSCTP(p[:65536], s.defaultPayloadType)
		assert.False(t, strings.Contains(err.Error(), "larger than maximum"), "should be false")

		_, err = s.WriteSCTP(p[:65537], s.defaultPayloadType)
		assert.True(t, strings.Contains(err.Error(), "larger than maximum"), "should be false")
	})

	t.Run("explicit", func(t *testing.T) {
		loggerFactory := logging.NewDefaultLoggerFactory()
		a := createAssociation(Config{
			MaxMessageSize: 30000,
			LoggerFactory:  loggerFactory,
		})
		assert.NotNil(t, a, "should succeed")
		assert.Equal(t, uint32(30000), a.MaxMessageSize(), "should match")

		s := a.createStream(1, false)
		assert.NotNil(t, s, "should succeed")

		p := make([]byte, 30001)
		var err error
		_, err = s.WriteSCTP(p[:30000], s.defaultPayloadType)
		assert.False(t, strings.Contains(err.Error(), "larger than maximum"), "should be false")

		_, err = s.WriteSCTP(p[:30001], s.defaultPayloadType)
		assert.True(t, strings.Contains(err.Error(), "larger than maximum"), "should be false")
	})

	t.Run("set value", func(t *testing.T) {
		loggerFactory := logging.NewDefaultLoggerFactory()
		a := createAssociation(Config{
			LoggerFactory: loggerFactory,
		})
		assert.NotNil(t, a, "should succeed")
		assert.Equal(t, uint32(65536), a.MaxMessageSize(), "should match")
		a.SetMaxMessageSize(20000)
		assert.Equal(t, uint32(20000), a.MaxMessageSize(), "should match")
	})
}

type dumbConnInboundHandler func([]byte)

type dumbConn2 struct {
	net.Conn
	packets              [][]byte
	closed               bool
	localAddr            net.Addr
	remoteAddr           net.Addr
	remoteInboundHandler dumbConnInboundHandler
	mutex                sync.Mutex
	cond                 *sync.Cond
}

func newDumbConn2(localAddr, remoteAddr net.Addr) *dumbConn2 {
	c := &dumbConn2{
		packets:    [][]byte{},
		localAddr:  localAddr,
		remoteAddr: remoteAddr,
	}
	c.cond = sync.NewCond(&c.mutex)
	return c
}

// Implement the net.Conn interface methods
func (c *dumbConn2) Read(b []byte) (n int, err error) {
	c.mutex.Lock()
	defer c.mutex.Unlock()

	for {
		if len(c.packets) > 0 {
			packet := c.packets[0]
			c.packets = c.packets[1:]
			n := copy(b, packet)
			return n, nil
		}

		if c.closed {
			return 0, io.EOF
		}

		c.cond.Wait()
	}
}

func (c *dumbConn2) Write(b []byte) (int, error) {
	c.mutex.Lock()
	closed := c.closed
	c.mutex.Unlock()

	if closed {
		return 0, &net.OpError{Op: "write", Net: "udp", Addr: c.remoteAddr, Err: net.ErrClosed}
	}
	c.remoteInboundHandler(b)
	return len(b), nil
}

func (c *dumbConn2) Close() error {
	c.mutex.Lock()
	defer c.mutex.Unlock()

	c.closed = true
	c.cond.Signal()
	return nil
}

func (c *dumbConn2) LocalAddr() net.Addr {
	// Unused by Association
	return c.localAddr
}

func (c *dumbConn2) RemoteAddr() net.Addr {
	// Unused by Association
	return c.remoteAddr
}

func (c *dumbConn2) inboundHandler(packet []byte) {
	c.mutex.Lock()
	defer c.mutex.Unlock()

	if !c.closed {
		c.packets = append(c.packets, packet)
		c.cond.Signal()
	}
}

// crateUDPConnPair creates a pair of net.UDPConn objects that are connected with each other
func createUDPConnPair() (net.Conn, net.Conn) {
	addr1 := &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: 1234}
	addr2 := &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: 5678}
	conn1 := newDumbConn2(addr1, addr2)
	conn2 := newDumbConn2(addr2, addr1)
	conn1.remoteInboundHandler = conn2.inboundHandler
	conn2.remoteInboundHandler = conn1.inboundHandler
	return conn1, conn2
}

func createAssocs() (*Association, *Association, error) {
	udp1, udp2 := createUDPConnPair()

	loggerFactory := logging.NewDefaultLoggerFactory()

	a1Chan := make(chan interface{})
	a2Chan := make(chan interface{})

	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()

	go func() {
		a, err2 := createClientWithContext(ctx, Config{
			NetConn:       udp1,
			LoggerFactory: loggerFactory,
		})
		if err2 != nil {
			a1Chan <- err2
		} else {
			a1Chan <- a
		}
	}()

	go func() {
		a, err2 := createClientWithContext(ctx, Config{
			NetConn:       udp2,
			LoggerFactory: loggerFactory,
		})
		if err2 != nil {
			a2Chan <- err2
		} else {
			a2Chan <- a
		}
	}()

	var a1 *Association
	var a2 *Association

loop:
	for {
		select {
		case v1 := <-a1Chan:
			switch v := v1.(type) {
			case *Association:
				a1 = v
				if a2 != nil {
					break loop
				}
			case error:
				return nil, nil, v
			}
		case v2 := <-a2Chan:
			switch v := v2.(type) {
			case *Association:
				a2 = v
				if a1 != nil {
					break loop
				}
			case error:
				return nil, nil, v
			}
		}
	}
	return a1, a2, nil
}

// udpDiscardReader blocks all reads after block is set to true.
// This allows us to send arbitrary packets on a stream and block the packets received in response
type udpDiscardReader struct {
	net.Conn
	ctx   context.Context
	block atomic.Bool
}

func (d *udpDiscardReader) Read(b []byte) (n int, err error) {
	if d.block.Load() {
		<-d.ctx.Done()
		return 0, d.ctx.Err()
	}
	return d.Conn.Read(b)
}

func createAssociationPair(udpConn1 net.Conn, udpConn2 net.Conn) (*Association, *Association, error) {
	return createAssociationPairWithConfig(udpConn1, udpConn2, Config{})
}

func createAssociationPairWithConfig(udpConn1 net.Conn, udpConn2 net.Conn, config Config) (*Association, *Association, error) {
	loggerFactory := logging.NewDefaultLoggerFactory()

	a1Chan := make(chan interface{})
	a2Chan := make(chan interface{})

	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()

	go func() {
		cfg := config
		cfg.NetConn = udpConn1
		cfg.LoggerFactory = loggerFactory
		a, err2 := createClientWithContext(ctx, cfg)
		if err2 != nil {
			a1Chan <- err2
		} else {
			a1Chan <- a
		}
	}()

	go func() {
		cfg := config
		cfg.NetConn = udpConn2
		cfg.LoggerFactory = loggerFactory
		if cfg.MaxReceiveBufferSize == 0 {
			cfg.MaxReceiveBufferSize = 100_000
		}
		a, err2 := createClientWithContext(ctx, cfg)
		if err2 != nil {
			a2Chan <- err2
		} else {
			a2Chan <- a
		}
	}()

	var a1 *Association
	var a2 *Association

loop:
	for {
		select {
		case v1 := <-a1Chan:
			switch v := v1.(type) {
			case *Association:
				a1 = v
				if a2 != nil {
					break loop
				}
			case error:
				return nil, nil, v
			}
		case v2 := <-a2Chan:
			switch v := v2.(type) {
			case *Association:
				a2 = v
				if a1 != nil {
					break loop
				}
			case error:
				return nil, nil, v
			}
		}
	}
	return a1, a2, nil
}

func noErrorClose(t *testing.T, closeF func() error) {
	t.Helper()
	require.NoError(t, closeF())
}

// readMyNextTSN uses a lock to read the myNextTSN field of the association.
// Avoids a data race.
func readMyNextTSN(a *Association) uint32 {
	a.lock.Lock()
	defer a.lock.Unlock()
	return a.myNextTSN
}

func TestAssociationReceiveWindow(t *testing.T) {
	udp1, udp2 := createUDPConnPair()
	ctx, cancel := context.WithCancel(context.Background())
	dudp1 := &udpDiscardReader{Conn: udp1, ctx: ctx}
	// a1 is the association used for sending data
	// a2 is the association with receive window of 100kB which we will
	// try to bypass
	a1, a2, err := createAssociationPair(dudp1, udp2)
	require.NoError(t, err)
	defer noErrorClose(t, a2.Close)
	defer noErrorClose(t, a1.Close)
	s1, err := a1.OpenStream(1, PayloadTypeWebRTCBinary)
	require.NoError(t, err)
	defer s1.Close() // nolint:errcheck,gosec
	_, err = s1.WriteSCTP([]byte("hello"), PayloadTypeWebRTCBinary)
	require.NoError(t, err)
	dudp1.block.Store(true)

	_, err = s1.WriteSCTP([]byte("hello"), PayloadTypeWebRTCBinary)
	require.NoError(t, err)
	s2, err := a2.AcceptStream()
	require.NoError(t, err)
	require.Equal(t, uint16(1), s2.streamIdentifier)

	done := make(chan bool)
	go func() {
		chunks := s1.packetize(make([]byte, 1000), PayloadTypeWebRTCBinary)
		chunks = chunks[:1]
		chunk := chunks[0]
		// Fake the TSN and enqueue 1 chunk with a very high tsn in the payload queue
		chunk.tsn = readMyNextTSN(a1) + 1e9
		for chunk.tsn > readMyNextTSN(a1) {
			select {
			case <-done:
				return
			default:
			}
			chunk.tsn--
			pp := a1.bundleDataChunksIntoPackets(chunks)
			for _, p := range pp {
				raw, err := p.marshal(true)
				if err != nil {
					return
				}
				_, err = a1.netConn.Write(raw)
				if err != nil {
					return
				}
			}
			if chunk.tsn%10 == 0 {
				time.Sleep(10 * time.Millisecond)
			}
		}
	}()

	for cnt := 0; cnt < 15; cnt++ {
		bytesQueued := s2.getNumBytesInReassemblyQueue()
		if bytesQueued > 5_000_000 {
			t.Error("too many bytes enqueued with receive window of 10kb", bytesQueued)
			break
		}
		t.Log("bytes queued", bytesQueued)
		time.Sleep(1 * time.Second)
	}
	close(done)
	cancel()
}

func TestAssociationFastRtxWnd(t *testing.T) {
	udp1, udp2 := createUDPConnPair()
	a1, a2, err := createAssociationPairWithConfig(udp1, udp2, Config{MinCwnd: 14000, FastRtxWnd: 14000})
	require.NoError(t, err)
	defer noErrorClose(t, a2.Close)
	defer noErrorClose(t, a1.Close)
	s1, err := a1.OpenStream(1, PayloadTypeWebRTCBinary)
	require.NoError(t, err)
	defer noErrorClose(t, s1.Close)
	_, err = s1.WriteSCTP([]byte("hello"), PayloadTypeWebRTCBinary)
	require.NoError(t, err)
	_, err = a2.AcceptStream()
	require.NoError(t, err)

	a1.rtoMgr.setRTO(1000, true)
	// ack the hello packet
	time.Sleep(1 * time.Second)

	require.Equal(t, a1.minCwnd, a1.CWND())

	var shouldDrop atomic.Bool
	var dropCounter atomic.Uint32
	dbConn1, ok := udp1.(*dumbConn2)
	require.True(t, ok)
	dbConn2, ok := udp2.(*dumbConn2)
	require.True(t, ok)
	dbConn1.remoteInboundHandler = func(packet []byte) {
		if !shouldDrop.Load() {
			dbConn2.inboundHandler(packet)
		} else {
			dropCounter.Add(1)
		}
	}

	// intercept SACK
	var lastSACK atomic.Pointer[chunkSelectiveAck]
	dbConn2.remoteInboundHandler = func(buf []byte) {
		p := &packet{}
		require.NoError(t, p.unmarshal(true, buf))
		for _, c := range p.chunks {
			if ack, aok := c.(*chunkSelectiveAck); aok {
				lastSACK.Store(ack)
			}
		}
		dbConn1.inboundHandler(buf)
	}

	_, err = s1.WriteSCTP([]byte("hello"), PayloadTypeWebRTCBinary)
	require.NoError(t, err)
	require.Eventually(t, func() bool { return lastSACK.Load() != nil }, 1*time.Second, 10*time.Millisecond)

	shouldDrop.Store(true)
	// send packets and dropped
	buf := make([]byte, 700)
	for i := 0; i < 20; i++ {
		_, err = s1.WriteSCTP(buf, PayloadTypeWebRTCBinary)
		require.NoError(t, err)
	}

	require.Eventually(t, func() bool { return dropCounter.Load() >= 15 }, 5*time.Second, 10*time.Millisecond, "drop %d", dropCounter.Load())

	require.Zero(t, a1.stats.getNumFastRetrans())
	require.False(t, a1.inFastRecovery)

	// sack to trigger fast retransmit
	ack := *(lastSACK.Load())
	ack.gapAckBlocks = []gapAckBlock{{start: 11}}
	for i := 11; i < 14; i++ {
		ack.gapAckBlocks[0].end = uint16(i)
		pkt := a1.createPacket([]chunk{&ack})
		pktBuf, err1 := pkt.marshal(true)
		require.NoError(t, err1)
		dbConn1.inboundHandler(pktBuf)
	}

	require.Eventually(t, func() bool {
		a1.lock.RLock()
		defer a1.lock.RUnlock()
		return a1.inFastRecovery
	}, 5*time.Second, 10*time.Millisecond)
	require.GreaterOrEqual(t, uint64(10), a1.stats.getNumFastRetrans())

	// 7.2.4 b)  In fast-recovery AND the Cumulative TSN Ack Point advanced
	//     the miss indications are incremented for all TSNs reported missing
	//     in the SACK.
	a1.lock.Lock()
	lastTSN := a1.inflightQueue.chunks.Back().tsn
	lastTSNMinusTwo := lastTSN - 2
	lastChunk := a1.inflightQueue.chunks.Back()
	lastChunkMinusTwo, ok := a1.inflightQueue.get(lastTSNMinusTwo)
	a1.lock.Unlock()
	require.True(t, ok)
	require.True(t, lastTSN > ack.cumulativeTSNAck+uint32(ack.gapAckBlocks[0].end)+3)

	// sack with cumAckPoint advanced, lastTSN should not be marked as missing
	ack.cumulativeTSNAck++
	end := lastTSN - 1 - ack.cumulativeTSNAck
	ack.gapAckBlocks = append(ack.gapAckBlocks, gapAckBlock{start: uint16(end), end: uint16(end)})
	pkt := a1.createPacket([]chunk{&ack})
	pktBuf, err := pkt.marshal(true)
	require.NoError(t, err)
	dbConn1.inboundHandler(pktBuf)
	require.Eventually(t, func() bool {
		a1.lock.Lock()
		defer a1.lock.Unlock()
		return lastChunkMinusTwo.missIndicator == 1 && lastChunk.missIndicator == 0
	}, 5*time.Second, 10*time.Millisecond)
}

func TestAssociationMaxTSNOffset(t *testing.T) {
	udp1, udp2 := createUDPConnPair()
	// a1 is the association used for sending data
	// a2 is the association with receive window of 100kB which we will
	// try to bypass
	a1, a2, err := createAssociationPair(udp1, udp2)
	require.NoError(t, err)
	defer noErrorClose(t, a2.Close)
	defer noErrorClose(t, a1.Close)
	s1, err := a1.OpenStream(1, PayloadTypeWebRTCBinary)
	require.NoError(t, err)
	defer noErrorClose(t, s1.Close)
	_, err = s1.WriteSCTP([]byte("hello"), PayloadTypeWebRTCBinary)
	require.NoError(t, err)
	_, err = s1.WriteSCTP([]byte("hello"), PayloadTypeWebRTCBinary)
	require.NoError(t, err)
	s2, err := a2.AcceptStream()
	require.NoError(t, err)
	require.Equal(t, uint16(1), s2.streamIdentifier)

	chunks := s1.packetize(make([]byte, 1000), PayloadTypeWebRTCBinary)
	chunks = chunks[:1]
	sendChunk := func(tsn uint32) {
		chunk := chunks[0]
		// Fake the TSN and enqueue 1 chunk with a very high tsn in the payload queue
		chunk.tsn = tsn
		pp := a1.bundleDataChunksIntoPackets(chunks)
		for _, p := range pp {
			raw, err := p.marshal(true)
			if err != nil {
				t.Fatal(err)
				return
			}
			_, err = a1.netConn.Write(raw)
			if err != nil {
				t.Fatal(err)
				return
			}
		}
	}
	sendChunk(readMyNextTSN(a1) + 100_000)
	time.Sleep(100 * time.Millisecond)
	require.Less(t, s2.getNumBytesInReassemblyQueue(), 1000)

	sendChunk(readMyNextTSN(a1) + 10_000)
	time.Sleep(100 * time.Millisecond)
	require.Less(t, s2.getNumBytesInReassemblyQueue(), 1000)

	sendChunk(readMyNextTSN(a1) + minTSNOffset - 100)
	time.Sleep(100 * time.Millisecond)
	require.Greater(t, s2.getNumBytesInReassemblyQueue(), 1000)
}

func TestAssociation_Shutdown(t *testing.T) {
	checkGoroutineLeaks(t)

	a1, a2, err := createAssocs()
	require.NoError(t, err)

	s11, err := a1.OpenStream(1, PayloadTypeWebRTCString)
	require.NoError(t, err)

	s21, err := a2.OpenStream(1, PayloadTypeWebRTCString)
	require.NoError(t, err)

	testData := []byte("test")

	i, err := s11.Write(testData)
	assert.Equal(t, len(testData), i)
	assert.NoError(t, err)

	buf := make([]byte, len(testData))
	i, err = s21.Read(buf)
	assert.Equal(t, len(testData), i)
	assert.NoError(t, err)
	assert.Equal(t, testData, buf)

	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
	defer cancel()

	err = a1.Shutdown(ctx)
	require.NoError(t, err)

	// Wait for close read loop channels to prevent flaky tests.
	select {
	case <-a2.readLoopCloseCh:
	case <-time.After(1 * time.Second):
		assert.Fail(t, "timed out waiting for a2 read loop to close")
	}
}

func TestAssociation_ShutdownDuringWrite(t *testing.T) {
	checkGoroutineLeaks(t)

	a1, a2, err := createAssocs()
	require.NoError(t, err)

	s11, err := a1.OpenStream(1, PayloadTypeWebRTCString)
	require.NoError(t, err)

	s21, err := a2.OpenStream(1, PayloadTypeWebRTCString)
	require.NoError(t, err)

	writingDone := make(chan struct{})

	go func() {
		defer close(writingDone)

		var i byte

		for {
			i++

			if i%100 == 0 {
				time.Sleep(20 * time.Millisecond)
			}

			_, writeErr := s21.Write([]byte{i})
			if writeErr != nil {
				return
			}
		}
	}()

	testData := []byte("test")

	i, err := s11.Write(testData)
	assert.Equal(t, len(testData), i)
	assert.NoError(t, err)

	buf := make([]byte, len(testData))
	i, err = s21.Read(buf)
	assert.Equal(t, len(testData), i)
	assert.NoError(t, err)
	assert.Equal(t, testData, buf)

	// running this test with -race flag is very slow so timeout needs to be high.
	timeout := 5 * time.Minute

	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	err = a1.Shutdown(ctx)
	require.NoError(t, err, "timed out waiting for a1 shutdown to complete")

	select {
	case <-writingDone:
	case <-time.After(timeout):
		assert.Fail(t, "timed out waiting writing goroutine to exit")
	}

	// Wait for close read loop channels to prevent flaky tests.
	select {
	case <-a2.readLoopCloseCh:
	case <-time.After(timeout):
		assert.Fail(t, "timed out waiting for a2 read loop to close")
	}
}

func TestAssociation_HandlePacketInCookieWaitState(t *testing.T) {
	loggerFactory := logging.NewDefaultLoggerFactory()

	testCases := map[string]struct {
		inputPacket *packet
		skipClose   bool
	}{
		"InitAck": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks: []chunk{
					&chunkInitAck{
						chunkInitCommon: chunkInitCommon{
							initiateTag:                    1,
							numInboundStreams:              1,
							numOutboundStreams:             1,
							advertisedReceiverWindowCredit: 1500,
						},
					},
				},
			},
		},
		"Abort": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks:          []chunk{&chunkAbort{}},
			},
			// Prevent "use of close network connection" error on close.
			skipClose: true,
		},
		"CoockeEcho": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks:          []chunk{&chunkCookieEcho{}},
			},
		},
		"HeartBeat": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks:          []chunk{&chunkHeartbeat{}},
			},
		},
		"PayloadData": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks:          []chunk{&chunkPayloadData{}},
			},
		},
		"Sack": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks: []chunk{&chunkSelectiveAck{
					cumulativeTSNAck:               1000,
					advertisedReceiverWindowCredit: 1500,
					gapAckBlocks: []gapAckBlock{
						{start: 100, end: 200},
					},
				}},
			},
		},
		"Reconfig": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks: []chunk{&chunkReconfig{
					paramA: &paramOutgoingResetRequest{},
					paramB: &paramReconfigResponse{},
				}},
			},
		},
		"ForwardTSN": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks: []chunk{&chunkForwardTSN{
					newCumulativeTSN: 100,
				}},
			},
		},
		"Error": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks:          []chunk{&chunkError{}},
			},
		},
		"Shutdown": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks:          []chunk{&chunkShutdown{}},
			},
		},
		"ShutdownAck": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks:          []chunk{&chunkShutdownAck{}},
			},
		},
		"ShutdownComplete": {
			inputPacket: &packet{
				sourcePort:      1,
				destinationPort: 1,
				chunks:          []chunk{&chunkShutdownComplete{}},
			},
		},
	}

	for name, testCase := range testCases {
		testCase := testCase
		t.Run(name, func(t *testing.T) {
			aConn, charlieConn := pipeDump()
			a := createAssociation(Config{
				NetConn:              aConn,
				MaxReceiveBufferSize: 0,
				LoggerFactory:        loggerFactory,
			})
			a.init(true)

			if !testCase.skipClose {
				defer func() {
					assert.NoError(t, a.close())
				}()
			}

			packet, err := a.marshalPacket(testCase.inputPacket)
			assert.NoError(t, err)
			_, err = charlieConn.Write(packet)
			assert.NoError(t, err)

			// Should not panic.
			time.Sleep(100 * time.Millisecond)
		})
	}
}

func TestAssociation_Abort(t *testing.T) {
	checkGoroutineLeaks(t)

	a1, a2, err := createAssocs()
	require.NoError(t, err)

	s11, err := a1.OpenStream(1, PayloadTypeWebRTCString)
	require.NoError(t, err)

	s21, err := a2.OpenStream(1, PayloadTypeWebRTCString)
	require.NoError(t, err)

	testData := []byte("test")

	i, err := s11.Write(testData)
	assert.Equal(t, len(testData), i)
	assert.NoError(t, err)

	buf := make([]byte, len(testData))
	i, err = s21.Read(buf)
	assert.Equal(t, len(testData), i)
	assert.NoError(t, err)
	assert.Equal(t, testData, buf)

	a1.Abort("1234")

	// Wait for close read loop channels to prevent flaky tests.
	select {
	case <-a2.readLoopCloseCh:
	case <-time.After(1 * time.Second):
		assert.Fail(t, "timed out waiting for a2 read loop to close")
	}

	i, err = s21.Read(buf)
	assert.Equal(t, i, 0, "expected no data read")
	assert.Error(t, err, "User Initiated Abort: 1234", "expected abort reason")
}

// TestAssociation_createClientWithContext tests that the client is closed when the context is canceled.
func TestAssociation_createClientWithContext(t *testing.T) {
	// Limit runtime in case of deadlocks
	lim := test.TimeOut(time.Second * 5)
	defer lim.Stop()

	checkGoroutineLeaks(t)

	udp1, udp2 := createUDPConnPair()

	loggerFactory := logging.NewDefaultLoggerFactory()

	errCh1 := make(chan error)
	errCh2 := make(chan error)

	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)

	go func() {
		_, err2 := createClientWithContext(ctx, Config{
			NetConn:       udp1,
			LoggerFactory: loggerFactory,
		})
		if err2 != nil {
			errCh1 <- err2
		} else {
			errCh1 <- nil
		}
	}()

	go func() {
		_, err2 := createClientWithContext(ctx, Config{
			NetConn:       udp2,
			LoggerFactory: loggerFactory,
		})
		if err2 != nil {
			errCh2 <- err2
		} else {
			errCh2 <- nil
		}
	}()

	// Cancel the context immediately
	cancel()

	var err1 error
	var err2 error
loop:
	for {
		select {
		case err1 = <-errCh1:
			if err1 != nil && err2 != nil {
				break loop
			}
		case err2 = <-errCh2:
			if err1 != nil && err2 != nil {
				break loop
			}
		}
	}

	assert.Error(t, err1, "context canceled")
	assert.Error(t, err2, "context canceled")
}

type customLogger struct {
	expectZeroChecksum bool
	t                  *testing.T
}

func (c customLogger) Trace(string)                  {}
func (c customLogger) Tracef(string, ...interface{}) {}
func (c customLogger) Debug(string)                  {}
func (c customLogger) Debugf(format string, args ...interface{}) {
	if format == "[%s] sendZeroChecksum=%t (on initAck)" {
		assert.Equal(c.t, args[1], c.expectZeroChecksum)
	}
}
func (c customLogger) Info(string)                   {}
func (c customLogger) Infof(string, ...interface{})  {}
func (c customLogger) Warn(string)                   {}
func (c customLogger) Warnf(string, ...interface{})  {}
func (c customLogger) Error(string)                  {}
func (c customLogger) Errorf(string, ...interface{}) {}

func (c customLogger) NewLogger(string) logging.LeveledLogger {
	return c
}

func TestAssociation_ZeroChecksum(t *testing.T) {
	checkGoroutineLeaks(t)

	lim := test.TimeOut(time.Second * 10)
	defer lim.Stop()

	for _, testCase := range []struct {
		clientZeroChecksum, serverZeroChecksum, expectChecksumEnabled bool
	}{
		{true, true, true},
		{false, false, false},
		{true, false, false},
		{false, true, true},
	} {
		a1chan, a2chan := make(chan *Association), make(chan *Association)

		udp1, udp2 := createUDPConnPair()

		go func() {
			a1, err := Client(Config{
				NetConn:            udp1,
				LoggerFactory:      &customLogger{testCase.expectChecksumEnabled, t},
				EnableZeroChecksum: testCase.clientZeroChecksum,
			})
			assert.NoError(t, err)
			a1chan <- a1
		}()

		go func() {
			a2, err := Server(Config{
				NetConn:            udp2,
				LoggerFactory:      &customLogger{testCase.expectChecksumEnabled, t},
				EnableZeroChecksum: testCase.serverZeroChecksum,
			})
			assert.NoError(t, err)
			a2chan <- a2
		}()

		a1, a2 := <-a1chan, <-a2chan

		writeStream, err := a1.OpenStream(1, PayloadTypeWebRTCString)
		require.NoError(t, err)

		readStream, err := a2.OpenStream(1, PayloadTypeWebRTCString)
		require.NoError(t, err)

		testData := []byte("test")
		_, err = writeStream.Write(testData)
		require.NoError(t, err)

		buf := make([]byte, len(testData))
		_, err = readStream.Read(buf)
		assert.NoError(t, err)
		assert.Equal(t, testData, buf)

		require.NoError(t, a1.Close())
		require.NoError(t, a2.Close())
	}
}

func TestDataChunkBundlingIntoPacket(t *testing.T) {
	a := &Association{mtu: initialMTU}
	chunks := make([]*chunkPayloadData, 300)
	for i := 0; i < 300; i++ {
		chunks[i] = &chunkPayloadData{userData: []byte{1}}
	}
	packets := a.bundleDataChunksIntoPackets(chunks)
	for _, p := range packets {
		raw, err := p.marshal(false)
		require.NoError(t, err)
		if len(raw) > int(initialMTU) {
			t.Error("packet too long: ", len(raw))
		}
	}
}

func TestAssociation_ReconfigRequestsLimited(t *testing.T) {
	checkGoroutineLeaks(t)

	lim := test.TimeOut(time.Second * 10)
	defer lim.Stop()

	a1chan, a2chan := make(chan *Association), make(chan *Association)

	udp1, udp2 := createUDPConnPair()

	go func() {
		a1, err := Client(Config{
			NetConn:       udp1,
			LoggerFactory: logging.NewDefaultLoggerFactory(),
		})
		assert.NoError(t, err)
		a1chan <- a1
	}()

	go func() {
		a2, err := Server(Config{
			NetConn:       udp2,
			LoggerFactory: logging.NewDefaultLoggerFactory(),
		})
		assert.NoError(t, err)
		a2chan <- a2
	}()

	a1, a2 := <-a1chan, <-a2chan

	writeStream, err := a1.OpenStream(1, PayloadTypeWebRTCString)
	require.NoError(t, err)

	readStream, err := a2.OpenStream(1, PayloadTypeWebRTCString)
	require.NoError(t, err)

	// exchange some data
	testData := []byte("test")
	_, err = writeStream.Write(testData)
	require.NoError(t, err)

	buf := make([]byte, len(testData))
	_, err = readStream.Read(buf)
	assert.NoError(t, err)
	assert.Equal(t, testData, buf)

	a1.lock.RLock()
	tsn := a1.myNextTSN
	a1.lock.RUnlock()
	for i := 0; i < maxReconfigRequests+100; i++ {
		c := &chunkReconfig{
			paramA: &paramOutgoingResetRequest{
				reconfigRequestSequenceNumber: 10 + uint32(i),
				senderLastTSN:                 tsn + 10, // has to be enqueued
				streamIdentifiers:             []uint16{uint16(i)},
			},
		}
		p := a1.createPacket([]chunk{c})
		buf, err := p.marshal(true)
		require.NoError(t, err)
		_, err = a1.netConn.Write(buf)
		require.NoError(t, err)
		if i%100 == 0 {
			time.Sleep(100 * time.Millisecond)
		}
	}
	// Let a2 process the requests
	time.Sleep(2 * time.Second)
	a2.lock.RLock()
	require.LessOrEqual(t, len(a2.reconfigRequests), maxReconfigRequests)
	a2.lock.RUnlock()

	require.NoError(t, a1.Close())
	require.NoError(t, a2.Close())
}

func TestAssociation_OpenStreamAfterClose(t *testing.T) {
	checkGoroutineLeaks(t)

	a1, a2, err := createAssocs()
	require.NoError(t, err)

	require.NoError(t, a1.Close())
	require.NoError(t, a2.Close())

	_, err = a1.OpenStream(1, PayloadTypeWebRTCString)
	require.ErrorIs(t, err, ErrAssociationClosed)

	_, err = a2.OpenStream(1, PayloadTypeWebRTCString)
	require.ErrorIs(t, err, ErrAssociationClosed)
}

// https://github.com/pion/sctp/pull/350
// may need to run with a high test count to reproduce if there
// is ever a regression.
func TestAssociation_OpenStreamAfterInternalClose(t *testing.T) {
	checkGoroutineLeaks(t)

	a1, a2, err := createAssocs()
	require.NoError(t, err)

	require.NoError(t, a1.netConn.Close())
	require.NoError(t, a2.netConn.Close())

	_, err = a1.OpenStream(1, PayloadTypeWebRTCString)
	require.True(t, err == nil || errors.Is(err, ErrAssociationClosed))

	_, err = a2.OpenStream(1, PayloadTypeWebRTCString)
	require.True(t, err == nil || errors.Is(err, ErrAssociationClosed))

	require.NoError(t, a1.Close())
	require.NoError(t, a2.Close())

	require.Equal(t, 0, len(a1.streams))
	require.Equal(t, 0, len(a2.streams))
}