log.Fatal(err)
	}
	wg.Add(2)
	go func() {
		defer wg.Done()
		defer ln.Close()
		c, err := ln.Accept()
		if err != nil {
			log.Fatal(err)
		}
		defer c.Close()
		cf, err := c.(*net.TCPConn).File()
		if err != nil {
			log.Fatal(err)
		}
		defer cf.Close()
		if err := syscall.SetNonblock(int(cf.Fd()), false); err != nil {
			log.Fatal(err)
		}
		// See comments in testPipe.

		t.Fatalf("failed to assert to net.TCPListener")
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()

		tcpConn, terr := tcpListener.AcceptTCP()
		if terr != nil {
			t.Errorf("failed to accept new connection. %v", terr)
			return
		}
		deadlineconn := New(tcpConn)
		deadlineconn.WithReadDeadline(time.Second)
		deadlineconn.WithWriteDeadline(time.Second)
		defer deadlineconn.Close()

		// Read a line

The new type [KeepAliveConfig] permits fine-tuning the keep-alive
options for TCP connections, via a new [TCPConn.SetKeepAliveConfig]

// license that can be found in the LICENSE file.

package net

import (
	"internal/syscall/windows"
	"syscall"
)

// SetKeepAliveConfig configures keep-alive messages sent by the operating system.
func (c *TCPConn) SetKeepAliveConfig(config KeepAliveConfig) error {
	if !c.ok() {
		return syscall.EINVAL
	}

	if err := setKeepAlive(c.fd, config.Enable); err != nil {

		writeLog.Lock()
		writeLog.log = append(writeLog.log, size)
		writeLog.Unlock()
	}
	var want bytes.Buffer
	for i := 0; i < chunks; i++ {
		want.WriteByte(byte(i))
	}

	withTCPConnPair(t, func(c *TCPConn) error {
		buffers := make(Buffers, chunks)
		for i := range buffers {
			buffers[i] = want.Bytes()[i : i+1]
		}
		var n int64
		var err error
		if useCopy {
			n, err = io.Copy(c, &buffers)

	lr, ok := r.(*io.LimitedReader)
	if ok {
		remain, r = lr.N, lr.R
		if remain <= 0 {
			return 0, nil, true
		}
	}

	var s *netFD
	switch v := r.(type) {
	case *TCPConn:
		s = v.fd
	case tcpConnWithoutWriteTo:
		s = v.fd
	case *UnixConn:
		if v.fd.net != "unix" {
			return 0, nil, false
		}
		s = v.fd
	default:
		return 0, nil, false
	}

//go:build (!windows && !solaris) || illumos

package net

import "syscall"

// SetKeepAliveConfig configures keep-alive messages sent by the operating system.
func (c *TCPConn) SetKeepAliveConfig(config KeepAliveConfig) error {
	if !c.ok() {
		return syscall.EINVAL
	}

	if err := setKeepAlive(c.fd, config.Enable); err != nil {

// license that can be found in the LICENSE file.

//go:build !linux

package net

import (
	"context"
)

func (sd *sysDialer) dialMPTCP(ctx context.Context, laddr, raddr *TCPAddr) (*TCPConn, error) {
	return sd.dialTCP(ctx, laddr, raddr)
}

func (sl *sysListener) listenMPTCP(ctx context.Context, laddr *TCPAddr) (*TCPListener, error) {
	return sl.listenTCP(ctx, laddr)
}

		if n := r.(*io.LimitedReader).N; n != int64(wantN) {
			t.Errorf("r.N = %d, want %d", n, wantN)
		}
	}

	// poll.Splice is expected to be called when the source is not
	// a wrapper or the destination is TCPConn.
	if tc.limitReadSize == 0 || tc.downNet == "tcp" {
		// We should have called poll.Splice with the right file descriptor arguments.
		if n > 0 && !hook.called {
			t.Fatal("expected poll.Splice to be called")
		}

// license that can be found in the LICENSE file.

package net

import (
	"context"
)

var (
	// if non-nil, overrides dialTCP.
	testHookDialTCP func(ctx context.Context, net string, laddr, raddr *TCPAddr) (*TCPConn, error)

	testHookLookupIP = func(
		ctx context.Context,
		fn func(context.Context, string, string) ([]IPAddr, error),
		network string,
		host string,
	) ([]IPAddr, error) {
		return fn(ctx, network, host)