func setKeepAliveIdle(fd *netFD, d time.Duration) error {
	if d < 0 {
		return nil
	}

	cmd := "keepalive " + itoa.Itoa(int(d/time.Millisecond))
	_, e := fd.ctl.WriteAt([]byte(cmd), 0)
	return e
}

func setKeepAliveInterval(_ *netFD, d time.Duration) error {
	if d < 0 {
		return nil
	}
	return syscall.EPLAN9
}

func setKeepAliveCount(_ *netFD, n int) error {
	if n < 0 {
		return nil
	}
	return syscall.EPLAN9

	"time"
)

func setNoDelay(fd *netFD, noDelay bool) error {
	return syscall.ENOPROTOOPT
}

func setKeepAliveIdle(fd *netFD, d time.Duration) error {
	return syscall.ENOPROTOOPT
}

func setKeepAliveInterval(fd *netFD, d time.Duration) error {
	return syscall.ENOPROTOOPT
}

func setKeepAliveCount(fd *netFD, n int) error {
	return syscall.ENOPROTOOPT

)

func setKeepAliveIdle(_ *netFD, d time.Duration) error {
	if d < 0 {
		return nil
	}
	// OpenBSD has no user-settable per-socket TCP keepalive
	// options.
	return syscall.ENOPROTOOPT
}

func setKeepAliveInterval(_ *netFD, d time.Duration) error {
	if d < 0 {
		return nil
	}
	// OpenBSD has no user-settable per-socket TCP keepalive
	// options.
	return syscall.ENOPROTOOPT
}

	}
	if err := setKeepAliveIdle(c.fd, config.Idle); err != nil {
		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	if err := setKeepAliveInterval(c.fd, config.Interval); err != nil {
		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	if err := setKeepAliveCount(c.fd, config.Count); err != nil {

		if err := setKeepAliveIdle(c.fd, config.Idle); err != nil {
			return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
		}
		if err := setKeepAliveInterval(c.fd, config.Interval); err != nil {
			return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
		}

	secs := int(roundDurationUp(d, time.Second))
	err := fd.pfd.SetsockoptInt(syscall.IPPROTO_TCP, syscall.TCP_KEEPALIVE, secs)
	runtime.KeepAlive(fd)
	return wrapSyscallError("setsockopt", err)
}

func setKeepAliveInterval(fd *netFD, d time.Duration) error {
	if d == 0 {
		d = defaultTCPKeepAliveInterval
	} else if d < 0 {
		return nil
	}

	// The kernel expects seconds so round to next highest second.

	secs := int(roundDurationUp(d, time.Second))
	err := fd.pfd.SetsockoptInt(syscall.IPPROTO_TCP, syscall.TCP_KEEPIDLE, secs)
	runtime.KeepAlive(fd)
	return wrapSyscallError("setsockopt", err)
}

func setKeepAliveInterval(fd *netFD, d time.Duration) error {
	if d == 0 {
		d = defaultTCPKeepAliveInterval
	} else if d < 0 {
		return nil
	}

	// The kernel expects seconds so round to next highest second.

	secs := int(roundDurationUp(d, time.Second))
	err := fd.pfd.SetsockoptInt(syscall.IPPROTO_TCP, sysTCP_KEEPIDLE, secs)
	runtime.KeepAlive(fd)
	return wrapSyscallError("setsockopt", err)
}

func setKeepAliveInterval(fd *netFD, d time.Duration) error {
	if !unix.SupportTCPKeepAliveIdleIntvlCNT() {
		return syscall.EPROTOTYPE
	}

	if d == 0 {
		d = defaultTCPKeepAliveInterval
	} else if d < 0 {
		return nil
	}

	}
	if unix.SupportTCPKeepAliveIdleIntvlCNT() {
		if err := setKeepAliveIdle(c.fd, config.Idle); err != nil {
			return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
		}
		if err := setKeepAliveInterval(c.fd, config.Interval); err != nil {
			return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
		}
		if err := setKeepAliveCount(c.fd, config.Count); err != nil {

	secs := int(roundDurationUp(d, time.Second))
	err := fd.pfd.SetsockoptInt(syscall.IPPROTO_TCP, windows.TCP_KEEPIDLE, secs)
	runtime.KeepAlive(fd)
	return os.NewSyscallError("setsockopt", err)
}

func setKeepAliveInterval(fd *netFD, d time.Duration) error {
	if !windows.SupportTCPKeepAliveInterval() {
		return setKeepAliveIdleAndInterval(fd, -1, d)
	}

	if d == 0 {
		d = defaultTCPKeepAliveInterval
	} else if d < 0 {