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_KEEPINTVL, secs)
	runtime.KeepAlive(fd)
	return wrapSyscallError("setsockopt", err)
}

	if c.fd.isConnected && addr != nil {
		return 0, 0, ErrWriteToConnected
	}
	if !c.fd.isConnected && addr == nil {
		return 0, 0, errMissingAddress
	}
	sa, err := addr.sockaddr(c.fd.family)
	if err != nil {
		return 0, 0, err
	}
	return c.fd.writeMsg(b, oob, sa)
}

func (c *UDPConn) writeMsgAddrPort(b, oob []byte, addr netip.AddrPort) (n, oobn int, err error) {
	if c.fd.isConnected && addr.IsValid() {

type fakeNs struct {
	closed *atomic.Bool
	fd     uintptr
	inode  uint64
}

func newFakeNs(fd uintptr) *fakeNs {
	// the fake inode is the fd! magic.
	return &fakeNs{closed: &atomic.Bool{}, fd: fd, inode: uint64(fd)}
}

func newFakeNsInode(fd uintptr, inode uint64) *fakeNs {
	return &fakeNs{closed: &atomic.Bool{}, fd: fd, inode: inode}
}

// Fd returns the file descriptor
func (f *fakeNs) Fd() uintptr {

	}
	sa, err := addr.sockaddr(c.fd.family)
	if err != nil {
		return 0, err
	}
	return c.fd.writeTo(b, sa)
}

func (c *IPConn) writeMsg(b, oob []byte, addr *IPAddr) (n, oobn int, err error) {
	if c.fd.isConnected {
		return 0, 0, ErrWriteToConnected
	}
	if addr == nil {
		return 0, 0, errMissingAddress
	}
	sa, err := addr.sockaddr(c.fd.family)
	if err != nil {
		return 0, 0, err
	}

		// reissued the fd in a later call to open(2), leading
		// to crashes being written to the wrong file.
		//
		// So, we duplicate the fd to obtain a private one
		// that cannot be closed by the user.
		// This also alleviates us from concerns about the
		// lifetime and finalization of f.
		// (DupCloseOnExec returns an fd, not a *File, so
		// there is no finalizer, and we are responsible for

	runtime.KeepAlive(fd)
	return wrapSyscallError("setsockopt", err)
}

func setKeepAliveCount(fd *netFD, n int) error {
	if !unix.SupportTCPKeepAliveIdleIntvlCNT() {
		return syscall.EPROTOTYPE
	}

	if n == 0 {
		n = defaultTCPKeepAliveCount
	} else if n < 0 {
		return nil
	}
	err := fd.pfd.SetsockoptInt(syscall.IPPROTO_TCP, sysTCP_KEEPCNT, n)
	runtime.KeepAlive(fd)

package poll

import (
	"io"
	"syscall"
)

// SendFile wraps the TransmitFile call.
func SendFile(fd *FD, src syscall.Handle, n int64) (written int64, err error) {
	defer func() {
		TestHookDidSendFile(fd, 0, written, err, written > 0)
	}()
	if fd.kind == kindPipe {
		// TransmitFile does not work with pipes
		return 0, syscall.ESPIPE
	}

	return c.fd.writeTo(b, sa)
}

func (c *UnixConn) writeMsg(b, oob []byte, addr *UnixAddr) (n, oobn int, err error) {
	if c.fd.sotype == syscall.SOCK_DGRAM && c.fd.isConnected {
		return 0, 0, ErrWriteToConnected
	}
	var sa syscall.Sockaddr
	if addr != nil {
		if addr.Net != sotypeToNet(c.fd.sotype) {
			return 0, 0, syscall.EAFNOSUPPORT
		}
		sa = &syscall.SockaddrUnix{Name: addr.Name}
	}

)

const (
	Sys_GETEUID = sys_GETEUID
)

func Tcgetpgrp(fd int) (pgid int32, err error) {
	_, _, errno := Syscall6(SYS_IOCTL, uintptr(fd), uintptr(TIOCGPGRP), uintptr(unsafe.Pointer(&pgid)), 0, 0, 0)
	if errno != 0 {
		return -1, errno
	}
	return pgid, nil
}

func Tcsetpgrp(fd int, pgid int32) (err error) {
	_, _, errno := Syscall6(SYS_IOCTL, uintptr(fd), uintptr(TIOCSPGRP), uintptr(unsafe.Pointer(&pgid)), 0, 0, 0)

		}
		println("runtime: netpoll: break fd ready for", ev.filter)
		throw("runtime: netpoll: break fd ready for something unexpected")
	}
	return false
}

func drainWakeupEvent(_ int32) {
	var buf [16]byte
	read(int32(netpollBreakRd), noescape(unsafe.Pointer(&buf[0])), int32(len(buf)))
}

func netpollIsPollDescriptor(fd uintptr) bool {
	return fd == uintptr(kq) || fd == netpollBreakRd || fd == netpollBreakWr