if err := fd.readLock(); err != nil {
		return 0, err
	}
	defer fd.readUnlock()
	if err := fd.pd.prepareRead(fd.isFile); err != nil {
		return 0, err
	}
	for {
		n, err := unix.RecvfromInet6(fd.Sysfd, p, 0, from)
		if err != nil {
			if err == syscall.EINTR {
				continue
			}
			n = 0
			if err == syscall.EAGAIN && fd.pd.pollable() {
				if err = fd.pd.waitRead(fd.isFile); err == nil {