func getTimeval(t time.Time) *unix.Timeval {
nsec := int64(t.Sub(time.Now()))
timeval := unix.NsecToTimeval(nsec)
return &timeval
}
func (pc *packetSock) SetReadTimeout(t time.Duration) error {
tv := unix.NsecToTimeval(t.Nanoseconds())
return unix.SetsockoptTimeval(pc.fd, unix.SOL_SOCKET, unix.SO_RCVTIMEO, &tv)
}