/*这个信号函数，处理一些程序退出时的动作*/

static void sig_int(int signo)

{

  struct sockaddr_nl kpeer;

  struct msg_to_kernel message;



  memset(&kpeer, 0, sizeof(kpeer));

  kpeer.nl_family = AF_NETLINK;

  kpeer.nl_pid    = 0;

  kpeer.nl_groups = 0;



  memset(&message, 0, sizeof(message));

  message.hdr.nlmsg_len = NLMSG_LENGTH(0);

  message.hdr.nlmsg_flags = 0;

  message.hdr.nlmsg_type = IMP2_CLOSE;

  message.hdr.nlmsg_pid = getpid();



/*向内核发送一个消息，由nlmsg_type表明，应用程序将关闭*/

sendto(skfd, &message, message.hdr.nlmsg_len, 0,
(struct sockaddr *)(&kpeer),         sizeof(kpeer));



  close(skfd);

  exit(0);

}