/*imp1_u.c*/#include <unistd.h>#include <stdio.h>#include <sys/socket.h>#include <linux/in.h>#include "imp1.h"#define UMSG      "a message from userspace\n"#define UMSG_LEN  sizeof("a message from userspace\n")char kmsg[64];int main(void){  int sockfd;  int len;  sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);  if(sockfd < 0)    {      printf("can not create a socket\n");      return -1;    }  /*call function data_to_kernel()*/  setsockopt(sockfd, IPPROTO_IP, IMP1_SET, UMSG, UMSG_LEN);  len = sizeof(char)*64;  /*call function data_from_kernel()*/  getsockopt(sockfd, IPPROTO_IP, IMP1_GET, kmsg, &len);  printf("kmsg: %s", kmsg);  close(sockfd);  return 0;}