C(Linux)中的TUNTAP接口：无法使用sendto()捕获TUNTAP上发送的UD

我所做的是从克隆设备/ dev / net / tun分配接口,打开它并给它一个ip地址：

int tun_setup(char *dev,int flags) {

  struct sockaddr_in  my_addr;
  struct ifreq ifr;
  int fd,err;
  string clonedev = "/dev/net/tun";

  // Open clone device file descriptor
  if( (fd = open(clonedev.c_str(),O_RDWR)) < 0 ) {
    perror("Opening /dev/net/tun");
    return fd;
  }

  // Initialise interface parameters structure
  memset(&ifr,sizeof(ifr));

  // Set up flags
  ifr.ifr_flags = flags;

  // Set up interface name
  if (*dev) {
    strncpy(ifr.ifr_name,dev,IFNAMSIZ);
  }

  // Put interface in TUN mode
  if( (err = ioctl(fd,TUNSETIFF,(void *)&ifr)) < 0 ) {
    perror("ioctl(TUNSETIFF)");
    close(fd);
    return err;
  }

  strcpy(dev,ifr.ifr_name);

  // Create a socket
  if ( (s = socket(AF_INET,SOCK_DGRAM,0)) < 0) {
  perror("socket");
      exit(1);
  }

  // Get interface flags
  if (ioctl(s,SIOCGIFFLAGS,&ifr) < 0) {
    perror("cannot get interface flags");
    exit(1);
  }

  // Turn on interface
  ifr.ifr_flags |= IFF_UP;
  if (ioctl(s,SIOCSIFFLAGS,&ifr) < 0) {
    fprintf(stderr,"ifup: failed ");
    perror(ifr.ifr_name);
    exit(1);
  }

  // Set interface address
  bzero((char *) &my_addr,sizeof(my_addr));
  my_addr.sin_family = AF_INET;
  my_addr.sin_addr.s_addr = htonl(inet_network("192.168.2.1"));
  memcpy(&ifr.ifr_addr,&my_addr,sizeof(struct sockaddr));

  if (ioctl(s,SIOCSIFADDR,"Cannot set IP address. ");
    perror(ifr.ifr_name);
    exit(1);
  }

  // Return interface file descriptor
  return fd;
}

然后我创建一个线程,它将对创建的接口的文件描述符进行poll(),并在事件发生时读取()其他一些东西.

void* tun_readThreadProc (void* param) {
  struct pollfd fds[1];
  int nread;
  unsigned char buffer[BUFFERSIZE];
  fds[0].fd = tun_fd;
  fds[0].events = POLLIN;

  printf("%s : Entered. tun_fd = %d n",__FUNCTION__,tun_fd);

  for(;;)
  {
    printf("%s : Entered loopn",__FUNCTION__);
    if((poll(fds,1,-1)) == -1)
    {
      perror("poll");
      exit(1);
    }

    printf("%s : Poll sensed somethingn",__FUNCTION__);

    if((nread = read(tun_fd,buffer,BUFFERSIZE)) < 0)
    {
      perror("read");
      close(tun_fd);
      exit(1);
    }

    printf("%s : Read something : %d bytesn",nread);
  }
  return 0;
}

在程序的另一部分,我将UDP套接字绑定到此TUNTAP接口的IP地址.

void socketInit( void )
{
  int                 on = 1;
  struct sockaddr_in  my_addr;
  unsigned short DefaultPort = 47808;

  // Create a socket
  if ( (s1 = socket(AF_INET,0)) < 0) {
    perror("socket");
    exit(1);
  }

  // Bind to it
  bzero((char *) &my_addr,sizeof(my_addr));
  my_addr.sin_family = AF_INET;
  my_addr.sin_addr.s_addr = htonl(inet_network("192.168.2.1"));
  my_addr.sin_port = htons(DefaultPort);

  if ( (bind(s,(struct sockaddr *) &my_addr,sizeof(my_addr)) < 0) ) {
    perror("bind");
  }
  // Allow it to broadcast
  if (setsockopt(s,SOL_SOCKET,SO_BROADCAST,(char *)&on,sizeof(on)) < 0) {
    perror("setsockopt");
  }
}

在另一个函数中,我使用sendto()来发送带有此套接字的数据包.我应该使用poll()read()线程捕获这些数据包,然后在串行端口上发送它们,但poll()从不捕获TUNTAP接口上的事件.

我可以使用ping -I tun0 [some destination](tun0 = TUNTAP接口的名称)来ping通此接口

但是如果我使用ping -I 192.168.2.1 [某个目的地](192.168.2.1 = TUNTAP接口地址),它将通过默认接口(eth0,物理网卡).

我能够通过Wireshark验证这一点.

这很可能是ip路由配置问题……

如果有人能帮助我,我会很高兴.