绑定vs SO_BINDTODEVICE套接字

Question

我在linux上运行一个项目(ubuntu 13.10),它使用原始套接字连接到设备.

这是我的代码:

/* builed socket */
if ((sockfd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL))) == -1) {
  perror("listener: socket");
  return -1;
}

/* Set interface to promiscuous mode */
strncpy(ifopts.ifr_name, ifName, IFNAMSIZ-1);
ioctl(sockfd, SIOCGIFFLAGS, &ifopts);
ifopts.ifr_flags |= IFF_PROMISC;
ioctl(sockfd, SIOCSIFFLAGS, &ifopts);

/* Allow the socket to be reused - incase connection is closed prematurely */
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &sockopt, sizeof sockopt) == -1) {
  perror("setsockopt");
  close(sockfd);
  return -2;
}

但是我的计算机上有2块NIC卡,我只想听其中一张.让我们说道德.我发现两个选项bind和SO_BINDTODEVICE如下:

/* option 1. Bind to device */
if (setsockopt(sockfd, SOL_SOCKET, SO_BINDTODEVICE, ifName, IFNAMSIZ-1) == -1)  {
  perror("SO_BINDTODEVICE");
  close(sockfd);
  return -4;
}


/* option 2. Bind to device */
memset(&sock_address, 0, sizeof(sock_address));
sock_address.sll_family = PF_PACKET;
sock_address.sll_protocol = htons(ETH_P_ALL);
sock_address.sll_ifindex = if_nametoindex(ifName);
if (bind(sockfd, (struct sockaddr*) &sock_address, sizeof(sock_address)) < 0) {
  perror("bind failed\n");
  close(sockfd);
  return -4;
}

只有绑定工作.所以我的问题是两者之间有什么区别？

Answer 1

从Linux man-page man 7 socket for socket选项SO_BINDTODEVICE:

请注意,这仅适用于某些套接字类型,尤其是AF_INET套接字.数据包套接字不支持它(在那里使用普通绑定(2)).