c - 在 Linux 中通过 SIOCGIFCONF 轮询接口(interface)名称

Question

我正在尝试轮询网络设备名称。我从各种片段中拼凑而成，

1. http://unixhelp.ed.ac.uk/CGI/man-cgi?netdevice+7
2. http://lists.apple.com/archives/Unix-porting/2002/Apr/msg00134.html
3. http://ubuntuforums.org/showthread.php?t=1421487

但我的输出只是乱码。

#include <stdio.h>
#include <stdlib.h>
#include <net/route.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>

#define BUFLEN 1024
#define SEQ 9999

int main (int argc, const char* argv[])
{
  // File descriptor for socket
  int socketfd;
  struct ifconf conf;
  struct ifreq req[10];
  struct ifreq *ifr;

  printf("Opening socket...");
  socketfd = socket(AF_ROUTE, SOCK_RAW, 0);
  if (socketfd >= 0) {
    printf(" OK\n");
    conf.ifc_len = sizeof(req);
    conf.ifc_buf = (__caddr_t) req;
    ioctl(socketfd,SIOCGIFCONF,&conf);

    printf("Discovering interfaces...\n");
    int i;
    for (i=0; i<conf.ifc_len/sizeof(req[0]); i++) {
      ifr = &conf.ifc_req[i];
      printf("%d. %s\n", i+1, req[i].ifr_name);
    }
  }
  else {
    printf("Failed!\n");
  }
  return 0;
}

输出:

Opening socket... OK
Discovering interfaces...
?u???}??Gh???
2. p?9}?
3.
4. v?=?n??u?`?y??]g?<?~?v??
5.
6.
7.
8. ?v?T?
9. ?|?mw??j??v??h??|??v?T00~??v?$?|??|?@
10. T00~??v?$?|??|?@

我试着逐一输出 ifr_name 数组的每个字符，看看它们是否以 null 结尾，但变化不大。我的程序的每次迭代都会输出不同的东西，所以这让我觉得我引用了错误的东西。有人可以提供一些关于我可能做错了什么的见解吗？

Answer 1

这是我为 Mac OS X 编写的一些代码:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <arpa/inet.h>
#include <netinet/in.h>

/* This is defined on Mac OS X */
#ifndef _SIZEOF_ADDR_IFREQ
#define _SIZEOF_ADDR_IFREQ sizeof
#endif

int main (int argc, const char* argv[])
{
  // File descriptor for socket
  int socketfd;
  struct ifconf conf;
  char data[4096];
  struct ifreq *ifr;
  char addrbuf[1024];
  int i;

  printf("Opening socket...");
  socketfd = socket(AF_INET, SOCK_DGRAM, 0);
  if (socketfd >= 0) {
    printf(" OK\n");
    conf.ifc_len = sizeof(data);
    conf.ifc_buf = (caddr_t) data;
    if (ioctl(socketfd,SIOCGIFCONF,&conf) < 0) {
      perror("ioctl");
    }

    printf("Discovering interfaces...\n");
    i = 0;
    ifr = (struct ifreq*)data;
    while ((char*)ifr < data+conf.ifc_len) {
      switch (ifr->ifr_addr.sa_family) {
        case AF_INET:
            ++i;
            printf("%d. %s : %s\n", i, ifr->ifr_name, inet_ntop(ifr->ifr_addr.sa_family, &((struct sockaddr_in*)&ifr->ifr_addr)->sin_addr, addrbuf, sizeof(addrbuf)));
            break;
#if 0
        case AF_INET6:
            ++i;
            printf("%d. %s : %s\n", i, ifr->ifr_name, inet_ntop(ifr->ifr_addr.sa_family, &((struct sockaddr_in6*)&ifr->ifr_addr)->sin6_addr, addrbuf, sizeof(addrbuf)));
            break;
#endif
      }
      ifr = (struct ifreq*)((char*)ifr +_SIZEOF_ADDR_IFREQ(*ifr));
    }
    close(socketfd);
  }
  else {
    printf(" Failed!\n");
  }
  return 0;
}