如何才能知道C中接口的IP地址？

Question

假設我正在運行一個名爲IpAddresses.c的程序。我希望該程序根據每個接口獲取此設備具有的所有IP地址。就像ifconfig。我怎樣才能做到這一點？

我對ioctl瞭解不多，但我讀過它可能對我有幫助。

Answer 1

只需使用getifaddrs()。這裏有一個例子：

#include <arpa/inet.h> 
#include <sys/socket.h> 
#include <ifaddrs.h> 
#include <stdio.h> 

int main() 
{ 
    struct ifaddrs *ifap, *ifa; 
    struct sockaddr_in *sa; 
    char *addr; 

    getifaddrs (&ifap); 
    for (ifa = ifap; ifa; ifa = ifa->ifa_next) { 
     if (ifa->ifa_addr->sa_family==AF_INET) { 
      sa = (struct sockaddr_in *) ifa->ifa_addr; 
      addr = inet_ntoa(sa->sin_addr); 
      printf("Interface: %s\tAddress: %s\n", ifa->ifa_name, addr); 
     } 
    } 

    freeifaddrs(ifap); 
    return 0; 
} 

而這裏的輸出我得到我的機器上：

Interface: lo Address: 127.0.0.1 
Interface: eth0 Address: 69.72.234.7 
Interface: eth0:1  Address: 10.207.9.3 

Answer 2

檢查出（Windows特定）IP Helper API - 幸運的是，您不需要ioctl這在Windows上。

Answer 3

你可以嘗試這樣的事情：

struct ifreq ifr[MAX_INTERFACES]; 
struct ifconf ifc; 
memset(ifr, 0, sizeof(ifr)); 
ifc.ifc_len = sizeof(ifr); 
ifc.ifc_req = ifr; 

// Get the list of interfaces 
if (ioctl(sock, SIOCGIFCONF, &ifc) == -1) { 
    fprintf(stderr, "ioctl SIOCGIFCONF failed: %d", errno); 
} 

for (int i=0; i < ifc.ifc_len/sizeof(struct ifreq); ++i) { 
    if (ifr[i].ifr_addr.sa_family != AF_INET) { 
     continue; 
    } 

    // Maybe some more filtering based on SIOCGIFFLAGS 

    // Your code 
} 

Answer 4

看到這個其他堆棧溢出問題，Enumerating each IP address assigned to network interfaces。

總之，您可以使用：

• ioctl(SIOCGIFCONF) - >傳統的ioctl
• getifaddrs() - >從的BSDi，現在也可以在Linux和BSD的。
• RTNETLINK（Linux）的

Answer 5

下面是一些Linux的示例代碼，可以幫助你。

#include <stdio.h> 
#include <net/if.h> 
#include <netinet/in.h> 
#include <sys/ioctl.h> 
#include <sys/types.h> 
#include <sys/socket.h> 

#define INT_TO_ADDR(_addr) \ 
(_addr & 0xFF), \ 
(_addr >> 8 & 0xFF), \ 
(_addr >> 16 & 0xFF), \ 
(_addr >> 24 & 0xFF) 

int main() 
{ 
    struct ifconf ifc; 
    struct ifreq ifr[10]; 
    int sd, ifc_num, addr, bcast, mask, network, i; 

    /* Create a socket so we can use ioctl on the file 
    * descriptor to retrieve the interface info. 
    */ 

    sd = socket(PF_INET, SOCK_DGRAM, 0); 
    if (sd > 0) 
    { 
     ifc.ifc_len = sizeof(ifr); 
     ifc.ifc_ifcu.ifcu_buf = (caddr_t)ifr; 

     if (ioctl(sd, SIOCGIFCONF, &ifc) == 0) 
     { 
      ifc_num = ifc.ifc_len/sizeof(struct ifreq); 
      printf("%d interfaces found\n", ifc_num); 

      for (i = 0; i < ifc_num; ++i) 
      { 
       if (ifr[i].ifr_addr.sa_family != AF_INET) 
       { 
        continue; 
       } 

       /* display the interface name */ 
       printf("%d) interface: %s\n", i+1, ifr[i].ifr_name); 

       /* Retrieve the IP address, broadcast address, and subnet mask. */ 
       if (ioctl(sd, SIOCGIFADDR, &ifr[i]) == 0) 
       { 
        addr = ((struct sockaddr_in *)(&ifr[i].ifr_addr))->sin_addr.s_addr; 
        printf("%d) address: %d.%d.%d.%d\n", i+1, INT_TO_ADDR(addr)); 
       } 
       if (ioctl(sd, SIOCGIFBRDADDR, &ifr[i]) == 0) 
       { 
        bcast = ((struct sockaddr_in *)(&ifr[i].ifr_broadaddr))->sin_addr.s_addr; 
        printf("%d) broadcast: %d.%d.%d.%d\n", i+1, INT_TO_ADDR(bcast)); 
       } 
       if (ioctl(sd, SIOCGIFNETMASK, &ifr[i]) == 0) 
       { 
        mask = ((struct sockaddr_in *)(&ifr[i].ifr_netmask))->sin_addr.s_addr; 
        printf("%d) netmask: %d.%d.%d.%d\n", i+1, INT_TO_ADDR(mask)); 
       }     

       /* Compute the current network value from the address and netmask. */ 
       network = addr & mask; 
       printf("%d) network: %d.%d.%d.%d\n", i+1, INT_TO_ADDR(network)); 
      }      
     } 

     close(sd); 
    } 

    return 0; 
} 

Answer 6

使用getifaddrs()解決方案是巨大的。我建議只有一個提高：

--- chrisaycock 
+++ normando 
@@ -11,7 +11,7 @@ 

    getifaddrs (&ifap); 
    for (ifa = ifap; ifa; ifa = ifa->ifa_next) { 
-  if (ifa->ifa_addr->sa_family==AF_INET) { 
+  if (ifa->ifa_addr && ifa->ifa_addr->sa_family==AF_INET) { 
      sa = (struct sockaddr_in *) ifa->ifa_addr; 
      addr = inet_ntoa(sa->sin_addr); 
      printf("Interface: %s\tAddress: %s\n", ifa->ifa_name, addr); 

只因爲我自己得到了分割錯誤。