我怎样才能知道C中接口的IP地址？

Question

假设我正在运行一个名为 IpAddresses.c 的程序。我希望该程序根据每个接口获取该设备拥有的所有 IP 地址。就像 ifconfig 一样。我怎样才能做到这一点？

我对 ioctl 了解不多，但我读过它可能对我有帮助。

Answer 1

只需使用 getifaddrs() 即可。这是一个例子：

#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 && 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;
}

这是我在我的机器上得到的输出：

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

Answer 2

这里有一些 Linux 示例代码可能会对您有所帮助。

#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 3

使用 getifaddrs() 的解决方案是伟大的。我只建议一项改进：

--- 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);

只是因为我自己遇到了分段错误。

Answer 4

请参阅另一个 Stack Overflow 问题，枚举分配给的每个 IP 地址网络接口。

总之，您可以使用：

• ioctl(SIOCGIFCONF) ->传统的 ioctl
• getifaddrs() ->来自 BSDi，现在也可以在 Linux 和 BSD 上使用。
• RTNETLINK（Linux）

Answer 5

你可以尝试这样的事情：

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);
}

struct ifreq *ifr_iterator = ifc.ireq;
int i = 0;
size_t len;
while (i < ifc.ifc_len) {
   /* DO STUFF */
   // Maybe some more filtering based on SIOCGIFFLAGS 
   // Your code
   // Use ifr_iterator-> ...

   len = IFNAMSIZ + ifr_iterator->ifr_addr.sa_len;
   ifr_iterator = (struct ifreq *)((char *)ifr_iterator + len);
   i += len;
}

Answer 6

查看（特定于 Windows）IP Helper API - 幸运的是，在 Windows 上您不需要 ioctl 来实现此目的。

Answer 7

如果您还需要 IP6 地址，您可以像这样扩展接受的答案：

#include <arpa/inet.h>
#include <ifaddrs.h>
#include <stdio.h>
#include <netdb.h>

int main() {
    struct ifaddrs *ifap;
    getifaddrs(&ifap);
    for (struct ifaddrs *ifa = ifap; ifa; ifa = ifa->ifa_next) {
        if (ifa->ifa_addr && (ifa->ifa_addr->sa_family == AF_INET6)) {
            char addr[INET6_ADDRSTRLEN];
            getnameinfo(ifa->ifa_addr, sizeof(struct sockaddr_in6), addr, sizeof(addr), NULL, 0, NI_NUMERICHOST);
            printf("Interface: %s\tAddress: %s\n", ifa->ifa_name, addr);
        } else if (ifa->ifa_addr && ifa->ifa_addr->sa_family == AF_INET) {
            struct sockaddr_in *sa = (struct sockaddr_in *)ifa->ifa_addr;
            char *addr = inet_ntoa(sa->sin_addr);
            printf("Interface: %s\tAddress: %s\n", ifa->ifa_name, addr);
        }
    }
    freeifaddrs(ifap);
    return 0;
}