通过getifaddrs获取网络接口的名称、mac地址、子网掩码、ip地址、网关,请写出C程序

好的，以下是一个使用getifaddrs函数获取网络接口信息的C程序，包括名称、MAC地址、子网掩码、IP地址和网关信息。请注意，获取网关信息需要使用系统调用来实现，因此这个程序只能在类Unix系统上运行。

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

int main(int argc, char *argv[]) {
    struct ifaddrs *ifaddr, *ifa;
    int family, s, n;
    char host[NI_MAXHOST];
    char gateway[NI_MAXHOST];
    char mac[18];

    if (getifaddrs(&ifaddr) == -1) {
        perror("getifaddrs");
        return EXIT_FAILURE;
    }

    /* Walk through linked list, maintaining head pointer so we
       can free list later */

    for (ifa = ifaddr, n = 0; ifa != NULL; ifa = ifa->ifa_next, n++) {
        if (ifa->ifa_addr == NULL) {
            continue;
        }

        family = ifa->ifa_addr->sa_family;

        /* Display interface name and family (including symbolic
           form of the latter for the common families) */

        printf("%-8s %s (%d)\n",
               ifa->ifa_name,
               (family == AF_PACKET) ? "AF_PACKET" :
               (family == AF_INET) ? "AF_INET" :
               (family == AF_INET6) ? "AF_INET6" : "???",
               family);

        /* For an AF_PACKET interface, display the MAC address. */

        if (family == AF_PACKET && ifa->ifa_data != NULL) {
            struct sockaddr_ll *s = (struct sockaddr_ll*)ifa->ifa_addr;
            sprintf(mac, "%02x:%02x:%02x:%02x:%02x:%02x",
                    s->sll_addr[0], s->sll_addr[1], s->sll_addr[2],
                    s->sll_addr[3], s->sll_addr[4], s->sll_addr[5]);
            printf("\t\tAddress: %s\n", mac);
        }

        /* For an AF_INET or AF_INET6 interface, display the
           address and subnet mask */

        else if (family == AF_INET || family == AF_INET6) {
            s = socket(family, SOCK_DGRAM, 0);
            if (s == -1) {
                perror("socket");
                return EXIT_FAILURE;
            }

            if (getnameinfo(ifa->ifa_addr,
                            (family == AF_INET) ? sizeof(struct sockaddr_in) :
                            sizeof(struct sockaddr_in6),
                            host, NI_MAXHOST,
                            NULL, 0, NI_NUMERICHOST) == 0) {
                printf("\t\tAddress: <%s>\n", host);
            }

            if (getnameinfo(ifa->ifa_netmask,
                            (family == AF_INET) ? sizeof(struct sockaddr_in) :
                            sizeof(struct sockaddr_in6),
                            host, NI_MAXHOST,
                            NULL, 0, NI_NUMERICHOST) == 0) {
                printf("\t\tNetmask: <%s>\n", host);
            }

            /*Get the gateway address*/

            if (family == AF_INET) {
                struct rtentry *route;
                memset(&route, 0, sizeof(route));
                route->rt_dst.sa_family = AF_INET;
                ((struct sockaddr_in *) &route->rt_dst)->sin_addr.s_addr = 0;
                route->rt_flags = RTF_UP;
                if (ioctl(s, SIOCADDRT, &route) < 0) {
                    perror("SIOCADDRT failed");
                    return EXIT_FAILURE;
                }

                struct sockaddr_in *addr;
                for (ifa = ifaddr; ifa; ifa = ifa->ifa_next) {
                    if (ifa->ifa_addr && ifa->ifa_addr->sa_family == AF_INET) {
                        addr = (struct sockaddr_in *) ifa->ifa_addr;
                        if (ifa->ifa_flags & IFF_LOOPBACK) {
                            continue;
                        }
                        if (addr->sin_addr.s_addr == ((struct sockaddr_in *) &route->rt_dst)->sin_addr.s_addr) {
                            continue;
                        }
                        if (ioctl(s, SIOCGIFHWADDR, ifa) == -1) {
                            perror("ioctl failed");
                            return EXIT_FAILURE;
                        }
                        if (ifa->ifa_addr) {
                            inet_ntop(AF_INET, &addr->sin_addr, gateway, NI_MAXHOST);
                            printf("\t\tGateway: %s\n", gateway);
                        }
                    }
                }
                if (ioctl(s, SIOCDELRT, &route) < 0) {
                    perror("SIOCDELRT failed");
                    return EXIT_FAILURE;
                }
            }
            close(s);
        }
    }

    freeifaddrs(ifaddr);
    return EXIT_SUCCESS;
}

这个程序将会打印出每个网络接口的名称、MAC地址、IP地址、子网掩码和网关信息。如果某个接口没有网关，它将不会打印网关信息。