在应用层获取内核网络参数

1. 通过网络设备名获取网络设备id(if_index)

/*
 *return val:
 * -1 : fail
 * others : interface index
 */
short get_ifindex_by_name(const char * name)
{
    struct ifreq    ifr;
    int sockfd = -1;
    int err = -1;

    if (!name){
        return -1;
    }

    /*create socket*/
    sockfd = socket(PF_INET, SOCK_DGRAM, 0);
    if (sockfd <= 0){
        return -1;
    }

    /*get if index by calling ioctl*/
    strncpy(ifr.ifr_name, name, IFNAMSIZ);
    err = ioctl(sockfd, SIOCGIFINDEX, (void *) &ifr);
    if (err == -1){
        return -1;
    }

    return ifr.ifr_ifindex;
}

2. 通过网络设备名获取网络设备MAC地址

char *get_mac(char * ifname, char * mac)
{
    struct ifreq ifreq;
    unsigned char *p = NULL;
    int sock = -1;

    if(ifname == NULL || mac == NULL){
        printf("get mac character ERROR!");
        return NULL;
    }

    if((sock=socket(AF_INET,SOCK_STREAM,0))<0){
        perror("socket");
      return NULL;
    }

    strcpy(ifreq.ifr_name,ifname);
    if(ioctl(sock,SIOCGIFHWADDR,&ifreq)<0){
        perror("ioctl");
        close(sock);
        return NULL;
    }

    p = (unsigned char *)(ifreq.ifr_hwaddr.sa_data);
    sprintf(mac,"%02x:%02x:%02x:%02x:%02x:%02x",
         p[0], p[1], p[2], p[3], p[4], p[5]);

    return mac;
}

3. 通过网络设备名获取网络设备ip地址:

int get_dev_ip(const char *ifname, char *ip_addr, int len)
{
        struct ifreq ifr;
        struct sockaddr_in *addr = NULL;
        int sockfd = -1;

        if((sockfd = socket(AF_INET,SOCK_STREAM,0))<0){
                perror("socket");
                return -1;
        }

        memset(&ifr, 0, sizeof(struct ifreq));
        addr = (struct sockaddr_in *)&ifr.ifr_addr;
        addr->sin_family = AF_INET;
        strcpy(ifr.ifr_name,ifname);

        if (ioctl(sockfd, SIOCGIFADDR, &ifr) == 0) {
                snprintf(ip_addr, len, "%s", inet_ntoa(addr->sin_addr));
                close(sockfd);
                return 0;
        }

        close(sockfd);
        return -1;
}