linux获取局域网、公网IP地址以及主机名

int IsLANIP(unsigned int nIP){    // filter LAN IP's    // -------------------------------------------    // 0.*    // 10.0.0.0 - 10.255.255.255  class A    // 172.16.0.0 - 172.31.255.255  class B    // 192.168.0.0 - 192.168.255.255 class C    unsigned char nFirst = (unsigned char)nIP;    unsigned char nSecond = (unsigned char)(nIP >> 8);    /* check this 1st, because those LANs IPs are mostly spreaded    */    if (nFirst==192 && nSecond==168)         return 1;    if (nFirst==172 && nSecond>=16 && nSecond<=31)        return 1;    if (nFirst==0 || nFirst==10)        return 1;    if(nFirst==127)        return 1;    if(nFirst==169 && nSecond==254)        return 1;    return 0; }void get_server_info(char* public_ip,char* local_ip,char* hostname,size_t hostname_size){    struct sockaddr_in *sin = NULL;    struct ifaddrs *ifa = NULL, *ifList;    *public_ip = 0;    *local_ip = 0;    *hostname=0;    gethostname(hostname,hostname_size);        if (getifaddrs(&ifList) < 0)        return;    for (ifa = ifList; ifa != NULL; ifa = ifa->ifa_next)    {        if(ifa->ifa_addr->sa_family == AF_INET)        {            if(strcmp(ifa->ifa_name,"lo")==0){                continue;            }            sin = (struct sockaddr_in *)ifa->ifa_addr;            if(!IsLANIP(sin->sin_addr.s_addr)){                strcpy(public_ip,inet_ntoa(sin->sin_addr));            }            else                strcpy(local_ip,inet_ntoa(sin->sin_addr));        }    }    freeifaddrs(ifList);}