iOS获取OpenUUID

#pragma mark - 获取MAC地址
+ (NSString *)obtainMacAddress {
    int                    mib[6];
    size_t                 len;
    char                   *buf;
    unsigned char          *ptr;
    struct if_msghdr       *ifm;
    struct sockaddr_dl     *sdl;
    
    mib[0] = CTL_NET;
    mib[1] = AF_ROUTE;
    mib[2] = 0;
    mib[3] = AF_LINK;
    mib[4] = NET_RT_IFLIST;
    
    if ((mib[5] = if_nametoindex("en0")) == 0) {
        printf("Error: if_nametoindex error\n");
        return NULL;
    }
    
    if (sysctl(mib, 6, NULL, &len, NULL, 0) < 0) {
        printf("Error: sysctl, take 1\n");
        return NULL;
    }
    
    if ((buf = malloc(len)) == NULL) {
        printf("Could not allocate memory. error!\n");
        return NULL;
    }
    
    if (sysctl(mib, 6, buf, &len, NULL, 0) > 0) {
        free(buf);
        printf("Error: sysctl, take 2");
        return NULL;
    }
    
    ifm = (struct if_msghdr *)buf;
    sdl = (struct sockaddr_dl *)(ifm + 1);
    ptr = (unsigned char *)LLADDR(sdl);
    NSString *outstring = [NSString stringWithFormat:@"%02x%02x%02x%02x%02x%02x",
                           *ptr, *(ptr+1), *(ptr+2), *(ptr+3), *(ptr+4), *(ptr+5)];
    free(buf);
    
    return [outstring uppercaseString];
}

#pragma mark - 获取设备UUID
- (void)obtainDeviceOpenUUID {
    if (![kUserDefaults objectForKey:kOpenUUIDKey]) {
        NSString *uuid = nil;
        if ([[[UIDevice currentDevice] systemVersion] floatValue] < 6.0) {
            uuid = [NSString obtainMacAddress]; // 6.0以前用MAC地址作为UID
        } else {
            // identifierForVendor 6.0后可用
            uuid = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
        }
        [kUserDefaults setObject:uuid forKey:kOpenUUIDKey];
    }
    return;
}