今天偶然看到了这位兄台的文章https://www.jianshu.com/p/8005d7e05944判断是否是vpn，哈哈这哥们还真是脑洞大开。
其实在这位老兄https://github.com/dustturtle/RealReachability的项目包含了检测VPN的方法

通过判断tap tun ipsec ppp 这些字段是否在CFNetworkCopySystemProxySettings里来判断vpn是否开启

局部代码

NSDictionary *dict = CFBridgingRelease(CFNetworkCopySystemProxySettings());
        NSArray *keys = [dict[@"__SCOPED__"] allKeys];
        for (NSString *key in keys) {
            if ([key rangeOfString:@"tap"].location != NSNotFound ||
                [key rangeOfString:@"tun"].location != NSNotFound ||
                [key rangeOfString:@"ipsec"].location != NSNotFound ||
                [key rangeOfString:@"ppp"].location != NSNotFound){
                flag = YES;
                break;
            }
        }

整个方法

- (BOOL)isVPNOn
{
   BOOL flag = NO;
   NSString *version = [UIDevice currentDevice].systemVersion;
   // need two ways to judge this.
   if (version.doubleValue >= 9.0)
   {
       NSDictionary *dict = CFBridgingRelease(CFNetworkCopySystemProxySettings());
       NSArray *keys = [dict[@"__SCOPED__"] allKeys];
       for (NSString *key in keys) {
           if ([key rangeOfString:@"tap"].location != NSNotFound ||
               [key rangeOfString:@"tun"].location != NSNotFound ||
               [key rangeOfString:@"ipsec"].location != NSNotFound ||
               [key rangeOfString:@"ppp"].location != NSNotFound){
               flag = YES;
               break;
           }
       }
   }
   else
   {
       struct ifaddrs *interfaces = NULL;
       struct ifaddrs *temp_addr = NULL;
       int success = 0;
       
       // retrieve the current interfaces - returns 0 on success
       success = getifaddrs(&interfaces);
       if (success == 0)
       {
           // Loop through linked list of interfaces
           temp_addr = interfaces;
           while (temp_addr != NULL)
           {
               NSString *string = [NSString stringWithFormat:@"%s" , temp_addr->ifa_name];
               if ([string rangeOfString:@"tap"].location != NSNotFound ||
                   [string rangeOfString:@"tun"].location != NSNotFound ||
                   [string rangeOfString:@"ipsec"].location != NSNotFound ||
                   [string rangeOfString:@"ppp"].location != NSNotFound)
               {
                   flag = YES;
                   break;
               }
               temp_addr = temp_addr->ifa_next;
           }
       }
       
       // Free memory
       freeifaddrs(interfaces);
   }


   return flag;
}

这个是判断系统的vpn状态，还有一种是调起vpnExtension或着说NEVPNManager的时候的vpn状态可以通过实例化NEVPNManager，然后通过manager.connection.status来获取当前的vpn状态