L2TPOverIPsec VPN stopped working with initWithRemoteNetwork

Hi

I am building NETransparentProxyProvider proxy. Observing a problem with L2TP over IPsec VPN. As soon as the following UDP filter is set. L2TP over IPSec VPN is disconnected after some time.

 includeRule = [[NENetworkRule alloc] initWithRemoteNetwork:nil
                                 remotePrefix:0
                                 localNetwork:nil
                                  localPrefix:0
                                   protocol:NENetworkRuleProtocolUDP
                                   direction:NETrafficDirectionOutbound];

In this case, Wireshark capture shows only outgoing packets on the ppp0 interface.

I also set up exception rules:

1. 500/4500 UDP ports bypass.

  NSString *ipAddress = [NSString stringWithUTF8String:"0.0.0.0"];
  NSString *portNum = [NSString stringWithUTF8String: "500"];
  NWHostEndpoint *endpoint = [NWHostEndpoint endpointWithHostname:ipAddress port:portNum];
  NENetworkRule *rule = [[NENetworkRule alloc]
                  initWithDestinationNetwork:endpoint
                  prefix:0 protocol:NENetworkRuleProtocolAny];
  [excludeRules addObject:rule];
   
  ipAddress = [NSString stringWithUTF8String:"0.0.0.0"];
  portNum = [NSString stringWithUTF8String: "4500"];
  endpoint = [NWHostEndpoint endpointWithHostname:ipAddress port:portNum];
  rule = [[NENetworkRule alloc]
      initWithDestinationNetwork:endpoint
      prefix:0 protocol:NENetworkRuleProtocolAny];
  [excludeRules addObject:rule];

1. Always returning NO in handleNewUDPFlow

  initialRemoteEndpoint:(NWEndpoint *)remoteEndpoint {
    return NO;
}

Both options did not resolve the issue.

Please let give me some pointers to resolve it.

I am running 11.3.1