Viewing Current State

The following sample code demonstrates how to find all filters that might affect a server application.

Note  The filter conditions are the same as those supported by the downlevel IsPortAllowed API.


#include <windows.h>
#include <fwpmu.h>
#include <stdio.h>

#pragma comment (lib, "fwpuclnt.lib")

#define EXIT_ON_ERROR(fnName) \
   if (result != ERROR_SUCCESS) \
   { \
      printf(#fnName " = 0x%08X\n", result); \
      goto CLEANUP; \
   }

DWORD InitFilterConditions(
         __in_opt PCWSTR appPath,
         __in_opt const SOCKADDR* localAddr,
         __in_opt UINT8 ipProtocol,
         __in UINT32 numCondsIn,
         __out_ecount_part(numCondsIn, *numCondsOut)
            FWPM_FILTER_CONDITION0* conds,
         __out UINT32* numCondsOut,
         __deref_out FWP_BYTE_BLOB** appId
         )
{
    return 0;
}

DWORD FindMatchingFilters(
         __in HANDLE engine,
         __in const GUID* layerKey,
         __in_opt PCWSTR appPath,
         __in_opt const SOCKADDR* localAddr,
         __in_opt UINT8 ipProtocol,
         __deref_out_ecount(*numFilters) FWPM_FILTER0*** filters,
         __out UINT32* numFilters
         )
{
   DWORD result = ERROR_SUCCESS;
   FWPM_FILTER_CONDITION0 conds[4];
   UINT32 numConds;
   FWP_BYTE_BLOB* appBlob = NULL;
   FWPM_FILTER_ENUM_TEMPLATE0 enumTempl;
   HANDLE enumHandle = NULL;

   result = InitFilterConditions(
               appPath,
               &localAddr,
               ipProtocol,
               ARRAYSIZE(conds),
               conds,
               &numConds,
               &appBlob
               );
   EXIT_ON_ERROR(InitFilterConditions);

   memset(&enumTempl, 0, sizeof(enumTempl));
   enumTempl.layerKey = *layerKey;
   enumTempl.numFilterConditions = numConds;
   if (numConds > 0)
   {
      enumTempl.filterCondition = conds;
   }
   // We want to see all filters regardless of action.
   enumTempl.actionMask = 0xFFFFFFFF;

   result = FwpmFilterCreateEnumHandle0(
               engine,
               &enumTempl,
               &enumHandle
               );
   EXIT_ON_ERROR(FwpmFilterCreateEnumHandle0);

   result = FwpmFilterEnum0(
               engine,
               enumHandle,
               INFINITE,
               filters,
               numFilters
               );
   EXIT_ON_ERROR(FwpmFilterEnum0);

CLEANUP:
   FwpmFilterDestroyEnumHandle0(engine, enumHandle);
   FwpmFreeMemory0((void**)&appBlob);
   return result;
}

DWORD wmain(int argc,
            wchar_t* argv[])
{
   UNREFERENCED_PARAMETER(argc);
   UNREFERENCED_PARAMETER(argv);
   
   // Open a session to the filter engine
   HANDLE engineHandle = 0;

   // Use dynamic sessions for efficiency and safety:
   //  - All objects associated with the dynamic session are deleted with one call.
   //  - Filtering policy objects are deleted even when the application crashes. 
   FWPM_SESSION0 session;
   memset(&session, 0, sizeof(session));
   session.flags = FWPM_SESSION_FLAG_DYNAMIC;

   UINT32 numFilters = 0;
   FWPM_FILTER0** filters = 0;
   DWORD result = FwpmEngineOpen0(NULL, RPC_C_AUTHN_WINNT, NULL, &session, &engineHandle);
   EXIT_ON_ERROR(FwpmEngineOpen0);

   result = FindMatchingFilters(
         engineHandle,
         &FWPM_LAYER_ALE_AUTH_LISTEN_V4,
         0,
         0,
         0,
         &filters,
         &numFilters
         );

CLEANUP:  
   if (result != ERROR_SUCCESS)
   {
       printf("Error: %x\n", result);
   }
   else
   {
       for (int i = 0; i < numFilters; i++)
       {
              printf("\n%d. %ws", i + 1, (filters[i])->displayData.name);
       }
       printf("\nSuccess: %d filters", numFilters);
   }

 FwpmFreeMemory0((void**)filters);

 return result;
}


 

 

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