Menggunakan Panggilan Balik Pemberitahuan Peristiwa

Prosedur berikut menguraikan langkah-langkah yang harus digunakan klien untuk menerima pesan pemberitahuan perubahan dari RTM_EVENT_CALLBACK. Kode sampel yang mengikuti menunjukkan cara menerapkan prosedur.

Cara mengambil pesan pemberitahuan perubahan

1. Panggil RtmGetChangedDests untuk mengambil serangkaian perubahan.
2. Proses perubahan.
3. Rilis tujuan menggunakan RtmReleaseChangedDests.
4. Ulangi langkah 1, 2, dan 3 hingga RtmGetChangedDests mengembalikan ERROR_NO_MORE_ITEMS.

Contoh kode berikut menunjukkan cara memproses panggilan balik RTM_EVENT_CALLBACK yang diterima dari manajer tabel perutean.

#include <windows.h>
#include <ras.h>

// Macro to allocate an RTM_DEST_INFO on the stack
#define ALLOC_RTM_DEST_INFO(NumViews, NumInfos)
        (PRTM_DEST_INFO) _alloca(RTM_SIZE_OF_DEST_INFO(NumViews) * NumInfos)

// Routing table manager entity event callback

DWORD
EntityEventCallback (
    IN      RTM_ENTITY_HANDLE               RtmRegHandle,
    IN      RTM_EVENT_TYPE                  EventType,
    IN      PVOID                           Context1,
    IN      PVOID                           Context2
    )
{
    RTM_ENTITY_HANDLE EntityHandle;
    PENTITY_CHARS     EntityChars;
    PRTM_ENTITY_INFO  EntityInfo;
    RTM_NOTIFY_HANDLE NotifyHandle;
    PRTM_DEST_INFO    DestInfos;
    ULONG             DestInfoSize;
    UINT              NumDests;
    UINT              NumViews, i;
    UINT              MaxHandles;
    RTM_ROUTE_HANDLE  RouteHandle;
    PRTM_ROUTE_INFO   RoutePointer;
    DWORD             ChangeFlags;
    DWORD             Status;

    Print("\nEvent callback called for %p :", RtmRegHandle);

    Print("\n\tEntity Event = ");

    Status = ERROR_NOT_SUPPORTED;

    switch (EventType)
    {
    case RTM_ENTITY_REGISTERED:

                // Get the handle and information of the entity that registered
        
        EntityHandle = (RTM_ENTITY_HANDLE) Context1;
        EntityInfo   = (PRTM_ENTITY_INFO)  Context2;

        Print("Registration\n\tEntity Handle = %p\n\tEntity IdInst = %p\n\n",
              EntityHandle,
              EntityInfo->EntityId);

                // Do something if you are interested in the entity
                ;

        Status = NO_ERROR;
        break;

    case RTM_ENTITY_DEREGISTERED:

                // Get the handle and information of the entity that deregistered
        
        EntityHandle = (RTM_ENTITY_HANDLE) Context1;
        EntityInfo   = (PRTM_ENTITY_INFO)  Context2;

        Print("Deregistration\n\tEntity Handle = %p\n\tEntity IdInst = %p\n\n",
               EntityHandle,
              EntityInfo->EntityId);

                // Do something if you are interested in the entity
                ;

        Status = NO_ERROR;
        break;

    case RTM_CHANGE_NOTIFICATION:

        // Get the notification registration on which changes exist and
        // context supplied in RtmRegisterForChangeNotification
        
        NotifyHandle = (RTM_NOTIFY_HANDLE) Context1;

        NotifyContext = (PVOID) Context2; // Unused

        Print("Changes Available\n\tNotify Handle = %p\n\tNotify Context = %p\n\n",
              NotifyHandle,
              NotifyContext);

        MaxHandles = RegnProfile.MaxHandlesInEnum;

        NumViews = RegnProfile.NumberOfViews;

        DestInfoSize = RTM_SIZE_OF_DEST_INFO(NumViews);

                // Get all changes to destinations
        
        DestInfos = ALLOC_RTM_DEST_INFO(NumViews, MaxHandles);

        do
        {
            // Try to get as many as possible in one routing table managercall
            NumDests = MaxHandles;

            Status = RtmGetChangedDests(RtmRegHandle,
                                        NotifyHandle,
                                        &NumDests,
                                        DestInfos);

            ASSERT((Status == NO_ERROR) || (Status == ERROR_NO_MORE_ITEMS));

            DestInfo = (PRTM_DEST_INFO) DestInfos;

            for (i = 0; i < NumDests; i++)
            {
                                // Process the current destination information
                
                // Assuming you asked for unicast view information,
                ASSERT(DestInfo->ViewInfo[0].ViewId == RTM_VIEW_ID_UCAST);

                // Get the best unicast route for the destination.
                NewBestRoute = DestInfo.ViewInfo[0].Route;

                // Do whatever you want with above route
                ...

                // Move to the next changed one
                DestInfo = (PRTM_DEST_INFO) ((PUCHAR)DestInfo + DestInfoSize);
            }

            RtmReleaseChangedDests(RtmRegHandle,
                                   NotifyHandle,
                                   NumDests,
                                   DestInfos);
        }
        while (NumDests > 0);

        Status = NO_ERROR;
        break;

    case RTM_ROUTE_EXPIRED:

                // Get handle and a direct pointer to the route whose timer expired
        
        RouteHandle = (RTM_ROUTE_HANDLE) Context1;

        RoutePointer = (PRTM_ROUTE_INFO) Context2;

        Print("Route Aged Out\n\tRoute Handle = %p\n\tRoute Pointer = %p\n\n",
               RouteHandle,
              RoutePointer);

        // To just let the routing table manager delete the route, return ERROR_NOT_SUPPORTED
        // If you return any other value, the routing table manager assumes that you have
        // handled the time-out condition in callback for route timer expiration
        
        // Suppose we just want to update the metric and leave the route 

        Status = RtmLockRoute(RtmRegHandle,
                              RouteHandle,
                              TRUE,
                              TRUE,
                              NULL);

        // Check(Status, 46);

        if (Status == NO_ERROR)
        {
            // Set the metric to indicate that it is unreachable
            RoutePointer->PrefInfo.Metric = METRIC_UNREACHABLE;

            Status = RtmUpdateAndUnlockRoute(RtmRegHandle,
                                             RouteHandle,
                                             INFINITE,        // To stay forever
                                             NULL,
                                             0,
                                             NULL,
                                             &ChangeFlags);
            ASSERT(Status == NO_ERROR);
        }

        // If ERROR_NOT_SUPPORTED not returned, release the handle
        RtmReleaseRoutes(RtmRegHandle, 1, &RouteHandle);

        Status = NO_ERROR;
        break;
    }

    return Status;
}