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Resolving Host Names and IP Addresses

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Beginning with Windows 7, a kernel name resolution feature allows kernel-mode components to perform protocol-independent translation between Unicode host names and transport addresses. You can use the following Winsock Kernel (WSK) client-level functions to perform this name resolution:

These functions perform name-address translation similarly to the user-mode functions FreeAddrInfoW, GetAddrInfoW, and GetNameInfoW, respectively.

To take advantage of this feature, you must compile or recompile your driver with the NTDDI_VERSION macro set to NTDDI_WIN7 or greater.

In order for your driver to use kernel name resolution functionality, it must perform the following calling sequence:

  1. Call WskRegister to register with WSK.

  2. Call WskCaptureProviderNPI to capture the WSK provider Network Programming Interface (NPI).

  3. When you are done using the WSK provider NPI, call WskReleaseProviderNPI to release the WSK provider NPI.

  4. Call WskDeregister to deregister the WSK application.

The following code example uses the above calling sequence to show how a WSK application can call the WskGetAddressInfo function to translate a host name to a transport address.

NTSTATUS
SyncIrpCompletionRoutine(
    __in PDEVICE_OBJECT Reserved,
    __in PIRP Irp,
    __in PVOID Context
    )
{    
    PKEVENT compEvent = (PKEVENT)Context;
    UNREFERENCED_PARAMETER(Reserved);
    UNREFERENCED_PARAMETER(Irp);
    KeSetEvent(compEvent, 2, FALSE);    
    return STATUS_MORE_PROCESSING_REQUIRED;
}

NTSTATUS
KernelNameResolutionSample(
    __in PCWSTR NodeName,
    __in_opt PCWSTR ServiceName,
    __in_opt PADDRINFOEXW Hints,
    __in PWSK_PROVIDER_NPI WskProviderNpi
    )
{
    NTSTATUS status;
    PIRP irp;
    KEVENT completionEvent;
    UNICODE_STRING uniNodeName, uniServiceName, *uniServiceNamePtr;
    PADDRINFOEXW results;

    PAGED_CODE();
    //
    // Initialize UNICODE_STRING structures for NodeName and ServiceName 
    //
 
    RtlInitUnicodeString(&uniNodeName, NodeName);

    if(ServiceName == NULL) {
        uniServiceNamePtr = NULL;
    }
    else {
        RtlInitUnicodeString(&uniServiceName, ServiceName);
        uniServiceNamePtr = &uniServiceName;
    }

    //
    // Use an event object to synchronously wait for the 
    // WskGetAddressInfo request to be completed. 
    //
 
    KeInitializeEvent(&completionEvent, SynchronizationEvent, FALSE);

    //
    // Allocate an IRP for the WskGetAddressInfo request, and set the 
    // IRP completion routine, which will signal the completionEvent
    // when the request is completed.
    //
 
    irp = IoAllocateIrp(1, FALSE);
    if(irp == NULL) {
        return STATUS_INSUFFICIENT_RESOURCES;
    }        

    IoSetCompletionRoutine(irp, SyncIrpCompletionRoutine, 
  &completionEvent, TRUE, TRUE, TRUE);

    //
    // Make the WskGetAddressInfo request.
    //
 
    WskProviderNpi->Dispatch->WskGetAddressInfo (
        WskProviderNpi->Client,
        &uniNodeName,
        uniServiceNamePtr,
        NS_ALL,
        NULL, // Provider
        Hints,
        &results, 
        NULL, // OwningProcess
        NULL, // OwningThread
        irp);

    //
    // Wait for completion. Note that processing of name resolution results
    // can also be handled directly within the IRP completion routine, but
    // for simplicity, this example shows how to wait synchronously for 
    // completion.
    //
 
    KeWaitForSingleObject(&completionEvent, Executive, 
                        KernelMode, FALSE, NULL);

    status = irp->IoStatus.Status;

    IoFreeIrp(irp);

    if(!NT_SUCCESS(status)) {
        return status;
    }

    //
    // Process the name resolution results by iterating through the addresses
    // within the returned ADDRINFOEXW structure.
    //
 
   results; // your code here

    //
    // Release the returned ADDRINFOEXW structure when no longer needed.
    //
 
    WskProviderNpi->Dispatch->WskFreeAddressInfo(
        WskProviderNpi->Client,
        results);

    return status;
}