LPNSPLOOKUPSERVICEBEGIN callback function (ws2spi.h)

Article
10/13/2021

The NSPLookupServiceBegin function initiates a client query of a name service provider that is constrained by the information contained within a WSAQUERYSET structure.

NSPLookupServiceBegin only returns a handle, which should be used by subsequent calls to NSPLookupServiceNext to get the actual results. Because this operation cannot be canceled, it should be implemented to execute quickly. While it is acceptable to initiate a network query, this function should not require a response to return successfully.

Syntax

LPNSPLOOKUPSERVICEBEGIN Lpnsplookupservicebegin;

INT Lpnsplookupservicebegin(
  [in]  LPGUID lpProviderId,
  [in]  LPWSAQUERYSETW lpqsRestrictions,
  [in]  LPWSASERVICECLASSINFOW lpServiceClassInfo,
  [in]  DWORD dwControlFlags,
  [out] LPHANDLE lphLookup
)
{...}

Parameters

[in] lpProviderId

A pointer to the name service provider identifier to query.

[in] lpqsRestrictions

A pointer to the search criteria. See Remarks.

[in] lpServiceClassInfo

A pointer to the WSASERVICECLASSINFO structure that contains schema information for the service.

[in] dwControlFlags

A value that controls the depth of the search.

Value	Meaning
LUP_DEEP 0x0001	Queries down the hierarchy of a provider as opposed to just the first level.
LUP_CONTAINERS 0x0002	Returns containers only.
LUP_NOCONTAINERS 0x0004	Returns no containers.
LUP_NEAREST 0x0008	If possible, returns results in the order of distance. The measure of distance is provider specific.
LUP_RETURN_NAME 0x0010	Retrieves the name as lpszServiceInstanceName.
LUP_RETURN_TYPE 0x0020	Retrieves the type as lpServiceClassId.
LUP_RETURN_VERSION 0x0040	Retrieves the version as lpVersion.
LUP_RETURN_COMMENT 0x0080	Retrieves the comment as lpszComment.
LUP_RETURN_ADDR 0x0100	Retrieves the addresses as lpcsaBuffer.
LUP_RETURN_BLOB 0x0200	Retrieves the private data as lpBlob.
LUP_RETURN_ALIASES 0x0400	Any available alias information is to be returned in successive calls to NSPLookupServiceNext, and each alias returned will have the RESULT_IS_ALIAS flag set.
LUP_RETURN_QUERY_STRING 0x0800	Retrieves the query string as lpszQueryString.
LUP_RETURN_ALL 0x0ff0	Retrieves information including the name, type, version, comment, address, blob, aliases, and query string.
LUP_FLUSHCACHE 0x1000	If the provider has cached information, ignore the cache and query the namespace itself.
LUP_FLUSHPREVIOUS 0x2000	Used as a value for the dwControlFlags parameter in NSPLookupServiceNext. Setting this flag instructs the provider to discard the last result set, which was too large for the supplied buffer, and move on to the next result set.
LUP_NON_AUTHORITATIVE 0x4000	Indicates that the namespace provider should included non-authoritative results for names.
LUP_RES_RESERVICE 0x8000	Indicates whether prime response is in the remote or local part of CSADDR_INFO structure. The other part must be usable in either case. This option applies only to service instance requests.
LUP_SECURE 0x8000	Indicates that the namespace provider should use a secure query. This option only applies to name query requests.
LUP_RETURN_PREFERRED_NAMES 0x10000	Indicates that the namespace provider should return only preferred names.
LUP_ADDRCONFIG 0x100000	Indicates that the namespace provider should return the address configuration.
LUP_DUAL_ADDR 0x200000	Indicates that the namespace provider should return the dual addresses. This option only applies to dual-mode sockets (IPv6 and IPv4 mapped addresses).

[out] lphLookup

A pointer to the handle to be used in subsequent calls to NSPLookupServiceNext in order to retrieve the results set.

Return value

The function should return NO_ERROR (zero) if the routine succeeds. It should return SOCKET_ERROR (–1) if the routine fails and it must set the appropriate error code using WSASetLastError.

Error code	Meaning
WSA_NOT_ENOUGH_MEMORY	There is not enough memory available to perform this operation.
WSAEINVAL	One or more parameters were invalid, or missing, for this provider.
WSAEOPNOTSUPP	The operation is not supported. This error is returned if the namespace provider does not implement this function.
WSANO_DATA	The name was found in the database, but it does not have the correct associated data that is resolved for.
WSASERVICE_NOT_FOUND	Service is unknown. The service cannot be found in the specified namespace.

Remarks

If LUP_CONTAINERS is specified in a call, avoid all other restriction values. If any are supplied, the name service provider must decide if it can support this restriction over the containers. If not, it should return an error.

Some name service providers may have other means of finding containers. For example, containers can all be of some well-known type, or of a set of well-known types, and therefore a query restriction could be created for finding them. No matter what other means the name service provider has for locating containers, LUP_CONTAINERS and LUP_NOCONTAINERS take precedence. Therefore, if a query restriction is given that includes containers, specifying LUP_NOCONTAINERS will prevent the container items from being returned. Similarly, no matter what the query restriction, if LUP_CONTAINERS is given, only containers should be returned. If a namespace does not support containers and LUP_CONTAINERS is specified, it should return WSANO_DATA.

The preferred method of obtaining the containers within another container, is the call:

dwStatus = NSPLookupServiceBegin(
    lpqsRestrictions,
    LUP_CONTAINERS,
    lphLookup);

followed by the requisite number of NSPLookupServiceNext calls. This will return all containers contained immediately within the starting context; that is, it is not a deep query. With this, one can map the address space structure by walking the hierarchy, perhaps enumerating the content of selected containers. Subsequent uses of NSPLookupServiceBegin use the containers returned from a previous call.

Forming Queries

As mentioned, a WSAQUERYSET structure is used as an input parameter to NSPLookupServiceBegin to qualify the query. The following table lists WSAQUERYSET member names and describes how the WSAQUERYSET is used to construct a query. When a member is marked as (Optional) a null pointer can be supplied, indicating that the parameter will not be used as a search criteria. For more information, see Query-Related Data Structures.

WSAQUERYSET member name	Query interpretation
dwSize	Will be set to sizeof(WSAQUERYSET). This is a versioning mechanism.
dwOutputFlags	Ignored for queries.
lpszServiceInstanceName	Optional. Referenced string contains service name. The semantics for wildcarding within the string are not defined, but can be supported by certain namespace providers.
lpServiceClassId	Required. GUID corresponding to the service class.
lpVersion	Optional. References desired version number and provides version comparison semantics (that is, version must match exactly, or version must be not less than the value supplied).
lpszComment	Ignored for queries.
dwNameSpace	Identifier of a single namespace in which to constrain the search, or NS_ALL to include all namespaces.
lpNSProviderId	Optional. References the GUID of a specific namespace provider and limits the query to this provider only.
lpszContext	Optional. Specifies the starting point of the query in a hierarchical namespace.
dwNumberOfProtocols	Size, in bytes, of the number of entries in the protocol constraint array, can be zero.
lpafpProtocols	Optional. A references to an array of AFPROTOCOLS structures. Only services that use these protocols will be returned. It is permissible for the value AF_UNSPEC to appear as a protocol family value, signifying a wildcard. Namespace providers may supply information about any service that uses the corresponding protocol, regardless of address family.
lpszQueryString	Optional. Some namespaces (such as whois++) support rich SQL-like queries contained in a simple text string. This parameter is used to specify that string.
dwNumberOfCsAddrs	Ignored for queries.
lpcsaBuffer	Ignored for queries.
lpBlob	Optional. A pointer to a provider-specific entity.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	ws2spi.h

WSAQUERYSET member name	Query interpretation
dwSize	Will be set to sizeof(WSAQUERYSET). This is a versioning mechanism.
dwOutputFlags	Ignored for queries.
lpszServiceInstanceName	Optional. Referenced string contains service name. The semantics for wildcarding within the string are not defined, but can be supported by certain namespace providers.
lpServiceClassId	Required. GUID corresponding to the service class.
lpVersion	Optional. References desired version number and provides version comparison semantics (that is, version must match exactly, or version must be not less than the value supplied).
lpszComment	Ignored for queries.
dwNameSpace	Identifier of a single namespace in which to constrain the search, or NS_ALL to include all namespaces.
lpNSProviderId	Optional. References the GUID of a specific namespace provider and limits the query to this provider only.
lpszContext	Optional. Specifies the starting point of the query in a hierarchical namespace.
dwNumberOfProtocols	Size, in bytes, of the number of entries in the protocol constraint array, can be zero.
lpafpProtocols	Optional. A references to an array of AFPROTOCOLS structures. Only services that use these protocols will be returned. It is permissible for the value AF_UNSPEC to appear as a protocol family value, signifying a wildcard. Namespace providers may supply information about any service that uses the corresponding protocol, regardless of address family.
lpszQueryString	Optional. Some namespaces (such as whois++) support rich SQL-like queries contained in a simple text string. This parameter is used to specify that string.
dwNumberOfCsAddrs	Ignored for queries.
lpcsaBuffer	Ignored for queries.
lpBlob	Optional. A pointer to a provider-specific entity.

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