LPNSPV2LOOKUPSERVICEBEGIN callback function (ws2spi.h)

Article
10/13/2021

The NSPv2LookupServiceBegin function initiates a client query of a namespace version-2 service provider that is constrained by the information contained within a WSAQUERYSET2 structure.

Syntax

LPNSPV2LOOKUPSERVICEBEGIN Lpnspv2lookupservicebegin;

INT Lpnspv2lookupservicebegin(
  [in]  LPGUID lpProviderId,
  [in]  LPWSAQUERYSET2W lpqsRestrictions,
  [in]  DWORD dwControlFlags,
  [out] LPVOID lpvClientSessionArg,
  [out] LPHANDLE lphLookup
)
{...}

Parameters

[in] lpProviderId

A pointer to the identifier for the namespace service provider to query.

[in] lpqsRestrictions

A pointer to the search criteria. See Remarks.

[in] dwControlFlags

A set of flags that affect the search. This parameter can be a combination of the following values defined in the Winsock2.h header file.

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 NSPv2LookupServiceNextEx, 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 NSPv2LookupServiceNextEx. 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).
LUP_DISABLE_IDN_ENCODING 0x800000	Indicates that the namespace provider should disable automatic International Domain Names encoding. This value is supported on Windows 8 and Windows Server 2012

[out] lpvClientSessionArg

A pointer to the client session.

[out] lphLookup

A pointer to the handle to be used in subsequent calls to NSPv2LookupServiceNextEx 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 (that is, 1) if the routine fails and it must set the appropriate error code using WSASetLastError.

Error code	Meaning
WSAEINVAL	One or more parameters were invalid, or missing, for this provider.
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	The service is unknown. The service cannot be found in the specified namespace.
WSA_NOT_ENOUGH_MEMORY	There is not enough memory available to perform this operation.

Remarks

The NSPv2LookupServiceBegin function is used as part of the namespace service provider version-2 (NSPv2) architecture available on Windows Vista and later.

On Windows Vista and Windows Server 2008, the NSPv2LookupServiceBegin function can only be used for operations on NS_EMAIL namespace providers.

The NSPv2LookupServiceBegin function only returns a handle, which should be used by subsequent calls to NSPv2LookupServiceNextEx 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.

The NSPv2Startup function is called each time a new client process begins using namespace provider. Providers may use the client session argument pointed to by the ppvClientSessionArg parameter to store information about this session. If a value was specified for the client session argument in the call to the NSPv2Startup function, then this same client session argument is passed in the lpvClientSessionArg parameter to the NSPv2LookupServiceBegin function.

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 = NSPv2LookupServiceBegin(
    lpProviderId,
    lpqsRestrictions,
    LUP_CONTAINERS,
    lpClientSession,
    lphLookup);

followed by the requisite number of NSPv2LookupServiceNextEx 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 NSPv2LookupServiceBegin use the containers returned from a previous call.

Forming Queries

The WSAQUERYSET2 structure is used as an input parameter to NSPv2LookupServiceBegin to qualify the query. The following table lists **WSAQUERYSET2** member names and describes how the **WSAQUERYSET2** is used to construct a query. Members labeled as optional and dependent on the requirements of the NSPv2 provider may be supplied as a **NULL** pointer when unused as a search criteria by the namespace provider. For more information, see Query-Related Data Structures.

WSAQUERYSET2 member name	Query interpretation
dwSize	Will be set to sizeof(WSAQUERYSET2). This is a versioning mechanism.
lpszServiceInstanceName	A string that contains the service name. The semantics for wildcarding within the string are not defined, but can be supported by certain namespace providers. This member is optional, dependent on the requirements of the NSPv2 service provider.
lpVersion	The desired version number that provides version comparison semantics (that is, version must match exactly, or version must be not less than the value supplied). This member is optional, dependent on the requirements of the NSPv2 service provider.
lpszComment	This member is ignored for queries.
dwNameSpace	The identifier of a single namespace in which to constrain the search, or NS_ALL to include all namespaces.
lpNSProviderId	The GUID of a specific namespace provider that limits the query to this provider only. This member is optional, dependent on the requirements of the NSPv2 service provider.
lpszContext	The starting point of the query in a hierarchical namespace. This member is optional, dependent on the requirements of the NSPv2 service provider.
dwNumberOfProtocols	The size, in bytes, of the number of entries in the protocol constraint array. This member can be zero.
lpafpProtocols	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. This member is optional, dependent on the requirements of the NSPv2 service provider.
lpszQueryString	Some namespaces (such as whois++) support rich SQL-like queries contained in a simple text string. This parameter is used to specify that string.This member is optional, dependent on the requirements of the NSPv2 service provider.
dwNumberOfCsAddrs	This member is ignored for queries.
lpcsaBuffer	This member is ignored for queries.
dwOutputFlags	This member is ignored for queries.
lpBlob	A pointer to a provider-specific entity. This member is optional, dependent on the requirements of the NSPv2 service provider.

Requirements

Requirement	Value
Minimum supported client	Windows Vista [desktop apps only]
Minimum supported server	Windows Server 2008 [desktop apps only]
Target Platform	Windows
Header	ws2spi.h

WSAQUERYSET2 member name	Query interpretation
dwSize	Will be set to sizeof(WSAQUERYSET2). This is a versioning mechanism.
lpszServiceInstanceName	A string that contains the service name. The semantics for wildcarding within the string are not defined, but can be supported by certain namespace providers. This member is optional, dependent on the requirements of the NSPv2 service provider.
lpVersion	The desired version number that provides version comparison semantics (that is, version must match exactly, or version must be not less than the value supplied). This member is optional, dependent on the requirements of the NSPv2 service provider.
lpszComment	This member is ignored for queries.
dwNameSpace	The identifier of a single namespace in which to constrain the search, or NS_ALL to include all namespaces.
lpNSProviderId	The GUID of a specific namespace provider that limits the query to this provider only. This member is optional, dependent on the requirements of the NSPv2 service provider.
lpszContext	The starting point of the query in a hierarchical namespace. This member is optional, dependent on the requirements of the NSPv2 service provider.
dwNumberOfProtocols	The size, in bytes, of the number of entries in the protocol constraint array. This member can be zero.
lpafpProtocols	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. This member is optional, dependent on the requirements of the NSPv2 service provider.
lpszQueryString	Some namespaces (such as whois++) support rich SQL-like queries contained in a simple text string. This parameter is used to specify that string.This member is optional, dependent on the requirements of the NSPv2 service provider.
dwNumberOfCsAddrs	This member is ignored for queries.
lpcsaBuffer	This member is ignored for queries.
dwOutputFlags	This member is ignored for queries.
lpBlob	A pointer to a provider-specific entity. This member is optional, dependent on the requirements of the NSPv2 service provider.

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