<div class="content"><p> </p><p>The <b>R_DhcpEnumSubnetClientsVQ</b> method is used to retrieve
all DHCPv4 clients serviced from the specified IPv4 subnet. This method returns
DHCPv4 clients from all IPv4 subnets if the subnet address specified is zero.
The caller of this function can free the memory pointed to by the <i>ClientInfo</i>
parameter and its member the <b>Clients</b> array by calling the function <b>midl_user_free</b>
(section <span><a href="a7e5f2d1-04b7-4363-bdc0-76a1099664eb" data-linktype="relative-path">3</a></span>).</p><dl>
<dd>
<div><pre> DWORD R_DhcpEnumSubnetClientsVQ(
   [in, unique, string] DHCP_SRV_HANDLE ServerIpAddress,
   [in] DHCP_IP_ADDRESS SubnetAddress,
   [in, out] DHCP_RESUME_HANDLE* ResumeHandle,
   [in] DWORD PreferredMaximum,
   [out] LPDHCP_CLIENT_INFO_ARRAY_VQ* ClientInfo,
   [out] DWORD* ClientsRead,
   [out] DWORD* ClientsTotal
 );
</pre></div>
</dd></dl><p><b>ServerIpAddress: </b>The IP address/host name of
the DHCP server. This parameter is unused.</p><p><b>SubnetAddress: </b>This is of type <span><a href="5122557b-b85d-4982-8ffb-98d8d934e353" data-linktype="relative-path">DHCP_IP_ADDRESS (section 2.2.1.2.1)</a></span>
that contains the IPv4 subnet ID from which DHCPv4 clients are enumerated. If
this parameter is set to 0, the DHCPv4 clients from all the IPv4 subnets are
returned.</p><p><b>ResumeHandle: </b>This is a pointer of type <span><a href="a6e4cdc0-4f71-4922-ade1-7a5392f9e920" data-linktype="relative-path">DHCP_RESUME_HANDLE (section 2.2.1.2.6)</a></span>
that identifies the enumeration operation. Initially, this value MUST be set to
zero, with a successful call returning the handle value used for subsequent
enumeration requests. This field contains the last IPv4 address retrieved.</p><p><b>PreferredMaximum: </b>This is of type <span><a href="../ms-dtyp/262627d8-3418-4627-9218-4ffe110850b2" data-linktype="relative-path">DWORD</a></span>,
specifying the preferred maximum number of bytes to return. The minimum value
is 1,024 bytes (1 kilobyte), and the maximum value is 65,536 bytes (64
kilobytes); if the input value is greater or less than this range, it MUST be
set to the maximum or minimum value, respectively. To retrieve all the DHCPv4
clients serviced by a specific IPv4 subnet, 0xFFFFFFFF is specified.</p><p><b>ClientInfo: </b>This is a pointer of type <span><a href="5f96067f-e22c-40bd-9f65-bde24f1ca5fa" data-linktype="relative-path">LPDHCP_CLIENT_INFO_ARRAY_VQ</a></span>
that points to the location that contains the DHCPv4 client lease record array.</p><p><b>ClientsRead: </b>This is a pointer to a DWORD that
specifies the number of DHCPv4 client lease records read in the <i>ClientInfo</i>
parameter. The caller MUST allocate memory for this parameter equal to the size
of data type DWORD.</p><p><b>ClientsTotal: </b>This is a pointer to a DWORD
that specifies the number of DHCPv4 client lease records remaining from the
current position. For example, if there are 100 DHCPv4 lease record clients for
an IPv4 subnet, and if 10 DHCPv4 lease records are enumerated per call, then
for the first time this would have a value of 90.<a id="Appendix_A_Target_42"></a><a aria-label="Product behavior note 42" href="afab0546-79ae-4764-8dab-27a85cca5145#Appendix_A_42" data-linktype="relative-path">&lt;42&gt;</a> The
caller MUST allocate memory for this parameter equal to the size of data type
DWORD.</p><p><b>Return Values: </b>A 32-bit unsigned integer value
that indicates return status. A return value ERROR_SUCCESS (0x00000000)
indicates that the operation was completed successfully, else it contains a
Win32 error code, as specified in <span><a href="../ms-erref/1bc92ddf-b79e-413c-bbaa-99a5281a6c90" data-linktype="relative-path">[MS-ERREF]</a></span>.
This error code value can correspond to a DHCP-specific failure, which takes a
value between 20000 and 20099, or any generic failure.</p><dl>
<dd>
<table><thead>
  <tr>
   <th>
   <p>Return value/code</p>
   </th>
   <th>
   <p>Description</p>
   </th>
  </tr>
 </thead><tbody><tr>
  <td>
  <p>0x00000000</p>
  <p>ERROR_SUCCESS</p>
  </td>
  <td>
  <p>The call was successful.</p>
  </td>
 </tr><tr>
  <td>
  <p>0x000000EA</p>
  <p>ERROR_MORE_DATA</p>
  </td>
  <td>
  <p>There are more elements available to enumerate.</p>
  </td>
 </tr><tr>
  <td>
  <p>0x00000103</p>
  <p>ERROR_NO_MORE_ITEMS</p>
  </td>
  <td>
  <p>There are no more elements left to enumerate.</p>
  </td>
 </tr><tr>
  <td>
  <p>0x00004E2D</p>
  <p>ERROR_DHCP_JET_ERROR</p>
  </td>
  <td>
  <p>An error occurred while accessing the DHCP server
  database.</p>
  </td>
 </tr></tbody></table>
</dd></dl><p>The opnum field value for this method is 47.</p><p>When processing this call, the DHCP server MUST do the
following:</p><ul><li><p><span><span> 
</span></span>Validate that this method is authorized for read access per
section <span><a href="baec2112-1146-4c42-b77e-b706e170a590" data-linktype="relative-path">3.5.4</a></span>. If not,
return the error ERROR_ACCESS_DENIED.</p>
</li><li><p><span><span> 
</span></span>Retrieve the <b>DHCPv4ClientsList</b> ADM element member of the <b>DHCPv4Scope</b>
ADM element entry corresponding to the <i>SubnetAddress</i> parameter from the
server ADM element <b>DHCPv4ScopesList</b>. If the <i>SubnetAddress</i>
parameter is 0, retrieve <b>DHCPv4ClientsList</b> ADM element member of all the
<b>DHCPv4Scope</b> ADM element entries in server ADM element <b>DHCPv4ScopesList</b>.</p>
</li><li><p><span><span> 
</span></span>If the <i>SubnetAddress</i> parameter is non-zero and the <b>DHCPv4Scope</b>
ADM element object corresponding to it is not found, then point parameters <i>ClientsRead</i>,
<i>ClientsTotal</i> and <i>ResumeHandle</i> to 0. Also set the <i>NumElements</i>
member in the <i>ClientInfo</i> parameter to 0 and return ERROR_SUCCESS.</p>
</li><li><p><span><span> 
</span></span>If the <i>ResumeHandle</i> parameter points to 0x00000000, the
enumeration MUST start from the first entry of the <b>DHCPv4ClientsList</b> ADM
element.</p>
</li><li><p><span><span> 
</span></span>If the <i>ResumeHandle</i> parameter points to 0x00000000, and
there are no entries in the <b>DHCPv4ClientsList</b> ADM element of all the <b>DHCPv4Scope</b>
ADM element entries present in the <b>DHCPv4ScopesList</b> ADM element, then
return ERROR_NO_MORE_ITEMS. If there are no entries in the <b>DHCPv4ClientsList</b>
ADM element of <b>DHCPv4Scope</b> ADM element entry corresponding to the <i>SubnetAddress</i>
parameter on the DHCPv4 server database, but there are <b>DHCPv4Client</b> ADM
element entries in the <b>DHCPv4ClientsList</b> ADM element of other <b>DHCPv4Scope</b>
ADM element entries configured on the server, then return ERROR_SUCCESS.</p>
</li><li><p><span><span> 
</span></span>If the <i>ResumeHandle</i> parameter points to a nonzero value,
the server MUST continue enumeration based on the value of <i>ResumeHandle</i>.
If the IPv4 address contained in the <i>ResumeHandle</i> parameter does not
match the <b>ClientIpAddress</b> member of any <b>DHCPv4Client</b> ADM element
in any of the <b>DHCPv4Scope</b> ADM element entries corresponding to the <i>SubnetAddress</i>
parameter or when the specified <i>SubnetAddress</i> parameter value is 0x0,
then return ERROR_DHCP_JET_ERROR.</p>
</li><li><p><span><span> 
</span></span>The <i>PreferredMaximum</i> parameter specifies the maximum
number of bytes that the server can allocate and return to the caller
containing the data related to the DHCPv4 client <span><a href="a9d6a415-4de6-4058-befe-ca2e42764485#gt_e6d76b31-2852-4bd5-8fbb-8e82a3cedb29" data-linktype="relative-path">lease records</a></span>.</p>
</li><li><p><span><span> 
</span></span>If the <i>PreferredMaximum</i> parameter is less than 1024, it is
assigned 1024, and if the <i>PreferredMaximum</i> parameter is greater than
65536, it is assigned 65536.</p>
</li><li><p><span><span> 
</span></span>The actual number of records that corresponds to a given <i>PreferredMaximum</i>
value can be determined only at runtime.</p>
</li><li><p><span><span> 
</span></span>Allocate memory for <i>PreferredMaximum</i> number of bytes.</p>
</li><li><p><span><span> 
</span></span>Copy the <b>DHCPv4Client</b> ADM element entry from the <b>DHCPv4ClientsList</b>
ADM element entries corresponding to the <i>SubnetAddress</i> parameter in the
allocated memory, and then proceed to the next record. If the <i>SubnetAddress</i>
parameter is zero, copy the <b>DHCPv4Client</b> ADM element entry from all <b>DHCPv4ClientsList</b>
members of all the <b>DHCPv4Scope</b> ADM element entries in the server ADM
element <b>DHCPv4ScopesList</b>.</p>
</li><li><p><span><span> 
</span></span>If the retrieve operation has reached the maximum number of <b>DHCPv4Client</b>
ADM element entries that can be accommodated in the <i>PreferredMaximum</i>
parameter, and there are still more <b>DHCPv4Client</b> ADM element entries in <b>DHCPv4ClientsList</b>
ADM element entries, set the <i>ClientsTotal</i> parameter to the number of <b>DHCPv4Client</b>
ADM element entries that are not yet enumerated, and set the <i>ClientsRead</i>
parameter to the number of <b>DHCPv4Client</b> ADM element entries that are
enumerated in this retrieve operation. Set the <i>ResumeHandle</i> parameter to
the <b>ClientIpAddress</b> member of the last <b>DHCPv4Client</b> ADM element
entry read, and return ERROR_MORE_DATA.</p>
</li><li><p><span><span> 
</span></span>If the number of bytes specified by the <i>PreferredMaximum</i>
parameter is more than the total memory occupied by <b>DHCPv4Client</b> ADM
element entries, set the <i>ClientsTotal</i> parameter to the total number of <b>DHCPv4Client</b>
ADM element entries enumerated in that retrieve operation, and set the <i>ClientsRead</i>
parameter to the number of <b>DHCPv4Client</b> ADM element entries that are
enumerated in this retrieve operation. Set the <i>ResumeHandle</i> parameter to
0, and return ERROR_SUCCESS.</p>
</li></ul><p><b>Exceptions Thrown:</b> No exceptions SHOULD be thrown
beyond those thrown by the underlying RPC protocol <span><a href="../ms-rpce/290c38b1-92fe-4229-91e6-4fc376610c15" data-linktype="relative-path">[MS-RPCE]</a></span>.</p></div>