To use the IP Helper functions in kernel mode, miniport drivers must include the Netioapi.h header file, and link against Netio.lib.
When miniport drivers specify EnableDhcp equal to zero they are required to perform the following operations to notify the MB Service about any of the following events:
Set IP address for the MB interface
Set default gateway address
Update DNS addresses
IP addresses and default gateways that are set by using the IP Helper API persist network connect or disconnect events, or both. Therefore, if the new IP address or default gateway, or both, values are different than the values currently set, the miniport driver should first clear the previous values before setting new values on a network connection event.
Note Miniport drivers can find the LUID and Index of the MB interface from the NetLuid or IfIndex members of NDIS_MINIPORT_INIT_PARAMETERS structure that is passed to the miniport driver's MiniportInitializeEx function.
Resetting the IP Address and Gateway Address
Certain changes to the TCP/IP stack, such as the loading of a mandatory filter driver, can remove the IP and gateway addresses set by the IP helper functions. Miniport drivers must reset the IP and gateway addresses if changes to the TCP/IP stack remove the settings.
Miniport drivers should use following procedure to be notified when the addresses are removed, and must be reset again.
During driver initialization, miniport drivers should specify a callback function to register for IP interface change notifications using NotifyIpInterfaceChange. Windows will call the function wheneven an IP interface is added, deleted or changed.
During adapter initialization, miniport drivers should save in miniport driver's local adapter context the LUID value from the NDIS_MINIPORT_INIT_PARAMETERS structure that is passed to the miniport driver's MiniportInitializeEx function. The value contains the NetLuid which identifies adapter's interface, which is used in the notification callback.
In the notification callback, Windows passes the following parameters to the notification function registered with NotifyIpInterfaceChange:
- A pointer to a MIB_IPINTERFACE_ROW structure, which contains the NetLuid of the miniport adapter's interface.
- The type of notification, which can be MibAddInstance, MibDeleteInstance or MibParameterNotification.
Miniport drivers should reset the IP and gateway addresses when the adapter is in a connected state, and the notification type is MibAddInstance, and the NetLuid in MIB_IPINTERFACE_ROW corresponds to one of the miniport driver's adapters, which was saved during adapter initialization.
Miniport drivers should then follow the Setting the IP Address for the MB Interface and Setting Default Gateway Address procedures to reset the respective addresses.
During driver unload, miniport drivers should unregister the notification callback function using the CancelMibChangeNotify2 IP helper function.
Setting the IP Address for the MB Interface
To set an IPv4 address, use the following procedure. You can use similar IP Helper functionality to set an IPv6 address.
Use the GetUnicastIpAddressTable IP Helper function to find all the IP address entries in the system.
For each entry whose InterfaceLuid value matches the InterfaceLuid of the MB interface:
- Find the IP address entry that matches the IP address used in previous connection. First time connections will not have a previous IP address.
- If the new IP address is different than the previous IP address, delete the IP address entry for previous connection IP addresses by using the DeleteUnicastIpAddressEntry IP Helper function.
- If the new IP address is the same as the previous IP address, verify that the desired entry already exists.
If the miniport driver did not find the desired IP address entry in the previous loop, it should add a new entry.
- Set the InterfaceLuid or InterfaceIndex members, as appropriate.
- Set the OnlinePrefixLength member. This is the number of bits that have a value of one in the subnet mask. For example, if the subnet mask is 255.255.255.0, OnlinePrefixLength should be 24.
- Set the Address member.
- Set the PrefixOrigin member to IpPrefixOriginManual.
Pass the initialized MIB_UNICASTADDRESS_ROW structure to the CreateUnicastIpAddressEntry IP Helper function to create the IP address entry.
Setting Default Gateway Address
To set an IPv4 gateway address, use the following procedure. You can use similar IP Helper functionality to set an IPv6 gateway address.
Use GetIpForwardTable2 IP Helper function to obtain all the routing entries in the system.
For each entry whose InterfaceLuid value matches the InterfaceLuid value of the MB interface and DestinationPrefix is "0.0.0.0/0", call the DeleteIpForwardEntry2 IP Helper function to delete the route if NextHop is not equal to the new gateway address. Otherwise, the routing entry is already in the system.
If the miniport driver did not find the desired routing entry in the previous loop, it should add a new entry by using the InitializeIpForwardEntry IP Helper function to initialize a MIB_IPFORWARD_ROW2 structure. Initialize the following members of the structure:
InterfaceLuid or InterfaceIndex .
Set DestinationPrefix to 0.0.0.0/0 for default gateway. (Prefix = 0.0.0.0 and PrefixLength = 0)
Set NextHop to the IP address of the default gateway.
Other members are set to default values during initialization. Miniport drivers should use default values for those members.
To Set DNS Addresses
- Set the NameServer registry key as described in MB DNS Updates to notify Windows about updated DNS addresses.