private static uint HandleChainDlls(IntPtr ChainDlls, uint CalloutVersion)
{
// ChainDlls is in REG_MULTI_SZ format (non-empty strings separated by null, terminated with an additional null)
// read next dll in chain
var chainDllPath = Marshal.PtrToStringUni(ChainDlls);
// check if no dlls (or we are the last in the chain)
if (chainDllPath == null || chainDllPath.Length == 0)
{
ChainTable = new DHCP_CALLOUT_TABLE();
return(ERROR_SUCCESS);
}
// ensure dll exists
if (!File.Exists(chainDllPath))
{
return(0x2); // FILE_NOT_FOUND
}
// load dll
ChainLibraryHandle = Win32Api.LoadLibrary(chainDllPath);
if (ChainLibraryHandle == IntPtr.Zero)
{
return((uint)Marshal.GetLastWin32Error());
}
// locate DhcpServerCalloutEntry export
var chainCalloutEntryAddress = Win32Api.GetProcAddress(ChainLibraryHandle, "DhcpServerCalloutEntry");
if (chainCalloutEntryAddress == IntPtr.Zero)
{
return((uint)Marshal.GetLastWin32Error());
}
// prepare arguments
var chainCalloutEntryDelegate = (DhcpServerCalloutEntryDelegate)Marshal.GetDelegateForFunctionPointer
(chainCalloutEntryAddress, typeof(DhcpServerCalloutEntryDelegate));
// ChainDlls should pass a pointer to the next dll (or the final termination null)
var chainDllsNext = ChainDlls + Encoding.Unicode.GetByteCount(chainDllPath) + 2;
var calloutTbl = new DHCP_CALLOUT_TABLE();
// call chain dll
var subsequentResult = chainCalloutEntryDelegate(chainDllsNext, CalloutVersion, ref calloutTbl);
if (subsequentResult != ERROR_SUCCESS)
{
return(subsequentResult);
}
// store chain dll's callout table
ChainTable = calloutTbl;
return(ERROR_SUCCESS);
}
private static uint DeriveHooks(ref DHCP_CALLOUT_TABLE CalloutTbl)
{
// always hook control
CalloutTbl.DhcpControlHook = new DhcpControlHookUnsafeDelegate(HandleControlHook);
// NewPkt
if (ConsumerRequirements.HasFlag(CalloutConsumerSupportFlags.NewPacket))
{
// consumer required
CalloutTbl.DhcpNewPktHook = new DhcpNewPktHookUnsafeDelegate(HandleNewPktHook);
}
else if (ChainTable.DhcpNewPktHook != null)
{
// only chain required
CalloutTbl.DhcpNewPktHook = ChainTable.DhcpNewPktHook;
}
else
{
CalloutTbl.DhcpNewPktHook = null;
}
// PktDrop
if (ConsumerRequirements.HasFlag(CalloutConsumerSupportFlags.PacketDrop))
{
// consumer required
CalloutTbl.DhcpPktDropHook = new DhcpPktDropHookUnsafeDelegate(HandleDhcpPktDropHook);
}
else if (ChainTable.DhcpPktDropHook != null)
{
// only chain required
CalloutTbl.DhcpPktDropHook = ChainTable.DhcpPktDropHook;
}
else
{
CalloutTbl.DhcpPktDropHook = null;
}
// PktSend
if (ConsumerRequirements.HasFlag(CalloutConsumerSupportFlags.PacketSend))
{
// consumer required
CalloutTbl.DhcpPktSendHook = new DhcpPktSendHookUnsafeDelegate(HandlePktSendHook);
}
else if (ChainTable.DhcpPktSendHook != null)
{
// only chain required
CalloutTbl.DhcpPktSendHook = ChainTable.DhcpPktSendHook;
}
else
{
CalloutTbl.DhcpPktSendHook = null;
}
// AddressDel
if (ConsumerRequirements.HasFlag(CalloutConsumerSupportFlags.AddressDelete))
{
// consumer required
CalloutTbl.DhcpAddressDelHook = new DhcpAddressDelHookUnsafeDelegate(HandleAddressDelHook);
}
else if (ChainTable.DhcpAddressDelHook != null)
{
// only chain required
CalloutTbl.DhcpAddressDelHook = ChainTable.DhcpAddressDelHook;
}
else
{
CalloutTbl.DhcpAddressDelHook = null;
}
// AddressOffer
if (ConsumerRequirements.HasFlag(CalloutConsumerSupportFlags.AddressOffer))
{
// consumer required
CalloutTbl.DhcpAddressOfferHook = new DhcpAddressOfferHookUnsafeDelegate(HandleAddressOfferHook);
}
else if (ChainTable.DhcpAddressOfferHook != null)
{
// only chain required
CalloutTbl.DhcpAddressOfferHook = ChainTable.DhcpAddressOfferHook;
}
else
{
CalloutTbl.DhcpAddressOfferHook = null;
}
// HandleOptions
// Hook is only derived if the ApiVersion is 0 (as the ServerOptions could change if the version is incremented).
if (ApiVersion == 0 && ConsumerRequirements.HasFlag(CalloutConsumerSupportFlags.HandleOptions))
{
// consumer required
CalloutTbl.DhcpHandleOptionsHook = new DhcpHandleOptionsHookUnsafeDelegate(HandleHandleOptionsHook);
}
else if (ChainTable.DhcpHandleOptionsHook != null)
{
// only chain required
CalloutTbl.DhcpHandleOptionsHook = ChainTable.DhcpHandleOptionsHook;
}
else
{
CalloutTbl.DhcpHandleOptionsHook = null;
}
// DeleteClient
if (ConsumerRequirements.HasFlag(CalloutConsumerSupportFlags.DeleteClient))
{
// consumer required
CalloutTbl.DhcpDeleteClientHook = new DhcpDeleteClientHookUnsafeDelegate(HandleDeleteClientHook);
}
else if (ChainTable.DhcpDeleteClientHook != null)
{
// only chain required
CalloutTbl.DhcpDeleteClientHook = ChainTable.DhcpDeleteClientHook;
}
else
{
CalloutTbl.DhcpDeleteClientHook = null;
}
// Extension - not supported by DhcpServerAPI
if (ChainTable.DhcpExtensionHook != IntPtr.Zero)
{
CalloutTbl.DhcpExtensionHook = ChainTable.DhcpExtensionHook;
}
else
{
CalloutTbl.DhcpExtensionHook = IntPtr.Zero;
}
// Reserved - not supported by DhcpServerAPI
if (ChainTable.DhcpReservedHook != IntPtr.Zero)
{
CalloutTbl.DhcpReservedHook = ChainTable.DhcpReservedHook;
}
else
{
CalloutTbl.DhcpReservedHook = IntPtr.Zero;
}
return(ERROR_SUCCESS);
}
private static uint DhcpServerCalloutEntry(IntPtr ChainDlls, uint CalloutVersion, ref DHCP_CALLOUT_TABLE CalloutTbl)
{
AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;
ApiVersion = CalloutVersion;
// locate and initialize consumers
var initConsumersResult = InitializeConsumers();
if (initConsumersResult != ERROR_SUCCESS)
{
return(initConsumersResult);
}
// chain subsequent dll
var chainDllResult = HandleChainDlls(ChainDlls, CalloutVersion);
if (chainDllResult != ERROR_SUCCESS)
{
return(chainDllResult);
}
// derive hooks
var deriveResult = DeriveHooks(ref CalloutTbl);
if (deriveResult != ERROR_SUCCESS)
{
return(deriveResult);
}
return(ERROR_SUCCESS);
}
