From 4b9adaa971f7bce059749de282dff8169de01255 Mon Sep 17 00:00:00 2001
From: Eric Kohl <eric.kohl@reactos.org>
Date: Mon, 6 Apr 2026 13:42:03 +0200
Subject: [PATCH] [DHCPCSVC] Add the client code and server stub for
 DhcpFallbackRefreshParams

DhcpFallbackRefreshParams is called by the TCPIP notification object after the alternate configuration has been changed.
---
 base/services/dhcpcsvc/dhcp/api.c    | 39 +++++++++++++++++++++++++---
 base/services/dhcpcsvc/dhcpcsvc.c    | 34 +++++++++++++++++++++++-
 base/services/dhcpcsvc/dhcpcsvc.spec |  2 +-
 sdk/include/psdk/dhcpcapi.h          |  5 ++++
 sdk/include/reactos/idl/dhcpcsvc.idl | 11 ++++++--
 5 files changed, 83 insertions(+), 8 deletions(-)

diff --git a/base/services/dhcpcsvc/dhcp/api.c b/base/services/dhcpcsvc/dhcp/api.c
index 5730fa5db03..933ff83abdc 100644
--- a/base/services/dhcpcsvc/dhcp/api.c
+++ b/base/services/dhcpcsvc/dhcp/api.c
@@ -86,7 +86,7 @@ Server_AcquireParameters(
     struct protocol* proto;
     DWORD ret = ERROR_SUCCESS;
 
-    DPRINT("Server_AcquireParameters()\n");
+    DPRINT("Server_AcquireParameters(%S)\n", AdapterName);
 
     ApiLock();
 
@@ -131,7 +131,7 @@ Server_ReleaseParameters(
     struct protocol* proto;
     DWORD ret = ERROR_SUCCESS;
 
-    DPRINT("Server_ReleaseParameters()\n");
+    DPRINT("Server_ReleaseParameters(%S)\n", AdapterName);
 
     ApiLock();
 
@@ -162,6 +162,37 @@ done:
 /* Function 2 */
 DWORD
 __stdcall
+Server_FallbackRefreshParams(
+    _In_ PDHCP_SERVER_NAME ServerName,
+    _In_ LPWSTR AdapterName)
+{
+    PDHCP_ADAPTER Adapter;
+    DWORD ret = ERROR_SUCCESS;
+
+    DPRINT("Server_FallbackRefreshParams(%S)\n", AdapterName);
+
+    ApiLock();
+
+    Adapter = AdapterFindName(AdapterName);
+    if (Adapter == NULL)
+    {
+        ret = ERROR_FILE_NOT_FOUND;
+        goto done;
+    }
+
+    DPRINT("Adapter: %p\n", Adapter);
+
+    /* FIXME */
+
+done:
+    ApiUnlock();
+
+    return ret;
+}
+
+/* Function 3 */
+DWORD
+__stdcall
 Server_QueryHWInfo(
     _In_ PDHCP_SERVER_NAME ServerName,
     _In_ DWORD AdapterIndex,
@@ -195,7 +226,7 @@ done:
     return ret;
 }
 
-/* Function 3 */
+/* Function 4 */
 DWORD
 __stdcall
 Server_StaticRefreshParams(
@@ -252,7 +283,7 @@ done:
     return ret;
 }
 
-/* Function 4 */
+/* Function 5 */
 DWORD
 __stdcall
 Server_RemoveDNSRegistrations(
diff --git a/base/services/dhcpcsvc/dhcpcsvc.c b/base/services/dhcpcsvc/dhcpcsvc.c
index 9dc7d322772..a347aad56fd 100644
--- a/base/services/dhcpcsvc/dhcpcsvc.c
+++ b/base/services/dhcpcsvc/dhcpcsvc.c
@@ -293,7 +293,39 @@ DhcpEnumClasses(
 }
 
 /*!
- * Enumerates the DHCP user classes for the given adapter
+ * Notify the DHCP client to refresh its fallback configuration
+ *
+ * \param[in] AdapterName
+ *        Name (GUID) of the Adapter
+ *
+ * \return ERROR_SUCCESS on success
+ *
+ * \remarks Undocumented by Microsoft
+ */
+DWORD
+APIENTRY
+DhcpFallbackRefreshParams(
+    _In_ PWSTR AdapterName)
+{
+    DWORD ret;
+
+    DPRINT("DhcpFallbackRefreshParams(%S)\n", AdapterName);
+
+    RpcTryExcept
+    {
+        ret = Client_FallbackRefreshParams(NULL, AdapterName);
+    }
+    RpcExcept(EXCEPTION_EXECUTE_HANDLER)
+    {
+        ret = I_RpcMapWin32Status(RpcExceptionCode());
+    }
+    RpcEndExcept;
+
+    return ret;
+}
+
+/*!
+ * Notify the DHCP client of PNP events
  *
  * \param[in] Unknown1
  *        Unknown
diff --git a/base/services/dhcpcsvc/dhcpcsvc.spec b/base/services/dhcpcsvc/dhcpcsvc.spec
index 84109c57534..1df9fdbcbb6 100644
--- a/base/services/dhcpcsvc/dhcpcsvc.spec
+++ b/base/services/dhcpcsvc/dhcpcsvc.spec
@@ -13,7 +13,7 @@
 @ stub DhcpDeRegisterOptions
 @ stub DhcpDeRegisterParamChange
 @ stdcall DhcpEnumClasses(long wstr long long)
-@ stub DhcpFallbackRefreshParams
+@ stdcall DhcpFallbackRefreshParams(wstr)
 @ stdcall DhcpHandlePnPEvent(long long wstr long long)
 @ stub DhcpLeaseIpAddress
 @ stub DhcpLeaseIpAddressEx
diff --git a/sdk/include/psdk/dhcpcapi.h b/sdk/include/psdk/dhcpcapi.h
index ec876d9804d..1bba6ac5116 100644
--- a/sdk/include/psdk/dhcpcapi.h
+++ b/sdk/include/psdk/dhcpcapi.h
@@ -33,6 +33,11 @@ DhcpEnumClasses(
     _In_ DWORD Unknown3,
     _In_ DWORD Unknown4);
 
+DWORD
+APIENTRY
+DhcpFallbackRefreshParams(
+    _In_ PWSTR AdapterName);
+
 DWORD
 APIENTRY
 DhcpHandlePnPEvent(
diff --git a/sdk/include/reactos/idl/dhcpcsvc.idl b/sdk/include/reactos/idl/dhcpcsvc.idl
index c17b013cce9..0172c78204e 100644
--- a/sdk/include/reactos/idl/dhcpcsvc.idl
+++ b/sdk/include/reactos/idl/dhcpcsvc.idl
@@ -37,6 +37,13 @@ interface dhcpcsvc
     /* Function 2 */
     DWORD
     __stdcall
+    FallbackRefreshParams(
+        [in, string, unique] PDHCP_SERVER_NAME ServerName,
+        [in, string] LPWSTR AdapterName);
+
+    /* Function 3 */
+    DWORD
+    __stdcall
     QueryHWInfo(
         [in, string, unique] PDHCP_SERVER_NAME ServerName,
         [in] DWORD AdapterIndex,
@@ -44,7 +51,7 @@ interface dhcpcsvc
         [out] PDWORD Mtu,
         [out] PDWORD Speed);
 
-    /* Function 3 */
+    /* Function 4 */
     DWORD
     __stdcall
     StaticRefreshParams(
@@ -53,7 +60,7 @@ interface dhcpcsvc
         [in] DWORD Address,
         [in] DWORD Netmask);
 
-    /* Function 4 */
+    /* Function 5 */
     DWORD
     __stdcall
     RemoveDNSRegistrations(