[TCPIP] Read the interface metric from the registry or use the automatic metric feature

- Read the interface metric from the registry.
- Assign an automatic metric to an interface if a registry value is not available.
- Determine the automatic metric from the link speed. The metric for the loopback interface is always 1.

Author: EricKohl

drivers/network/tcpip/datalink/lan.c

@@ -576,6 +576,7 @@ BOOLEAN ReadIpConfiguration(PIP_INTERFACE Interface)
     UNICODE_STRING Netmask = RTL_CONSTANT_STRING(L"SubnetMask");
     UNICODE_STRING Gateway = RTL_CONSTANT_STRING(L"DefaultGateway");
     UNICODE_STRING EnableDhcp = RTL_CONSTANT_STRING(L"EnableDHCP");
+    UNICODE_STRING InterfaceMetric = RTL_CONSTANT_STRING(L"InterfaceMetric");
     UNICODE_STRING Prefix = RTL_CONSTANT_STRING(L"\\Registry\\Machine\\SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\Interfaces\\");
     UNICODE_STRING TcpipRegistryPath;
     UNICODE_STRING RegistryDataU;
@@ -619,6 +620,21 @@ BOOLEAN ReadIpConfiguration(PIP_INTERFACE Interface)
             return FALSE;
         }
 
+        /* Read the InterfaceMetric value */
+        Interface->Metric = 0;
+        Status = ZwQueryValueKey(ParameterHandle,
+                                 &InterfaceMetric,
+                                 KeyValuePartialInformation,
+                                 KeyValueInfo,
+                                 KeyValueInfoLength,
+                                 &Unused);
+        if (NT_SUCCESS(Status) && KeyValueInfo->DataLength == sizeof(ULONG))
+        {
+            Interface->Metric = (UINT)*(PULONG)KeyValueInfo->Data;
+            if (Interface->Metric > 9999)
+                Interface->Metric = 9999;
+        }
+
         /* Read the EnableDHCP entry */
         Status = ZwQueryValueKey(ParameterHandle,
                                  &EnableDhcp,
@@ -700,7 +716,7 @@ BOOLEAN ReadIpConfiguration(PIP_INTERFACE Interface)
                     AddrInitIPv4(&Router, inet_addr(RegistryDataA.Buffer));
 
                     if (!AddrIsUnspecified(&Router))
-                        RouterCreateRoute(&DefaultMask, &DefaultMask, &Router, Interface, 1);
+                        RouterCreateRoute(&DefaultMask, &DefaultMask, &Router, Interface);
 
                     RtlFreeAnsiString(&RegistryDataA);
                 }

drivers/network/tcpip/include/ip.h

@@ -156,6 +156,7 @@ typedef struct _IP_INTERFACE {
     UINT  MinFrameSize;           /* Minimum frame size in bytes */
     UINT  MTU;                    /* Maximum transmission unit */
     UINT  Speed;                  /* Link speed */
+    UINT  Metric;                 /* Interface metric */
     IP_ADDRESS Unicast;           /* Unicast address */
     IP_ADDRESS PointToPoint;      /* Point to point address */
     IP_ADDRESS Netmask;           /* Netmask */

drivers/network/tcpip/include/router.h

@@ -34,8 +34,7 @@ PFIB_ENTRY RouterCreateRoute(
     PIP_ADDRESS NetworkAddress,
     PIP_ADDRESS Netmask,
     PIP_ADDRESS RouterAddress,
-    PIP_INTERFACE Interface,
-    UINT Metric);
+    PIP_INTERFACE Interface);
 
 NTSTATUS RouterStartup(
     VOID);
@@ -49,4 +48,6 @@ UINT CountFIBs(PIP_INTERFACE IF);
 
 UINT CopyFIBs( PIP_INTERFACE IF, PFIB_ENTRY Target );
 
+UINT ProcessAutoMetric(PIP_INTERFACE Interface);
+
 /* EOF */

drivers/network/tcpip/ip/network/router.c

@@ -17,7 +17,37 @@
 LIST_ENTRY FIBListHead;
 KSPIN_LOCK FIBLock;
 
-void RouterDumpRoutes() {
+UINT
+ProcessAutoMetric(
+    _In_ PIP_INTERFACE Interface)
+{
+    if (Interface == Loopback)
+        return 1;
+
+    if (Interface->Metric != 0)
+        return Interface->Metric;
+
+    /* Auto metric */
+    if (Interface->Speed > 2000000000)
+        return 5;
+    else if (Interface->Speed > 200000000)
+        return 10;
+    else if (Interface->Speed > 80000000)
+        return 20;
+    else if (Interface->Speed > 20000000)
+        return 25;
+    else if (Interface->Speed > 4000000)
+        return 30;
+    else if (Interface->Speed > 500000)
+        return 40;
+    else
+        return 50;
+}
+
+
+VOID
+RouterDumpRoutes(VOID)
+{
     PLIST_ENTRY CurrentEntry;
     PLIST_ENTRY NextEntry;
     PFIB_ENTRY Current;
@@ -422,16 +452,14 @@ PFIB_ENTRY RouterCreateRoute(
     PIP_ADDRESS NetworkAddress,
     PIP_ADDRESS Netmask,
     PIP_ADDRESS RouterAddress,
-    PIP_INTERFACE Interface,
-    UINT Metric)
+    PIP_INTERFACE Interface)
 /*
  * FUNCTION: Creates a route with IPv4 addresses as parameters
  * ARGUMENTS:
  *     NetworkAddress = Address of network
  *     Netmask        = Netmask of network
  *     RouterAddress  = Address of router to use
- *     NTE            = Pointer to NTE to use
- *     Metric         = Cost of this route
+ *     Interface      = Network interface
  * RETURNS:
  *     Pointer to FIB entry if the route was created, NULL if not.
  *     The FIB entry references the NTE. The caller is responsible
@@ -475,7 +503,7 @@ PFIB_ENTRY RouterCreateRoute(
         return NULL;
     }
 
-    return RouterAddRoute(NetworkAddress, Netmask, NCE, Metric);
+    return RouterAddRoute(NetworkAddress, Netmask, NCE, ProcessAutoMetric(Interface));
 }
 
 

drivers/network/tcpip/tcpip/ninfo.c

@@ -327,8 +327,8 @@ TDI_STATUS InfoTdiSetRoute(PIP_INTERFACE IF, PVOID Buffer, UINT BufferSize)
 
     if( Route->Type == IP_ROUTE_TYPE_ADD ) { /* Add the route */
         TI_DbgPrint(DEBUG_INFO,("Adding route (%s)\n", A2S(&Address)));
-	if (!RouterCreateRoute( &Address, &Netmask, &Router,
-			       IF, Route->Metric1))
+        IF->Metric = Route->Metric1;
+	if (!RouterCreateRoute(&Address, &Netmask, &Router, IF))
 	    return TDI_NO_RESOURCES;
 
         return TDI_SUCCESS;