iphlpapi: Don't allocate gobs of memory when the route table is empty.

dlls/iphlpapi/iphlpapi_main.c

@@ -1222,9 +1222,10 @@ DWORD WINAPI GetIpForwardTable(PMIB_IPFORWARDTABLE pIpForwardTable, PULONG pdwSi
     ret = ERROR_INVALID_PARAMETER;
   else {
     DWORD numRoutes = getNumRoutes();
-    ULONG sizeNeeded = sizeof(MIB_IPFORWARDTABLE) + (numRoutes - 1) *
-     sizeof(MIB_IPFORWARDROW);
+    ULONG sizeNeeded = sizeof(MIB_IPFORWARDTABLE);
 
+    if (numRoutes > 1)
+      sizeNeeded += (numRoutes - 1) * sizeof(MIB_IPFORWARDROW);
     if (!pIpForwardTable || *pdwSize < sizeNeeded) {
       *pdwSize = sizeNeeded;
       ret = ERROR_INSUFFICIENT_BUFFER;
@@ -1234,8 +1235,9 @@ DWORD WINAPI GetIpForwardTable(PMIB_IPFORWARDTABLE pIpForwardTable, PULONG pdwSi
 
       ret = getRouteTable(&table, GetProcessHeap(), 0);
       if (!ret) {
-        sizeNeeded = sizeof(MIB_IPFORWARDTABLE) + (table->dwNumEntries - 1) *
-         sizeof(MIB_IPFORWARDROW);
+        sizeNeeded = sizeof(MIB_IPFORWARDTABLE);
+        if (table->dwNumEntries > 1)
+          sizeNeeded += (table->dwNumEntries - 1) * sizeof(MIB_IPFORWARDROW);
         if (*pdwSize < sizeNeeded) {
           *pdwSize = sizeNeeded;
           ret = ERROR_INSUFFICIENT_BUFFER;

dlls/iphlpapi/ipstats.c

@@ -777,9 +777,12 @@ DWORD getRouteTable(PMIB_IPFORWARDTABLE *ppIpForwardTable, HANDLE heap,
     ret = ERROR_INVALID_PARAMETER;
   else {
     DWORD numRoutes = getNumRoutes();
-    PMIB_IPFORWARDTABLE table = HeapAlloc(heap, flags,
-     sizeof(MIB_IPFORWARDTABLE) + (numRoutes - 1) * sizeof(MIB_IPFORWARDROW));
+    DWORD size = sizeof(MIB_IPFORWARDTABLE);
+    PMIB_IPFORWARDTABLE table;
 
+    if (numRoutes > 1)
+      size += (numRoutes - 1) * sizeof(MIB_IPFORWARDROW);
+    table = HeapAlloc(heap, flags, size);
     if (table) {
 #if defined(HAVE_SYS_SYSCTL_H) && defined(NET_RT_DUMP)
        int mib[6] = {CTL_NET, PF_ROUTE, 0, PF_INET, NET_RT_DUMP, 0};