Fix FNMP multi-NB filtering logic and test case (#17)

* add support for multiple NBs per NBL on TX filtering path

* fix whitespace

* fix tests on 2019

* fix previous fix

* fix filtering and test case

Author: mtfriesen

src/sys/fnio/filter.c

@@ -176,22 +176,26 @@ FnIoGetFilteredFrame(
     }
 
     NetBuffer = NET_BUFFER_LIST_FIRST_NB(Nbl);
+    ASSERT(NetBuffer != NULL);
 
-    for (UINT32 NbIndex = 0; NbIndex < SubIndex; NbIndex++) {
-        if (NetBuffer == NULL) {
-            Status = STATUS_NOT_FOUND;
-            goto Exit;
-        }
-
+    do {
         //
         // Only count NBs that match the filter.
         //
-        if (!FnIoFilterNb(Filter, NetBuffer)) {
-            NbIndex--;
+        if (FnIoFilterNb(Filter, NetBuffer)) {
+            if (SubIndex == 0) {
+                break;
+            } else {
+                SubIndex--;
+            }
         }
 
         NetBuffer = NetBuffer->Next;
-    }
+        if (NetBuffer == NULL) {
+            Status = STATUS_NOT_FOUND;
+            goto Exit;
+        }
+    } while (TRUE);
 
     BufferCount = 0;
     OutputSize = sizeof(*Frame);

test/functional/tests.cpp

@@ -639,13 +639,13 @@ BasicTx()
     BOOLEAN Uso = TRUE;
 
     UCHAR UdpPayload[] = "BasicTx0BasicTx1";
-    UCHAR Pattern[UDP_HEADER_BACKFILL(AF_INET) + (sizeof(UdpPayload) - 1) / 2];
+    UCHAR Pattern[UDP_HEADER_BACKFILL(AF_INET) + sizeof(UdpPayload) / 2 - 1];
     UCHAR Mask[sizeof(Pattern)];
     UINT32 ExpectedUdpPayloadSize = sizeof(UdpPayload) / 2;
     UINT32 SendSize = sizeof(UdpPayload);
 
     RtlZeroMemory(Pattern, sizeof(Pattern));
-    RtlCopyMemory(Pattern + UDP_HEADER_BACKFILL(AF_INET), UdpPayload, (sizeof(UdpPayload) - 1) / 2);
+    RtlCopyMemory(Pattern + UDP_HEADER_BACKFILL(AF_INET), UdpPayload, sizeof(UdpPayload) / 2 - 1);
 
     RtlZeroMemory(Mask, sizeof(Mask));
     for (int i = UDP_HEADER_BACKFILL(AF_INET); i < sizeof(Mask); i++) {