Fix some issues with Radiotap headers.

Only the BPF header must be contiguous. By treating Radiotap header
specially, we ended up with uninitialized bytes at the beginning of
802.11 frames, and an equivalent amount truncated from the end.

Also, we were not considering the length of the Radiotap header in
checking if there was enough free space in the circular buffer. This
could lead to overlapping/overwriting frames that should be dropped
instead.

Possibly related issues:
* nmap/nmap#1001
* nmap/nmap#1028
* nmap/nmap#1036

packetWin7/npf/npf/Read.c

@@ -1158,7 +1158,11 @@ NPF_TapExForEachOpen(
 					if (fres > TotalPacketSize)
 						fres = TotalPacketSize;
 
-					if (fres + sizeof(struct PacketHeader) > LocalData->Free)
+					if (fres + sizeof(struct PacketHeader)
+#ifdef HAVE_DOT11_SUPPORT
+							+ Dot11RadiotapHeaderSize
+#endif
+							> LocalData->Free)
 					{
 						LocalData->Dropped++;
 						IF_LOUD(DbgPrint("LocalData->Dropped++, fres = %d, LocalData->Free = %d\n", fres, LocalData->Free);)
@@ -1220,10 +1224,17 @@ NPF_TapExForEachOpen(
 							// the NewHeader structure, at least, otherwise we skip the producer
 							increment += Open->Size - LocalData->P; // at the beginning of the buffer (p = 0), and decrement the free bytes appropriately
 							LocalData->P = 0;
+							//the Radiotap header will be fragmented in the buffer (aka, it will skip the buffer boundary)
+							ToCopy = Open->Size - LocalData->P;
+							NdisMoveMappedMemory(LocalData->Buffer + LocalData->P, Dot11RadiotapHeader, ToCopy);
+							NdisMoveMappedMemory(LocalData->Buffer + 0, Dot11RadiotapHeader + ToCopy, Dot11RadiotapHeaderSize - ToCopy);
+							LocalData->P = Dot11RadiotapHeaderSize - ToCopy;
+						}
+						else
+						{
+							NdisMoveMappedMemory(LocalData->Buffer + LocalData->P, Dot11RadiotapHeader, Dot11RadiotapHeaderSize);
+							LocalData->P += Dot11RadiotapHeaderSize;
 						}
-
-						NdisMoveMappedMemory(LocalData->Buffer + LocalData->P, Dot11RadiotapHeader, Dot11RadiotapHeaderSize);
-						LocalData->P += Dot11RadiotapHeaderSize;
 						if (LocalData->P == Open->Size)
 							LocalData->P = 0;
 						increment += Dot11RadiotapHeaderSize;