--- gvpe/src/device.h	2011/09/16 17:59:46	1.24
+++ gvpe/src/device.h	2013/07/17 16:40:57	1.26
@@ -42,6 +42,9 @@
 struct net_packet
 {
   u32 len; // actually u16, but padding...
+  // upto 4 bytes at the end might get overwritten when decrypting,
+  // which means len, above, is regularly overwritten with part
+  // of the random prefix when RAND_BYTES=12.
 
   u8 &operator[] (u16 offset) const;
   u8 *at (u16 offset) const;
@@ -58,9 +61,9 @@
       memmove ((void *)&(*this)[0], (void *)&(*this)[hdrsize], len);
     }
 
-  void skip_ipv4_hdr (u16 extra = 0)
+  u16 ipv4_hdr_len () const
     {
-      skip_hdr ((((*this)[0] & 15) << 2) + extra);
+      return ((*this)[0] & 15) << 2;
     }
 
   void set (const net_packet &pkt)