--- gvpe/src/device.h	2008/08/07 17:54:27	1.22
+++ 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;
@@ -58,6 +61,11 @@
       memmove ((void *)&(*this)[0], (void *)&(*this)[hdrsize], len);
     }
 
+  u16 ipv4_hdr_len () const
+    {
+      return ((*this)[0] & 15) << 2;
+    }
+
   void set (const net_packet &pkt)
     {
       len = pkt.len;
@@ -97,13 +105,13 @@
   u8 data_[MAXSIZE];
 };
 
-inline 
+inline
 u8 &net_packet::operator[] (u16 offset) const
 {
   return ((data_packet *)this)->data_[offset];
 }
 
-inline 
+inline
 u8 *net_packet::at (u16 offset) const
 {
   return &((*this)[offset]);