Introduce l{2,3,4}_hdr_offset fields in the buffer metadata

To save space in the first cacheline following is changed:

- total_length_not_including_first_buffer moved to the 2nd cacheline.
This field is used only when VLIB_BUFFER_TOTAL_LENGTH_VALID and
VLIB_BUFFER_NEXT_PRESENT are both set.

- free_list_index is now stored in 4bits inside flags, which
allows up to 16 free lists. In case we need more we can store index
in the 2nd cachelin

Change-Id: Ic8521350819391af470d31d3fa1013e67ecb7681
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vnet/bfd/bfd_udp.c b/src/vnet/bfd/bfd_udp.c
index 346c549..06b843c 100644
--- a/src/vnet/bfd/bfd_udp.c
+++ b/src/vnet/bfd/bfd_udp.c
@@ -843,7 +843,7 @@
 		       udp_header_t ** udp)
 {
   /* sanity check first */
-  const i32 start = vnet_buffer (b)->ip.start_of_ip_header;
+  const i32 start = vnet_buffer (b)->l3_hdr_offset;
   if (start < 0 && start < sizeof (b->pre_data))
     {
       BFD_ERR ("Start of ip header is before pre_data, ignoring");
@@ -1000,7 +1000,7 @@
 		       udp_header_t ** udp)
 {
   /* sanity check first */
-  const i32 start = vnet_buffer (b)->ip.start_of_ip_header;
+  const i32 start = vnet_buffer (b)->l3_hdr_offset;
   if (start < 0 && start < sizeof (b->pre_data))
     {
       BFD_ERR ("Start of ip header is before pre_data, ignoring");