vlib: refactor checksum offload support

Type: refactor

This patch refactors the offload flags in vlib_buffer_t.
There are two main reasons behind this refactoring.
First, offload flags are insufficient to represent outer
and inner headers offloads. Second, room for these flags
in first cacheline of vlib_buffer_t is also limited.

This patch introduces a generic offload flag in first
cacheline. And detailed offload flags in 2nd cacheline
of the structure for performance optimization.

Change-Id: Icc363a142fb9208ec7113ab5bbfc8230181f6004
Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com>
diff --git a/src/vnet/udp/udp_inlines.h b/src/vnet/udp/udp_inlines.h
index ec800f9..067289c 100644
--- a/src/vnet/udp/udp_inlines.h
+++ b/src/vnet/udp/udp_inlines.h
@@ -35,7 +35,7 @@
   uh->checksum = 0;
   uh->length = clib_host_to_net_u16 (udp_len);
   if (offload_csum)
-    b->flags |= VNET_BUFFER_F_OFFLOAD_UDP_CKSUM;
+    vnet_buffer_offload_flags_set (b, VNET_BUFFER_OFFLOAD_F_UDP_CKSUM);
   vnet_buffer (b)->l4_hdr_offset = (u8 *) uh - b->data;
   b->flags |= VNET_BUFFER_F_L4_HDR_OFFSET_VALID;
   return uh;