tcp: add option to pass opaque to next node

Type:feature

Change-Id: I0b72954a6ae6a05abe0761cb4f227072863f127b
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vnet/buffer.h b/src/vnet/buffer.h
index 812fe74..324c903 100644
--- a/src/vnet/buffer.h
+++ b/src/vnet/buffer.h
@@ -327,7 +327,11 @@
     struct
     {
       u32 connection_index;
-      u32 seq_number;
+      union
+      {
+	u32 seq_number;
+	u32 next_node_opaque;
+      };
       u32 seq_end;
       u32 ack_number;
       u16 hdr_offset;		/**< offset relative to ip hdr */