Dynamically compute ip feature subgraph order

This change-set enables plugins to add themselves to the ip4/ip6
feature subgraphs without having to modify core vpp engine code
at all. Add VNET_IP4/IP6_UNICAST/MULTICAST_FEATURE_INIT macros
which express the required ordering constraints, and off you go.

Along the way, added an implementation of Warshall's algorithm to
vppinfra; to compute the positive transitive closure of a relation. In
this case, the relation is "feature A runs before feature B."

With that in hand, ip_feature_init_cast(...) computes a partial order
across the set of configured feature subgraph nodes.

In unit-testing, we discovered VPP-145 - ip4/6 inacl wiped out
vnet_buffer(b)->ip>current_config_index, which exists in main. So, we
fixed that by moving b->trace_index, adding b->current_config_index,
and removing the ip opaque union current_config_index.

Change-Id: Iff132116f66413dc6b31ac3377198c7a32d51f48
Signed-off-by: Dave Barach <dave@barachs.net>

1 files changed, 7 insertions, 7 deletions

diff --git a/vlib/vlib/buffer.h b/vlib/vlib/buffer.h
index e11085b72a0..52749572509 100644
--- a/vlib/vlib/buffer.h
+++ b/vlib/vlib/buffer.h
@@ -108,16 +108,10 @@ typedef struct {
      total length given here give total number of bytes in buffer chain.
   */
 
-
   u32 next_buffer;   /**< Next buffer for this linked-list of buffers.
                         Only valid if VLIB_BUFFER_NEXT_PRESENT flag is set. 
                      */
 
-  u32 trace_index; /**< Specifies index into trace buffer 
-                      if VLIB_PACKET_IS_TRACED flag is set. 
-                   */
-
-
   u32 clone_count; /**< Specifies whether this buffer should be 
                       reinitialized when freed. It will be reinitialized 
                       if the value is 0. This field can be used
@@ -129,13 +123,19 @@ typedef struct {
   vlib_error_t error;   /**< Error code for buffers to be enqueued 
                            to error handler. 
                         */
+  u32 current_config_index; /**< Used by feature subgraph arcs to
+                               visit enabled feature nodes
+                            */
 
   u32 opaque[8]; /**< Opaque data used by sub-graphs for their own purposes. 
                     See .../vnet/vnet/buffer.h
                  */
   CLIB_CACHE_LINE_ALIGN_MARK(cacheline1);
 
-  u32 opaque2[16];  /**< More opaque data, in its own cache line */
+  u32 trace_index; /**< Specifies index into trace buffer 
+                      if VLIB_PACKET_IS_TRACED flag is set. 
+                   */
+  u32 opaque2[15];  /**< More opaque data, currently unused */
 
   /***** end of second cache line */
   CLIB_CACHE_LINE_ALIGN_MARK(cacheline2);