fib: midchain adjacency optimisations

Type: improvement

 - inline some common encap fixup functions into the midchain
   rewrite node so we don't incur the cost of the virtual function call
 - change the copy 'guess' from ethernet_header (which will never happen) to an ip4 header
 - add adj-midchain-tx to multiarch sources
 - don't run adj-midchain-tx as a feature, instead put this node as the
   adj's next and at the end of the feature arc.
 - cache the feature arc config index (to save the cache miss going to fetch it)
 - don't check if features are enabled when taking the arc (since we know they are)

the last two changes will also benefit normal adjacencies taking the arc (i.e. for NAT, ACLs, etc)

for IPSec:
 - don't run esp_encrypt as a feature, instead when required insert this
   node into the adj's next and into the end of the feature arc. this
   implies that encrypt is always 'the last feature' run, which is
   symmetric with decrypt always being the first.
 - esp_encrpyt for tunnels has adj-midchain-tx as next node

Change-Id: Ida0af56a704302cf2d7797ded5f118a781e8acb7
Signed-off-by: Neale Ranns <nranns@cisco.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/src/vnet/adj/adj_midchain.h b/src/vnet/adj/adj_midchain.h
index 1f5deaecd95..5fb0ee8efb3 100644
--- a/src/vnet/adj/adj_midchain.h
+++ b/src/vnet/adj/adj_midchain.h
@@ -52,6 +52,27 @@ extern void adj_nbr_midchain_update_rewrite(adj_index_t adj_index,
 
 /**
  * @brief
+ *  Return the adjacency's next node to its default value
+ *
+ * @param adj_index
+ *  The index of the neighbour adjacency.
+ */
+extern void adj_nbr_midchain_reset_next_node(adj_index_t adj_index);
+
+/**
+ * @brief
+ *  Update the VLIB node to which packets are sent post processing
+ *
+ * @param adj_index
+ *  The index of the neighbour adjacency.
+ *
+ * @param node node-index to send to
+ */
+extern void adj_nbr_midchain_update_next_node(adj_index_t adj_index,
+                                              u32 node_index);
+
+/**
+ * @brief
  *  [re]stack a midchain. 'Stacking' is the act of forming parent-child
  *  relationships in the data-plane graph. Do NOT use this function to
  *  stack on a DPO type that might form a loop.
@@ -139,4 +160,6 @@ extern void adj_midchain_delegate_restack(adj_index_t ai);
  */
 extern void adj_midchain_delegate_unstack(adj_index_t ai);
 
+extern u8 adj_is_midchain (adj_index_t ai);
+
 #endif