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, 15 insertions, 4 deletions

diff --git a/src/vnet/adj/rewrite.h b/src/vnet/adj/rewrite.h
index 5c1d24ea890..c23edbe1f60 100644
--- a/src/vnet/adj/rewrite.h
+++ b/src/vnet/adj/rewrite.h
@@ -55,10 +55,15 @@ typedef enum vnet_rewrite_flags_t_
    * This adjacency/interface has output features configured
    */
   VNET_REWRITE_HAS_FEATURES = (1 << 0),
+
+  /**
+   * this adj performs IP4 over IP4 fixup
+   */
+  VNET_REWRITE_FIXUP_IP4_O_4 = (1 << 1),
 } __attribute__ ((packed)) vnet_rewrite_flags_t;
 
-/* *INDENT-OFF* */
-typedef CLIB_PACKED (struct {
+typedef struct vnet_rewrite_header_t_
+{
   /* Interface to mark re-written packets with. */
   u32 sw_if_index;
 
@@ -83,8 +88,7 @@ typedef CLIB_PACKED (struct {
 
   /* Rewrite string starting at end and going backwards. */
   u8 data[0];
-}) vnet_rewrite_header_t;
-/* *INDENT-ON* */
+} __clib_packed vnet_rewrite_header_t;
 
 /**
  * At 16 bytes of rewrite herader we have enought space left for a IPv6
@@ -114,6 +118,13 @@ STATIC_ASSERT (sizeof (vnet_rewrite_header_t) <= 16,
                     sizeof (vnet_rewrite_header_t)]; \
   }
 
+typedef struct __rewrite_unused_t__
+{
+  VNET_DECLARE_REWRITE;
+} __rewrite_unused_t;
+
+STATIC_ASSERT_SIZEOF (__rewrite_unused_t, 128);
+
 always_inline void
 vnet_rewrite_clear_data_internal (vnet_rewrite_header_t * rw, int max_size)
 {