Improve mechanism for using loopback interface as BVI for BDs

When loopback interface is configured as BVI, instead of changing its
output node from loopN-output to l2-input, the loopN-output node is now
kept while its next tx node is changed from ethernet-input to l2-input.
The packet setup previously done in bvi_to_l2 as part of l2-input is now
performed in the loop output node.

This change adds an extra node in the BVI output path but provides the
following improvements:
1. IP address/route created on loopback prior to it being configured as
   BVI will still work properly. The requirement to (re)configure IP/route
   on loopback after it is configured as BVI is removed.
2. The output stats for loopback interfaces are always provided irrespective
   of their BVI configuration.
3. The loopback-BVI output stats can be batch updated outside the packet
   loop in output node, instead of per packet update in l2-input node,
   making l2-input node more efficient for BVI packets.
4. Restore original node property as implemented in node.c function
   vlib_node_add_next_with_slot() where next node indices stored in next
   slots of each node will remain unique.
5. Packet trace for BVI output includes loopN output node which provides
   useful packet data.

Change-Id: I7f5bc72ef953a367363a179088210596881f9e73
Signed-off-by: John Lo <loj@cisco.com>

1 files changed, 0 insertions, 3 deletions

diff --git a/vnet/vnet/l2/l2_bd.h b/vnet/vnet/l2/l2_bd.h
index 9ff0a864c59..034f2b39875 100644
--- a/vnet/vnet/l2/l2_bd.h
+++ b/vnet/vnet/l2/l2_bd.h
@@ -59,9 +59,6 @@ typedef struct {
   // set to ~0 if there is no BVI
   u32 bvi_sw_if_index;
 
-  // output node index for bvi interface before it was changed to l2-input
-  u32 saved_bvi_output_node_index;
-
   // bridge domain id, not to be confused with bd_index
   u32 bd_id;