Change ARP and IP6-ND nodes to use interface-output node for output

The current mechanism for setting up arp-input and ip6-discover-neighbor
output nodes for interfaces using their interface link up/down callback
function is inefficient and has potential timing issue, as observed for
bonded interface. Now both nodes will setup output interface sw_if_index
in the the sw_if_index[VLIB_TX] field of current packet buffer and then
use the interface-ouput node to tx the packet.

One side effect is that vlib_node_add_next_with_slot() needs to be
modified to allow the same output node-id to be put at the specified
slot, even if another slot contain that same node-id already exist. This
requirement is caused by BVI support where all loopback interfaces set
up as BVIs will have the same output node-id being l2-input while, for
output-interface node, the output slot must match the hw_if_index of the
interface.

Change-Id: I18bd1d4fe9bea047018796f7b8a4d4c20ee31d6e
Signed-off-by: John Lo <loj@cisco.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/vlib/vlib/node.c b/vlib/vlib/node.c
index 40ef7c71a51..573b3a79567 100644
--- a/vlib/vlib/node.c
+++ b/vlib/vlib/node.c
@@ -177,10 +177,9 @@ vlib_node_add_next_with_slot (vlib_main_t * vm,
 
   if ((p = hash_get (node->next_slot_by_node, next_node_index)))
     {
-      /* Next already exists: slot must match. */
-      if (slot != ~0)
-	ASSERT (slot == p[0]);
-      return p[0];
+      /* Next already exists: use it if slot not specified or the same. */
+      if ((slot == ~0) || (slot == p[0]))
+	  return p[0];
     }
 
   if (slot == ~0)
@@ -190,7 +189,7 @@ vlib_node_add_next_with_slot (vlib_main_t * vm,
   vec_validate (node->n_vectors_by_next_node, slot);
 
   node->next_nodes[slot] = next_node_index;
-  hash_set (node->next_slot_by_node, next_node_index, slot);
+  if (!p) hash_set (node->next_slot_by_node, next_node_index, slot);
 
   vlib_node_runtime_update (vm, node_index, slot);