FIB2.0: Adjacency complete pull model (VPP-487)

Change the adjacency completion model to pull not push.

A complete adjacency has a rewirte string, an incomplete one does not. the re-write string for a peer comes either from a discovery protocol (i.e. ARP/ND) or can be directly derived from the link type (i.e. GRE tunnels). Which method it is, is interface type specific.
For each packet type sent on a link to a peer there is a corresponding adjacency. For example, if there is a peer 10.0.0.1 on Eth0 and we need to send to it IPv4 and MPLS packets, there will be two adjacencies; one for the IPv4 and one for the MPLS packets. The adjacencies are thus distinguished by the packets the carry, this is known as the adjacency's 'link-type'. It is not an L3 packet type, since the adjacency can have a link type of Ethernet (for L2 over GRE).
The discovery protocols are not aware of all the link types required - only the FIB is. the FIB will create adjacencies as and when they are required, and it is thus then desirable to 'pull' from the discovery protocol the re-write required. The alternative (that we have now) is that the discovery protocol pushes (i.e. creates) adjacencies for each link type - this creates more adjacencies than we need.
To pull, FIB now requests from the interface-type to 'complete' the adjacency. The interface can then delegate to the discovery protocol (on ethernet links) or directly build the re-write (i.e on GRE).

Change-Id: I61451789ae03f26b1012d8d6524007b769b6c6ee
Signed-off-by: Neale Ranns <nranns@cisco.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/vnet/vnet/fib/fib_path.c b/vnet/vnet/fib/fib_path.c
index bea17218547..ba42e6be545 100644
--- a/vnet/vnet/fib/fib_path.c
+++ b/vnet/vnet/fib/fib_path.c
@@ -757,6 +757,20 @@ fib_path_back_walk_notify (fib_node_t *node,
 		fib_path_proto_to_chain_type(path->fp_nh_proto),
 		&path->fp_dpo);
 	}
+	if (FIB_NODE_BW_REASON_FLAG_ADJ_UPDATE & ctx->fnbw_reason)
+	{
+	    /*
+	     * ADJ updates (complete<->incomplete) do not need to propagate to
+	     * recursive entries.
+	     * The only reason its needed as far back as here, is that the adj
+	     * and the incomplete adj are a different DPO type, so the LBs need
+	     * to re-stack.
+	     * If this walk was quashed in the fib_entry, then any non-fib_path
+	     * children (like tunnels that collapse out the LB when they stack)
+	     * would not see the update.
+	     */
+	    return (FIB_NODE_BACK_WALK_CONTINUE);
+	}
 	break;
     case FIB_PATH_TYPE_ATTACHED_NEXT_HOP:
 	/*