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, 13 insertions, 14 deletions

diff --git a/vnet/vnet/llc/llc.c b/vnet/vnet/llc/llc.c
index 0496e8d48ce..975207b651d 100644
--- a/vnet/vnet/llc/llc.c
+++ b/vnet/vnet/llc/llc.c
@@ -155,31 +155,30 @@ unformat_llc_header (unformat_input_t * input, va_list * args)
   return 1;
 }
 
-static uword
-llc_set_rewrite (vnet_main_t * vnm,
-		 u32 sw_if_index,
-		 u32 l3_type,
-		 void *dst_address, void *rewrite, uword max_rewrite_bytes)
+static u8 *
+llc_build_rewrite (vnet_main_t * vnm,
+		   u32 sw_if_index,
+		   vnet_link_t link_type, const void *dst_address)
 {
-  llc_header_t *h = rewrite;
+  llc_header_t *h;
+  u8 *rewrite = NULL;
   llc_protocol_t protocol;
 
-  if (max_rewrite_bytes < sizeof (h[0]))
-    return 0;
-
-  switch (l3_type)
+  switch (link_type)
     {
-#define _(a,b) case VNET_L3_PACKET_TYPE_##a: protocol = LLC_PROTOCOL_##b; break
+#define _(a,b) case VNET_LINK_##a: protocol = LLC_PROTOCOL_##b; break
       _(IP4, ip4);
 #undef _
     default:
-      return 0;
+      return (NULL);
     }
 
+  vec_validate (rewrite, sizeof (*h) - 1);
+  h = (llc_header_t *) rewrite;
   h->src_sap = h->dst_sap = protocol;
   h->control = 0x3;
 
-  return sizeof (h[0]);
+  return (rewrite);
 }
 
 /* *INDENT-OFF* */
@@ -187,7 +186,7 @@ VNET_HW_INTERFACE_CLASS (llc_hw_interface_class) = {
   .name = "LLC",
   .format_header = format_llc_header_with_length,
   .unformat_header = unformat_llc_header,
-  .set_rewrite = llc_set_rewrite,
+  .build_rewrite = llc_build_rewrite,
 };
 /* *INDENT-ON* */