FIB Interpose Source

The interpose source allows the source/provider to insert/interpose
a DPO in the forwarding chain of the FIB entry ahead of the forwarding
provided by the next best source. For example if the API source (i.e
the 'control plane') has provided an adjacency for forwarding, then
an interpose source (e.g. a monitoring service) couold interpose a
replicatte DPO to copy the traffic to another location AND forward
using the API's adjacency.
To use the interose feature an existing source (i.e FIB_SOURCE_PLUGIN_HI)
cn specifiy as a flag FIB_ENTRY_FLAG_INTERPOSE and provide a DPO to
interpose. One might also consider using interpose in conjunction with
FIB_ENTRY_FLAG_COVER_INHERIT to ensure the interpose object affects
all prefixes in the sub-tree.

Change-Id: I8b2737b985f8f7c08123406d0491881def347b52
Signed-off-by: Neale Ranns <nranns@cisco.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/src/vnet/dpo/dpo.h b/src/vnet/dpo/dpo.h
index 21a2ae2a33d..0eeca67b74b 100644
--- a/src/vnet/dpo/dpo.h
+++ b/src/vnet/dpo/dpo.h
@@ -225,6 +225,14 @@ extern void dpo_lock(dpo_id_t *dpo);
 extern void dpo_unlock(dpo_id_t *dpo);
 
 /**
+ * @brief
+ *  Make an interpose DPO from an original
+ */
+extern void dpo_mk_interpose(const dpo_id_t *original,
+                             const dpo_id_t *parent,
+                             dpo_id_t *clone);
+
+/**
  * @brief Set/create a DPO ID
  * The DPO will be locked.
  *
@@ -374,6 +382,18 @@ typedef u32* (*dpo_get_next_node_t)(const dpo_id_t *dpo);
 typedef u32 (*dpo_get_urpf_t)(const dpo_id_t *dpo);
 
 /**
+ * @brief Called during FIB interposition when the originally
+ * registered DPO is used to 'clone' an instance for interposition
+ * at a particular location in the FIB graph.
+ * The parent is the next DPO in the chain that the clone will
+ * be used instead of. The clone may then choose to stack itself
+ * on the parent.
+ */
+typedef void (*dpo_mk_interpose_t)(const dpo_id_t *original,
+                                   const dpo_id_t *parent,
+                                   dpo_id_t *clone);
+
+/**
  * @brief A virtual function table regisitered for a DPO type
  */
 typedef struct dpo_vft_t_
@@ -405,6 +425,10 @@ typedef struct dpo_vft_t_
      * Get uRPF interface
      */
     dpo_get_urpf_t dv_get_urpf;
+    /**
+     * Signal on an interposed child that the parent has changed
+     */
+    dpo_mk_interpose_t dv_mk_interpose;
 } dpo_vft_t;