BFD-FIB interactions

- single-hop BFD: attach a delegate to the appropriate adjacency
- multi-hop BFD [not supported yet]: attach a delegate to the FIB entry.

adjacency/fib_entry state tracks the BFD session state. when the state is down the object does not contribute forwarding hence and hence dependent objects will not use it.
For example, if a route is ECMP via two adjacencies and one of them is BFD down, then only the other is used to forward (i.e. we don't drop half the traffic).

Change-Id: I0ef53e20e73b067001a132cd0a3045408811a822
Signed-off-by: Neale Ranns <nranns@cisco.com>

3 files changed, 73 insertions, 2 deletions

diff --git a/src/vnet/bfd/bfd_main.c b/src/vnet/bfd/bfd_main.c
index 2b70a20c9fd..66b31ce502c 100644
--- a/src/vnet/bfd/bfd_main.c
+++ b/src/vnet/bfd/bfd_main.c
@@ -101,6 +101,7 @@ bfd_set_defaults (bfd_main_t * bm, bfd_session_t * bs)
   bs->local_diag = BFD_DIAG_CODE_no_diag;
   bs->remote_state = BFD_STATE_down;
   bs->remote_discr = 0;
+  bs->hop_type = BFD_HOP_TYPE_SINGLE;
   bs->config_desired_min_tx_usec = BFD_DEFAULT_DESIRED_MIN_TX_USEC;
   bs->config_desired_min_tx_clocks = bm->default_desired_min_tx_clocks;
   bs->effective_desired_min_tx_clocks = bm->default_desired_min_tx_clocks;
@@ -387,6 +388,17 @@ bfd_set_remote_required_min_echo_rx (bfd_main_t * bm, bfd_session_t * bs,
     }
 }
 
+static void
+bfd_notify_listeners (bfd_main_t * bm,
+		      bfd_listen_event_e event, const bfd_session_t * bs)
+{
+  bfd_notify_fn_t *fn;
+  vec_foreach (fn, bm->listeners)
+  {
+    (*fn) (event, bs);
+  }
+}
+
 void
 bfd_session_start (bfd_main_t * bm, bfd_session_t * bs)
 {
@@ -396,6 +408,7 @@ bfd_session_start (bfd_main_t * bm, bfd_session_t * bs)
   bfd_recalc_tx_interval (bm, bs);
   vlib_process_signal_event (bm->vlib_main, bm->bfd_process_node_index,
 			     BFD_EVENT_NEW_SESSION, bs->bs_idx);
+  bfd_notify_listeners (bm, BFD_LISTEN_EVENT_CREATE, bs);
 }
 
 void
@@ -533,6 +546,7 @@ bfd_on_state_change (bfd_main_t * bm, bfd_session_t * bs, u64 now,
       bfd_set_timer (bm, bs, now, handling_wakeup);
       break;
     }
+  bfd_notify_listeners (bm, BFD_LISTEN_EVENT_UPDATE, bs);
 }
 
 static void
@@ -1121,6 +1135,14 @@ bfd_hw_interface_up_down (vnet_main_t * vnm, u32 hw_if_index, u32 flags)
 
 VNET_HW_INTERFACE_LINK_UP_DOWN_FUNCTION (bfd_hw_interface_up_down);
 
+void
+bfd_register_listener (bfd_notify_fn_t fn)
+{
+  bfd_main_t *bm = &bfd_main;
+
+  vec_add1 (bm->listeners, fn);
+}
+
 /*
  * setup function
  */
@@ -1180,6 +1202,7 @@ bfd_get_session (bfd_main_t * bm, bfd_transport_e t)
 void
 bfd_put_session (bfd_main_t * bm, bfd_session_t * bs)
 {
+  bfd_notify_listeners (bm, BFD_LISTEN_EVENT_DELETE, bs);
   if (bs->auth.curr_key)
     {
       --bs->auth.curr_key->use_count;
diff --git a/src/vnet/bfd/bfd_main.h b/src/vnet/bfd/bfd_main.h
index d722a55274c..93adac3dc8d 100644
--- a/src/vnet/bfd/bfd_main.h
+++ b/src/vnet/bfd/bfd_main.h
@@ -66,6 +66,20 @@ typedef enum
 #undef F
 } bfd_poll_state_e;
 
+/**
+ * hop types
+ */
+#define foreach_bfd_hop(F)                     \
+  F (SINGLE, "single")                         \
+  F (MULTI,  "multi")                          \
+
+typedef enum
+{
+#define F(sym, str) BFD_HOP_TYPE_##sym,
+  foreach_bfd_hop (F)
+#undef F
+} bfd_hop_type_e;
+
 typedef struct bfd_session_s
 {
   /** index in bfd_main.sessions pool */
@@ -77,6 +91,9 @@ typedef struct bfd_session_s
   /** remote session state */
   bfd_state_e remote_state;
 
+  /** BFD hop type */
+  bfd_hop_type_e hop_type;
+
   /** local diagnostics */
   bfd_diag_code_e local_diag;
 
@@ -220,6 +237,26 @@ typedef struct bfd_session_s
   };
 } bfd_session_t;
 
+/**
+ * listener events
+ */
+#define foreach_bfd_listen_event(F)            \
+  F (CREATE, "sesion-created")                 \
+  F (UPDATE, "session-updated")                \
+  F (DELETE, "session-deleted")
+
+typedef enum
+{
+#define F(sym, str) BFD_LISTEN_EVENT_##sym,
+  foreach_bfd_listen_event (F)
+#undef F
+} bfd_listen_event_e;
+
+/**
+ * session nitification call back function type
+ */
+typedef void (*bfd_notify_fn_t) (bfd_listen_event_e, const bfd_session_t *);
+
 typedef struct
 {
   /** pool of bfd sessions context data */
@@ -259,6 +296,8 @@ typedef struct
   /** hashmap - index in pool auth_keys by conf_key_id */
   u32 *auth_key_by_conf_key_id;
 
+  /** A vector of callback notification functions */
+  bfd_notify_fn_t *listeners;
 } bfd_main_t;
 
 extern bfd_main_t bfd_main;
@@ -345,6 +384,11 @@ const char *bfd_poll_state_string (bfd_poll_state_e state);
  */
 #define BFD_REQUIRED_MIN_RX_USEC_WHILE_ECHO USEC_PER_SECOND
 
+/**
+ * Register a callback function to receive session notifications.
+ */
+void bfd_register_listener (bfd_notify_fn_t fn);
+
 #endif /* __included_bfd_main_h__ */
 
 /*
diff --git a/src/vnet/bfd/bfd_udp.h b/src/vnet/bfd/bfd_udp.h
index a4adbadf861..87868104f98 100644
--- a/src/vnet/bfd/bfd_udp.h
+++ b/src/vnet/bfd/bfd_udp.h
@@ -27,8 +27,12 @@
 /* *INDENT-OFF* */
 /** identifier of BFD session based on UDP transport only */
 typedef CLIB_PACKED (struct {
-  /** interface to which the session is tied */
-  u32 sw_if_index;
+  union {
+    /** interface to which the session is tied - single-hop */
+    u32 sw_if_index;
+    /** the FIB index the peer is in - multi-hop*/
+    u32 fib_index;
+  };
   /** local address */
   ip46_address_t local_addr;
   /** peer address */