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>

1 files changed, 104 insertions, 0 deletions

diff --git a/src/vnet/adj/adj_delegate.h b/src/vnet/adj/adj_delegate.h
new file mode 100644
index 00000000000..176512039d6
--- /dev/null
+++ b/src/vnet/adj/adj_delegate.h
@@ -0,0 +1,104 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __ADJ_DELEGATE_T__
+#define __ADJ_DELEGATE_T__
+
+#include <vnet/adj/adj.h>
+
+/**
+ * Delegate types
+ */
+typedef enum adj_delegate_type_t_ {
+    /**
+     * BFD session state
+     */
+    ADJ_DELEGATE_BFD,
+} adj_delegate_type_t;
+
+#define FOR_EACH_ADJ_DELEGATE(_adj, _adt, _aed, _body)        \
+{                                                             \
+    for (_adt = ADJ_DELEGATE_BFD;                             \
+         _adt <= ADJ_DELEGATE_BFD;                            \
+         _adt++)                                              \
+    {                                                         \
+        _aed = adj_delegate_get(_adj, _adt);                  \
+        if (NULL != _aed) {                                   \
+            _body;                                            \
+        }                                                     \
+    }                                                         \
+}
+
+/**
+ * Distillation of the BFD session states into a go/no-go for using
+ * the associated tracked adjacency
+ */
+typedef enum adj_bfd_state_t_
+{
+    ADJ_BFD_STATE_DOWN,
+    ADJ_BFD_STATE_UP,
+} adj_bfd_state_t;
+
+/**
+ * A Delagate is a means to implement the Delagation design pattern;
+ * the extension of an object's functionality through the composition of,
+ * and delgation to, other objects.
+ * These 'other' objects are delegates. Delagates are thus attached to
+ * ADJ objects to extend their functionality.
+ */
+typedef struct adj_delegate_t_
+{
+    /**
+     * The ADJ entry object to which the delagate is attached
+     */
+    adj_index_t ad_adj_index;
+
+    /**
+     * The delagate type
+     */
+    adj_delegate_type_t ad_type;
+
+    /**
+     * A union of data for the different delegate types
+     */
+    union
+    {
+        /**
+         * BFD delegate daa
+         */
+        struct {
+            /**
+             * BFD session state
+             */
+            adj_bfd_state_t ad_bfd_state;
+            /**
+             * BFD session index
+             */
+            u32 ad_bfd_index;
+        };
+    };
+} adj_delegate_t;
+
+extern void adj_delegate_remove(ip_adjacency_t *adj,
+                                adj_delegate_type_t type);
+
+extern adj_delegate_t *adj_delegate_find_or_add(ip_adjacency_t *adj,
+                                                adj_delegate_type_t fdt);
+extern adj_delegate_t *adj_delegate_get(const ip_adjacency_t *adj,
+                                        adj_delegate_type_t type);
+
+extern u8 *format_adj_deletegate(u8 * s, va_list * args);
+
+#endif