Class-Based Forwarding (#1193)

This PR defines class-based forwarding. It contains two aspects:

Assignment of a Forwarding Class to a packet, via QOS map or ACL

New next-hop group type: SAI_NEXT_HOP_GROUP_TYPE_CLASS_BASED

Where member selection is based on the forwarding-class of the packet.

Signed-off-by: Jason Bos <jbos@cisco.com>

doc/ECMP/Class-Based-Forwarding.md

@@ -0,0 +1,211 @@
+# Class-based Forwarding
+
+Title       | Class-based Forwarding
+------------|----------------
+Authors     | Cisco
+Status      | In review
+Type        | Standards track
+Created     | 04/14/2021
+SAI-Version | 1.8
+
+Class-based forwarding provides a method to steer traffic among multiple paths through the network by policy rather than, or in combination with, traditional ECMP/UCMP flow-hashing.
+
+A new type of next-hop group is introduced:
+
+```
+typedef enum _sai_next_hop_group_type_t
+{
+...
+    /** Next hop group is class-based, with members selected by Forwarding class */
+    SAI_NEXT_HOP_GROUP_TYPE_CLASS_BASED,
+...
+} sai_next_hop_group_type_t;
+```
+
+The behavior of SAI_NEXT_HOP_GROUP_TYPE_CLASS_BASED differs from the traditional SAI_NEXT_HOP_GROUP_TYPE_ECMP, in that each packet will have a Forwarding class that chooses next-hop group member index.
+
+This is accomplished by directly mapping each forwarding class to the group member index, via map configured to the next-hop group object.
+
+```
+    /**
+     * @brief Member selection map
+     *
+     * @type sai_object_id_t
+     * @flags CREATE_AND_SET
+     * @objects SAI_OBJECT_TYPE_NEXT_HOP_GROUP_MAP
+     * @allownull true
+     * @default SAI_NULL_OBJECT_ID
+     * @validonly SAI_NEXT_HOP_GROUP_ATTR_TYPE == SAI_NEXT_HOP_GROUP_TYPE_CLASS_BASED
+     */
+    SAI_NEXT_HOP_GROUP_ATTR_SELECTION_MAP,
+```
+
+If a packet arrives with a forwarding-class which is not present in the map, the chosen index shall be 0.
+
+```
+typedef  enum  _sai_next_hop_group_member_attr_t
+{
+...
+    /**
+     * @brief Object index in the next-hop group.
+     *
+     * Index specifying the strict member's order.
+     * Allowed value range for is from 0 to SAI_NEXT_HOP_GROUP_ATTR_REAL_SIZE - 1.
+     * Should only be used if the type of owning group is SAI_NEXT_HOP_GROUP_TYPE_FINE_GRAIN_ECMP
+     * or SAI_NEXT_HOP_GROUP_TYPE_CLASS_BASED.
+     *
+     * @type sai_uint32_t
+     * @flags CREATE_ONLY
+     * @default 0
+     */
+    SAI_NEXT_HOP_GROUP_MEMBER_ATTR_INDEX,
+...
+} sai_next_hop_group_member_attr_t;
+```
+
+If the map selects an index for which a member does not exist, the packet shall be treated as having a next-hop of SAI_NULL_OBJECT_ID, dropping the packet.
+
+Members of type next-hop or next-hop groups of type ECMP shall be allowed. To allow this, next-hop group member type is extended to allow other next-hop groups:
+
+```
+   /**
+     * @brief Next hop id
+     *
+     * @type sai_object_id_t
+     * @flags MANDATORY_ON_CREATE | CREATE_AND_SET
+     * @objects SAI_OBJECT_TYPE_NEXT_HOP, <b>SAI_OBJECT_TYPE_NEXT_HOP_GROUP</b>
+     */
+    SAI_NEXT_HOP_GROUP_MEMBER_ATTR_NEXT_HOP_ID,
+```
+
+*Note: While this would also be a means to configure a hierarchical ECMP, hierarchical ECMP is outside the scope of this proposal.*
+
+The forwarding-class for a packet may be selected via qos-map or ACL.
+
+```
+typedef  enum  _sai_qos_map_type_t
+{
+...
+    /** QOS Map to set DSCP to Forwarding class */
+    SAI_QOS_MAP_TYPE_DSCP_TO_FORWARDING_CLASS = 0x0000000d,
+
+    /** QOS Map to set EXP to Forwarding class */
+    SAI_QOS_MAP_TYPE_MPLS_EXP_TO_FORWARDING_CLASS = 0x0000000e,
+...
+} sai_qos_map_type_t;
+```
+
+```
+typedef enum _sai_acl_entry_attr_t
+...
+    /**
+     *  @brief  Set Forwarding Class
+     *
+     *  @type  sai_acl_action_data_t  sai_uint8_t
+     *  @flags  CREATE_AND_SET
+     *  @default  disabled
+     */
+    SAI_ACL_ENTRY_ATTR_ACTION_SET_FORWARDING_CLASS,
+...
+}  sai_acl_entry_attr_t;
+```
+
+If the packet is not assigned a forwarding-class, then the forwarding-class of the packet shall be 0. For example, if no qos-map or ACL is configured. Normal QOS/ACL precedence rules apply; if supported by the implementation, the ACL would override the QOS MAP decision.
+
+*Resource monitoring considerations:*
+
+The attribute SAI_SWITCH_ATTR_MAX_NUMBER_OF_FORWARDING_CLASSES may be used to identify the maximum forwarding-class allowed.
+
+The SAI_OBJECT_TYPE_NEXT_HOP_GROUP_MAP object is a resource. The sai_object_type_get_availability() API may be used to query the maximum number of permitted maps.
+
+*Class-based forwarding group configuration example:*
+```
+/******************************************************
+ * Create a forwarding-class -> index map.
+ * In this example, map 8 forwarding-classes to 2 members.
+ *   FC 0-5 -> index 0
+ *   FC 6-7 -> index 1
+ ******************************************************/
+ const int num_forwarding_classes = 8;
+ const int num_members = 2;
+
+ sai_object_id_t nh_group_map;
+
+ sai_map_t fc_map[num_forwarding_classes];
+ for (int fc = 0; fc < num_forwarding_classes; ++fc) {
+    fc_map[fc].key = fc;
+    if (fc >= 6) {
+       fc_map[fc].value = 1;
+    } else {
+       fc_map[fc].value = 0;
+    }
+ }
+
+ sai_map_list_t fc_map_list;
+ fc_map_list.key.count = num_forwarding_classes;
+ fc_map_list.key.list = fc_map;
+
+ attr.id = SAI_NEXT_HOP_GROUP_MAP_ATTR_TYPE;
+ attr.value.u32 = SAI_NEXT_HOP_GROUP_MAP_TYPE_FORWARDING_CLASS_TO_INDEX;
+ attrs.push_back(attr);
+
+ attr.id = SAI_NEXT_HOP_GROUP_MAP_ATTR_MAP_TO_VALUE_LIST;
+ attr.value.maplist = fc_map_list;
+ attrs.push_back(attr);
+
+ sai_next_hop_group_api->create_next_hop_group_map(
+     &nh_group_map,
+     g_switch_id,
+     attrs.size(),
+     attrs.data());
+
+ /*****************************************************
+  * Create a class-based forwarding group
+  *****************************************************/
+ attrs.clear();
+
+ sai_object_id_t nh_group;
+
+ attr.id = SAI_NEXT_HOP_GROUP_ATTR_TYPE;
+ attr.value.u32 = SAI_NEXT_HOP_GROUP_TYPE_CLASS_BASED;
+ attrs.push_back(attr);
+
+ attr.id = SAI_NEXT_HOP_GROUP_ATTR_CONFIGURED_SIZE;
+ attr.value.u32 = num_members;
+ attrs.push_back(attr);
+
+ attr.id = SAI_NEXT_HOP_GROUP_ATTR_SELECTION_MAP;
+ attr.value.oid = nh_group_map;
+ attrs.push_back(attr);
+
+ sai_next_hop_group_api->create_next_hop_group(
+     &nh_group,
+     g_switch_id,
+     attrs.size(),
+     attrs.data());
+
+ /*****************************************************
+  * Create members
+  *****************************************************/
+ attrs.clear();
+
+ for (index = 0; index < num_members; ++index) {
+     attr.id = SAI_NEXT_HOP_GROUP_MEMBER_ATTR_NEXT_HOP_GROUP_ID;
+     attr.value.oid = nh_group;
+     attrs.push_back(attr);
+
+     attr.id = SAI_NEXT_HOP_GROUP_MEMBER_ATTR_NEXT_HOP_ID;
+     attr.value.oid = destinations[index]; // Next-hop or ECMP group
+     attrs.push_back(attr);
+
+     attr.id = SAI_NEXT_HOP_GROUP_MEMBER_ATTR_INDEX;
+     attr.value.u32 = index;
+     attrs.push_back(attr);
+
+     sai_next_hop_group_api->create_next_hop_group_member(
+         &members[member_index],
+         g_switch_id,
+         attrs.size(),
+         attrs.data());
+ }
+```

inc/saiacl.h

@@ -272,7 +272,10 @@ typedef enum _sai_acl_action_type_t
     SAI_ACL_ACTION_TYPE_SET_ECMP_HASH_ID = 0x00000030,
 
     /** Associate with virtual router */
-    SAI_ACL_ACTION_TYPE_SET_VRF = 0x00000031
+    SAI_ACL_ACTION_TYPE_SET_VRF = 0x00000031,
+
+    /** Set Forwarding class */
+    SAI_ACL_ACTION_TYPE_SET_FORWARDING_CLASS = 0x00000034,
 
 } sai_acl_action_type_t;
 
@@ -2922,10 +2925,19 @@ typedef enum _sai_acl_entry_attr_t
      */
     SAI_ACL_ENTRY_ATTR_ACTION_SET_VRF = SAI_ACL_ENTRY_ATTR_ACTION_START + 0x31,
 
+    /**
+     * @brief Set Forwarding Class
+     *
+     * @type sai_acl_action_data_t sai_uint8_t
+     * @flags CREATE_AND_SET
+     * @default disabled
+     */
+    SAI_ACL_ENTRY_ATTR_ACTION_SET_FORWARDING_CLASS = SAI_ACL_ENTRY_ATTR_ACTION_START + 0x34,
+
     /**
      * @brief End of Rule Actions
      */
-    SAI_ACL_ENTRY_ATTR_ACTION_END = SAI_ACL_ENTRY_ATTR_ACTION_ADD_VLAN_PRI,
+    SAI_ACL_ENTRY_ATTR_ACTION_END = SAI_ACL_ENTRY_ATTR_ACTION_SET_FORWARDING_CLASS,
 
     /**
      * @brief End of ACL Entry attributes