Add support for creating/modifying IPMC group with member list. (opencomputeproject#2121)

Signed-off-by: Kishore Gummadidala <[email protected]>
Co-authored-by: Kishore Gummadidala <[email protected]>

Author: erohsik

doc/IP-Multicast/MulticastWithMembers.md

@@ -0,0 +1,29 @@
+### IP Multicast Group with members
+
+Allow IP Multicast Group to be created/modified by specifying the list of members
+
+### Motivation
+
+The existing IPMC workflow
+* Create a IPMC group
+* Add/remove members to this group
+
+We describe a sample workflow
+* A is added to the group
+* B is added to the group
+* The path to A goes down, so an alternate member A' is added
+* Subsequently the primary path to A is restored, so A' needs to be swapped with A
+
+We have two ways to acheive this.
+* remove A' and then add A leading to a small window where no traffic is received by the receiver.
+* add A and then remove A' leading to a small window wheret duplicate traffic is received.
+
+We'd like to avoid both of these scenarios.
+
+### Proposal
+
+Specify the full current list of multicast group members at create and update time.
+
+* Introduce an attribute specifying that the IPMC group members are specified upfront.
+* Add a IPMC group attribute for the list of members
+

inc/saiipmcgroup.h

@@ -60,6 +60,26 @@ typedef enum _sai_ipmc_group_attr_t
      */
     SAI_IPMC_GROUP_ATTR_IPMC_MEMBER_LIST,
 
+    /**
+     * @brief Flag indicating that the member list is specified at create time
+     *
+     * @type bool
+     * @flags CREATE_ONLY
+     * @default false
+     */
+    SAI_IPMC_GROUP_ATTR_IPMC_GROUP_WITH_MEMBERS,
+
+    /**
+     * @brief IPMC output list
+     *
+     * @type sai_object_list_t
+     * @flags CREATE_AND_SET
+     * @objects SAI_OBJECT_TYPE_NEXT_HOP
+     * @default empty
+     * @validonly SAI_IPMC_GROUP_ATTR_IPMC_GROUP_WITH_MEMBERS == true
+     */
+    SAI_IPMC_GROUP_ATTR_IPMC_OUTPUT_LIST,
+
     /**
      * @brief End of attributes
      */