Update dhcpv6 options and performance

doc/DHCPv6_relay/DHCPv6-relay-agent-High-Level-Design.md

@@ -19,12 +19,15 @@
   - [CONFIG DB schema](#config-db-schema)
   - [YANG Model schema](#yang-model-schema)
   - [Option 79 for client link-layer address](#option-79-for-client-link-layer-address)
+  - [Option 18 for Interface-ID](#option-18-for-interface-id)
+  - [Config Update](#config-update)
   - [Option for Dual ToR](#option-for-dual-tor)
   - [Feature table](#feature-table)
   - [RADV modification](#radv-modification)
   - [CoPP manager](#copp-manager)
   - [Source IP](#source-ip)
 * [Performance](#performance)
+* [Scalability](#scalability)
 * [Testing](#testing)
 
 # Scope
@@ -166,33 +169,138 @@ RELAY-REPLY
 DHCP|intf-i|dhcpv6_servers: ["dhcp-server-0", "dhcp-server-1", ...., "dhcp-server-n-1"]
 
 DHCP|intf-i|dhcpv6_option|rfc6939_support: "true"
+
+DHCP|intf-i|dhcpv6_option|interface_id: "true"
+</pre>
+
+<pre>
+{
+        "DHCP_RELAY" :{
+                "Vlan100" : {
+                        "dhcpv6_servers" : ["fc02:2000::2"]
+			"dhcpv6_option|rfc6939_support" : "true"
+			"dhcpv6_option|interface_id" : "true"
+                }
+        }
+}
 </pre>
 
 # YANG Model schema
 
 sonic-dhcpv6-relay.yang
 <pre>
-module DHCP  
-    container DHCP {  	
-        list VLAN_LIST {
-    		key name;
-   		    leaf name {
-    			type string;
-  		    }
-   		    leaf dhcpv6_servers {
-     		    	type inet6:ip-address;
-  		    }
-		    leaf dhcpv6_option|rfc6939_support {
-			    type bool;
-		    }
+module sonic-dhcpv6-relay {
+
+	namespace "http://github.com/Azure/sonic-dhcpv6-relay";
+
+	prefix sdhcpv6relay;
+
+	yang-version 1.1;
+
+	import ietf-inet-types {
+		prefix inet;
+	}
+
+	organization "SONiC";
+
+	contact "SONiC";
+
+	description "DHCPv6 Relay yang Module for SONiC OS";
+
+	revision 2021-10-30 {
+		description "First Revision";
+	}
+
+	container sonic-dhcpv6-relay {
+
+		container DHCP_RELAY {
+
+			description "DHCP_RELAY part of config_db.json";
+
+			list DHCP_RELAY_LIST {
+
+				key "name";
+
+				leaf name {
+					type string;
+				}
+
+        leaf-list dhcpv6_servers {
+                description "Configure the dhcpv6 servers";
+                type inet:ipv6-address;
         }
+
+        leaf dhcpv6_option|rfc6939_support {
+                description "Set rfc6939 for the relay";
+        		    type bool;
+		    }
+
+        leaf dhcpv6_option|interface_id {
+                description "Set interface-id for the relay";
+        		    type bool;
+		    }
     }
+  }
 }
 </pre>
 
 # Option 79 for client link-layer address
 
-Option 79 should be enabled by default and can be disabled through command line.
+Option 79 should be enabled by default and can be disabled through editing config_db.json and reapplying configuration or config database directly by the following commands:
+
+Usage:
+```
+redis-cli -n 4 hset DHCP_RELAY|<vlan> dhcpv6_option|rfc6939_support <true/false>
+config vlan dhcp_relay add <vlan_id> <dhcp_relay_destination_ip>
+```
+Restart dhcp_relay after updating ipv6 helper information.
+
+Or edit directly in config_db.json and apply config_reload:
+```
+/etc/sonic/config_db.json:
+{
+        "DHCP_RELAY" :{
+                "Vlan100" : {
+                        "dhcpv6_servers" : ["fc02:2000::2"]
+			"dhcpv6_option|rfc6939_support" : "true"
+                }
+        }
+}
+
+sudo config reload
+```
+
+# Option 18 for Interface-ID
+
+Option 18 is disabled by default and can be enabled through editing config_db.json and reapplying configuration or config database directly by the following commands:
+
+Usage:
+```
+config vlan dhcp_relay add <vlan_id> <dhcp_relay_destination_ip>
+redis-cli -n 4 hset DHCP_RELAY|<vlan> dhcpv6_option|interface_id <true/false>
+```
+Or edit directly in config_db.json and apply config_reload:
+/etc/sonic/config_db.json:
+{
+        "DHCP_RELAY" :{
+                "Vlan100" : {
+                        "dhcpv6_servers" : ["fc02:2000::2"],
+			"dhcpv6_option|interface_id" : "true"
+                }
+        }
+}
+
+sudo config reload
+
+Example:
+```
+admin@sonic:~$ redis-cli -n 4 hset DHCP_RELAY|Vlan1000 dhcpv6_option|interface_id true
+```
+
+# Config Update
+
+We have shifted from VLAN table to DHCP_RELAY table to store ipv6 helper information.
+Only DHCP_RELAY table needs to be updated for the versions containing PR https://github.com/sonic-net/sonic-buildimage/pull/10654, or version 20201231.75 and 20181130.98 and above
 
 # Option for Dual ToR
 
@@ -224,6 +332,17 @@ Configurable option to use loopback address for dual ToR
 
 SONiC DHCP relay agent is currently not relaying many DHCP requests. Frequency arrival rate of DHCP packets is not high so it is not going to affect performance.
 
+# Scalability
+Typical number of vlans used with dhcp6relay is around 2 vlans. Performance degration and high CPU utilization is seen on devices with more than 25 vlans configured, especially devices with weaker CPU's.
+Tests have shown functionality and performance degradation when there are more than 20 vlans configured on weaker CPU's.
+
+•	25 Vlans - Passed on SPC1.
+
+•	100 and 50 Vlans - Failed on SPC1.
+
+•	100 Vlans - Passed on SPC2 and SPC3 with high CPU utilization.
+
+
 # Testing
 
 Use counter to check if DHCP messages are forwarded successfully using DHCPv6 relay agent