Add new Next Hop Type and allow Next Hop to be an IPMC Group Member (#…

…2041) * Add new Next Hop Type and allow Next Hop to be an IPMC Group Member Signed-off-by: Manali Holankar <manali.holankar@gmail.com>
opencomputeproject · Aug 5, 2024 · c907595 · c907595
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diff --git a/doc/IP-Multicast/MulticastNextHopRewrite.md b/doc/IP-Multicast/MulticastNextHopRewrite.md
@@ -0,0 +1,80 @@
+# SAI attributes for disabling L3 rewrites
+
+# for IP Multicast forwarding
+
+```
+Author:mholankar@
+```
+
+## Overview
+
+This document discusses requirements and the SAI spec proposal for disabling rewriting fields (SourceMAC, VLAN) as part of IPMC routing.
+
+## Background
+
+### SAI pipeline for IPMC forwarding. After Multicast Replication, the egress
+
+### pipeline is very similar to Unicast Forwarding. The reference pipeline is
+
+### fromUnicastForwarding.
+
+- Nexthop sets the egress RIF and NextHopIP
+- Neighbor table lookup on NextHopIP to set packet's destination MAC address
+- Egress RIF lookup to set packet's source MAC address, VLAN and port.
+
+## Requirements
+
+We require knobs for disabling rewrites to following fields as part of Multicast forwarding flows
+
+```
+● Src MAC disable
+● Vlan rewrite disable
+```
+
+We have scenarios where we need knobs for disabling header field rewrites, for Multicast Replication.
+
+Case1:For certain flows, the switch does MulticastReplication for a VLAN tagged packet. However, we do not want the VLAN tag to be over-written during replication, we want the replication to retain the VLAN tag. For such a case we would like to disable L3 VLAN rewrite. Please note: that when a disable L3 Vlan rewrite
+flag is enabled, it does allow for untagged packets to get replicated.
+
+Case2: For some scenarios, we may want to rewrite the SRC MAC. Having NextHop based knobs for such rewrites would be very helpful.
+
+In summary, with SDN based forwarding, Controller treats the L2 fields like any other header field which can be controlled and requires them to be configured flexibility as part of MulticastReplication.
+
+## Proposal
+
+Since we require capability to disable the rewrites for certain Multicast flows and not for all flows via/to neighbor, the best option is to have these as part of NextHop object:
+
+- SAI_NEXT_HOP_ATTR_DISABLE_SRC_MAC_REWRITE
+- SAI_NEXT_HOP_ATTR_DISABLE_DST_MAC_REWRITE
+- SAI_NEXT_HOP_ATTR_DISABLE_VLAN_REWRITE
+
+### Example SAI object creation for an IPMCGroup:
+
+- Create a **SAI_OBJECT_TYPE_IPMC_GROUP** for the multicast group with the following attributes.
+- Create a SAI_OBJECT_TYPE_ROUTER_INTERFACE with following attributes:
+● SAI_ROUTER_INTERFACE_ATTR_VIRTUAL_ROUTER_ID
+● SAI_ROUTER_INTERFACE_ATTR_SRC_MAC_ADDRESS
+● SAI_ROUTER_INTERFACE_ATTR_TYPE=SAI_ROUTER_INTERFACE_TYPE_
+
+  ```
+  PORT
+  ```
+
+● SAI_ROUTER_INTERFACE_ATTR_PORT_ID
+- Create a SAI_OBJECT_TYPE_NEIGHBOR_ENTRY for each neighbor with:
+● "ip"=Link local address ● "rif" ● "switch id"
+● SAI_NEIGHBOR_ENTRY_ATTR_DST_MAC_ADDRESS(optional)
+● SAI_NEIGHBOR_ENTRY_ATTR_NO_HOST_ROUTE=true
+- Create SAI_OBJECT_TYPE_NEXT_HOP with:
+● SAI_NEXT_HOP_ATTR_TYPE=SAI_NEXT_HOP_TYPE_IPMC
+● SAI_NEXT_HOP_ATTR_ROUTER_INTERFACE_ID
+● SAI_NEXT_HOP_ATTR_IP="ip"of neighbor
+
+```
+● SAI_NEXT_HOP_ATTR_DISABLE_SRC_MAC_REWRITE=true
+● SAI_NEXT_HOP_ATTR_DISABLE_VLAN_REWRITE=true
+```
+
+- Create a **SAI_OBJECT_TYPE_IPMC_GROUP_MEMBER** with following attributes:
+● SAI_IPMC_GROUP_MEMBER_ATTR_IPMC_GROUP_ID with ipmc_group_oid
+● SAI_IPMC_GROUP_MEMBER_ATTR_IPMC_OUTPUT_ID with next_hop_oid
diff --git a/inc/saiipmcgroup.h b/inc/saiipmcgroup.h
@@ -94,7 +94,7 @@ typedef enum _sai_ipmc_group_member_attr_t
      *
      * @type sai_object_id_t
      * @flags MANDATORY_ON_CREATE | CREATE_ONLY
-     * @objects SAI_OBJECT_TYPE_ROUTER_INTERFACE, SAI_OBJECT_TYPE_TUNNEL
+     * @objects SAI_OBJECT_TYPE_ROUTER_INTERFACE, SAI_OBJECT_TYPE_TUNNEL, SAI_OBJECT_TYPE_NEXT_HOP
      */
     SAI_IPMC_GROUP_MEMBER_ATTR_IPMC_OUTPUT_ID,
 

diff --git a/inc/sainexthop.h b/inc/sainexthop.h
@@ -50,6 +50,8 @@ typedef enum _sai_next_hop_type_t
     /** SRV6 SID List */
     SAI_NEXT_HOP_TYPE_SRV6_SIDLIST,
 
+    /** IPMC next hop */
+    SAI_NEXT_HOP_TYPE_IPMC,
 } sai_next_hop_type_t;
 
 /**
@@ -76,7 +78,7 @@ typedef enum _sai_next_hop_attr_t
      *
      * @type sai_ip_address_t
      * @flags MANDATORY_ON_CREATE | CREATE_ONLY
-     * @condition SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_IP or SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_MPLS or SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_TUNNEL_ENCAP
+     * @condition SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_IP or SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_MPLS or SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_TUNNEL_ENCAP or SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_IPMC
      */
     SAI_NEXT_HOP_ATTR_IP,
 
@@ -86,7 +88,7 @@ typedef enum _sai_next_hop_attr_t
      * @type sai_object_id_t
      * @flags MANDATORY_ON_CREATE | CREATE_ONLY
      * @objects SAI_OBJECT_TYPE_ROUTER_INTERFACE
-     * @condition SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_IP or SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_MPLS
+     * @condition SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_IP or SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_MPLS or SAI_NEXT_HOP_ATTR_TYPE == SAI_NEXT_HOP_TYPE_IPMC
      */
     SAI_NEXT_HOP_ATTR_ROUTER_INTERFACE_ID,