[VRF]When assigning a loopback interface to Vrf, the ip2me route gets added in default VRF

[dgsudharsan]

Description

Sometimes when adding a loopback interface to a non default VRF ip2me route gets added in default VRF. This is due to the below handling

In normal scenario when VRF is bound to interface, there will be an interface del followed by setting VRF. Below is an example

2024-10-13.20:17:22.950331|INTF_TABLE:Loopback3|SET|NULL:NULL|mac_addr:00:00:00:00:00:00
2024-10-13.20:17:35.237876|INTF_TABLE:Loopback3|DEL
2024-10-13.20:17:35.291212|INTF_TABLE:Loopback3|SET|vrf_name:Vrf_0003|mac_addr:00:00:00:00:00:00
2024-10-13.20:17:42.787366|INTF_TABLE:Loopback3:2.2.2.2/32|SET|scope:global|family:IPv4

However in some scenarios the DEL message is missed.

2024-10-13.20:41:58.482724|INTF_TABLE:Loopback3|SET|NULL:NULL|mac_addr:00:00:00:00:00:00
2024-10-13.20:41:59.997430|INTF_TABLE:Loopback3|SET|vrf_name:Vrf_0003|mac_addr:00:00:00:00:00:00
2024-10-13.20:42:02.151584|INTF_TABLE:Loopback3:2.2.2.2/32|SET|scope:global|family:IPv4

Due to the below check the VRF for the interface is not updated

sonic-swss/orchagent/intfsorch.cpp

Line 840 in e71eb2d

if (m_syncdIntfses.find(alias) == m_syncdIntfses.end())

Intfmgrd when it receives del it updates appl_db and state_db

sonic-swss/cfgmgr/intfmgr.cpp

Line 1052 in e71eb2d

m_stateIntfTable.del(alias);

Due to intfmgr removing del from state_db, the CLI proceeds to do set command

https://github.com/nvidia-sonic/sonic-utilities/blob/649e76192a23d4c1ff22d752000a9229b8ffbb9d/config/main.py#L5671

However orchagent might not have processed the previous DEL message. Thus when a SET comes the optimization results in DEL getting ignored and thus VRF not getting updated.

This results in the ip2me route for the Loopback getting programmed in the default vrf

2024-10-13.20:42:02.151879|c|SAI_OBJECT_TYPE_ROUTE_ENTRY:{"dest":"2.2.2.2/32","switch_id":"oid:0x21000000000000","vr":"oid:0x3000000000002"}|SAI_ROUTE_ENTRY_ATTR_PACKET_ACTION=SAI_PACKET_ACTION_FORWARD|SAI_ROUTE_ENTRY_ATTR_NEXT_HOP_ID=oid:0x1000000000001

Steps to reproduce the issue:

1. config loopback add Loopback2
2. attach gdb to orchagent. don't press continue so it is stalled.
3. config interface vrf bind Loopback2
4. press continue in GDB
5. Assign ip address to Loopback2. The route would be created in default vrf

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