[chassis] Remote ASIC SYSTEM_INTERFACE is not created if it is received before remote SYSTEM_LAG from the Chassis DB

[sanmalho-git]

Description

In a Sonic chassis the Chassis DB is used to exchange SYSTEM_LAG and SYSTEM_INTERFACE on the LAG from one asic to another. The asic where the LAG and the Interface are local – creates entries in the Chassis DB. These tables are subscribed to and received by the OrchAgent on the other ASICs. Sometimes it is possible that the OrchAgent received the SYSTEM_INTERFACE entry (for a LAG) before it receives the entry for the SYSTEM_LAG (on which the interface is to be created). In this scenario it is expected that the OrchAgent waits until the LAG creation and then then create the ROUTER_INTERFACE on top of it. But because of a bug in the IntfsOrch code for handling remote system interface – the ROUTER_INTERFACE is never created.

Steps to reproduce the issue:

1. Validate that neighbor entry for all the eBGP peers on all the asics are present on all the asics in the chassis. For a T2 topology, this can be done as below:

admin@sonic:~$ sudo ip netns exec asic0 ip neigh show | grep 10.0.0  | wc -l
52
admin@ixre-egl-board7:~$ sudo ip netns exec asic0 ip neigh show | grep fc00  | wc -l
52

2. Reboot the supervisor card on a T2 chassis, which in turn would cause all the linecards to reboot.
3. After all cards rebooted and eBGP's are up, validate that neighbor entry for all the eBGP peers on all the asics are present on all the asics in the chassis

Describe the results you received:

Number of ip neigh entries for ipv4 and ipv6 eBGP peers in a T2 topology don't add up to 104 on all the asics.

Describe the results you expected:

Number of ip neigh entries for ipv4 and ipv6 eBGP peers in a T2 topology should add up to 104 on all the asics.

Output of show version:

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Additional information you deem important (e.g. issue happens only occasionally):