[chassis][multi-asic]: Add support for vendor LC ip range for macvlan ip (#22008)

[anamehra]

Signed-off-by: Anand Mehra [email protected]

Why I did it

As per current design, macvlan IP start with an offset of 10 from miplane Ip subnet base ip on a namespace.
In some platforms this may cause conflict if the LC midplane ip for any slot falls in that range. The IP conflict cause midplane traffic loss.

In Cisco Chassis, macvlan IP may conflict with LC midplane IP range. This conflict causes midplane traffic loss for conflicting ip and affects any LC namespace transaction with Supervisor.

To prevent any conflict, Venddor may provide an offset to be used to generate macvlan IP address to prevent any conflict with midplane IP address.

Work item tracking

• Microsoft ADO (31798758):

How I did it

Added an ip_offset value which Vendor may provide based on their midplane ip range to generate safe IP address for macvlan in namespace.

The lc_ip_offset offset needs to be set in /usr/share/sonic/device//chassisdb.conf file for the LC where an offset is required.

cat chassisdb.conf
chassis_db_address=127.0.0.3
midplane_subnet=127.0.0.0/16
lc_ip_offset=100

How to verify it

After boot, check eth1 IP address in namespaces. The IP addresses should not conflict with any expected LC eth1-midplane IP or any other IP in the system.

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205
• 202211

Tested branch (Please provide the tested image version)

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)

[anamehra]

Hi @yejianquan , for your viz. Thanks

[yejianquan]

LGTM