static route expiry feature support in 202012

[jcaiMR]

static route expiry feature support in 202012. This is double commit job from master to 202012.

Why I did it

Modify BgpCfgD to support static route expiry

How I did it

Add a new class StaticRouteTimer to monitor old and unrefreshed static routes in APP DB and remove them

How to verify it

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

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

Description for the changelog

Ensure to add label/tag for the feature raised. example - PR#2174 under sonic-utilities repo. where, Generic Config and Update feature has been labelled as GCU.

Link to config_db schema for YANG module changes

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

New key/value in appl_db:
sonic-db-cli APPL_DB hmset 'STATIC_ROUTE:default:5.5.5.0/24' nexthop 10.0.0.27 expiry 'false'
sonic-db-cli APPL_DB hmset 'STATIC_ROUTE:default:5.5.5.0/24' nexthop 10.0.0.27 expiry 'true' refresh 'true'

sonic-db-cli APPL_DB hmset 'STATIC_ROUTE:default:2001::1/64' nexthop 2002::1 expiry 'false'
sonic-db-cli APPL_DB hmset 'STATIC_ROUTE:default:2001::1/64' nexthop 2002::1 expiry 'true' refresh 'true'

expiry == 'false' means non-persistent static route, but will never expire in APPL_DB
refresh == 'true' means non-persistent static route and will be timeout under the control of STATIC_ROUTE_EXPIRY_TIME specified timeout value.

[StormLiangMS]

LGTM

[lgtm-com]

This pull request introduces 1 alert when merging a7499c3 into 3c88bee - view on LGTM.com

new alerts:

• 1 for Unused import

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