[portsorch]: Optimize link flap handling for single member portchannels

[prabhataravind]

• When a member link in a single-member portchannel goes down, update the portchannel state nexthop group members quicker to enable faster NHG update and route convergence after link flap.

What I did:

• To improve convergence time after link flap on a single member portchannel.

Why I did it:

• Accelerated NHG update when the one and only member link in a single-member portchannel goes down.

How I verified it:

• By shutting down member links from fanout switches and verifying that NHG updates are sent down earlier.

  2024 Jun 5 02:21:17.081264 str2-7050cx3-acs-14 NOTICE restapi#root: Waiting for certificates... 2024 Jun 5 02:21:24.817707 str2-7050cx3-acs-14 INFO syncd#syncd: [none] SAI_API_PORT:_brcm_sai_link_event_cb:1558 Port 119 link down event cause: LOCAL 2024 Jun 5 02:21:24.818583 str2-7050cx3-acs-14 NOTICE swss#orchagent: :- doTask: Get port state change notification id:1000000000020 status:2 2024 Jun 5 02:21:24.818583 str2-7050cx3-acs-14 NOTICE swss#orchagent: :- updatePortOperStatus: Port Ethernet112 oper state set from up to down 2024 Jun 5 02:21:24.827560 str2-7050cx3-acs-14 NOTICE swss#orchagent: :- setHostIntfsOperStatus: Set operation status DOWN to host interface Ethernet112 2024 Jun 5 02:21:24.827560 str2-7050cx3-acs-14 NOTICE swss#orchagent: :- publish: EVENT_PUBLISHED: {"sonic-events- swss:if-state":{"ifname":"Ethernet112","status":"down","timestamp":"2024-06-05T02:21:24.825801Z"}} 2024 Jun 5 02:21:24.827560 str2-7050cx3-acs-14 NOTICE swss#orchagent: :- updatePortOperStatus: Port PortChannel101 oper state set from up to down 2024 Jun 5 02:21:24.831134 str2-7050cx3-acs-14 INFO syncd#syncd: [none] SAI_API_NEXT_HOP_GROUP:brcm_sai_xgs_nexthop_group_member_remove:557 ecmp 200000 nhid 1(0) wt 0 ol-if 400002 ul-if 0 2024 Jun 5 02:21:24.834889 str2-7050cx3-acs-14 INFO systemd-networkd[1107262]: Ethernet112: Lost carrier 2024 Jun 5 02:21:24.835075 str2-7050cx3-acs-14 WARNING systemd-networkd[1107262]: PortChannel101: rtnl: failed to convert received route, ignoring: No such file or directory 2024 Jun 5 02:21:24.835275 str2-7050cx3-acs-14 INFO systemd-networkd[1107262]: PortChannel101: Lost carrier 2024 Jun 5 02:21:24.836659 str2-7050cx3-acs-14 INFO syncd#syncd: [none] SAI_API_NEXT_HOP_GROUP:brcm_sai_xgs_nexthop_group_member_remove:557 ecmp 200001 nhid 5(0) wt 0 ol-if 400006 ul-if 0