[xcvrd] xcvrd crashes due to PR https://github.com/sonic-net/sonic-platform-common/pull/397

[Junchao-Mellanox]

Description

xcvrd crashes due to PR sonic-net/sonic-platform-common#397.

In this PR, it added a new line:

self.vdm_dict = self.get_vdm(self.vdm.VDM_REAL_VALUE)

However, self.vdm might be None due to this line: https://github.com/sonic-net/sonic-platform-common/blob/2606cd5fb0a58fc956577602235a9f8f84a887c6/sonic_platform_base/sonic_xcvr/api/public/cmis.py#L31

So, if the CMIS cable is flat memory, the call to "self.vdm.VDM_REAL_VALUE" always crashes:

Mar 25 15:31:40.777905 sonic ERR pmon#xcvrd: Exception occured at DomInfoUpdateTask thread due to AttributeError("'NoneType' object has no attribute 'VDM_REAL_VALUE'")
Mar 25 15:31:40.779557 sonic ERR pmon#xcvrd: Traceback (most recent call last):
Mar 25 15:31:40.779616 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/xcvrd/xcvrd.py", line 1744, in run
Mar 25 15:31:40.779616 sonic ERR pmon#xcvrd:     self.task_worker()
Mar 25 15:31:40.779616 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/xcvrd/xcvrd.py", line 1716, in task_worker
Mar 25 15:31:40.779633 sonic ERR pmon#xcvrd:     post_port_dom_info_to_db(logical_port_name, self.port_mapping, self.xcvr_table_helper.get_dom_tbl(asic_index), self.task_stopping_event, dom_info_cache=dom_info_cache)
Mar 25 15:31:40.779644 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/xcvrd/xcvrd.py", line 627, in post_port_dom_info_to_db
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:     dom_info_dict = _wrapper_get_transceiver_dom_info(physical_port)
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/xcvrd/xcvrd.py", line 279, in _wrapper_get_transceiver_dom_info
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:     return platform_chassis.get_sfp(physical_port).get_transceiver_bulk_status()
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/sonic_platform_base/sonic_xcvr/sfp_optoe_base.py", line 32, in get_transceiver_bulk_status
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:     return api.get_transceiver_bulk_status() if api is not None else None
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/sonic_platform_base/sonic_xcvr/api/public/cmis.py", line 233, in get_transceiver_bulk_status
Mar 25 15:31:40.779816 sonic ERR pmon#xcvrd:     self.vdm_dict = self.get_vdm(self.vdm.VDM_REAL_VALUE)
Mar 25 15:31:40.779816 sonic ERR pmon#xcvrd: AttributeError: 'NoneType' object has no attribute 'VDM_REAL_VALUE'
Mar 25 15:31:40.779816 sonic ERR pmon#xcvrd: Xcvrd: exception found at child thread DomInfoUpdateTask due to AttributeError("'NoneType' object has no attribute 'VDM_REAL_VALUE'")
Mar 25 15:31:40.779827 sonic ERR pmon#xcvrd: Exiting main loop as child thread raised exception!

Steps to reproduce the issue:

1. Insert a CMIS cable which has flat memory
2. Start sonic
3. Check syslog, you will see the crash in short

Describe the results you received:

Mar 25 15:31:40.777905 sonic ERR pmon#xcvrd: Exception occured at DomInfoUpdateTask thread due to AttributeError("'NoneType' object has no attribute 'VDM_REAL_VALUE'")
Mar 25 15:31:40.779557 sonic ERR pmon#xcvrd: Traceback (most recent call last):
Mar 25 15:31:40.779616 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/xcvrd/xcvrd.py", line 1744, in run
Mar 25 15:31:40.779616 sonic ERR pmon#xcvrd:     self.task_worker()
Mar 25 15:31:40.779616 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/xcvrd/xcvrd.py", line 1716, in task_worker
Mar 25 15:31:40.779633 sonic ERR pmon#xcvrd:     post_port_dom_info_to_db(logical_port_name, self.port_mapping, self.xcvr_table_helper.get_dom_tbl(asic_index), self.task_stopping_event, dom_info_cache=dom_info_cache)
Mar 25 15:31:40.779644 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/xcvrd/xcvrd.py", line 627, in post_port_dom_info_to_db
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:     dom_info_dict = _wrapper_get_transceiver_dom_info(physical_port)
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/xcvrd/xcvrd.py", line 279, in _wrapper_get_transceiver_dom_info
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:     return platform_chassis.get_sfp(physical_port).get_transceiver_bulk_status()
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/sonic_platform_base/sonic_xcvr/sfp_optoe_base.py", line 32, in get_transceiver_bulk_status
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:     return api.get_transceiver_bulk_status() if api is not None else None
Mar 25 15:31:40.779784 sonic ERR pmon#xcvrd:   File "/usr/local/lib/python3.9/dist-packages/sonic_platform_base/sonic_xcvr/api/public/cmis.py", line 233, in get_transceiver_bulk_status
Mar 25 15:31:40.779816 sonic ERR pmon#xcvrd:     self.vdm_dict = self.get_vdm(self.vdm.VDM_REAL_VALUE)
Mar 25 15:31:40.779816 sonic ERR pmon#xcvrd: AttributeError: 'NoneType' object has no attribute 'VDM_REAL_VALUE'
Mar 25 15:31:40.779816 sonic ERR pmon#xcvrd: Xcvrd: exception found at child thread DomInfoUpdateTask due to AttributeError("'NoneType' object has no attribute 'VDM_REAL_VALUE'")
Mar 25 15:31:40.779827 sonic ERR pmon#xcvrd: Exiting main loop as child thread raised exception!

Describe the results you expected:

No crashes

Output of show version:

SONiC-OS-master.505826-568149081

Output of show techsupport:

(paste your output here or download and attach the file here )

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

[Junchao-Mellanox]

Hi @chiourung, could you please check this?
@prgeor for awareness.