lldp_syncd: continuous complaints of Failed to get system capabilities

[yxieca]

Description

Steps to reproduce the issue:

1. run nightly test on arista 7050cx3 platform

Describe the results you received:
Throughout the whole test period, lldp_syncd has been complaining with following ERROR level message and caused various testcases to fail due to loganalyzer caught this complaint.

syslog.58.gz:Nov 12 08:13:48.506123 str2-7050cx3-acs-06 ERR lldp#lldp-syncd message repeated 3 times: [ [lldp_syncd] ERROR: Failed to get system capabilities]
syslog.58.gz:Nov 12 08:13:53.185800 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog.30.gz:Nov 12 08:48:45.298817 str2-7050cx3-acs-06 ERR lldp#lldp-syncd message repeated 207 times: [ [lldp_syncd] ERROR: Failed to get system capabilities]
syslog.30.gz:Nov 12 08:49:33.204235 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog.30.gz:Nov 12 08:51:44.095083 str2-7050cx3-acs-06 ERR lldp#lldp-syncd message repeated 12 times: [ [lldp_syncd] ERROR: Failed to get system capabilities]
syslog.30.gz:Nov 12 08:52:04.194876 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog.30.gz:Nov 12 08:52:34.582895 str2-7050cx3-acs-06 ERR lldp#lldp-syncd message repeated 3 times: [ [lldp_syncd] ERROR: Failed to get system capabilities]
syslog.30.gz:Nov 12 08:53:22.892214 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog.6.gz:Nov 12 09:52:37.383686 str2-7050cx3-acs-06 ERR lldp#lldp-syncd message repeated 353 times: [ [lldp_syncd] ERROR: Failed to get system capabilities]
syslog.6.gz:Nov 12 09:52:44.960146 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog.6.gz:Nov 12 09:52:55.013824 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog.6.gz:Nov 12 09:55:12.202408 str2-7050cx3-acs-06 ERR lldp#lldp-syncd message repeated 13 times: [ [lldp_syncd] ERROR: Failed to get system capabilities]
syslog.6.gz:Nov 12 09:55:15.792351 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog.3.gz:Nov 12 09:57:16.158855 str2-7050cx3-acs-06 ERR lldp#lldp-syncd message repeated 11 times: [ [lldp_syncd] ERROR: Failed to get system capabilities]
syslog.3.gz:Nov 12 09:58:05.243887 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog.3.gz:Nov 12 09:58:15.824529 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog.3.gz:Nov 12 09:58:25.876357 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog:Nov 12 10:09:14.192442 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities
syslog:Nov 12 10:09:24.230264 str2-7050cx3-acs-06 ERR lldp#lldp-syncd [lldp_syncd] ERROR: Failed to get system capabilities

Describe the results you expected:

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

**Output of `show version`:**

```

SONiC Software Version: SONiC.master.481-b5121dcf
Distribution: Debian 10.6
Kernel: 4.19.0-9-2-amd64
Build commit: b5121dc
Build date: Tue Nov 10 10:27:57 UTC 2020
Built by: johnar@jenkins-worker-8

Platform: x86_64-arista_7050cx3_32s
HwSKU: Arista-7050CX3-32S-C32
ASIC: broadcom
Serial Number: JPW20281061
Uptime: 17:02:17 up 6:48, 1 user, load average: 1.19, 1.40, 1.44 ```

**Attach debug file `sudo generate_dump`:**

```
(paste your output here)
```

[yxieca]

Further log analysis shows that this error message was associated with either dut reboot or config reload.

[lguohan]

debug a little bit. seems like some neighbor device on eth0 send invalid lldp messages.

Interface:    eth0, via: LLDP, RID: 1, Time: 0 day, 05:33:06
  Chassis:     
    ChassisID:    mac 50:2f:a8:a5:03:d5
  Port:        
    PortID:       ifname Ethernet1/14
    TTL:          120
  Unknown TLVs:
    TLV:          OUI: 00,01,42, SubType: 1, Len: 1 01
    TLV:          OUI: 00,01,42, SubType: 2, Len: 16 05,DC,05,DC,05,DC,05,DC,05,DC,05,DC,05,DC,05,DC

[lguohan]

tcpdump

admin@str2-7050cx3-acs-03:~$ sudo tcpdump -vvvni eth0 -Qin ether proto 0x88cc 
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
18:48:33.118967 LLDP, length 59
        Chassis ID TLV (1), length 7
          Subtype MAC address (4): 50:2f:a8:a5:03:d5
          0x0000:  0450 2fa8 a503 d5
        Port ID TLV (2), length 13
          Subtype Interface Name (5): Ethernet1/14
          0x0000:  0545 7468 6572 6e65 7431 2f31 34
        Time to Live TLV (3), length 2: TTL 120s
          0x0000:  0078
        Organization specific TLV (127), length 5: OUI Unknown (0x000142)
          0x0000:  0001 4201 01
        Organization specific TLV (127), length 20: OUI Unknown (0x000142)
          0x0000:  0001 4202 05dc 05dc 05dc 05dc 05dc 05dc
          0x0010:  05dc 05dc
        End TLV (0), length 0