emulated arista ignores our lldp packets

[Nieuwejaar]

In an a4x2 environment, the emulated Arista router is ignoring our LLDP packets.

LLDP is enabled on sidecar 0, which connects to Arista switch 1 on Ethernet port 2. We have LLDP-receive enabled:

cr1#show lldp ethernet 2
[...]

Port          Tx Enabled    Rx Enabled
---------- ---------------- ----------
Et2           Yes           Yes  

With tcpdump, we can see them arriving at the switch:

21:51:29.776896 LLDP, length 98
        Chassis ID TLV (1), length 3
          Subtype Chassis component (1): g0
        Port ID TLV (2), length 8
          Subtype Interface Name (5): qsfp0/0
        Time to Live TLV (3), length 2: TTL 120s
        System Name TLV (5), length 2: g0
        System Description TLV (6), length 65
          Oxide sled model: i86pc, Sidecar revision: softnpu_front_2_rear_4
        System Capabilities TLV (7), length 4
          System  Capabilities [Router] (0x0010)
          Enabled Capabilities [Router] (0x0010)
        End TLV (0), length 0
[...]

For some reason, these packets aren't being accepted/processed by Eos. They don't even appear to get far enough to register as errors:

cr1#show lldp counters
[...]        

Port          Tx Frames    Tx Length Exceeded
---------- --------------- ------------------
Et1           110          0                 
Et2           110          0                 
Et3           110          0                 

Port     Rx Frames     Rx Errors     Rx Discard     TLVs Discard   TLVs Unknown
------- ------------ ------------- -------------- ---------------- ------------
Et1      0             0             0              0              0           
Et2      0             0             0              0              0           
Et3      0             0             0              0              0   

Weirdly, a physical Arista switch is happy with LLDP packets from a real sidecar:

eveningstar#show lldp neighbors ethernet 26/1
Last table change time   : 8:34:13 ago
Number of table inserts  : 9
Number of table deletes  : 6
Number of table drops    : 0
Number of table age-outs : 3

Port            Neighbor Device ID       Neighbor Port ID    TTL 
------------ ------------------------ ---------------------- --- 
Et26/1          BRM44220001              qsfp0/0             120 

eveningstar#show lldp neighbors ethernet 26/1 detail
Interface Ethernet26/1 detected 1 LLDP neighbors:

  Neighbor "BRM44220001"/"qsfp0/0", age 7 seconds
  Discovered 8:34:21 ago; Last changed 8:34:21 ago
  - Chassis ID type: Chassis component (1)
    Chassis ID     : "BRM44220001"
  - Port ID type: Interface name(5)

A simple Venn diagram approach would suggest a problem in sidecar-lite and/or softnpu, but the tcpdump log shows that the packets are making it out of our emulated switch, which makes that less likely.

[rcgoodfellow]

We are using Arista containerized EOS (cEOS). I suspect this is either not supported by cEOS or the linux plumbing into the cEOS container is not passing LLDP traffic. The arista interfaces are plumbed here so you could tcpdump those on cr1 or cr2 to see if you see the lldp packets. You could also instal lldpd on linux to see if that works.