What Just Happened (WJH)

The following example configures two separate channels:

• The forwarding channel monitors layer 2, layer 3, and tunnel packet drops.
• The layer-1 channel monitors layer 1 packet drops.

cumulus@switch:~$ nv set system wjh channel forwarding trigger l2
cumulus@switch:~$ nv set system wjh channel forwarding trigger l3
cumulus@switch:~$ nv set system wjh channel forwarding trigger tunnel
cumulus@switch:~$ nv set system wjh channel layer-1 trigger l1
cumulus@switch:~$ nv config apply

You can stop monitoring specific packet drops by unsetting a category in the channel list. The following command example stops monitoring layer 2 packet drops that are in the forwarding channel:

cumulus@switch:~$ nv unset system wjh channel forwarding trigger l2
cumulus@switch:~$ nv config apply

To remove a channel, run the nv unset system wjh channel <channel> command. The following command example removes the layer-1 channel:

cumulus@switch:~$ nv unset system wjh channel layer-1 
cumulus@switch:~$ nv config apply

Edit the /etc/what-just-happened/what-just-happened.json file:

• For each drop category you want to monitor, include the drop category value inside the square brackets ([]).
• For each drop category you do not want to monitor, remove the drop category value from inside the square brackets.

After you edit the file, you must restart the WJH service with the sudo systemctl restart what-just-happened command.

The following example configures a channel to monitor layer 2, layer 3, and tunnel packet drops and a channel to monitor layer 1 packet drops.

cumulus@switch:~$ sudo nano /etc/what-just-happened/what-just-happened.json
{
    "what-just-happened": {
        "channels": {
            "forwarding": {
                "drop_category_list": [
                    "l2",
                    "l3",
                    "tunnel"
                ]
            },
            "layer-1": {
                "drop_category_list": [
                    "l1"
                ]
            }
        }
    }
}

cumulus@switch:~$ sudo systemctl restart what-just-happened

The following example configures a channel to monitor buffer packet drops and a channel to monitor ACL packet drops.

cumulus@switch:~$ sudo nano /etc/what-just-happened/what-just-happened.json
{
    "what-just-happened": {
        "channels": {
            "buffer": {
                "drop_category_list": ["buffer"]
            },
            "acl": {
                "drop_category_list": ["acl"]
            }
        }
    }
}

cumulus@switch:~$ sudo systemctl restart what-just-happened

To show information about packet drops for all the channels you configure, run the nv show system wjh packet-buffer command. The command output includes the reason for the drop and the recommended action to take.

You can also show the WJH configuration on the switch:

• To show the configuration for a channel, run the nv show system wjh channel <channel> command. For example, nv show system wjh channel forwarding.
• To show the configuration for packet drop categories in a channel, run the nv show system wjh channel <channel> trigger command. For example, nv show system wjh channel forwarding trigger.

The following example shows information about layer 1 packet drops:

cumulus@switch:~$ nv show system wjh packet-buffer
#   dMAC  dPort  Dst IP:Port  EthType  Drop group  IP Proto  Drop reason - Recommended action                         Severity  sMAC  sPort    Src IP:Port  Timestamp              VLAN
--  ----  -----  -----------  -------  ----------  --------  -------------------------------------------------------  --------  ----  -------  -----------  ---------------------  ----
1   N/A   N/A    N/A          N/A      L1          N/A       Generic L1 event - Check layer 1 aggregated information  Warn      N/A   swp17    N/A          22/11/03 01:00:35.458  N/A
2   N/A   N/A    N/A          N/A      L1          N/A       Generic L1 event - Check layer 1 aggregated information  Warn      N/A   swp18    N/A          22/11/03 01:00:35.458  N/A
3   N/A   N/A    N/A          N/A      L1          N/A       Generic L1 event - Check layer 1 aggregated information  Warn      N/A   swp19    N/A          22/11/03 01:00:35.458  N/A
4   N/A   N/A    N/A          N/A      L1          N/A       Generic L1 event - Check layer 1 aggregated information  Warn      N/A   swp20    N/A          22/11/03 01:00:35.458  N/A

You can run the following commands from the command line.

Run the what-just-happened -h command to see all the WJH command options.

To show all dropped packets and the reason for the drop, run the NVUE nv show system wjh packet-buffer command or the what-just-happened poll command.

The following example shows that packets drop five times because the source MAC address equals the destination MAC address:

cumulus@switch:~$ what-just-happened poll --aggregate
Sample Window : 2021/06/16 12:57:23.046 - 2021/06/16 14:46:17.701

#  sPort  VLAN  sMAC               dMAC               EthType  Src IP:Port  Dst IP:Port  IP Proto  Count  Severity  Drop reason - Recommended action
-- ------ ----- ------------------ ------------------ -------- ------------ ------------ --------- ------ --------- -----------------------------------------------
1  swp4   N/A   44:38:39:00:a4:87  44:38:39:00:a4:87  IPv4     0.0.0.0:0    0.0.0.0:0    ip        100    Error     Source MAC equals destination MAC - Bad packet was received from peer
2  swp1   N/A   44:38:39:00:a4:80  44:38:39:00:a4:80  IPv4     0.0.0.0:0    0.0.0.0:0    ip        100    Error     Source MAC equals destination MAC - Bad packet was received from peer

The following command saves dropped packets to a file in PCAP format

cumulus@switch:~$ what-just-happened poll --export --no_metadata
PCAP file path : /var/log/mellanox/wjh/wjh_user_2021_06_16_12_03_15.pcap

#    Timestamp              sPort  dPort  VLAN  sMAC               dMAC               EthType  Src IP:Port  Dst IP:Port  IP Proto  Drop   Severity  Drop reason - Recommended action
                                                                                                                                   Group
---- ---------------------- ------ ------ ----- ------------------ ------------------ -------- ------------ ------------ --------- ------ --------- -----------------------------------------------
1    21/06/16 12:03:12.728  swp1   N/A    N/A   44:38:39:00:a4:84  44:38:39:00:a4:84  IPv4     N/A          N/A          N/A       L2     Error     Source MAC equals destination MAC - Bad packet as received from peer
2    21/06/16 12:03:12.728  swp1   N/A    N/A   44:38:39:00:a4:84  44:38:39:00:a4:84  IPv4     N/A          N/A          N/A       L2     Error     Source MAC equals destination MAC - Bad packet was received from peer
3    21/06/16 12:03:12.745  swp1   N/A    N/A   44:38:39:00:a4:84  44:38:39:00:a4:84  IPv4     N/A          N/A          N/A       L2     Error     Source MAC equals destination MAC - Bad packet was received from peer
4    21/06/16 12:03:12.745  swp1   N/A    N/A   44:38:39:00:a4:84  44:38:39:00:a4:84  IPv4     N/A          N/A          N/A       L2     Error     Source MAC equals destination MAC - Bad packet was received from peer

cumulus@switch:~$ nv set system wjh enable on
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo systemctl enable what-just-happened
cumulus@switch:~$ sudo systemctl start what-just-happened