Adding some sanity-checking to configdb.json parsing logic

[rodnymolina]

I'm adding some sanity-checking logic to prevent semantically-incorrect entries, present in any given config_db.json file, from being able to make it to sonic backends. This should tackle various issues observed in the past where a user could easily bring a system down or to an inconsistent state by introducing erroneous configuration while manually editing a config_db.json file.

To exercise this logic, user can either make use of the "--check-json" parameter offered by 'sonic-cfggen' (see examples below), or rely on the typical "config load/reload" CLI instructions. The changes associated to the second option will come as part of a different PR (in sonic-utilities repo).

Find some examples below of how this code operates:

<—- Tescase 1) Adding ‘interface’ associated to invalid ‘port’:

    "INTERFACE": {
         "Ethernet0|10.2.2.1/24": {},
             "Ethernet0|fc00:2:1::1/64": {},
             "Ethernet4|10.2.1.1/24": {},
             "Ethernet4|fc00:2:2::1/64": {},
             "Ethernet121|20.20.20.1/24": {}           <<<<——— inexistent interface
},

admin@lnos-x1-a-csw02:~$ /usr/local/bin/sonic-cfggen -j ~/config_db.json --check-json
Interface Ethernet121 not found in PORT table.

Invalid configuration detected. No configuration changes processed. Exiting...

<—- Problem fixed after eliminating invalid config entry:

admin@lnos-x1-a-csw02:~$ /usr/local/bin/sonic-cfggen -j ~/config_db.json --check-json
admin@lnos-x1-a-csw02:~$

<-— Testcase 2) Adding an inexistent port as a VLAN member:

    "VLAN": {
            "Vlan100": {
                "vlanid": "100",
                "admin_status": "up",
                "description": "Data Traffic",
                "members": [
                      "Ethernet16",
                      "Ethernet17"          <<<<—— inexistent port
                ],
                "mtu": "9100"
            }
     },

admin@lnos-x1-a-csw02:~$ /usr/local/bin/sonic-cfggen -j ~/config_db.json --check-json
VLAN member Ethernet17 not found in PORT table.

Invalid configuration detected. No configuration changes processed. Exiting...

<—- Problem fixed after eliminating invalid config entry:

admin@lnos-x1-a-csw02:~$ /usr/local/bin/sonic-cfggen -j ~/config_db.json --check-json
admin@lnos-x1-a-csw02:~$

<—- Testcase 3) Adding a VLAN_INTERFACE for an inexistent VLAN:

    "VLAN_INTERFACE": {
        "Vlan100|9.1.1.2/24": {
               "scope": "global",
               "family": "IPv4"
        },
        "Vlan100|fc00:9:2::2/64": {
               "scope": "global",
               "family": "IPv6"

        },
        "Vlan101|9.1.1.2/24": {          <<<<—— VLAN101 not defined in VLANS section
               "scope": "global",
               "family": "IPv4"
        }
},

admin@lnos-x1-a-csw02:~$ /usr/local/bin/sonic-cfggen -j ~/config_db.json --check-json
Vlan interface Vlan101 not found in VLAN table.

Invalid configuration detected. No configuration changes processed. Exiting...

<—- Problem fixed after eliminating invalid config entry:

admin@lnos-x1-a-csw02:~$ /usr/local/bin/sonic-cfggen -j ~/config_db.json --check-json
admin@lnos-x1-a-csw02:~$

<—- Testcase 4) Adding inexistent port for an neighbor entry:

    "DEVICE_NEIGHBOR": {
            "Ethernet0": {
               "name": "ARISTA01T2",
               "port": "Ethernet1"

        },
        "Ethernet2": {
              "name": "ARISTA02T2",
              "port": "Ethernet1"

        },
        "Ethernet4": {
              "name": "ARISTA03T2",
              "port": "Ethernet1"

        },
        "Ethernet5": {                        <<<<—— Inexistent port
               "name": "ARISTA04T2",
               "port": "Ethernet1"
        }
    },

admin@lnos-x1-a-csw02:~$ /usr/local/bin/sonic-cfggen -j ~/config_db.json --check-json
DEVICE_NEIGHBOR port Ethernet5 not found in PORT table.

Invalid configuration detected. No configuration changes processed. Exiting...

<—- Problem fixed after eliminating invalid config entry:

admin@lnos-x1-a-csw02:~$ /usr/local/bin/sonic-cfggen -j ~/config_db.json --check-json
admin@lnos-x1-a-csw02:~$

[lguohan]

@taoyl-ms , to review

[qiluo-msft]

Thanks @rodnymolina for the contribution! Would you like to merge the latest master and resolve the conflict?

[qiluo-msft]

It's better to validate by SONiC Yang models.