KEA refuses one particular dhcp6 client

[dinguz]

I'm getting this sequence of warnings, and it's always the same duid:

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WARN [kea-dhcp6.alloc-engine.0x1340fa505700] ALLOC_ENGINE_V6_ALLOC_FAIL_CLASSES duid=[00:03:00:01:da:c5:77:4c:86:f0], [no hwaddr info],
tid=0x41270a: Failed to allocate an IPv6 address for client with classes: ALL, UNKNOWN
WARN [kea-dhcp6.alloc-engine.0x1340fa505700] ALLOC_ENGINE_V6_ALLOC_FAIL_NO_POOLS duid=[00:03:00:01:da:c5:77:4c:86:f0], [no hwaddr info],
tid=0x41270a: no pools were available for the lease allocation
WARN [kea-dhcp6.alloc-engine.0x1340fa505700] ALLOC_ENGINE_V6_ALLOC_FAIL_SUBNET duid=[00:03:00:01:da:c5:77:4c:86:f0], [no hwaddr info],
tid=0x41270a: failed to allocate an IPv6 lease in the subnet 2a02:xxxx:xxxx::/64, subnet-id 1, shared network (none)

A ChatGPT consultation suggests the generated config has some kind of class restriction, because the client has both the classes ALL and UNKNOWN, hence it not being assigned a pool to distribute an address from. I looked in the generated config files, and it doesn't seem to use anything with classes or reservations.

This is my kea-dhcpd6.conf:

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{
    "Dhcp6": {
        "valid-lifetime": 4000,
        "interfaces-config": {
            "interfaces": [
                "igc0"
            ]
        },
        "lease-database": {
            "type": "memfile",
            "persist": true
        },
        "control-socket": {
            "socket-type": "unix",
            "socket-name": "\/var\/run\/kea6-ctrl-socket"
        },
        "loggers": [
            {
                "name": "kea-dhcp6",
                "output_options": [
                    {
                        "output": "syslog"
                    }
                ],
                "severity": "INFO"
            }
        ],
        "subnet6": [
            {
                "id": 1,
                "subnet": "2a02:xxxx:xxxx::\/64",
                "option-data": [],
                "pools": [
                    {
                        "pool": "2a02:xxxx:xxxx::1000-2a02:xxxx:xxxx::2000"
                    }
                ],
                "pd-pools": [],
                "reservations": [],
                "interface": "igc0",
                "pd-allocator": "random",
                "allocator": "random"
            }
        ],
        "hooks-libraries": [
            {
                "library": "\/usr\/local\/lib\/kea\/hooks\/libdhcp_lease_cmds.so"
            }
        ]
    }

Any ideas what the issue could be, or what to try further?

[pfry]

[...]
Any ideas what the issue could be, or what to try further?

Hard to say. Assuming you don't get a quick solution here, I would run a packet capture on the sequence and see if that sheds any light. I'm not accustomed to reading Kea logs and I don't use IPv6, so while I have some suspicions, I can't narrow them usefully. As a general rule, I'd look for unusual options from the client.

(Were you obfuscating your subnet in the config? If so, it's in the log, too.)