[Kea-users] ping-check-hooks – global vs subnet level enable-ping-check behavior

[Darren Ankney]

Hi Dipesh,

As you probably have already seen, the ARM isn't specific in this area.

Here:

https://gitlab.isc.org/isc-projects/kea/-/blob/master/src/hooks/dhcp/ping_check/config_cache.cc?ref_type=heads#L54-70

it appears that subnet specific user-context config (if exist) should
take precedence over the global configuration.

Here:

https://gitlab.isc.org/isc-projects/kea/-/blob/master/src/hooks/dhcp/ping_check/ping_check_mgr.cc?ref_type=heads#L92-145

It appears that you should see PING_CHECK_MGR_SUBNET_CONFIG_FAILED
logged if the user-context in the subnet did not parse correctly.  see
here: https://kea.readthedocs.io/en/kea-3.0.1/kea-messages.html#ping-check-mgr-subnet-config-failed

I would say that if you don't find this error in your logs and the
user context is not disabling the ping check at the subnet level, then
please open a Gitlab issue here:
https://gitlab.isc.org/isc-projects/kea/-/issues describing the
problem in detail.

Thank you,
Darren Ankney

On Fri, Aug 29, 2025 at 3:07 AM Dipesh Kayastha
<er.dipesh.kayastha at gmail.com> wrote:
>
> Hello Kea team,
>
> I am testing the libdhcp_ping_check.so hook library and observed some behavior I’d like clarification on.
>
> My configuration:
> "hooks-libraries": [
>   {
>     "library": "libdhcp_ping_check.so",
>     "parameters": {
>       "enable-ping-check": true
>     }
>   }
> ],
>
> "subnet4": [
>   {
>     "subnet": "20.20.20.0/24",
>     "user-context": {
>       "enable-ping-check": false
>     },
>     "pools": [
>       {
>         "pool": "20.20.20.8 - 20.20.20.10"
>       }
>     ]
>   }
> ]
>
> Expectation:
>
> Since I set "enable-ping-check": false at the subnet level, I expected no ICMP checks for leases in that subnet/pool.
>
> Observation:
>
> When running the server and requesting a lease, I still see ping-check activity in the logs:
>
> 2025-08-29 07:00:33.476 DEBUG [kea-dhcp4.ping-check-hooks] PING_CHECK_MGR_START_PING_CHECK for 20.20.20.8 ...
> 2025-08-29 07:00:33.477 DEBUG [kea-dhcp4.ping-check-hooks] PING_CHECK_CHANNEL_ECHO_REQUEST_SENT to address 20.20.20.8
> 2025-08-29 07:00:33.577 DEBUG [kea-dhcp4.ping-check-hooks] PING_CHECK_MGR_REPLY_TIMEOUT_EXPIRED for 20.20.20.8 ...
> 2025-08-29 07:00:33.577 DEBUG [kea-dhcp4.ping-check-hooks] PING_CHECK_MGR_LEASE_FREE_TO_USE address 20.20.20.8 ...
>
> Question:
>
> Is this the intended behavior (global parameter overriding subnet-level user-context),
> or should the "enable-ping-check": false at subnet level disable ICMP checks for that subnet?
>
> Thanks in advance for clarification.
>
> Regards,
> Dipesh
>
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