get_dhcp_ha reads kea/dhcpv4/get (the ha section) and
kea/dhcpv4/searchPeer: whether Kea's HA hook is on, this firewall's peer
name -- the % twin when left at its default -- and each peer's name,
role and HA URL. get_config_sync reads core/hasync/get: the address this
firewall pushes its configuration to and the ticked sync items, mapped to
the service names get_services reports; items that are no service stay
under `unmapped`. Both raise when the request fails.
Configuration, not state: Kea's control agent, which knows whether the
pair is in hot standby right now, listens on localhost only.
Needs napalm-device-types 4.11.0 (ConfigSyncMixin). NetOrk/netork#1125.
