@startuml

title DHCPv4 subnet selection (Kea 1.8.0)

agent "Entry point" as entry

agent "Try RAI link select" as rai_link_select

agent "Try subnet selection option" as subnet_select

rectangle "Relayed" as relayed {
 agent "Relay address matches subnet" as relay_subnet
 agent "Relay address matches shared network" as relay_network
 agent "Check client class" as relay_class
}

rectangle "Set address for lookup" as set_address {
 agent "Set relay address" as relay_address
 agent "Set client address" as client_address
 agent "Set source address" as source_address
}

rectangle "Try incoming interface" as interface {
 agent "Interface matches subnet" as interface_subnet
 agent "Interface matches shared network" as interface_network
 agent "Check client class" as interface_class
 agent "Set interface address" as interface_address
}

rectangle "Try address" as address {
 agent "Check subnet prefix" as inRange
 agent "Check client class" as address_class
}

agent "Found a subnet" as found

agent "Found no subnet" as not_found

agent "Callout subnet4_select" as subnet4_select

agent "Return a subnet" as success

agent "Return no subnet" as no_subnet

agent "Drop query" as drop

entry --> rai_link_select
rai_link_select --> subnet_select
subnet_select --> relayed : relayed
subnet_select --> set_address : not relayed
relayed --> relay_subnet
relay_subnet --> relay_network : no match
relay_subnet --> relay_class : match
relay_network --> set_address : no match
relay_network --> relay_class : match
relay_class ---> found : compatible
relay_class --> set_address : not compatible
set_address --> relay_address : try the relay address
relay_address -r-> client_address : has no relay address
client_address -r-> source_address : has no client address
source_address --> interface_subnet : no suitable address
relay_address --> inRange : has a relay address
client_address --> inRange : has a client address
source_address --> inRange : has source address and use unicast
interface_subnet ---> not_found : no interface
interface_subnet --> interface_class : match
interface_subnet --> interface_network : no match
interface_network --> interface_class : march
interface_network ---> not_found : no match
interface_class ---> found : compatible
interface_class ---> interface_address : not compatible
interface_address --> inRange : has an interface address
interface_address ---> not_found : no interface address
inRange ---> address_class : match
inRange ---> not_found : no match
address_class ---> found : compatible
address_class ---> not_found : not compatible
found --> subnet4_select
not_found --> subnet4_select
found -[hidden]> not_found
subnet4_select --> success : CONTINUE and subnet set
subnet4_select --> no_subnet : SKIP or subnet not set
subnet4_select --> drop : DROP

@enduml