@startuml

title requestLease4 algorithm (Kea 1.8.0)

start
:get lease for the client;

if (reserved address) then (yes)
  if (requested address) then (no)
    :requested address = reserved address;
  else (yes)
    if (requested address is reserved for another client) then (yes)
      :return no lease;
      stop
    else (no)
    endif
  endif
  if (lease for requested address) then (yes)
    if (active and owned by another client) then (yes)
      :return no lease;
      stop
    else (no)
    endif
  else (no)
  endif
  if (requested address == reserved address) then (no)
    if (lease for requested address) then (yes)
      if (active) then (yes)
        :return no lease;
        stop
      else (no)
      endif
    else (no)
    endif
    if (requested address in allowed pool) then (no)
      :return no lease;
      stop
    else (yes)
    endif
  else (yes)
  endif

else (no)

  if (requested address) then (yes)
    if (requested address is reserved for another client) then (yes)
      :return no lease;
      stop
    else (no)
    endif
    if (lease for requested address) then (yes)
      if (active and owned by another client) then (yes)
        :return no lease;
        stop
      else (no)
      endif
    else (no)
    endif
    if (requested address in allowed pool) then (no)
      :return no lease;
      stop
    else (yes)
    endif
  else (no)
    if (client lease and lease address in allowed pool) then (no)
      while (iterate over pools and subnets)
        :pick candidate address;
        if (candidate is reserved for another client) then (no)
          if (candidate is used by another thread) then (no)
            if (lease for candidate) then (no)
              :create and return new lease;
              stop
            else (yes)
              if (expired) then (yes)
                :reclaim expired lease;
                :update lease information;
                :callout lease4_select;
                if (callout return) then (SKIP)
                  :return no lease;
                  stop
                else (CONTINUE)
                  :update lease;
                  :return reused lease;
                  stop
                endif
              else (no)
              endif
            endif
          else (yes)
          endif
        else (yes)
        endif
      endwhile
      :maximum attempts;
      :return no lease;
      stop
    else (yes)
    endif
  endif
endif

' after check
if (client lease) then (yes)
  if (no requested address or requested address == client lease address) then (yes)
    if (has reserved address or client lease address in allowed pool) then (yes)
      :update lease information;
      if (old lease expired) then (yes)
        :reclaim expired lease;
      else (no)
      endif
      :callout lease4_renew;
      if (callout return) then (SKIP)
        :return old client lease;
        stop
      else (CONTINUE)
        :update lease;
        :return renewed client lease;
        stop
      endif
    else (no)
    endif
  else (no)
  endif
else (no)
endif

:get lease for requested address;
if (requested lease) then (yes)
  if (expired) then (no)
    :return no lease;
    stop
  else (yes)
    :reclaim expired lease;
    :update lease information;
    :callout lease4_select;
    if (callout return) then (SKIP)
      :return no lease;
      stop
    else (CONTINUE)
      :update lease;
      :return reused lease;
      stop
    endif
  endif
else (no)
 :create and return new lease;
 stop
endif

@enduml