"""
Implementation of Echo Request option handling as specified in :rfc:`4994`.
"""
from typing import List
from dhcpkit.ipv6.extensions.relay_echo_request import EchoRequestOption
from dhcpkit.ipv6.messages import RelayForwardMessage, RelayReplyMessage
from dhcpkit.ipv6.server.handlers import Handler, RelayHandler
from dhcpkit.ipv6.server.transaction_bundle import TransactionBundle
[docs]def create_cleanup_handlers() -> List[Handler]:
"""
Create handlers to clean up stuff in the transaction bundle
:return: Handlers to add to the handler chain
"""
return [RelayEchoRequestOptionHandler()]
[docs]class RelayEchoRequestOptionHandler(RelayHandler):
"""
When a server creates a Relay-Reply, it SHOULD perform ERO processing
after processing the ORO and other options processing. For each
option in the ERO:
a. If the option is already in the Relay-Reply, the server MUST
ignore that option and continue to process any remaining options
in the ERO.
b. If the option was not in the received Relay-Forward, the server
MUST ignore that option and continue to process any remaining
options in the ERO.
c. Otherwise, the server MUST copy the option, verbatim, from the
received Relay-Forward to the Relay-Reply, even if the server
does not otherwise recognize that option.
"""
[docs] def handle_relay(self, bundle: TransactionBundle,
relay_message_in: RelayForwardMessage, relay_message_out: RelayReplyMessage):
"""
Handle the options for each relay message pair.
:param bundle: The transaction bundle
:param relay_message_in: The incoming relay message
:param relay_message_out: Thr outgoing relay message
"""
# See if the relay message contains an ERO
ero = relay_message_in.get_option_of_type(EchoRequestOption)
if not ero:
# Nothing to do
return
for option_type in ero.requested_options:
# Don't do anything if the outgoing relay message already has this one
if any(option.option_type == option_type for option in relay_message_out.options):
continue
# Get the incoming options of the requested type
incoming_options = [option for option in relay_message_in.options if option.option_type == option_type]
for option in incoming_options:
# Make sure this option can go into this type of response
if not relay_message_out.may_contain(option):
return
# And append them to the outgoing message if possible
relay_message_out.options.append(option)