diff options
| -rw-r--r-- | interface-definitions/dhcp-relay.xml | 108 | ||||
| -rwxr-xr-x | src/conf_mode/dhcp_relay.py | 158 |
2 files changed, 266 insertions, 0 deletions
diff --git a/interface-definitions/dhcp-relay.xml b/interface-definitions/dhcp-relay.xml new file mode 100644 index 000000000..c918d25a3 --- /dev/null +++ b/interface-definitions/dhcp-relay.xml @@ -0,0 +1,108 @@ +<?xml version="1.0"?> +<!-- DHCP relay configuration --> +<interfaceDefinition> + <node name="service"> + <children> + <node name="dhcp-relay" owner="${vyos_conf_scripts_dir}/dhcp_relay.py"> + <properties> + <help>Host Configuration Protocol (DHCP) relay agent</help> + <priority>910</priority> + </properties> + <children> + <leafNode name="interface"> + <properties> + <help>DHCP relay interface [REQUIRED]</help> + <completionHelp> + <script>${vyos_completion_dir}/list_interfaces.py -b</script> + </completionHelp> + <multi/> + </properties> + </leafNode> + <node name="relay-options"> + <properties> + <help>Relay options</help> + </properties> + <children> + <leafNode name="hop-count"> + <properties> + <help>Policy to discard packets that have reached specified hop-count</help> + <valueHelp> + <format>1-255</format> + <description>Hop count (default: 10)</description> + </valueHelp> + <constraint> + <validator name="numeric" argument="--range 1-255"/> + </constraint> + <constraintErrorMessage>hop-count must be a value between 1 and 255</constraintErrorMessage> + </properties> + </leafNode> + <leafNode name="max-size"> + <properties> + <help>Maximum packet size to send to a DHCPv4/BOOTP server</help> + <valueHelp> + <format>64-1400</format> + <description>Maximum packet size (default: 576)</description> + </valueHelp> + <constraint> + <validator name="numeric" argument="--range 64-1400"/> + </constraint> + <constraintErrorMessage>max-size must be a value between 64 and 1400</constraintErrorMessage> + </properties> + </leafNode> + <leafNode name="port"> + <properties> + <help>Port number to listen on</help> + <valueHelp> + <format>1-65535</format> + <description>Port to listen on</description> + </valueHelp> + <constraint> + <validator name="numeric" argument="--range 1-65535"/> + </constraint> + <constraintErrorMessage>port must be a value between 1 and 65535</constraintErrorMessage> + </properties> + </leafNode> + <leafNode name="relay-agents-packets"> + <properties> + <help>Policy to handle incoming DHCPv4 packets which already contain relay agent options (default: forward)</help> + <valueHelp> + <format>append</format> + <description>append own relay options to packet</description> + </valueHelp> + <valueHelp> + <format>replace</format> + <description>replace existing agent option field</description> + </valueHelp> + <valueHelp> + <format>forward</format> + <description>forward packet unchanged</description> + </valueHelp> + <valueHelp> + <format>discard</format> + <description>discard packet (default action if giaddr not set in packet)</description> + </valueHelp> + <constraint> + <regex>(append|replace|forward|discard)</regex> + </constraint> + </properties> + </leafNode> + </children> + </node> + <leafNode name="server"> + <properties> + <help>DHCP server address</help> + <valueHelp> + <format>ipv4</format> + <description>DHCP server IPv4 address</description> + </valueHelp> + <multi/> + <constraint> + <validator name="ipv4-address"/> + </constraint> + </properties> + </leafNode> + </children> + </node> + </children> + </node> +</interfaceDefinition> diff --git a/src/conf_mode/dhcp_relay.py b/src/conf_mode/dhcp_relay.py new file mode 100755 index 000000000..f757491e0 --- /dev/null +++ b/src/conf_mode/dhcp_relay.py @@ -0,0 +1,158 @@ +#!/usr/bin/env python3 +# +# Copyright (C) 2018 VyOS maintainers and contributors +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License version 2 or later as +# published by the Free Software Foundation. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. +# +# + +import sys +import os +import jinja2 + +from vyos.config import Config +from vyos import ConfigError + +config_file = r'/etc/default/isc-dhcp-relay' + +# Please be careful if you edit the template. +config_tmpl = """ +### Autogenerated by dhcp_relay.py ### + +# Defaults for isc-dhcp-relay initscript +# sourced by /etc/init.d/isc-dhcp-relay + +# +# This is a POSIX shell fragment +# + +# What servers should the DHCP relay forward requests to? +SERVERS="{{ server | join(' ') }}" + +# On what interfaces should the DHCP relay (dhrelay) serve DHCP requests? +INTERFACES="{{ interface | join(' ') }}" + +# Additional options that are passed to the DHCP relay daemon? +OPTIONS="-4 -p {{ port }} {{ options | join(' ') }}" +""" + +default_config_data = { + 'interface': [], + 'server': [], + 'options': [], + 'port': '67', + 'hop_count': '10', + 'relay_agent_packets': 'forward' +} + +def get_config(): + relay = default_config_data + conf = Config() + if not conf.exists('service dhcp-relay'): + return None + else: + conf.set_level('service dhcp-relay') + + # Network interfaces to listen on + if conf.exists('interface'): + relay['interface'] = conf.return_values('interface') + + # Servers equal to the address of the DHCP server(s) + if conf.exists('server'): + relay['server'] = conf.return_values('server') + + conf.set_level('service dhcp-relay relay-options') + + if conf.exists('hop-count'): + count = '-c ' + conf.return_value('hop-count') + relay['options'].append(count) + + # Specify the maximum packet size to send to a DHCPv4/BOOTP server. + # This might be done to allow sufficient space for addition of relay agent + # options while still fitting into the Ethernet MTU size. + # + # Available in DHCPv4 mode only: + if conf.exists('max-size'): + size = '-A ' + conf.return_value('max-size') + relay['options'].append(size) + + # Listen and transmit on port <xy>. This is mostly useful for debugging + # purposes. Default is port 67 for DHCPv4/BOOTP, or port 547 for DHCPv6. + if conf.exists('port'): + relay['port'] = conf.return_value('port') + + # Control the handling of incoming DHCPv4 packets which already contain + # relay agent options. If such a packet does not have giaddr set in its + # header, the DHCP standard requires that the packet be discarded. However, + # if giaddr is set, the relay agent may handle the situation in four ways: + # It may append its own set of relay options to the packet, leaving the + # supplied option field intact; it may replace the existing agent option + # field; it may forward the packet unchanged; or, it may discard it. + # + # Available in DHCPv4 mode only: + if conf.exists('relay-agents-packets'): + pkt = '-m ' + conf.return_value('relay-agents-packets') + relay['options'].append(pkt) + + return relay + +def verify(relay): + # bail out early - looks like removal from running config + if relay is None: + return None + + if len(relay['interface']) < 2: + # We can only issue a warning otherwise old configurations might break + print('WARNING: At least two interfaces are required for DHCP relay\n' \ + 'to work\n') + + if 'lo' in relay['interface']: + raise ConfigError('DHCP relay does not support the loopback interface.') + + if len(relay['server']) == 0: + raise ConfigError('No DHCP relay server(s) configured.\n' \ + 'At least one DHCP relay server required.') + + return None + +def generate(relay): + # bail out early - looks like removal from running config + if relay is None: + return None + + tmpl = jinja2.Template(config_tmpl) + config_text = tmpl.render(relay) + with open(config_file, 'w') as f: + f.write(config_text) + + return None + +def apply(relay): + if relay is not None: + os.system('sudo systemctl restart isc-dhcp-relay.service') + else: + # DHCP relay support is removed in the commit + os.system('sudo systemctl stop isc-dhcp-relay.service') + os.unlink(config_file) + + return None + +if __name__ == '__main__': + try: + c = get_config() + verify(c) + generate(c) + apply(c) + except ConfigError as e: + print(e) + sys.exit(1) |