dhcp-server: T3936: Added support for DHCP Option 82

This commit adds support in both the CLI and the underlying code for
DHCP Option 82 to be used to filter/route DHCP address assignments.

The primary use case for this is to support enterprise switches which
can "tag" DHCP requests with physical real world informaiton such as
which switch first saw the request and which port it originated from
(known in this context as remote-id and circuit-id). Once
client-classes have been defined they can be assigned to subnets or
ranges so that only certain addresses get assigned to specific
requests.

There is also a corresponding documentation update which pairs with
this code change.

Author: cblackburn-igl

data/templates/dhcp-server/kea-dhcp4.conf.j2

@@ -23,6 +23,9 @@
             "persist": true,
             "name": "{{ lease_file }}"
         },
+{% if client_class is vyos_defined %}
+        "client-classes": {{ client_class | kea_client_class_json }},
+{% endif %}
         "option-def": [
             {
                 "name": "wpad-url",

interface-definitions/service_dhcp-server.xml.in

@@ -9,6 +9,43 @@
           <priority>911</priority>
         </properties>
         <children>
+          <tagNode name="client-class">
+            <properties>
+              <help>Client class name</help>
+              <constraint>
+                #include <include/constraint/alpha-numeric-hyphen-underscore-dot.xml.i>
+              </constraint>
+              <constraintErrorMessage>Shared network name may only contain letters, numbers and, dots, underscores, and hyphens</constraintErrorMessage>
+            </properties>
+            <children>
+              #include <include/generic-disable-node.xml.i>
+              <node name="option82">
+                <properties>
+                  <help>Match DHCP option 82 (relay agent information)</help>
+                </properties>
+                <children>
+                <leafNode name="circuit-id">
+                    <properties>
+                      <help>Filters on the contents of the circuit-id sub option.</help>
+                      <valueHelp>
+                        <format>txt</format>
+                        <description>Assumes ASCII text unless input starts with 0x in which case it is interpreted as raw hex</description>
+                      </valueHelp>
+                    </properties>
+                  </leafNode>
+                  <leafNode name="remote-id">
+                    <properties>
+                      <help>Filters on the contents of the remote-id sub option.</help>
+                      <valueHelp>
+                        <format>txt</format>
+                        <description>Assumes ASCII text unless input starts with 0x in which case it is interpreted as raw hex</description>
+                      </valueHelp>
+                    </properties>
+                  </leafNode>
+                </children>
+              </node>
+            </children>
+          </tagNode>
           #include <include/generic-disable-node.xml.i>
           <node name="dynamic-dns-update">
             <properties>
@@ -239,6 +276,14 @@
                   #include <include/dhcp/ping-check.xml.i>
                   #include <include/generic-description.xml.i>
                   #include <include/generic-disable-node.xml.i>
+                  <leafNode name="client-class">
+                    <properties>
+                      <help>DHCP client class</help>
+                        <completionHelp>
+                          <path>service dhcp-server client-class</path>
+                        </completionHelp>
+                    </properties>
+                  </leafNode>
                   <node name="dynamic-dns-update">
                     <properties>
                       <help>Dynamically update Domain Name System (RFC4702)</help>
@@ -290,6 +335,14 @@
                     </properties>
                     <children>
                       #include <include/dhcp/option-v4.xml.i>
+                      <leafNode name="client-class">
+                        <properties>
+                          <help>DHCP client class</help>
+                          <completionHelp>
+                            <path>service dhcp-server client-class</path>
+                          </completionHelp>
+                        </properties>
+                      </leafNode>
                       <leafNode name="start">
                         <properties>
                           <help>First IP address for DHCP lease range</help>

python/vyos/kea.py

@@ -169,6 +169,9 @@ def kea_parse_subnet(subnet, config):
     if 'ping_check' in config:
         out['user-context']['enable-ping-check'] = True
 
+    if 'client_class' in config:
+        out['client-class'] = config['client_class']
+
     if 'range' in config:
         pools = []
         for num, range_config in config['range'].items():
@@ -184,6 +187,9 @@ def kea_parse_subnet(subnet, config):
                 if 'bootfile_server' in range_config['option']:
                     pool['next-server'] = range_config['option']['bootfile_server']
 
+            if 'client_class' in range_config:
+                pool['client-class'] = range_config['client_class']
+
             pools.append(pool)
         out['pools'] = pools
 
@@ -661,3 +667,25 @@ def kea_get_server_leases(config, inet, pools=[], state=[], origin=None) -> list
                     data.pop(idx)
 
     return data
+
+def kea_build_client_class_test(config):
+    conditions = []
+
+    if "option82" in config:
+        if "circuit_id" in config["option82"]:
+            conditions.append("relay4[1].hex == 0x" + config["option82"]["circuit_id"].encode().hex().lower())
+        if "remote_id" in config["option82"]:
+            conditions.append("relay4[2].hex == 0x" + config["option82"]["remote_id"].encode().hex().lower())
+
+    is_first = True
+
+    test = ""
+    for condition in conditions:
+        if not is_first:
+            test += " and "
+
+        is_first = False
+
+        test += condition
+
+    return test

python/vyos/template.py

@@ -910,6 +910,25 @@ def kea_high_availability_json(config):
 
     return dumps(data)
 
+@register_filter('kea_client_class_json')
+def kea_client_class_json(client_classes):
+    from vyos.kea import kea_build_client_class_test
+    from json import dumps
+    out = []
+
+    for name, config in client_classes.items():
+        if 'disable' in config:
+            continue
+
+        client_class = {
+            'name': name,
+            'test': kea_build_client_class_test(config)
+        }
+
+        out.append(client_class)
+
+    return dumps(out, indent=4)
+
 @register_filter('kea_dynamic_dns_update_main_json')
 def kea_dynamic_dns_update_main_json(config):
     from vyos.kea import kea_parse_ddns_settings

smoketest/scripts/cli/test_service_dhcp-server.py

@@ -113,27 +113,7 @@ def test_dhcp_single_pool_range(self):
         range_1_start = inc_ip(subnet, 40)
         range_1_stop = inc_ip(subnet, 50)
 
-        self.cli_set(base_path + ['listen-interface', interface])
-
-        self.cli_set(base_path + ['shared-network-name', shared_net_name, 'ping-check'])
-
-        pool = base_path + ['shared-network-name', shared_net_name, 'subnet', subnet]
-        self.cli_set(pool + ['subnet-id', '1'])
-        self.cli_set(pool + ['ignore-client-id'])
-        self.cli_set(pool + ['ping-check'])
-        # we use the first subnet IP address as default gateway
-        self.cli_set(pool + ['option', 'default-router', router])
-        self.cli_set(pool + ['option', 'name-server', dns_1])
-        self.cli_set(pool + ['option', 'name-server', dns_2])
-        self.cli_set(pool + ['option', 'domain-name', domain_name])
-
-        # check validate() - No DHCP address range or active static-mapping set
-        with self.assertRaises(ConfigSessionError):
-            self.cli_commit()
-        self.cli_set(pool + ['range', '0', 'start', range_0_start])
-        self.cli_set(pool + ['range', '0', 'stop', range_0_stop])
-        self.cli_set(pool + ['range', '1', 'start', range_1_start])
-        self.cli_set(pool + ['range', '1', 'stop', range_1_stop])
+        self.setup_single_pool_range(range_0_start, range_0_stop, range_1_start, range_1_stop, shared_net_name)
 
         # commit changes
         self.cli_commit()
@@ -210,6 +190,84 @@ def test_dhcp_single_pool_range(self):
         # Check for running process
         self.verify_service_running()
 
+    def setup_single_pool_range(self, range_0_start, range_0_stop, range_1_start, range_1_stop, shared_net_name):
+        self.cli_set(base_path + ['listen-interface', interface])
+        self.cli_set(base_path + ['shared-network-name', shared_net_name, 'ping-check'])
+
+        pool = base_path + ['shared-network-name', shared_net_name, 'subnet', subnet]
+
+        self.cli_set(pool + ['subnet-id', '1'])
+        self.cli_set(pool + ['ignore-client-id'])
+        self.cli_set(pool + ['ping-check'])
+        # we use the first subnet IP address as default gateway
+        self.cli_set(pool + ['option', 'default-router', router])
+        self.cli_set(pool + ['option', 'name-server', dns_1])
+        self.cli_set(pool + ['option', 'name-server', dns_2])
+        self.cli_set(pool + ['option', 'domain-name', domain_name])
+
+        # check validate() - No DHCP address range or active static-mapping set
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+
+        self.cli_set(pool + ['range', '0', 'start', range_0_start])
+        self.cli_set(pool + ['range', '0', 'stop', range_0_stop])
+        self.cli_set(pool + ['range', '1', 'start', range_1_start])
+        self.cli_set(pool + ['range', '1', 'stop', range_1_stop])
+
+    def test_dhcp_client_class(self):
+        shared_net_name = 'SMOKE-1'
+
+        range_0_start = inc_ip(subnet, 10)
+        range_0_stop = inc_ip(subnet, 20)
+        range_1_start = inc_ip(subnet, 40)
+        range_1_stop = inc_ip(subnet, 50)
+
+        self.setup_single_pool_range(range_0_start, range_0_stop, range_1_start, range_1_stop, shared_net_name)
+
+        self.cli_set(base_path + ['shared-network-name', shared_net_name, 'subnet', subnet, 'client-class', 'test'])
+
+        # check validate() - Client class referenced that doesn't exist yet
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+
+        self.cli_delete(base_path + ['shared-network-name', shared_net_name, 'subnet', subnet, 'client-class', 'test'])
+
+        self.cli_set(base_path + ['shared-network-name', shared_net_name, 'subnet', subnet, 'range', '0', 'client-class', 'test'])
+
+        # check validate() - Client class referenced that doesn't exist yet
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+
+        self.cli_set(base_path + ['shared-network-name', shared_net_name, 'subnet', subnet, 'client-class', 'test'])
+
+        client_class = base_path + ['client-class', 'test']
+        self.cli_set(client_class + ['option82', 'circuit-id', 'foo'])
+        self.cli_set(client_class + ['option82', 'remote-id', 'bar'])
+
+        self.cli_commit()
+
+        config = read_file(KEA4_CONF)
+        obj = loads(config)
+
+        self.verify_config_value(
+            obj, ['Dhcp4', 'client-classes', 0], 'name', 'test'
+        )
+
+        self.verify_config_value(
+            obj, ['Dhcp4', 'client-classes', 0], 'test', 'relay4[1].hex == 0x666f6f and relay4[2].hex == 0x626172'
+        )
+
+        self.verify_config_value(
+            obj, ['Dhcp4', 'shared-networks', 0, 'subnet4', 0], 'client-class', 'test'
+        )
+
+        self.verify_config_value(
+            obj, ['Dhcp4', 'shared-networks', 0, 'subnet4', 0, 'pools', 0], 'client-class', 'test'
+        )
+
+        # Check for running process
+        self.verify_service_running()
+
     def test_dhcp_single_pool_options(self):
         shared_net_name = 'SMOKE-0815'
 

src/conf_mode/service_dhcp-server.py

@@ -231,6 +231,15 @@ def verify(dhcp):
                             f'DHCP static-route "{route}" requires router to be defined!'
                         )
 
+            # If a client class has been specified then it must exist
+            if 'client_class' in subnet_config:
+                client_class = subnet_config['client_class']
+                if 'client_class' not in dhcp:
+                    raise ConfigError(f'Client class "{client_class}" set in subnet "{subnet}" but does not exist')
+
+                if client_class not in dhcp['client_class'].keys():
+                    raise ConfigError(f'Client class "{client_class}" set in subnet "{subnet}" but does not exist')
+
             # Check if DHCP address range is inside configured subnet declaration
             if 'range' in subnet_config:
                 networks = []
@@ -240,6 +249,15 @@ def verify(dhcp):
                             f'DHCP range "{range}" start and stop address must be defined!'
                         )
 
+                    # If a client class has been specified then it must exist
+                    if 'client_class' in range_config:
+                        client_class = range_config['client_class']
+                        if 'client_class' not in dhcp:
+                            raise ConfigError(f'Client class "{client_class}" set in range "{range}" but does not exist')
+
+                        if client_class not in dhcp['client_class'].keys():
+                            raise ConfigError(f'Client class "{client_class}" set in range "{range}" but does not exist')
+
                     # Start/Stop address must be inside network
                     for key in ['start', 'stop']:
                         if ip_address(range_config[key]) not in ip_network(subnet):