network/dhcp: introduce global setting for DHCPv4 client identifier (#35783)

Typically, the same client identifier setting is used for all
interfaces. Hence, better to provide the system-wide setting to specify
the client identifier.

man/networkd.conf.xml

@@ -247,16 +247,29 @@
   <refsect1>
     <title>[DHCPv4] Section Options</title>
 
-    <para>This section configures the DHCP Unique Identifier (DUID) value used by DHCP protocol. DHCPv4
-    client protocol sends IAID and DUID to the DHCP server when acquiring a dynamic IPv4 address if
-    <option>ClientIdentifier=duid</option>. IAID and DUID allows a DHCP server to uniquely identify the
-    machine and the interface requesting a DHCP IP address. To configure IAID and ClientIdentifier, see
+    <para>This section configures the default configurations of DHCPv4 client. If the DHCPv4 client is
+    enabled on an interface, then the configurations below will be used by default unless explicitly
+    specified in the corresponding <filename>.network</filename> file. See also
     <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
     </para>
 
     <para>The following options are understood:</para>
 
     <variablelist class='network-directives'>
+      <varlistentry>
+        <term><varname>ClientIdentifier=</varname></term>
+        <listitem>
+          <para>Specifies the default DHCPv4 client identifier to be used. Takes one of <option>mac</option>
+          or <option>duid</option>. If set to <option>mac</option>, the MAC address of each link will be used.
+          If set to <option>duid</option>, an RFC4361-compliant Client ID, which is the combination of IAID
+          and DUID, is used. IAID can be configured by <varname>IAID=</varname> in each matching
+          <filename>.network</filename> file. DUID can be configured by <varname>DUIDType=</varname> and
+          <varname>DUIDRawData=</varname>. Defaults to <option>duid</option>.</para>
+
+        <xi:include href="version-info.xml" xpointer="v258"/>
+        </listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><varname>DUIDType=</varname></term>
         <listitem><para>Specifies how the DUID should be generated. See
@@ -354,11 +367,9 @@ DUIDRawData=00:00:ab:11:f9:2a:c2:77:29:f9:5c:00</programlisting>
   <refsect1>
     <title>[DHCPv6] Section Options</title>
 
-    <para>This section configures the DHCP Unique Identifier (DUID) value used by DHCPv6 protocol.
-    DHCPv6 client protocol sends the DHCP Unique Identifier and the interface Identity Association
-    Identifier (IAID) to a DHCPv6 server when acquiring a dynamic IPv6 address. IAID and DUID allows a
-    DHCPv6 server to uniquely identify the machine and the interface requesting a DHCP IP address. To
-    configure IAID, see
+    <para>This section configures the default configurations of DHCPv6 client. If the DHCPv6 client is
+    enabled on an interface, then the configurations below will be used by default unless explicitly
+    specified in the corresponding <filename>.network</filename> file. See also
     <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
     </para>
 

man/systemd.network.xml

@@ -2371,8 +2371,11 @@ NFTSet=prefix:netdev:filter:eth_ipv4_prefix</programlisting>
           <option>duid</option>. If set to <option>mac</option>, the MAC address of the link is used. If set
           to <option>duid</option>, an RFC4361-compliant Client ID, which is the combination of IAID and
           DUID, is used. IAID can be configured by <varname>IAID=</varname>. DUID can be configured by
-          <varname>DUIDType=</varname> and <varname>DUIDRawData=</varname>. Defaults to
-          <option>duid</option>.</para>
+          <varname>DUIDType=</varname> and <varname>DUIDRawData=</varname>. When
+          <varname>Anonymize=</varname> is enabled, <option>mac</option> is unconditionally used and the
+          specified value will be ignored. When unspecified, the value specified in the same setting in
+          <citerefentry><refentrytitle>networkd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+          will be used.</para>
 
         <xi:include href="version-info.xml" xpointer="v220"/>
         </listitem>

src/network/networkd-dhcp4.c

@@ -52,7 +52,7 @@ void network_adjust_dhcp4(Network *network) {
         }
 
         if (network->dhcp_client_identifier < 0)
-                network->dhcp_client_identifier = network->dhcp_anonymize ? DHCP_CLIENT_ID_MAC : DHCP_CLIENT_ID_DUID;
+                network->dhcp_client_identifier = network->dhcp_anonymize ? DHCP_CLIENT_ID_MAC : network->manager->dhcp_client_identifier;
 
         /* By default, RapidCommit= is enabled when Anonymize=no and neither AllowList= nor DenyList= is specified. */
         if (network->dhcp_use_rapid_commit < 0)

src/network/networkd-gperf.gperf

@@ -37,6 +37,7 @@ IPv6AcceptRA.UseDomains,                 config_parse_use_domains,
 IPv6AddressLabel.Prefix,                 config_parse_ipv6_address_label_section, IPV6_ADDRESS_LABEL_BY_MANAGER | IPV6_ADDRESS_LABEL_PREFIX, 0
 IPv6AddressLabel.Label,                  config_parse_ipv6_address_label_section, IPV6_ADDRESS_LABEL_BY_MANAGER | IPV6_ADDRESS_LABEL,        0
 DHCPv4.UseDomains,                       config_parse_use_domains,                0,                                                         offsetof(Manager, dhcp_use_domains)
+DHCPv4.ClientIdentifier,                 config_parse_dhcp_client_identifier,     0,                                                         offsetof(Manager, dhcp_client_identifier)
 DHCPv4.DUIDType,                         config_parse_duid_type,                  0,                                                         offsetof(Manager, dhcp_duid)
 DHCPv4.DUIDRawData,                      config_parse_duid_rawdata,               0,                                                         offsetof(Manager, dhcp_duid)
 DHCPv6.UseDomains,                       config_parse_use_domains,                0,                                                         offsetof(Manager, dhcp6_use_domains)

src/network/networkd-manager.c

@@ -647,6 +647,7 @@ int manager_new(Manager **ret, bool test_mode) {
                 .dhcp_use_domains = _USE_DOMAINS_INVALID,
                 .dhcp6_use_domains = _USE_DOMAINS_INVALID,
                 .ndisc_use_domains = _USE_DOMAINS_INVALID,
+                .dhcp_client_identifier = DHCP_CLIENT_ID_DUID,
                 .dhcp_duid.type = DUID_TYPE_EN,
                 .dhcp6_duid.type = DUID_TYPE_EN,
                 .duid_product_uuid.type = DUID_TYPE_UUID,

src/network/networkd-manager.h

@@ -78,6 +78,7 @@ struct Manager {
         UseDomains dhcp6_use_domains;
         UseDomains ndisc_use_domains;
 
+        DHCPClientIdentifier dhcp_client_identifier;
         DUID dhcp_duid;
         DUID dhcp6_duid;
         DUID duid_product_uuid;

src/network/networkd.conf

@@ -36,6 +36,7 @@
 #UseDomains=
 
 [DHCPv4]
+#ClientIdentifier=duid
 #DUIDType=vendor
 #DUIDRawData=
 #UseDomains=

test/test-network/conf/10-dhcp-client-id-duid.conf

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+[DHCPv4]
+ClientIdentifier=duid

test/test-network/conf/10-dhcp-client-id-mac.conf

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+[DHCPv4]
+ClientIdentifier=mac

test/test-network/systemd-networkd-tests.py

@@ -6742,8 +6742,9 @@ class NetworkdDHCPServerTests(unittest.TestCase, Utilities):
         self.assertIn('Gateway: 192.168.5.1', output)
         self.assertIn('Time Zone: Europe/Berlin', output)
 
-    def test_dhcp_server_static_lease(self):
+    def test_dhcp_server_static_lease_mac_by_network(self):
         copy_network_unit('25-veth.netdev', '25-dhcp-client-static-lease.network', '25-dhcp-server-static-lease.network')
+        copy_networkd_conf_dropin('10-dhcp-client-id-duid.conf')
         start_networkd()
         self.wait_online('veth99:routable', 'veth-peer:routable')
 
@@ -6752,7 +6753,18 @@ class NetworkdDHCPServerTests(unittest.TestCase, Utilities):
         self.assertIn('Address: 10.1.1.200 (DHCPv4 via 10.1.1.1)', output)
         self.assertIn('DHCPv4 Client ID: 12:34:56:78:9a:bc', output)
 
-    def test_dhcp_server_static_lease_default_client_id(self):
+    def test_dhcp_server_static_lease_mac_by_global(self):
+        copy_network_unit('25-veth.netdev', '25-dhcp-client.network', '25-dhcp-server-static-lease.network')
+        copy_networkd_conf_dropin('10-dhcp-client-id-mac.conf')
+        start_networkd()
+        self.wait_online('veth99:routable', 'veth-peer:routable')
+
+        output = networkctl_status('veth99')
+        print(output)
+        self.assertIn('Address: 10.1.1.200 (DHCPv4 via 10.1.1.1)', output)
+        self.assertIn('DHCPv4 Client ID: 12:34:56:78:9a:bc', output)
+
+    def test_dhcp_server_static_lease_duid(self):
         copy_network_unit('25-veth.netdev', '25-dhcp-client.network', '25-dhcp-server-static-lease.network')
         start_networkd()
         self.wait_online('veth99:routable', 'veth-peer:routable')