network: bridge: add support for IFLA_BRPORT_MAB

Since linux commit a35ec8e38cdd1766f29924ca391a01de20163931 ("bridge:
Add MAC Authentication Bypass (MAB) support"), included since v6.2, it
is possible to enable MAC Authentication Bypass for bridge ports. In
this mode the locked port learns again, but the learned fdb entries are
locked, allowing user space to unlock hosts based seen MAC addresses.

This requires learning to be enabled on the port, and link-local
learning disabled for the bridge.

Add support to systemd-network for setting the new attribute for bridge
ports.

man/systemd.network.xml

@@ -4630,6 +4630,15 @@ ServerAddress=192.168.0.1/24</programlisting>
           <para>Takes a boolean. Configures whether the port is "locked" and does not allow traffic forwarded
           until fully authenticated, e.g. via 802.1x. When unset, the kernel's default will be used.</para>
 
+          <xi:include href="version-info.xml" xpointer="v258"/>
+        </listitem>
+        <term><varname>MACAuthenticationBypass=</varname></term>
+        <listitem>
+          <para>Takes a boolean. Configures whether a locked port has "MAC Authentication Bypass" enabled and
+          creates newly learned fdb entries in a "locked" state. User space can authenticate these entries by
+          clearing the locked flag. Requires Learning to be enabled. When unset, the kernel's default will be
+          used.</para>
+
           <xi:include href="version-info.xml" xpointer="v258"/>
         </listitem>
       </varlistentry>

src/libsystemd/sd-netlink/netlink-types-rtnl.c

@@ -486,6 +486,7 @@ static const struct NLAPolicy rtnl_bridge_port_policies[] = {
         [IFLA_BRPORT_MCAST_EHT_HOSTS_LIMIT] = BUILD_POLICY(U32),
         [IFLA_BRPORT_MCAST_EHT_HOSTS_CNT]   = BUILD_POLICY(U32),
         [IFLA_BRPORT_LOCKED]                = BUILD_POLICY(U8),
+        [IFLA_BRPORT_MAB]                   = BUILD_POLICY(U8),
 };
 
 static const NLAPolicySetUnionElement rtnl_link_info_slave_data_policy_set_union_elements[] = {

src/network/networkd-network-gperf.gperf

@@ -384,6 +384,7 @@ Bridge.ProxyARPWiFi,                         config_parse_tristate,
 Bridge.Priority,                             config_parse_bridge_port_priority,                        0,                             offsetof(Network, priority)
 Bridge.MulticastRouter,                      config_parse_multicast_router,                            0,                             offsetof(Network, multicast_router)
 Bridge.Locked,                               config_parse_tristate,                                    0,                             offsetof(Network, bridge_locked)
+Bridge.MACAuthenticationBypass,              config_parse_tristate,                                    0,                             offsetof(Network, bridge_mac_authentication_bypass)
 BridgeFDB.MACAddress,                        config_parse_fdb_hwaddr,                                  0,                             0
 BridgeFDB.VLANId,                            config_parse_fdb_vlan_id,                                 0,                             0
 BridgeFDB.Destination,                       config_parse_fdb_destination,                             0,                             0

src/network/networkd-network.c

@@ -457,6 +457,7 @@ int network_load_one(Manager *manager, OrderedHashmap **networks, const char *fi
                 .priority = LINK_BRIDGE_PORT_PRIORITY_INVALID,
                 .multicast_router = _MULTICAST_ROUTER_INVALID,
                 .bridge_locked = -1,
+                .bridge_mac_authentication_bypass = -1,
 
                 .bridge_vlan_pvid = BRIDGE_VLAN_KEEP_PVID,
 

src/network/networkd-network.h

@@ -298,6 +298,7 @@ struct Network {
         uint16_t priority;
         MulticastRouter multicast_router;
         int bridge_locked;
+        int bridge_mac_authentication_bypass;
 
         /* Bridge VLAN */
         uint16_t bridge_vlan_pvid;

src/network/networkd-setlink.c

@@ -326,6 +326,12 @@ static int link_configure_fill_message(
                                 return r;
                 }
 
+                if (link->network->bridge_mac_authentication_bypass >= 0) {
+                        r = sd_netlink_message_append_u8(req, IFLA_BRPORT_MAB, link->network->bridge_mac_authentication_bypass);
+                        if (r < 0)
+                                return r;
+                }
+
                 r = sd_netlink_message_close_container(req);
                 if (r < 0)
                         return r;

test/test-network/conf/26-bridge-slave-interface-2.network

@@ -11,3 +11,4 @@ Bridge=bridge99
 [Bridge]
 Priority=0
 Locked=true
+MACAuthenticationBypass=true

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

@@ -5791,6 +5791,8 @@ class NetworkdBridgeTests(unittest.TestCase, Utilities):
         print(output)
         self.check_bridge_port_attr('bridge99', 'test1', 'priority',               '0')
         self.assertIn('locked on', output)
+        if ' mab ' in output: # This is new in kernel and iproute2 v6.2
+            self.assertIn('mab on', output)
 
     def test_bridge_property(self):
         copy_network_unit('11-dummy.netdev', '12-dummy.netdev', '26-bridge.netdev',