[routing-manager] derive on-link prefix from Extended PAN ID (#7695)

To align with latest Thread Specification.

src/core/border_router/routing_manager.cpp

@@ -47,6 +47,7 @@
 #include "common/log.hpp"
 #include "common/random.hpp"
 #include "common/settings.hpp"
+#include "meshcop/extended_panid.hpp"
 #include "net/ip6.hpp"
 #include "thread/network_data_leader.hpp"
 #include "thread/network_data_local.hpp"
@@ -101,7 +102,7 @@ Error RoutingManager::Init(uint32_t aInfraIfIndex, bool aInfraIfIsRunning)
 #if OPENTHREAD_CONFIG_BORDER_ROUTING_NAT64_ENABLE
     GenerateNat64Prefix();
 #endif
-    SuccessOrExit(error = LoadOrGenerateRandomOnLinkPrefix());
+    GenerateOnLinkPrefix();
 
     mInfraIfIndex = aInfraIfIndex;
 
@@ -222,37 +223,18 @@ void RoutingManager::GenerateNat64Prefix(void)
 }
 #endif
 
-Error RoutingManager::LoadOrGenerateRandomOnLinkPrefix(void)
+void RoutingManager::GenerateOnLinkPrefix(void)
 {
-    Error error     = kErrorNone;
-    bool  generated = false;
+    MeshCoP::ExtendedPanId extPanId = Get<MeshCoP::ExtendedPanIdManager>().GetExtPanId();
 
-    if (Get<Settings>().Read<Settings::OnLinkPrefix>(mLocalOnLinkPrefix) != kErrorNone ||
-        !mLocalOnLinkPrefix.IsUniqueLocal())
-    {
-        Ip6::NetworkPrefix randomOnLinkPrefix;
+    mLocalOnLinkPrefix.mPrefix.mFields.m8[0] = 0xfd;
+    // Global ID: 40 most significant bits of Extended PAN ID
+    memcpy(mLocalOnLinkPrefix.mPrefix.mFields.m8 + 1, extPanId.m8, 5);
+    // Subnet ID: 16 least significant bits of Extended PAN ID
+    memcpy(mLocalOnLinkPrefix.mPrefix.mFields.m8 + 6, extPanId.m8 + 6, 2);
+    mLocalOnLinkPrefix.SetLength(kOnLinkPrefixLength);
 
-        error = randomOnLinkPrefix.GenerateRandomUla();
-        if (error != kErrorNone)
-        {
-            LogCrit("Failed to generate random on-link prefix");
-            ExitNow();
-        }
-
-        mLocalOnLinkPrefix.Set(randomOnLinkPrefix);
-        mLocalOnLinkPrefix.SetSubnetId(0);
-
-        IgnoreError(Get<Settings>().Save<Settings::OnLinkPrefix>(mLocalOnLinkPrefix));
-        generated = true;
-    }
-
-    OT_UNUSED_VARIABLE(generated);
-
-    LogNote("Local on-link prefix: %s (%s)", mLocalOnLinkPrefix.ToString().AsCString(),
-            generated ? "generated" : "loaded");
-
-exit:
-    return error;
+    LogNote("Local on-link prefix: %s", mLocalOnLinkPrefix.ToString().AsCString());
 }
 
 void RoutingManager::EvaluateState(void)
@@ -397,6 +379,24 @@ void RoutingManager::HandleNotifierEvents(Events aEvents)
         StartRoutingPolicyEvaluationJitter(kRoutingPolicyEvaluationJitter);
     }
 
+    if (aEvents.Contains(kEventThreadExtPanIdChanged))
+    {
+        if (mIsAdvertisingLocalOnLinkPrefix)
+        {
+            RemoveExternalRoute(mLocalOnLinkPrefix);
+            // TODO: consider deprecating/invalidating existing
+            // on-link prefix
+            mIsAdvertisingLocalOnLinkPrefix = false;
+        }
+
+        GenerateOnLinkPrefix();
+
+        if (mIsRunning)
+        {
+            StartRoutingPolicyEvaluationJitter(kRoutingPolicyEvaluationJitter);
+        }
+    }
+
 exit:
     return;
 }

src/core/border_router/routing_manager.hpp

@@ -317,7 +317,7 @@ private:
     bool  IsEnabled(void) const { return mIsEnabled; }
     Error LoadOrGenerateRandomBrUlaPrefix(void);
     void  GenerateOmrPrefix(void);
-    Error LoadOrGenerateRandomOnLinkPrefix(void);
+    void  GenerateOnLinkPrefix(void);
 
     const Ip6::Prefix *EvaluateOnLinkPrefix(void);
 

tests/scripts/thread-cert/border_router/test_multi_border_routers.py

@@ -191,12 +191,13 @@ class MultiBorderRouters(thread_cert.TestCase):
         br2_omr_prefix = br2.get_br_omr_prefix()
         self.assertEqual(br2_omr_prefix, br2.get_netdata_omr_prefixes()[0])
 
-        # Only BR2 will keep the route for BR1's on-link prefix
-        # and add route for on-link prefix of its own.
-        self.assertEqual(len(br1.get_netdata_non_nat64_prefixes()), 2)
-        self.assertEqual(len(router1.get_netdata_non_nat64_prefixes()), 2)
-        self.assertEqual(len(br2.get_netdata_non_nat64_prefixes()), 2)
-        self.assertEqual(len(router2.get_netdata_non_nat64_prefixes()), 2)
+        # There should be no changes to the external route for the
+        # on-link prefix, given that the on-link prefix is derived
+        # from the Extended PAN ID.
+        self.assertEqual(len(br1.get_netdata_non_nat64_prefixes()), 1)
+        self.assertEqual(len(router1.get_netdata_non_nat64_prefixes()), 1)
+        self.assertEqual(len(br2.get_netdata_non_nat64_prefixes()), 1)
+        self.assertEqual(len(router2.get_netdata_non_nat64_prefixes()), 1)
 
         br2_on_link_prefix = br2.get_br_on_link_prefix()
         self.assertEqual(set(map(IPv6Network, br2.get_netdata_non_nat64_prefixes())),

tests/scripts/thread-cert/border_router/test_single_border_router.py

@@ -28,6 +28,7 @@
 #
 import logging
 import unittest
+from ipaddress import IPv6Network
 
 import config
 import thread_cert
@@ -326,6 +327,25 @@ class SingleBorderRouter(thread_cert.TestCase):
         self.assertTrue(router.ping(host.get_ip6_address(config.ADDRESS_TYPE.ONLINK_ULA)[0]))
         self.assertTrue(host.ping(router.get_ip6_address(config.ADDRESS_TYPE.OMR)[0], backbone=True))
 
+        #
+        # Case 7. Test if Border Router changes on-link prefix when
+        #         Extended PAN ID changes.
+        #
+
+        prefixA = br.get_br_on_link_prefix()
+
+        router.commissioner_start()
+        self.simulator.go(5)
+
+        router.send_mgmt_active_set(
+            active_timestamp=100,
+            extended_panid='0001020304050607',
+        )
+        self.simulator.go(10)
+
+        prefixB = br.get_br_on_link_prefix()
+        self.assertNotEqual(IPv6Network(prefixA), IPv6Network(prefixB))
+
 
 if __name__ == '__main__':
     unittest.main()

tests/scripts/thread-cert/border_router/test_vicarious_router_solicit.py

@@ -67,6 +67,7 @@ class MultiThreadNetworks(thread_cert.TestCase):
             'version': '1.2',
             'channel': CHANNEL1,
             'router_selection_jitter': 1,
+            'extended_panid': '0001020304050607'
         },
         ROUTER1: {
             'name': 'Router_1',
@@ -74,6 +75,7 @@ class MultiThreadNetworks(thread_cert.TestCase):
             'version': '1.2',
             'channel': CHANNEL1,
             'router_selection_jitter': 1,
+            'extended_panid': '0001020304050607'
         },
         BR2: {
             'name': 'BR_2',
@@ -82,6 +84,7 @@ class MultiThreadNetworks(thread_cert.TestCase):
             'version': '1.2',
             'channel': CHANNEL2,
             'router_selection_jitter': 1,
+            'extended_panid': '08090a0b0c0d0e0f'
         },
         ROUTER2: {
             'name': 'Router_2',
@@ -89,6 +92,7 @@ class MultiThreadNetworks(thread_cert.TestCase):
             'version': '1.2',
             'channel': CHANNEL2,
             'router_selection_jitter': 1,
+            'extended_panid': '08090a0b0c0d0e0f'
         },
         HOST: {
             'name': 'Host',

tests/scripts/thread-cert/thread_cert.py

@@ -183,6 +183,8 @@ class TestCase(NcpSupportMixin, unittest.TestCase):
             self.nodes[i].set_panid(params['panid'])
             self.nodes[i].set_mode(params['mode'])
 
+            if 'extended_panid' in params:
+                self.nodes[i].set_extpanid(params['extended_panid'])
             if 'partition_id' in params:
                 self.nodes[i].set_preferred_partition_id(params['partition_id'])
             if 'channel' in params: