[nexus] add mechanism to emulate node reset (#11662)

This commit adds a new mechanism to emulate a node reset on
`Nexus::Node`. This is realized by resetting all platform components
while ensuring the non-volatile `mSettings` remains unchanged, then
reinitializing the `ot::Instance` by invoking its constructor.

This is used to add a new `test_full_network_reset` test, which
emulates a full simultaneous reset of all nodes in a large network,
tracking how long it takes for the network to stabilize after the
reset event.

tests/nexus/CMakeLists.txt

@@ -114,5 +114,6 @@ endmacro()
 ot_nexus_test(border_agent)
 ot_nexus_test(dtls)
 ot_nexus_test(form_join)
+ot_nexus_test(full_network_reset)
 ot_nexus_test(large_network)
 ot_nexus_test(trel)

tests/nexus/platform/nexus_alarm.hpp

@@ -36,11 +36,8 @@ namespace Nexus {
 
 struct Alarm
 {
-    Alarm(void)
-        : mScheduled(false)
-    {
-    }
-
+    Alarm(void) { Reset(); }
+    void Reset(void) { mScheduled = false; }
     bool ShouldTrigger(Time aNow) const { return mScheduled && (aNow >= mAlarmTime); }
 
     bool mScheduled;

tests/nexus/platform/nexus_mdns.cpp

@@ -71,6 +71,12 @@ Mdns::Mdns(void)
     SuccessOrQuit(mIfAddresses.PushBack(address));
 }
 
+void Mdns::Reset(void)
+{
+    mEnabled = false;
+    mPendingTxList.Free();
+}
+
 Error Mdns::SetListeningEnabled(Instance &aInstance, bool aEnable, uint32_t aInfraIfIndex)
 {
     Error error = kErrorNone;

tests/nexus/platform/nexus_mdns.hpp

@@ -51,6 +51,7 @@ public:
     };
 
     Mdns(void);
+    void  Reset(void);
     Error SetListeningEnabled(Instance &aInstance, bool aEnable, uint32_t aInfraIfIndex);
     void  SendMulticast(Message &aMessage, uint32_t aInfraIfIndex);
     void  SendUnicast(Message &aMessage, const AddressInfo &aAddress);

tests/nexus/platform/nexus_node.cpp

@@ -32,6 +32,26 @@
 namespace ot {
 namespace Nexus {
 
+void Node::Reset(void)
+{
+    Instance *instance = &GetInstance();
+    uint32_t  id       = GetId();
+
+    mRadio.Reset();
+    mAlarm.Reset();
+    mMdns.Reset();
+    mPendingTasklet = false;
+#if OPENTHREAD_CONFIG_RADIO_LINK_TREL_ENABLE
+    mTrel.Reset();
+#endif
+
+    instance->~Instance();
+
+    instance = new (instance) Instance();
+    instance->SetId(id);
+    instance->AfterInit();
+}
+
 void Node::Form(void)
 {
     MeshCoP::Dataset::Info datasetInfo;

tests/nexus/platform/nexus_node.hpp

@@ -74,6 +74,7 @@ public:
         kAsSed,
     };
 
+    void Reset(void);
     void Form(void);
     void Join(Node &aNode, JoinMode aJoinMode = kAsFtd);
     void AllowList(Node &aNode);

tests/nexus/platform/nexus_radio.cpp

@@ -256,6 +256,15 @@ Radio::Radio(void)
 {
 }
 
+void Radio::Reset(void)
+{
+    mState           = kStateDisabled;
+    mPromiscuous     = false;
+    mSrcMatchEnabled = false;
+    mSrcMatchShortEntries.Clear();
+    mSrcMatchExtEntries.Clear();
+}
+
 bool Radio::CanReceiveOnChannel(uint8_t aChannel) const
 {
     bool canRx = false;

tests/nexus/platform/nexus_radio.hpp

@@ -59,6 +59,7 @@ struct Radio
     };
 
     Radio(void);
+    void Reset(void);
     bool CanReceiveOnChannel(uint8_t aChannel) const;
     bool Matches(const Mac::Address &aAddress, Mac::PanId aPanId) const;
     bool HasFramePendingFor(const Mac::Address &aAddress) const;

tests/nexus/platform/nexus_trel.cpp

@@ -80,6 +80,13 @@ Trel::Trel(void)
     ClearAllBytes(mCounters);
 }
 
+void Trel::Reset(void)
+{
+    mEnabled = false;
+    ClearAllBytes(mCounters);
+    mPendingTxList.Free();
+}
+
 void Trel::Enable(uint16_t &aUdpPort)
 {
     mEnabled = true;

tests/nexus/platform/nexus_trel.hpp

@@ -43,6 +43,7 @@ struct Trel
     typedef otPlatTrelCounters Counters;
 
     Trel(void);
+    void Reset(void);
     void Enable(uint16_t &aUdpPort);
     void Disable(void);
     void Send(const uint8_t *aUdpPayload, uint16_t aUdpPayloadLen, const Ip6::SockAddr &aDestSockAddr);

tests/nexus/test_full_network_reset.cpp

@@ -0,0 +1,190 @@
+/*
+ *  Copyright (c) 2025, The OpenThread Authors.
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ *  1. Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *  3. Neither the name of the copyright holder nor the
+ *     names of its contributors may be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *  POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "platform/nexus_core.hpp"
+#include "platform/nexus_node.hpp"
+
+namespace ot {
+namespace Nexus {
+
+static constexpr uint16_t kNumberOfRoles = (Mle::kRoleLeader + 1);
+
+typedef uint16_t RoleStats[kNumberOfRoles];
+
+static void CalculateRoleStats(Core &aNexus, RoleStats &aRoleStats)
+{
+    ClearAllBytes(aRoleStats);
+
+    for (Node &node : aNexus.GetNodes())
+    {
+        aRoleStats[node.Get<Mle::Mle>().GetRole()]++;
+    }
+}
+
+static bool CheckRoleStats(const RoleStats &aRoleStats)
+{
+    return (aRoleStats[Mle::kRoleLeader] == 1) && (aRoleStats[Mle::kRoleDetached] == 0) &&
+           (aRoleStats[Mle::kRoleDisabled] == 0);
+}
+
+void Test(void)
+{
+    static constexpr uint16_t kNumNodes = 200;
+
+    // All times in msec
+    static constexpr uint32_t kMaxWaitTime             = 20 * Time::kOneMinuteInMsec;
+    static constexpr uint32_t kStatCollectionInterval  = 500;
+    static constexpr uint32_t kExtraSimulTimeAfterPass = 5 * Time::kOneSecondInMsec;
+
+    Core      nexus;
+    Node     *leader;
+    RoleStats roleStats;
+    TimeMilli resetTime;
+
+    for (uint16_t i = 0; i < kNumNodes; i++)
+    {
+        nexus.CreateNode();
+    }
+
+    nexus.AdvanceTime(0);
+
+    Log("Starting %u nodes staggered", kNumNodes);
+
+    leader = nexus.GetNodes().GetHead();
+    leader->Form();
+
+    for (Node &node : nexus.GetNodes())
+    {
+        if (&node == leader)
+        {
+            continue;
+        }
+
+        node.Join(*leader);
+        nexus.AdvanceTime(Time::kOneSecondInMsec);
+    }
+
+    for (uint32_t step = 0; step < kMaxWaitTime / kStatCollectionInterval; step++)
+    {
+        if ((step % 20) == 0)
+        {
+            Log("+----------+----------+----------+----------+----------+");
+            Log("| Leader   | Router   | Child    | Detached | Disabled |");
+            Log("+----------+----------+----------+----------+----------+");
+        }
+
+        CalculateRoleStats(nexus, roleStats);
+
+        Log("| %8u | %8u | %8u | %8u | %8u |", roleStats[Mle::kRoleLeader], roleStats[Mle::kRoleRouter],
+            roleStats[Mle::kRoleChild], roleStats[Mle::kRoleDetached], roleStats[Mle::kRoleDisabled]);
+
+        nexus.AdvanceTime(kStatCollectionInterval);
+
+        if (CheckRoleStats(roleStats))
+        {
+            break;
+        }
+    }
+
+    VerifyOrQuit(CheckRoleStats(roleStats));
+
+    Log("=========================================================");
+    Log("All nodes are now part of the same partition");
+    Log("Resetting all the nodes in the network");
+    Log("=========================================================");
+
+    resetTime = nexus.GetNow();
+
+    for (Node &node : nexus.GetNodes())
+    {
+        node.Reset();
+    }
+
+    for (Node &node : nexus.GetNodes())
+    {
+        node.Get<ThreadNetif>().Up();
+        SuccessOrQuit(node.Get<Mle::Mle>().Start());
+    }
+
+    for (uint32_t step = 0; step < kMaxWaitTime / kStatCollectionInterval; step++)
+    {
+        if ((step % 20) == 0)
+        {
+            Log("+----------+----------+----------+----------+----------+");
+            Log("| Leader   | Router   | Child    | Detached | Disabled |");
+            Log("+----------+----------+----------+----------+----------+");
+        }
+
+        CalculateRoleStats(nexus, roleStats);
+
+        Log("| %8u | %8u | %8u | %8u | %8u |", roleStats[Mle::kRoleLeader], roleStats[Mle::kRoleRouter],
+            roleStats[Mle::kRoleChild], roleStats[Mle::kRoleDetached], roleStats[Mle::kRoleDisabled]);
+
+        nexus.AdvanceTime(kStatCollectionInterval);
+
+        if (CheckRoleStats(roleStats))
+        {
+            break;
+        }
+    }
+
+    Log("=========================================================");
+    Log("All nodes are restored");
+    Log("Network stabilized after %u sec", (nexus.GetNow() - resetTime) / Time::kOneSecondInMsec);
+    Log("=========================================================");
+
+    for (uint32_t step = 0; step < kExtraSimulTimeAfterPass / kStatCollectionInterval; step++)
+    {
+        if ((step % 20) == 0)
+        {
+            Log("+----------+----------+----------+----------+----------+");
+            Log("| Leader   | Router   | Child    | Detached | Disabled |");
+            Log("+----------+----------+----------+----------+----------+");
+        }
+
+        CalculateRoleStats(nexus, roleStats);
+
+        Log("| %8u | %8u | %8u | %8u | %8u |", roleStats[Mle::kRoleLeader], roleStats[Mle::kRoleRouter],
+            roleStats[Mle::kRoleChild], roleStats[Mle::kRoleDetached], roleStats[Mle::kRoleDisabled]);
+
+        nexus.AdvanceTime(kStatCollectionInterval);
+    }
+}
+
+} // namespace Nexus
+} // namespace ot
+
+int main(void)
+{
+    ot::Nexus::Test();
+    printf("All tests passed\n");
+    return 0;
+}