src/core/utils/child_supervision.cpp

/*
 *  Copyright (c) 2017, The OpenThread Authors.
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 *  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.
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 *     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
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 */

/**
 * @file
 *   This file implements the child supervision feature.
 */

#include "child_supervision.hpp"

#include "openthread-core-config.h"
#include "common/code_utils.hpp"
#include "common/instance.hpp"
#include "common/locator_getters.hpp"
#include "common/logging.hpp"
#include "thread/thread_netif.hpp"

namespace ot {
namespace Utils {

#if OPENTHREAD_CONFIG_CHILD_SUPERVISION_ENABLE

#if OPENTHREAD_FTD

ChildSupervisor::ChildSupervisor(Instance &aInstance)
    : InstanceLocator(aInstance)
    , mSupervisionInterval(kDefaultSupervisionInterval)
{
}

void ChildSupervisor::SetSupervisionInterval(uint16_t aInterval)
{
    mSupervisionInterval = aInterval;
    CheckState();
}

Child *ChildSupervisor::GetDestination(const Message &aMessage) const
{
    Child *  child = nullptr;
    uint16_t childIndex;

    VerifyOrExit(aMessage.GetType() == Message::kTypeSupervision);

    IgnoreError(aMessage.Read(0, childIndex));
    child = Get<ChildTable>().GetChildAtIndex(childIndex);

exit:
    return child;
}

void ChildSupervisor::SendMessage(Child &aChild)
{
    Message *message = nullptr;
    uint16_t childIndex;

    VerifyOrExit(aChild.GetIndirectMessageCount() == 0);

    message = Get<MessagePool>().Allocate(Message::kTypeSupervision, sizeof(uint8_t));
    VerifyOrExit(message != nullptr);

    // Supervision message is an empty payload 15.4 data frame.
    // The child index is stored here in the message content to allow
    // the destination of the message to be later retrieved using
    // `ChildSupervisor::GetDestination(message)`.

    childIndex = Get<ChildTable>().GetChildIndex(aChild);
    SuccessOrExit(message->Append(childIndex));

    SuccessOrExit(Get<ThreadNetif>().SendMessage(*message));
    message = nullptr;

    otLogInfoUtil("Sending supervision message to child 0x%04x", aChild.GetRloc16());

exit:
    FreeMessage(message);
}

void ChildSupervisor::UpdateOnSend(Child &aChild)
{
    aChild.ResetSecondsSinceLastSupervision();
}

void ChildSupervisor::HandleTimeTick(void)
{
    for (Child &child : Get<ChildTable>().Iterate(Child::kInStateValid))
    {
        child.IncrementSecondsSinceLastSupervision();

        if ((child.GetSecondsSinceLastSupervision() >= mSupervisionInterval) && !child.IsRxOnWhenIdle())
        {
            SendMessage(child);
        }
    }
}

void ChildSupervisor::CheckState(void)
{
    bool shouldRun = false;

    // Child Supervision should run if `mSupervisionInterval` is not
    // zero, Thread MLE operation is enabled, and there is at least one
    // "valid" child in the child table.

    shouldRun = ((mSupervisionInterval != 0) && !Get<Mle::MleRouter>().IsDisabled() &&
                 Get<ChildTable>().HasChildren(Child::kInStateValid));

    if (shouldRun && !Get<TimeTicker>().IsReceiverRegistered(TimeTicker::kChildSupervisor))
    {
        Get<TimeTicker>().RegisterReceiver(TimeTicker::kChildSupervisor);
        otLogInfoUtil("Starting Child Supervision");
    }

    if (!shouldRun && Get<TimeTicker>().IsReceiverRegistered(TimeTicker::kChildSupervisor))
    {
        Get<TimeTicker>().UnregisterReceiver(TimeTicker::kChildSupervisor);
        otLogInfoUtil("Stopping Child Supervision");
    }
}

void ChildSupervisor::HandleNotifierEvents(Events aEvents)
{
    if (aEvents.ContainsAny(kEventThreadRoleChanged | kEventThreadChildAdded | kEventThreadChildRemoved))
    {
        CheckState();
    }
}

#endif // #if OPENTHREAD_FTD

SupervisionListener::SupervisionListener(Instance &aInstance)
    : InstanceLocator(aInstance)
    , mTimeout(0)
    , mTimer(aInstance, SupervisionListener::HandleTimer)
{
    SetTimeout(kDefaultTimeout);
}

void SupervisionListener::Start(void)
{
    RestartTimer();
}

void SupervisionListener::Stop(void)
{
    mTimer.Stop();
}

void SupervisionListener::SetTimeout(uint16_t aTimeout)
{
    if (mTimeout != aTimeout)
    {
        mTimeout = aTimeout;
        RestartTimer();
    }
}

void SupervisionListener::UpdateOnReceive(const Mac::Address &aSourceAddress, bool aIsSecure)
{
    // If listener is enabled and device is a child and it received a secure frame from its parent, restart the timer.

    VerifyOrExit(mTimer.IsRunning() && aIsSecure && Get<Mle::MleRouter>().IsChild() &&
                 (Get<NeighborTable>().FindNeighbor(aSourceAddress) == &Get<Mle::MleRouter>().GetParent()));

    RestartTimer();

exit:
    return;
}

void SupervisionListener::RestartTimer(void)
{
    if ((mTimeout != 0) && !Get<Mle::MleRouter>().IsDisabled() && !Get<MeshForwarder>().GetRxOnWhenIdle())
    {
        mTimer.Start(Time::SecToMsec(mTimeout));
    }
    else
    {
        mTimer.Stop();
    }
}

void SupervisionListener::HandleTimer(Timer &aTimer)
{
    aTimer.Get<SupervisionListener>().HandleTimer();
}

void SupervisionListener::HandleTimer(void)
{
    VerifyOrExit(Get<Mle::MleRouter>().IsChild() && !Get<MeshForwarder>().GetRxOnWhenIdle());

    otLogWarnUtil("Supervision timeout. No frame from parent in %d sec", mTimeout);

    IgnoreError(Get<Mle::MleRouter>().SendChildUpdateRequest());

exit:
    RestartTimer();
}

#endif // #if OPENTHREAD_CONFIG_CHILD_SUPERVISION_ENABLE

} // namespace Utils
} // namespace ot