src/platform/Linux/DnssdImpl.cpp

/*
 *
 *    Copyright (c) 2020-2022 Project CHIP Authors
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

#include "DnssdImpl.h"

#include <algorithm>
#include <sstream>
#include <string.h>
#include <time.h>
#include <vector>

#include <netinet/in.h>

#include <lib/support/CHIPMem.h>
#include <lib/support/CHIPMemString.h>
#include <lib/support/CodeUtils.h>
#include <platform/internal/CHIPDeviceLayerInternal.h>
#include <system/SystemLayer.h>

using chip::Dnssd::DnssdServiceProtocol;
using chip::Dnssd::kDnssdTypeMaxSize;
using chip::Dnssd::TextEntry;
using chip::System::SocketEvents;
using std::chrono::duration_cast;
using std::chrono::microseconds;
using std::chrono::seconds;
using std::chrono::steady_clock;

namespace {

AvahiProtocol ToAvahiProtocol(chip::Inet::IPAddressType addressType)
{
#if INET_CONFIG_ENABLE_IPV4
    AvahiProtocol protocol;

    switch (addressType)
    {
    case chip::Inet::IPAddressType::kIPv4:
        protocol = AVAHI_PROTO_INET;
        break;
    case chip::Inet::IPAddressType::kIPv6:
        protocol = AVAHI_PROTO_INET6;
        break;
    default:
        protocol = AVAHI_PROTO_UNSPEC;
        break;
    }

    return protocol;
#else
    // We only support IPV6, never tell AVAHI about INET4 or UNSPEC because
    // UNSPEC may actually return IPv4 data.
    return AVAHI_PROTO_INET6;
#endif
}

chip::Inet::IPAddressType ToAddressType(AvahiProtocol protocol)
{
    chip::Inet::IPAddressType type;

    switch (protocol)
    {
#if INET_CONFIG_ENABLE_IPV4
    case AVAHI_PROTO_INET:
        type = chip::Inet::IPAddressType::kIPv4;
        break;
#endif
    case AVAHI_PROTO_INET6:
        type = chip::Inet::IPAddressType::kIPv6;
        break;
    default:
        type = chip::Inet::IPAddressType::kUnknown;
        break;
    }

    return type;
}

AvahiWatchEvent ToAvahiWatchEvent(SocketEvents events)
{
    return static_cast<AvahiWatchEvent>((events.Has(chip::System::SocketEventFlags::kRead) ? AVAHI_WATCH_IN : 0) |
                                        (events.Has(chip::System::SocketEventFlags::kWrite) ? AVAHI_WATCH_OUT : 0) |
                                        (events.Has(chip::System::SocketEventFlags::kError) ? AVAHI_WATCH_ERR : 0));
}

void AvahiWatchCallbackTrampoline(chip::System::SocketEvents events, intptr_t data)
{
    AvahiWatch * const watch = reinterpret_cast<AvahiWatch *>(data);
    watch->mPendingIO        = ToAvahiWatchEvent(events);
    watch->mCallback(watch, watch->mSocket, watch->mPendingIO, watch->mContext);
}

CHIP_ERROR MakeAvahiStringListFromTextEntries(TextEntry * entries, size_t size, AvahiStringList ** strListOut)
{
    *strListOut = avahi_string_list_new(nullptr, nullptr);

    for (size_t i = 0; i < size; i++)
    {
        uint8_t buf[chip::Dnssd::kDnssdTextMaxSize];
        size_t offset = static_cast<size_t>(snprintf(reinterpret_cast<char *>(buf), sizeof(buf), "%s=", entries[i].mKey));

        if (offset + entries[i].mDataSize > sizeof(buf))
        {
            avahi_string_list_free(*strListOut);
            *strListOut = nullptr;
            return CHIP_ERROR_INVALID_ARGUMENT;
        }

        memcpy(&buf[offset], entries[i].mData, entries[i].mDataSize);
        *strListOut = avahi_string_list_add_arbitrary(*strListOut, buf, offset + entries[i].mDataSize);
    }
    return CHIP_NO_ERROR;
}

const char * GetProtocolString(DnssdServiceProtocol protocol)
{
    return protocol == DnssdServiceProtocol::kDnssdProtocolUdp ? "_udp" : "_tcp";
}

std::string GetFullType(const char * type, DnssdServiceProtocol protocol)
{
    std::ostringstream typeBuilder;
    typeBuilder << type << "." << GetProtocolString(protocol);
    return typeBuilder.str();
}

} // namespace

namespace chip {
namespace Dnssd {

MdnsAvahi MdnsAvahi::sInstance;

Poller::Poller()
{
    mAvahiPoller.userdata         = this;
    mAvahiPoller.watch_new        = WatchNew;
    mAvahiPoller.watch_update     = WatchUpdate;
    mAvahiPoller.watch_get_events = WatchGetEvents;
    mAvahiPoller.watch_free       = WatchFree;

    mAvahiPoller.timeout_new    = TimeoutNew;
    mAvahiPoller.timeout_update = TimeoutUpdate;
    mAvahiPoller.timeout_free   = TimeoutFree;

    mEarliestTimeout = std::chrono::steady_clock::time_point();
}

AvahiWatch * Poller::WatchNew(const struct AvahiPoll * poller, int fd, AvahiWatchEvent event, AvahiWatchCallback callback,
                              void * context)
{
    return reinterpret_cast<Poller *>(poller->userdata)->WatchNew(fd, event, callback, context);
}

AvahiWatch * Poller::WatchNew(int fd, AvahiWatchEvent event, AvahiWatchCallback callback, void * context)
{
    VerifyOrDie(callback != nullptr && fd >= 0);

    auto watch     = std::make_unique<AvahiWatch>();
    watch->mSocket = fd;
    LogErrorOnFailure(DeviceLayer::SystemLayerSockets().StartWatchingSocket(fd, &watch->mSocketWatch));
    LogErrorOnFailure(DeviceLayer::SystemLayerSockets().SetCallback(watch->mSocketWatch, AvahiWatchCallbackTrampoline,
                                                                    reinterpret_cast<intptr_t>(watch.get())));
    WatchUpdate(watch.get(), event);
    watch->mCallback = callback;
    watch->mContext  = context;
    watch->mPoller   = this;
    mWatches.emplace_back(std::move(watch));

    return mWatches.back().get();
}

void Poller::WatchUpdate(AvahiWatch * watch, AvahiWatchEvent event)
{
    if (event & AVAHI_WATCH_IN)
    {
        LogErrorOnFailure(DeviceLayer::SystemLayerSockets().RequestCallbackOnPendingRead(watch->mSocketWatch));
    }
    else
    {
        LogErrorOnFailure(DeviceLayer::SystemLayerSockets().ClearCallbackOnPendingRead(watch->mSocketWatch));
    }
    if (event & AVAHI_WATCH_OUT)
    {
        LogErrorOnFailure(DeviceLayer::SystemLayerSockets().RequestCallbackOnPendingWrite(watch->mSocketWatch));
    }
    else
    {
        LogErrorOnFailure(DeviceLayer::SystemLayerSockets().ClearCallbackOnPendingWrite(watch->mSocketWatch));
    }
}

AvahiWatchEvent Poller::WatchGetEvents(AvahiWatch * watch)
{
    return watch->mPendingIO;
}

void Poller::WatchFree(AvahiWatch * watch)
{
    reinterpret_cast<Poller *>(watch->mPoller)->WatchFree(*watch);
}

void Poller::WatchFree(AvahiWatch & watch)
{
    DeviceLayer::SystemLayerSockets().StopWatchingSocket(&watch.mSocketWatch);
    mWatches.erase(std::remove_if(mWatches.begin(), mWatches.end(),
                                  [&watch](const std::unique_ptr<AvahiWatch> & aValue) { return aValue.get() == &watch; }),
                   mWatches.end());
}

AvahiTimeout * Poller::TimeoutNew(const AvahiPoll * poller, const struct timeval * timeout, AvahiTimeoutCallback callback,
                                  void * context)
{
    VerifyOrDie(poller != nullptr && callback != nullptr);

    return static_cast<Poller *>(poller->userdata)->TimeoutNew(timeout, callback, context);
}

steady_clock::time_point GetAbsTimeout(const struct timeval * timeout)
{
    steady_clock::time_point now        = steady_clock::now();
    steady_clock::time_point absTimeout = now;

    if (timeout != nullptr)
    {
        absTimeout += seconds(timeout->tv_sec);
        absTimeout += microseconds(timeout->tv_usec);
    }

    return absTimeout;
}

AvahiTimeout * Poller::TimeoutNew(const struct timeval * timeout, AvahiTimeoutCallback callback, void * context)
{
    mTimers.emplace_back(new AvahiTimeout{ GetAbsTimeout(timeout), callback, timeout != nullptr, context, this });
    AvahiTimeout * timer = mTimers.back().get();
    SystemTimerUpdate(timer);
    return timer;
}

void Poller::TimeoutUpdate(AvahiTimeout * timer, const struct timeval * timeout)
{
    if (timeout)
    {
        timer->mAbsTimeout = GetAbsTimeout(timeout);
        timer->mEnabled    = true;
        static_cast<Poller *>(timer->mPoller)->SystemTimerUpdate(timer);
    }
    else
    {
        timer->mEnabled = false;
    }
}

void Poller::TimeoutFree(AvahiTimeout * timer)
{
    static_cast<Poller *>(timer->mPoller)->TimeoutFree(*timer);
}

void Poller::TimeoutFree(AvahiTimeout & timer)
{
    mTimers.erase(std::remove_if(mTimers.begin(), mTimers.end(),
                                 [&timer](const std::unique_ptr<AvahiTimeout> & aValue) { return aValue.get() == &timer; }),
                  mTimers.end());
}

void Poller::SystemTimerCallback(System::Layer * layer, void * data)
{
    static_cast<Poller *>(data)->HandleTimeout();
}

void Poller::HandleTimeout()
{
    mEarliestTimeout             = std::chrono::steady_clock::time_point();
    steady_clock::time_point now = steady_clock::now();

    AvahiTimeout * earliest = nullptr;
    for (auto && timer : mTimers)
    {
        if (!timer->mEnabled)
        {
            continue;
        }
        if (timer->mAbsTimeout <= now)
        {
            timer->mCallback(timer.get(), timer->mContext);
        }
        else
        {
            if ((earliest == nullptr) || (timer->mAbsTimeout < earliest->mAbsTimeout))
            {
                earliest = timer.get();
            }
        }
    }
    if (earliest)
    {
        SystemTimerUpdate(earliest);
    }
}

void Poller::SystemTimerUpdate(AvahiTimeout * timer)
{
    if ((mEarliestTimeout == std::chrono::steady_clock::time_point()) || (timer->mAbsTimeout < mEarliestTimeout))
    {
        mEarliestTimeout = timer->mAbsTimeout;
        auto delay       = std::chrono::duration_cast<chip::System::Clock::Milliseconds32>(steady_clock::now() - mEarliestTimeout);
        DeviceLayer::SystemLayer().StartTimer(delay, SystemTimerCallback, this);
    }
}

CHIP_ERROR MdnsAvahi::Init(DnssdAsyncReturnCallback initCallback, DnssdAsyncReturnCallback errorCallback, void * context)
{
    CHIP_ERROR error = CHIP_NO_ERROR;
    int avahiError   = 0;

    Shutdown();

    VerifyOrExit(initCallback != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
    VerifyOrExit(errorCallback != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
    VerifyOrExit(mClient == nullptr && mPublishedGroups.empty(), error = CHIP_ERROR_INCORRECT_STATE);
    mInitCallback       = initCallback;
    mErrorCallback      = errorCallback;
    mAsyncReturnContext = context;
    mClient             = avahi_client_new(mPoller.GetAvahiPoll(), AVAHI_CLIENT_NO_FAIL, HandleClientState, this, &avahiError);
    VerifyOrExit(mClient != nullptr, error = CHIP_ERROR_OPEN_FAILED);
    VerifyOrExit(avahiError == 0, error = CHIP_ERROR_OPEN_FAILED);

exit:
    return error;
}

void MdnsAvahi::Shutdown()
{
    StopPublish();
    if (mClient)
    {
        avahi_client_free(mClient);
        mClient = nullptr;
    }
}

CHIP_ERROR MdnsAvahi::SetHostname(const char * hostname)
{
    CHIP_ERROR error = CHIP_NO_ERROR;

    VerifyOrExit(mClient != nullptr, error = CHIP_ERROR_INCORRECT_STATE);
    // Note: we do no longer set the primary hostname here, as other services
    // on the platform might not be happy with the matter mandated hostname.
    // Instead, we'll establish our own hostname when needed (see PublishService())
exit:
    return error;
}

void MdnsAvahi::HandleClientState(AvahiClient * client, AvahiClientState state, void * context)
{
    static_cast<MdnsAvahi *>(context)->HandleClientState(client, state);
}

void MdnsAvahi::HandleClientState(AvahiClient * client, AvahiClientState state)
{
    switch (state)
    {
    case AVAHI_CLIENT_S_RUNNING:
        ChipLogProgress(DeviceLayer, "Avahi client registered");
        mClient = client;
        // no longer create groups here, but on a by-service basis in PublishService()
        mInitCallback(mAsyncReturnContext, CHIP_NO_ERROR);
        break;
    case AVAHI_CLIENT_FAILURE:
        ChipLogError(DeviceLayer, "Avahi client failure");
        mErrorCallback(mAsyncReturnContext, CHIP_ERROR_INTERNAL);
        break;
    case AVAHI_CLIENT_S_COLLISION:
    case AVAHI_CLIENT_S_REGISTERING:
        ChipLogProgress(DeviceLayer, "Avahi re-register required");
        StopPublish();
        mErrorCallback(mAsyncReturnContext, CHIP_ERROR_FORCED_RESET);
        break;
    case AVAHI_CLIENT_CONNECTING:
        ChipLogProgress(DeviceLayer, "Avahi connecting");
        break;
    }
}

void MdnsAvahi::HandleGroupState(AvahiEntryGroup * group, AvahiEntryGroupState state, void * context)
{
    static_cast<MdnsAvahi *>(context)->HandleGroupState(group, state);
}

void MdnsAvahi::HandleGroupState(AvahiEntryGroup * group, AvahiEntryGroupState state)
{
    switch (state)
    {
    case AVAHI_ENTRY_GROUP_ESTABLISHED:
        ChipLogProgress(DeviceLayer, "Avahi group established");
        break;
    case AVAHI_ENTRY_GROUP_COLLISION:
        ChipLogError(DeviceLayer, "Avahi group collision");
        mErrorCallback(mAsyncReturnContext, CHIP_ERROR_MDNS_COLLISION);
        break;
    case AVAHI_ENTRY_GROUP_FAILURE:
        ChipLogError(DeviceLayer, "Avahi group internal failure %s",
                     avahi_strerror(avahi_client_errno(avahi_entry_group_get_client(group))));
        mErrorCallback(mAsyncReturnContext, CHIP_ERROR_INTERNAL);
        break;
    case AVAHI_ENTRY_GROUP_UNCOMMITED:
    case AVAHI_ENTRY_GROUP_REGISTERING:
        break;
    }
}

CHIP_ERROR MdnsAvahi::PublishService(const DnssdService & service, DnssdPublishCallback callback, void * context)
{
    std::ostringstream keyBuilder;
    std::string key;
    std::string type = GetFullType(service.mType, service.mProtocol);
    std::string matterHostname;
    CHIP_ERROR error          = CHIP_NO_ERROR;
    AvahiStringList * text    = nullptr;
    AvahiEntryGroup * group   = nullptr;
    const char * mainHostname = nullptr;
    AvahiIfIndex interface =
        service.mInterface.IsPresent() ? static_cast<AvahiIfIndex>(service.mInterface.GetPlatformInterface()) : AVAHI_IF_UNSPEC;
    AvahiProtocol protocol = ToAvahiProtocol(service.mAddressType);

    keyBuilder << service.mName << "." << type << service.mPort << "." << interface;
    key = keyBuilder.str();
    ChipLogProgress(DeviceLayer, "PublishService %s", key.c_str());
    auto publishedgroups_it = mPublishedGroups.find(key);
    if (publishedgroups_it != mPublishedGroups.end())
    {
        // same service was already published, we need to de-publish it first
        int avahiRet = avahi_entry_group_free(publishedgroups_it->second);
        if (avahiRet != AVAHI_OK)
        {
            ChipLogError(DeviceLayer, "Cannot remove avahi group: %s", avahi_strerror(avahiRet));
            ExitNow(error = CHIP_ERROR_INTERNAL);
        }
        mPublishedGroups.erase(publishedgroups_it);
    }

    // create fresh group
    group = avahi_entry_group_new(mClient, HandleGroupState, this);
    VerifyOrExit(group != nullptr, error = CHIP_ERROR_INTERNAL);

    // establish the host name (separately from avahi's default host name that the platform might have,
    // unless it matches the matter hostname)
    mainHostname = avahi_client_get_host_name(mClient);
    if (strcmp(mainHostname, service.mHostName) == 0)
    {
        // main host name is correct, we can use it
        matterHostname = std::string(mainHostname) + ".local";
    }
    else
    {
        // we need to establish a matter hostname separately from the platform's default hostname
        char b[chip::Inet::IPAddress::kMaxStringLength];
        SuccessOrExit(error = service.mInterface.GetInterfaceName(b, chip::Inet::IPAddress::kMaxStringLength));
        ChipLogDetail(DeviceLayer, "Using addresses from interface id=%d name=%s", service.mInterface.GetPlatformInterface(), b);
        matterHostname = std::string(service.mHostName) + ".local";
        // find addresses to publish
        for (chip::Inet::InterfaceAddressIterator addr_it; addr_it.HasCurrent(); addr_it.Next())
        {
            // only specific interface?
            if (service.mInterface.IsPresent() && addr_it.GetInterfaceId() != service.mInterface)
            {
                continue;
            }
            if (addr_it.IsUp())
            {
                if (addr_it.IsLoopback())
                {
                    // do not advertise loopback interface addresses
                    continue;
                }
                chip::Inet::IPAddress addr;
                if ((addr_it.GetAddress(addr) == CHIP_NO_ERROR) &&
                    ((service.mAddressType == chip::Inet::IPAddressType::kAny) ||
                     (addr.IsIPv6() && service.mAddressType == chip::Inet::IPAddressType::kIPv6)
#if INET_CONFIG_ENABLE_IPV4
                     || (addr.IsIPv4() && service.mAddressType == chip::Inet::IPAddressType::kIPv4)
#endif
                         ))
                {
                    VerifyOrExit(addr.ToString(b) != nullptr, error = CHIP_ERROR_INTERNAL);
                    AvahiAddress a;
                    VerifyOrExit(avahi_address_parse(b, AVAHI_PROTO_UNSPEC, &a) != nullptr, error = CHIP_ERROR_INTERNAL);
                    AvahiIfIndex thisinterface = static_cast<AvahiIfIndex>(addr_it.GetInterfaceId().GetPlatformInterface());
                    // Note: NO_REVERSE publish flag is needed because otherwise we can't have more than one hostname
                    //   for reverse resolving IP addresses back to hostnames
                    VerifyOrExit(avahi_entry_group_add_address(group,                        // group
                                                               thisinterface,                // interface
                                                               ToAvahiProtocol(addr.Type()), // protocol
                                                               AVAHI_PUBLISH_NO_REVERSE,     // publish flags
                                                               matterHostname.c_str(),       // hostname
                                                               &a                            // address
                                                               ) == 0,
                                 error = CHIP_ERROR_INTERNAL);
                }
            }
        }
    }

    // create the service
    SuccessOrExit(error = MakeAvahiStringListFromTextEntries(service.mTextEntries, service.mTextEntrySize, &text));

    VerifyOrExit(avahi_entry_group_add_service_strlst(group, interface, protocol,        // group, interface, protocol
                                                      static_cast<AvahiPublishFlags>(0), // publish flags
                                                      service.mName,                     // service name
                                                      type.c_str(),                      // type
                                                      nullptr,                           // domain
                                                      matterHostname.c_str(),            // host
                                                      service.mPort,                     // port
                                                      text) == 0,                        // TXT records StringList
                 error = CHIP_ERROR_INTERNAL);

    // add the subtypes
    for (size_t i = 0; i < service.mSubTypeSize; i++)
    {
        std::ostringstream sstream;

        sstream << service.mSubTypes[i] << "._sub." << type;

        VerifyOrExit(avahi_entry_group_add_service_subtype(group, interface, protocol, static_cast<AvahiPublishFlags>(0),
                                                           service.mName, type.c_str(), nullptr, sstream.str().c_str()) == 0,
                     error = CHIP_ERROR_INTERNAL);
    }
    VerifyOrExit(avahi_entry_group_commit(group) == 0, error = CHIP_ERROR_INTERNAL);

    // group is now published, pass it to the service map
    mPublishedGroups[key] = group;
    group                 = nullptr;

exit:
    if (group != nullptr)
    {
        avahi_entry_group_free(group);
    }

    if (text != nullptr)
    {
        avahi_string_list_free(text);
    }

    // Ideally the callback would be called from `HandleGroupState` when the `AVAHI_ENTRY_GROUP_ESTABLISHED` state
    // is received. But the current code use the `userdata` field to pass a pointer to the current MdnsAvahi instance
    // and this is all comes from MdnsAvahi::Init that does not have any clue about the `type` that *will* be published.
    // The code needs to be updated to support that callback properly.
    if (CHIP_NO_ERROR == error)
    {
        callback(context, type.c_str(), service.mName, CHIP_NO_ERROR);
    }
    else
    {
        ChipLogError(DeviceLayer, "PublishService failed: %s",
                     mClient ? avahi_strerror(avahi_client_errno(mClient)) : "no mClient");
        callback(context, nullptr, nullptr, error);
    }

    return error;
}

CHIP_ERROR MdnsAvahi::StopPublish()
{
    CHIP_ERROR error = CHIP_NO_ERROR;
    for (const auto & group : mPublishedGroups)
    {
        if (group.second)
        {
            int avahiRet = avahi_entry_group_free(group.second);
            if (avahiRet != AVAHI_OK)
            {
                ChipLogError(DeviceLayer, "Error freeing avahi group: %s", avahi_strerror(avahiRet));
                error = CHIP_ERROR_INTERNAL;
            }
        }
    }
    mPublishedGroups.clear();
    return error;
}

CHIP_ERROR MdnsAvahi::Browse(const char * type, DnssdServiceProtocol protocol, chip::Inet::IPAddressType addressType,
                             chip::Inet::InterfaceId interface, DnssdBrowseCallback callback, void * context,
                             intptr_t * browseIdentifier)
{
    AvahiServiceBrowser * browser;
    BrowseContext * browseContext = chip::Platform::New<BrowseContext>();
    AvahiIfIndex avahiInterface   = static_cast<AvahiIfIndex>(interface.GetPlatformInterface());

    browseContext->mInstance    = this;
    browseContext->mContext     = context;
    browseContext->mCallback    = callback;
    browseContext->mAddressType = addressType;
    if (!interface.IsPresent())
    {
        avahiInterface = AVAHI_IF_UNSPEC;
    }
    browseContext->mInterface     = avahiInterface;
    browseContext->mProtocol      = GetFullType(type, protocol);
    browseContext->mBrowseRetries = 0;
    browseContext->mStopped.store(false);

    browser = avahi_service_browser_new(mClient, avahiInterface, AVAHI_PROTO_UNSPEC, browseContext->mProtocol.c_str(), nullptr,
                                        static_cast<AvahiLookupFlags>(0), HandleBrowse, browseContext);
    // Otherwise the browser will be freed in the callback
    if (browser == nullptr)
    {
        chip::Platform::Delete(browseContext);
        *browseIdentifier = reinterpret_cast<intptr_t>(nullptr);
    }
    else
    {
        *browseIdentifier = reinterpret_cast<intptr_t>(browseContext);
    }

    return browser == nullptr ? CHIP_ERROR_INTERNAL : CHIP_NO_ERROR;
}

CHIP_ERROR MdnsAvahi::StopBrowse(intptr_t browseIdentifier)
{
    BrowseContext * browseContext = reinterpret_cast<BrowseContext *>(browseIdentifier);
    if (browseContext == nullptr)
    {
        return CHIP_ERROR_NOT_FOUND;
    }
    // Any running timers here will check mStopped before rescheduling. Leave the timer running
    // so we don't race on deletion of the browse context.
    browseContext->mStopped.store(true);
    return CHIP_NO_ERROR;
}

DnssdServiceProtocol GetProtocolInType(const char * type)
{
    const char * deliminator = strrchr(type, '.');

    if (deliminator == nullptr)
    {
        ChipLogError(Discovery, "Failed to find protocol in type: %s", StringOrNullMarker(type));
        return DnssdServiceProtocol::kDnssdProtocolUnknown;
    }

    if (strcmp("._tcp", deliminator) == 0)
    {
        return DnssdServiceProtocol::kDnssdProtocolTcp;
    }
    if (strcmp("._udp", deliminator) == 0)
    {
        return DnssdServiceProtocol::kDnssdProtocolUdp;
    }

    ChipLogError(Discovery, "Unknown protocol in type: %s", StringOrNullMarker(type));
    return DnssdServiceProtocol::kDnssdProtocolUnknown;
}

/// Copies the type from a string containing both type and protocol
///
/// e.g. if input is "foo.bar", output is "foo", input is 'a.b._tcp", output is "a.b"
template <size_t N>
void CopyTypeWithoutProtocol(char (&dest)[N], const char * typeAndProtocol)
{
    const char * dotPos          = strrchr(typeAndProtocol, '.');
    size_t lengthWithoutProtocol = (dotPos != nullptr) ? static_cast<size_t>(dotPos - typeAndProtocol) : N;

    Platform::CopyString(dest, typeAndProtocol);

    /// above copied everything including the protocol. Truncate the protocol away.
    if (lengthWithoutProtocol < N)
    {
        dest[lengthWithoutProtocol] = 0;
    }
}

void MdnsAvahi::BrowseRetryCallback(chip::System::Layer * aLayer, void * appState)
{
    BrowseContext * context = static_cast<BrowseContext *>(appState);
    // Don't schedule anything new if we've stopped.
    if (context->mStopped.load())
    {
        chip::Platform::Delete(context);
        return;
    }
    AvahiServiceBrowser * newBrowser =
        avahi_service_browser_new(context->mInstance->mClient, context->mInterface, AVAHI_PROTO_UNSPEC, context->mProtocol.c_str(),
                                  nullptr, static_cast<AvahiLookupFlags>(0), HandleBrowse, context);
    if (newBrowser == nullptr)
    {
        // If we failed to create the browser, this browse context is effectively done. We need to call the final callback and
        // delete the context.
        context->mCallback(context->mContext, context->mServices.data(), context->mServices.size(), true, CHIP_NO_ERROR);
        chip::Platform::Delete(context);
    }
}

void MdnsAvahi::HandleBrowse(AvahiServiceBrowser * browser, AvahiIfIndex interface, AvahiProtocol protocol, AvahiBrowserEvent event,
                             const char * name, const char * type, const char * domain, AvahiLookupResultFlags /*flags*/,
                             void * userdata)
{
    BrowseContext * context = static_cast<BrowseContext *>(userdata);

    switch (event)
    {
    case AVAHI_BROWSER_FAILURE:
        context->mCallback(context->mContext, nullptr, 0, true, CHIP_ERROR_INTERNAL);
        avahi_service_browser_free(browser);
        chip::Platform::Delete(context);
        break;
    case AVAHI_BROWSER_NEW:
        ChipLogProgress(DeviceLayer, "Avahi browse: cache new");
        if (strcmp("local", domain) == 0)
        {
            DnssdService service = {};

            Platform::CopyString(service.mName, name);
            CopyTypeWithoutProtocol(service.mType, type);
            service.mProtocol      = GetProtocolInType(type);
            service.mAddressType   = context->mAddressType;
            service.mTransportType = ToAddressType(protocol);
            service.mInterface     = Inet::InterfaceId::Null();
            if (interface != AVAHI_IF_UNSPEC)
            {
                service.mInterface = static_cast<chip::Inet::InterfaceId>(interface);
            }
            service.mType[kDnssdTypeMaxSize] = 0;
            context->mServices.push_back(service);
        }
        break;
    case AVAHI_BROWSER_ALL_FOR_NOW: {
        ChipLogProgress(DeviceLayer, "Avahi browse: all for now");
        bool needRetries = context->mBrowseRetries++ < kMaxBrowseRetries && !context->mStopped.load();
        // If we were already asked to stop, no need to send a callback - no one is listening.
        if (!context->mStopped.load())
        {
            context->mCallback(context->mContext, context->mServices.data(), context->mServices.size(), !needRetries,
                               CHIP_NO_ERROR);
        }
        avahi_service_browser_free(browser);
        if (needRetries)
        {
            context->mNextRetryDelay *= 2;
            // Hand the ownership of the context over to the timer. It will either schedule a new browse on the context,
            // triggering this function, or it will delete and not reschedule (if stopped).
            DeviceLayer::SystemLayer().StartTimer(context->mNextRetryDelay / 2, BrowseRetryCallback, context);
        }
        else
        {
            // We didn't schedule a timer, so we're responsible for deleting the context
            chip::Platform::Delete(context);
        }
        break;
    }
    case AVAHI_BROWSER_REMOVE:
        ChipLogProgress(DeviceLayer, "Avahi browse: remove");
        if (strcmp("local", domain) == 0)
        {
            context->mServices.erase(
                std::remove_if(context->mServices.begin(), context->mServices.end(), [name, type](const DnssdService & service) {
                    return strcmp(name, service.mName) == 0 && type == GetFullType(service.mType, service.mProtocol);
                }));
        }
        break;
    case AVAHI_BROWSER_CACHE_EXHAUSTED:
        ChipLogProgress(DeviceLayer, "Avahi browse: cache exhausted");
        break;
    }
}

MdnsAvahi::ResolveContext * MdnsAvahi::AllocateResolveContext()
{
    ResolveContext * context = chip::Platform::New<ResolveContext>();
    if (context == nullptr)
    {
        return nullptr;
    }

    context->mNumber = mResolveCount++;
    mAllocatedResolves.push_back(context);

    return context;
}

MdnsAvahi::ResolveContext * MdnsAvahi::ResolveContextForHandle(size_t handle)
{
    for (auto it : mAllocatedResolves)
    {
        if (it->mNumber == handle)
        {
            return it;
        }
    }
    return nullptr;
}

void MdnsAvahi::FreeResolveContext(size_t handle)
{
    for (auto it = mAllocatedResolves.begin(); it != mAllocatedResolves.end(); it++)
    {
        if ((*it)->mNumber == handle)
        {
            chip::Platform::Delete(*it);
            mAllocatedResolves.erase(it);
            return;
        }
    }
}

void MdnsAvahi::StopResolve(const char * name)
{
    auto truncate_end = std::remove_if(mAllocatedResolves.begin(), mAllocatedResolves.end(),
                                       [name](ResolveContext * ctx) { return strcmp(ctx->mName, name) == 0; });

    for (auto it = truncate_end; it != mAllocatedResolves.end(); it++)
    {
        (*it)->mCallback((*it)->mContext, nullptr, Span<Inet::IPAddress>(), CHIP_ERROR_CANCELLED);
        chip::Platform::Delete(*it);
    }

    mAllocatedResolves.erase(truncate_end, mAllocatedResolves.end());
}

CHIP_ERROR MdnsAvahi::Resolve(const char * name, const char * type, DnssdServiceProtocol protocol, Inet::IPAddressType addressType,
                              Inet::IPAddressType transportType, Inet::InterfaceId interface, DnssdResolveCallback callback,
                              void * context)
{
    AvahiIfIndex avahiInterface     = static_cast<AvahiIfIndex>(interface.GetPlatformInterface());
    ResolveContext * resolveContext = AllocateResolveContext();
    CHIP_ERROR error                = CHIP_NO_ERROR;
    resolveContext->mInstance       = this;
    resolveContext->mCallback       = callback;
    resolveContext->mContext        = context;

    if (!interface.IsPresent())
    {
        avahiInterface = AVAHI_IF_UNSPEC;
    }

    Platform::CopyString(resolveContext->mName, name);
    resolveContext->mInterface   = avahiInterface;
    resolveContext->mTransport   = ToAvahiProtocol(transportType);
    resolveContext->mAddressType = ToAvahiProtocol(addressType);
    resolveContext->mFullType    = GetFullType(type, protocol);

    AvahiServiceResolver * resolver =
        avahi_service_resolver_new(mClient, avahiInterface, resolveContext->mTransport, name, resolveContext->mFullType.c_str(),
                                   nullptr, resolveContext->mAddressType, static_cast<AvahiLookupFlags>(0), HandleResolve,
                                   reinterpret_cast<void *>(resolveContext->mNumber));
    // Otherwise the resolver will be freed in the callback
    if (resolver == nullptr)
    {
        error = CHIP_ERROR_INTERNAL;
        chip::Platform::Delete(resolveContext);
    }
    resolveContext->mResolver = resolver;

    return error;
}

void MdnsAvahi::HandleResolve(AvahiServiceResolver * resolver, AvahiIfIndex interface, AvahiProtocol protocol,
                              AvahiResolverEvent event, const char * name, const char * type, const char * /*domain*/,
                              const char * host_name, const AvahiAddress * address, uint16_t port, AvahiStringList * txt,
                              AvahiLookupResultFlags flags, void * userdata)
{
    size_t handle            = reinterpret_cast<size_t>(userdata);
    ResolveContext * context = sInstance.ResolveContextForHandle(handle);
    std::vector<TextEntry> textEntries;

    if (context == nullptr)
    {
        ChipLogError(Discovery, "Invalid context for handling resolves: %ld", static_cast<long>(handle));
        return;
    }

    switch (event)
    {
    case AVAHI_RESOLVER_FAILURE:
        if (context->mAttempts++ < 3)
        {
            ChipLogProgress(DeviceLayer, "Re-trying resolve");
            avahi_service_resolver_free(resolver);
            context->mResolver = avahi_service_resolver_new(
                context->mInstance->mClient, context->mInterface, context->mTransport, context->mName, context->mFullType.c_str(),
                nullptr, context->mAddressType, static_cast<AvahiLookupFlags>(0), HandleResolve, context);
            if (context->mResolver == nullptr)
            {
                ChipLogError(DeviceLayer, "Avahi resolve failed on retry");
                context->mCallback(context->mContext, nullptr, Span<Inet::IPAddress>(), CHIP_ERROR_INTERNAL);
                sInstance.FreeResolveContext(handle);
            }
            return;
        }
        ChipLogError(DeviceLayer, "Avahi resolve failed");
        context->mCallback(context->mContext, nullptr, Span<Inet::IPAddress>(), CHIP_ERROR_INTERNAL);
        break;
    case AVAHI_RESOLVER_FOUND:
        DnssdService result = {};

        ChipLogProgress(DeviceLayer, "Avahi resolve found");

        Platform::CopyString(result.mName, name);
        CopyTypeWithoutProtocol(result.mType, type);
        result.mProtocol    = GetProtocolInType(type);
        result.mPort        = port;
        result.mAddressType = ToAddressType(protocol);
        result.mInterface   = Inet::InterfaceId::Null();
        // It's not clear if we can get the actual value from avahi, so just assume default.
        result.mTtlSeconds = AVAHI_DEFAULT_TTL_HOST_NAME;
        if (interface != AVAHI_IF_UNSPEC)
        {
            result.mInterface = static_cast<chip::Inet::InterfaceId>(interface);
        }
        Platform::CopyString(result.mHostName, host_name);
        // Returned value is full QName, want only host part.
        char * dot = strchr(result.mHostName, '.');
        if (dot != nullptr)
        {
            *dot = '\0';
        }

        CHIP_ERROR result_err = CHIP_ERROR_INVALID_ADDRESS;
        chip::Inet::IPAddress ipAddress; // Will be set of result_err is set to CHIP_NO_ERROR
        if (address)
        {
            switch (address->proto)
            {
            case AVAHI_PROTO_INET:
#if INET_CONFIG_ENABLE_IPV4
                struct in_addr addr4;

                memcpy(&addr4, &(address->data.ipv4), sizeof(addr4));
                ipAddress  = chip::Inet::IPAddress(addr4);
                result_err = CHIP_NO_ERROR;
#else
                ChipLogError(Discovery, "Ignoring IPv4 mDNS address.");
#endif
                break;
            case AVAHI_PROTO_INET6:
                struct in6_addr addr6;

                memcpy(&addr6, &(address->data.ipv6), sizeof(addr6));
                ipAddress  = chip::Inet::IPAddress(addr6);
                result_err = CHIP_NO_ERROR;
                break;
            default:
                break;
            }
        }

        while (txt != nullptr)
        {
            for (size_t i = 0; i < txt->size; i++)
            {
                if (txt->text[i] == '=')
                {
                    txt->text[i] = '\0';
                    textEntries.push_back(TextEntry{ reinterpret_cast<char *>(txt->text), &txt->text[i + 1], txt->size - i - 1 });
                    break;
                }
            }
            txt = txt->next;
        }

        if (!textEntries.empty())
        {
            result.mTextEntries = textEntries.data();
        }
        result.mTextEntrySize = textEntries.size();

        if (result_err == CHIP_NO_ERROR)
        {
            context->mCallback(context->mContext, &result, Span<Inet::IPAddress>(&ipAddress, 1), CHIP_NO_ERROR);
        }
        else
        {
            context->mCallback(context->mContext, nullptr, Span<Inet::IPAddress>(), result_err);
        }
        break;
    }

    sInstance.FreeResolveContext(handle);
}

CHIP_ERROR ChipDnssdInit(DnssdAsyncReturnCallback initCallback, DnssdAsyncReturnCallback errorCallback, void * context)
{
    return MdnsAvahi::GetInstance().Init(initCallback, errorCallback, context);
}

void ChipDnssdShutdown()
{
    MdnsAvahi::GetInstance().Shutdown();
}

CHIP_ERROR ChipDnssdPublishService(const DnssdService * service, DnssdPublishCallback callback, void * context)
{
    VerifyOrReturnError(service != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
    VerifyOrReturnError(callback != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
    if (strcmp(service->mHostName, "") != 0)
    {
        ReturnErrorOnFailure(MdnsAvahi::GetInstance().SetHostname(service->mHostName));
    }

    return MdnsAvahi::GetInstance().PublishService(*service, callback, context);
}

CHIP_ERROR ChipDnssdRemoveServices()
{
    return MdnsAvahi::GetInstance().StopPublish();
}

CHIP_ERROR ChipDnssdFinalizeServiceUpdate()
{
    return CHIP_NO_ERROR;
}

CHIP_ERROR ChipDnssdBrowse(const char * type, DnssdServiceProtocol protocol, chip::Inet::IPAddressType addressType,
                           chip::Inet::InterfaceId interface, DnssdBrowseCallback callback, void * context,
                           intptr_t * browseIdentifier)
{
    return MdnsAvahi::GetInstance().Browse(type, protocol, addressType, interface, callback, context, browseIdentifier);
}

CHIP_ERROR ChipDnssdStopBrowse(intptr_t browseIdentifier)
{
    return MdnsAvahi::GetInstance().StopBrowse(browseIdentifier);
}

CHIP_ERROR ChipDnssdResolve(DnssdService * browseResult, chip::Inet::InterfaceId interface, DnssdResolveCallback callback,
                            void * context)

{
    VerifyOrReturnError(browseResult != nullptr, CHIP_ERROR_INVALID_ARGUMENT);

    return MdnsAvahi::GetInstance().Resolve(browseResult->mName, browseResult->mType, browseResult->mProtocol,
                                            browseResult->mAddressType, Inet::IPAddressType::kAny, interface, callback, context);
}

void ChipDnssdResolveNoLongerNeeded(const char * instanceName)
{
    MdnsAvahi::GetInstance().StopResolve(instanceName);
}

CHIP_ERROR ChipDnssdReconfirmRecord(const char * hostname, chip::Inet::IPAddress address, chip::Inet::InterfaceId interface)
{
    return CHIP_ERROR_NOT_IMPLEMENTED;
}

} // namespace Dnssd
} // namespace chip