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DNS-SD: Implement browse retries for avahi #28720

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merged 7 commits into from
Aug 22, 2023
Merged

DNS-SD: Implement browse retries for avahi #28720

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a4bfacd
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cecille Aug 16, 2023
d6f18d9
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cecille Aug 16, 2023
333ca02
Implement retries for Avahi
cecille Aug 16, 2023
5b451e8
Merge remote-tracking branch 'upstream/master' into avahi_retries
cecille Aug 16, 2023
971601e
Restyled by clang-format
restyled-commits Aug 16, 2023
445ad71
Actually hook up the stop
cecille Aug 17, 2023
df4efef
Fix the deletion on stop browse
cecille Aug 21, 2023
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77 changes: 69 additions & 8 deletions src/platform/Linux/DnssdImpl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -595,7 +595,8 @@ CHIP_ERROR MdnsAvahi::StopPublish()
}

CHIP_ERROR MdnsAvahi::Browse(const char * type, DnssdServiceProtocol protocol, chip::Inet::IPAddressType addressType,
chip::Inet::InterfaceId interface, DnssdBrowseCallback callback, void * context)
chip::Inet::InterfaceId interface, DnssdBrowseCallback callback, void * context,
intptr_t * browseIdentifier)
{
AvahiServiceBrowser * browser;
BrowseContext * browseContext = chip::Platform::New<BrowseContext>();
Expand All @@ -609,18 +610,40 @@ CHIP_ERROR MdnsAvahi::Browse(const char * type, DnssdServiceProtocol protocol, c
{
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, GetFullType(type, protocol).c_str(), nullptr,
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, '.');
Expand Down Expand Up @@ -662,6 +685,27 @@ void CopyTypeWithoutProtocol(char (&dest)[N], const char * typeAndProtocol)
}
}

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;
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}
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)
Expand Down Expand Up @@ -695,12 +739,30 @@ void MdnsAvahi::HandleBrowse(AvahiServiceBrowser * browser, AvahiIfIndex interfa
context->mServices.push_back(service);
}
break;
case AVAHI_BROWSER_ALL_FOR_NOW:
case AVAHI_BROWSER_ALL_FOR_NOW: {
ChipLogProgress(DeviceLayer, "Avahi browse: all for now");
context->mCallback(context->mContext, context->mServices.data(), context->mServices.size(), true, CHIP_NO_ERROR);
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);
chip::Platform::Delete(context);
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)
Expand Down Expand Up @@ -908,13 +970,12 @@ CHIP_ERROR ChipDnssdBrowse(const char * type, DnssdServiceProtocol protocol, chi
chip::Inet::InterfaceId interface, DnssdBrowseCallback callback, void * context,
intptr_t * browseIdentifier)
{
*browseIdentifier = reinterpret_cast<intptr_t>(nullptr);
return MdnsAvahi::GetInstance().Browse(type, protocol, addressType, interface, callback, context);
return MdnsAvahi::GetInstance().Browse(type, protocol, addressType, interface, callback, context, browseIdentifier);
}

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

CHIP_ERROR ChipDnssdResolve(DnssdService * browseResult, chip::Inet::InterfaceId interface, DnssdResolveCallback callback,
Expand Down
11 changes: 10 additions & 1 deletion src/platform/Linux/DnssdImpl.h
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
#include <sys/select.h>
#include <unistd.h>

#include <atomic>
#include <chrono>
#include <map>
#include <memory>
Expand Down Expand Up @@ -109,7 +110,8 @@ class MdnsAvahi
CHIP_ERROR PublishService(const DnssdService & service, DnssdPublishCallback callback, void * context);
CHIP_ERROR StopPublish();
CHIP_ERROR Browse(const char * type, DnssdServiceProtocol protocol, chip::Inet::IPAddressType addressType,
chip::Inet::InterfaceId interface, DnssdBrowseCallback callback, void * context);
chip::Inet::InterfaceId interface, DnssdBrowseCallback callback, void * context, intptr_t * browseIdentifier);
CHIP_ERROR StopBrowse(intptr_t browseIdentifier);
CHIP_ERROR Resolve(const char * name, const char * type, DnssdServiceProtocol protocol, chip::Inet::IPAddressType addressType,
chip::Inet::IPAddressType transportType, chip::Inet::InterfaceId interface, DnssdResolveCallback callback,
void * context);
Expand All @@ -126,6 +128,11 @@ class MdnsAvahi
void * mContext;
Inet::IPAddressType mAddressType;
std::vector<DnssdService> mServices;
size_t mBrowseRetries;
AvahiIfIndex mInterface;
std::string mProtocol;
chip::System::Clock::Timeout mNextRetryDelay = chip::System::Clock::Seconds16(1);
std::atomic_bool mStopped{ false };
};

struct ResolveContext
Expand Down Expand Up @@ -153,6 +160,7 @@ class MdnsAvahi
static void HandleBrowse(AvahiServiceBrowser * broswer, AvahiIfIndex interface, AvahiProtocol protocol, AvahiBrowserEvent event,
const char * name, const char * type, const char * domain, AvahiLookupResultFlags flags,
void * userdata);
static void BrowseRetryCallback(chip::System::Layer * aLayer, void * appState);
static void 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,
Expand All @@ -165,6 +173,7 @@ class MdnsAvahi
AvahiClient * mClient;
std::map<std::string, AvahiEntryGroup *> mPublishedGroups;
Poller mPoller;
static constexpr size_t kMaxBrowseRetries = 4;
};

} // namespace Dnssd
Expand Down
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