Add the ability for MDnsListener to actively refresh records

If the MDnsListener is listening for a record we care about, actively refresh
it.

BUG=336883
R=vitalybuka@chromium.org,szym@chromium.org

Review URL: https://codereview.chromium.org/132693025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247889 0039d316-1c4b-4281-b951-d872f2087c98

net/dns/mdns_cache.h

@@ -55,6 +55,7 @@ class NET_EXPORT_PRIVATE MDnsCache {
   enum UpdateType {
     RecordAdded,
     RecordChanged,
+    RecordRemoved,
     NoChange
   };
 

net/dns/mdns_client.h

@@ -113,6 +113,9 @@ class NET_EXPORT MDnsListener {
   // Start the listener. Return true on success.
   virtual bool Start() = 0;
 
+  // Actively refresh any received records.
+  virtual void SetActiveRefresh(bool active_refresh) = 0;
+
   // Get the host or service name for this query.
   // Return an empty string for no name.
   virtual const std::string& GetName() const = 0;

net/dns/mdns_client_impl.cc

@@ -26,6 +26,13 @@ namespace net {
 namespace {
 
 const unsigned MDnsTransactionTimeoutSeconds = 3;
+// The fractions of the record's original TTL after which an active listener
+// (one that had |SetActiveRefresh(true)| called) will send a query to refresh
+// its cache. This happens both at 85% of the original TTL and again at 95% of
+// the original TTL.
+const double kListenerRefreshRatio1 = 0.85;
+const double kListenerRefreshRatio2 = 0.95;
+const unsigned kMillisecondsPerSecond = 1000;
 
 }  // namespace
 
@@ -192,7 +199,7 @@ void MDnsClientImpl::Core::HandlePacket(DnsResponse* response,
   // Note: We store cache keys rather than record pointers to avoid
   // erroneous behavior in case a packet contains multiple exclusive
   // records with the same type and name.
-  std::map<MDnsCache::Key, MDnsListener::UpdateType> update_keys;
+  std::map<MDnsCache::Key, MDnsCache::UpdateType> update_keys;
 
   if (!response->InitParseWithoutQuery(bytes_read)) {
     LOG(WARNING) << "Could not understand an mDNS packet.";
@@ -235,29 +242,10 @@ void MDnsClientImpl::Core::HandlePacket(DnsResponse* response,
     // Cleanup time may have changed.
     ScheduleCleanup(cache_.next_expiration());
 
-    if (update != MDnsCache::NoChange) {
-      MDnsListener::UpdateType update_external;
-
-      switch (update) {
-        case MDnsCache::RecordAdded:
-          update_external = MDnsListener::RECORD_ADDED;
-          break;
-        case MDnsCache::RecordChanged:
-          update_external = MDnsListener::RECORD_CHANGED;
-          break;
-        case MDnsCache::NoChange:
-        default:
-          NOTREACHED();
-          // Dummy assignment to suppress compiler warning.
-          update_external = MDnsListener::RECORD_CHANGED;
-          break;
-      }
-
-      update_keys.insert(std::make_pair(update_key, update_external));
-    }
+    update_keys.insert(std::make_pair(update_key, update));
   }
 
-  for (std::map<MDnsCache::Key, MDnsListener::UpdateType>::iterator i =
+  for (std::map<MDnsCache::Key, MDnsCache::UpdateType>::iterator i =
            update_keys.begin(); i != update_keys.end(); i++) {
     const RecordParsed* record = cache_.LookupKey(i->first);
     if (!record)
@@ -311,14 +299,14 @@ void MDnsClientImpl::Core::OnConnectionError(int error) {
 }
 
 void MDnsClientImpl::Core::AlertListeners(
-    MDnsListener::UpdateType update_type,
+    MDnsCache::UpdateType update_type,
     const ListenerKey& key,
     const RecordParsed* record) {
   ListenerMap::iterator listener_map_iterator = listeners_.find(key);
   if (listener_map_iterator == listeners_.end()) return;
 
   FOR_EACH_OBSERVER(MDnsListenerImpl, *listener_map_iterator->second,
-                    AlertDelegate(update_type, record));
+                    HandleRecordUpdate(update_type, record));
 }
 
 void MDnsClientImpl::Core::AddListener(
@@ -392,7 +380,7 @@ void MDnsClientImpl::Core::DoCleanup() {
 
 void MDnsClientImpl::Core::OnRecordRemoved(
     const RecordParsed* record) {
-  AlertListeners(MDnsListener::RECORD_REMOVED,
+  AlertListeners(MDnsCache::RecordRemoved,
                  ListenerKey(record->name(), record->type()), record);
 }
 
@@ -449,7 +437,14 @@ MDnsListenerImpl::MDnsListenerImpl(
     MDnsListener::Delegate* delegate,
     MDnsClientImpl* client)
     : rrtype_(rrtype), name_(name), client_(client), delegate_(delegate),
-      started_(false) {
+      started_(false), active_refresh_(false) {
+}
+
+MDnsListenerImpl::~MDnsListenerImpl() {
+  if (started_) {
+    DCHECK(client_->core());
+    client_->core()->RemoveListener(this);
+  }
 }
 
 bool MDnsListenerImpl::Start() {
@@ -463,10 +458,15 @@ bool MDnsListenerImpl::Start() {
   return true;
 }
 
-MDnsListenerImpl::~MDnsListenerImpl() {
+void MDnsListenerImpl::SetActiveRefresh(bool active_refresh) {
+  active_refresh_ = active_refresh;
+
   if (started_) {
-    DCHECK(client_->core());
-    client_->core()->RemoveListener(this);
+    if (!active_refresh_) {
+      next_refresh_.Cancel();
+    } else if (last_update_ != base::Time()) {
+      ScheduleNextRefresh();
+    }
   }
 }
 
@@ -478,10 +478,40 @@ uint16 MDnsListenerImpl::GetType() const {
   return rrtype_;
 }
 
-void MDnsListenerImpl::AlertDelegate(MDnsListener::UpdateType update_type,
-                                     const RecordParsed* record) {
+void MDnsListenerImpl::HandleRecordUpdate(MDnsCache::UpdateType update_type,
+                                          const RecordParsed* record) {
   DCHECK(started_);
-  delegate_->OnRecordUpdate(update_type, record);
+
+  if (update_type != MDnsCache::RecordRemoved) {
+    ttl_ = record->ttl();
+    last_update_ = record->time_created();
+
+    ScheduleNextRefresh();
+  }
+
+  if (update_type != MDnsCache::NoChange) {
+    MDnsListener::UpdateType update_external;
+
+    switch (update_type) {
+      case MDnsCache::RecordAdded:
+        update_external = MDnsListener::RECORD_ADDED;
+        break;
+      case MDnsCache::RecordChanged:
+        update_external = MDnsListener::RECORD_CHANGED;
+        break;
+      case MDnsCache::RecordRemoved:
+        update_external = MDnsListener::RECORD_REMOVED;
+        break;
+      case MDnsCache::NoChange:
+      default:
+        NOTREACHED();
+        // Dummy assignment to suppress compiler warning.
+        update_external = MDnsListener::RECORD_CHANGED;
+        break;
+    }
+
+    delegate_->OnRecordUpdate(update_external, record);
+  }
 }
 
 void MDnsListenerImpl::AlertNsecRecord() {
@@ -489,6 +519,47 @@ void MDnsListenerImpl::AlertNsecRecord() {
   delegate_->OnNsecRecord(name_, rrtype_);
 }
 
+void MDnsListenerImpl::ScheduleNextRefresh() {
+  DCHECK(last_update_ != base::Time());
+
+  if (!active_refresh_)
+    return;
+
+  // A zero TTL is a goodbye packet and should not be refreshed.
+  if (ttl_ == 0) {
+    next_refresh_.Cancel();
+    return;
+  }
+
+  next_refresh_.Reset(base::Bind(&MDnsListenerImpl::DoRefresh,
+                                 AsWeakPtr()));
+
+  // Schedule refreshes at both 85% and 95% of the original TTL. These will both
+  // be canceled and rescheduled if the record's TTL is updated due to a
+  // response being received.
+  base::Time next_refresh1 = last_update_ + base::TimeDelta::FromMilliseconds(
+      static_cast<int>(kMillisecondsPerSecond *
+                       kListenerRefreshRatio1 * ttl_));
+
+  base::Time next_refresh2 = last_update_ + base::TimeDelta::FromMilliseconds(
+      static_cast<int>(kMillisecondsPerSecond *
+                       kListenerRefreshRatio2 * ttl_));
+
+  base::MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      next_refresh_.callback(),
+      next_refresh1 - base::Time::Now());
+
+  base::MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      next_refresh_.callback(),
+      next_refresh2 - base::Time::Now());
+}
+
+void MDnsListenerImpl::DoRefresh() {
+  client_->core()->SendQuery(rrtype_, name_);
+}
+
 MDnsTransactionImpl::MDnsTransactionImpl(
     uint16 rrtype,
     const std::string& name,

net/dns/mdns_client_impl.h

@@ -133,7 +133,7 @@ class NET_EXPORT_PRIVATE MDnsClientImpl : public MDnsClient {
     ListenerMap;
 
     // Alert listeners of an update to the cache.
-    void AlertListeners(MDnsListener::UpdateType update_type,
+    void AlertListeners(MDnsCache::UpdateType update_type,
                         const ListenerKey& key, const RecordParsed* record);
 
     // Schedule a cache cleanup to a specific time, cancelling other cleanups.
@@ -156,7 +156,7 @@ class NET_EXPORT_PRIVATE MDnsClientImpl : public MDnsClient {
     MDnsClientImpl* client_;
     MDnsCache cache_;
 
-    base::CancelableCallback<void()> cleanup_callback_;
+    base::CancelableClosure cleanup_callback_;
     base::Time scheduled_cleanup_;
 
     scoped_ptr<MDnsConnection> connection_;
@@ -204,6 +204,9 @@ class MDnsListenerImpl : public MDnsListener,
   // MDnsListener implementation:
   virtual bool Start() OVERRIDE;
 
+  // Actively refresh any received records.
+  virtual void SetActiveRefresh(bool active_refresh) OVERRIDE;
+
   virtual const std::string& GetName() const OVERRIDE;
 
   virtual uint16 GetType() const OVERRIDE;
@@ -211,19 +214,27 @@ class MDnsListenerImpl : public MDnsListener,
   MDnsListener::Delegate* delegate() { return delegate_; }
 
   // Alert the delegate of a record update.
-  void AlertDelegate(MDnsListener::UpdateType update_type,
-                     const RecordParsed* record_parsed);
+  void HandleRecordUpdate(MDnsCache::UpdateType update_type,
+                          const RecordParsed* record_parsed);
 
   // Alert the delegate of the existence of an Nsec record.
   void AlertNsecRecord();
 
  private:
+  void ScheduleNextRefresh();
+  void DoRefresh();
+
   uint16 rrtype_;
   std::string name_;
   MDnsClientImpl* client_;
   MDnsListener::Delegate* delegate_;
 
+  base::Time last_update_;
+  uint32 ttl_;
   bool started_;
+  bool active_refresh_;
+
+  base::CancelableClosure next_refresh_;
   DISALLOW_COPY_AND_ASSIGN(MDnsListenerImpl);
 };
 

net/dns/mdns_client_unittest.cc

@@ -241,6 +241,25 @@ const uint8 kQueryPacketPrivet[] = {
   0x00, 0x01,        // CLASS is IN.
 };
 
+const uint8 kQueryPacketPrivetA[] = {
+  // Header
+  0x00, 0x00,               // ID is zeroed out
+  0x00, 0x00,               // No flags.
+  0x00, 0x01,               // One question.
+  0x00, 0x00,               // 0 RRs (answers)
+  0x00, 0x00,               // 0 authority RRs
+  0x00, 0x00,               // 0 additional RRs
+
+  // Question
+  // This part is echoed back from the respective query.
+  0x07, '_', 'p', 'r', 'i', 'v', 'e', 't',
+  0x04, '_', 't', 'c', 'p',
+  0x05, 'l', 'o', 'c', 'a', 'l',
+  0x00,
+  0x00, 0x01,        // TYPE is A.
+  0x00, 0x01,        // CLASS is IN.
+};
+
 const uint8 kSamplePacketAdditionalOnly[] = {
   // Header
   0x00, 0x00,               // ID is zeroed out
@@ -303,8 +322,8 @@ const uint8 kSamplePacketAPrivet[] = {
   0x00,
   0x00, 0x01,        // TYPE is A.
   0x00, 0x01,        // CLASS is IN.
-  0x00, 0x01,        // TTL (4 bytes) is 20 hours, 47 minutes, 48 seconds.
-  0x24, 0x74,
+  0x00, 0x00,        // TTL (4 bytes) is 5 seconds
+  0x00, 0x05,
   0x00, 0x04,        // RDLENGTH is 4 bytes.
   0xc0, 0x0c,
   0x00, 0x02,
@@ -1008,6 +1027,31 @@ TEST_F(MDnsTest, NsecConflictRemoval) {
 }
 
 
+TEST_F(MDnsTest, RefreshQuery) {
+  StrictMock<MockListenerDelegate> delegate_privet;
+  scoped_ptr<MDnsListener> listener_privet =
+      test_client_.CreateListener(dns_protocol::kTypeA, "_privet._tcp.local",
+                                  &delegate_privet);
+
+  listener_privet->SetActiveRefresh(true);
+  ASSERT_TRUE(listener_privet->Start());
+
+  EXPECT_CALL(delegate_privet, OnRecordUpdate(MDnsListener::RECORD_ADDED, _));
+
+  SimulatePacketReceive(kSamplePacketAPrivet,
+                        sizeof(kSamplePacketAPrivet));
+
+  // Expecting 2 calls (one for ipv4 and one for ipv6) for each of the 2
+  // scheduled refresh queries.
+  EXPECT_CALL(socket_factory_, OnSendTo(
+      MakeString(kQueryPacketPrivetA, sizeof(kQueryPacketPrivetA))))
+      .Times(4);
+
+  EXPECT_CALL(delegate_privet, OnRecordUpdate(MDnsListener::RECORD_REMOVED, _));
+
+  RunFor(base::TimeDelta::FromSeconds(6));
+}
+
 // Note: These tests assume that the ipv4 socket will always be created first.
 // This is a simplifying assumption based on the way the code works now.
 class SimpleMockSocketFactory : public MDnsSocketFactory {