Bugfix: LocalDomainResolver double-calls its callback

LocalDomainResolver double-callback if both A and AAAA records are
present. Fix to check if callback has been called before starting the second
transaction.

BUG=

Review URL: https://chromiumcodereview.appspot.com/21014008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@214661 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 28 insertions, 5 deletions

diff --git a/chrome/utility/local_discovery/local_domain_resolver_unittest.cc b/chrome/utility/local_discovery/local_domain_resolver_unittest.cc
index c1fd51c..fe1cebf 100644
--- a/chrome/utility/local_discovery/local_domain_resolver_unittest.cc
+++ b/chrome/utility/local_discovery/local_domain_resolver_unittest.cc
@@ -167,6 +167,22 @@ TEST_F(LocalDomainResolverTest, ResolveDomainNone) {
   RunFor(base::TimeDelta::FromSeconds(4));
 }
 
+TEST_F(LocalDomainResolverTest, ResolveDomainPreferAFromCache) {
+  socket_factory_->SimulateReceive(
+      kSamplePacketA, sizeof(kSamplePacketAAAA));
+  socket_factory_->SimulateReceive(
+      kSamplePacketA, sizeof(kSamplePacketA));
+
+  LocalDomainResolverImpl resolver(
+      "myhello.local", net::ADDRESS_FAMILY_UNSPECIFIED,
+      base::Bind(&LocalDomainResolverTest::AddressCallback,
+                 base::Unretained(this)), &mdns_client_);
+
+  EXPECT_CALL(*this, AddressCallbackInternal(true, "1.2.3.4"));
+
+  resolver.Start();
+}
+
 }  // namespace
 
 }  // namespace local_discovery
diff --git a/chrome/utility/local_discovery/service_discovery_client_impl.cc b/chrome/utility/local_discovery/service_discovery_client_impl.cc
index 524f176..1df586d 100644
--- a/chrome/utility/local_discovery/service_discovery_client_impl.cc
+++ b/chrome/utility/local_discovery/service_discovery_client_impl.cc
@@ -406,10 +406,14 @@ void LocalDomainResolverImpl::Start() {
     transaction_a_->Start();
   }
 
-  if (address_family_ == net::ADDRESS_FAMILY_IPV6 ||
-      address_family_ == net::ADDRESS_FAMILY_UNSPECIFIED) {
-    transaction_aaaa_ = CreateTransaction(net::dns_protocol::kTypeAAAA);
-    transaction_aaaa_->Start();
+  // Callback may have finished syncrhonously during |transaction_a_->Start()|,
+  // check to make sure it hasn't before starting |transaction_aaaa_|.
+  if (!callback_.is_null()) {
+    if (address_family_ == net::ADDRESS_FAMILY_IPV6 ||
+        address_family_ == net::ADDRESS_FAMILY_UNSPECIFIED) {
+      transaction_aaaa_ = CreateTransaction(net::dns_protocol::kTypeAAAA);
+      transaction_aaaa_->Start();
+    }
   }
 }
 
@@ -449,7 +453,10 @@ void LocalDomainResolverImpl::OnTransactionComplete(
     }
   }
 
-  callback_.Run(result == net::MDnsTransaction::RESULT_RECORD, address);
+  if (!callback_.is_null()) {
+    callback_.Run(result == net::MDnsTransaction::RESULT_RECORD, address);
+    callback_.Reset();
+  }
 }
 
 }  // namespace local_discovery