Bug 938803 - Cancel DNS refresh requested in classes implementing nsAHttpTransaction r=mcmanus

netwerk/protocol/http/NullHttpTransaction.cpp

@@ -22,6 +22,7 @@ NullHttpTransaction::NullHttpTransaction(nsHttpConnectionInfo *ci,
                                          uint32_t caps)
   : mStatus(NS_OK)
   , mCaps(caps | NS_HTTP_ALLOW_KEEPALIVE)
+  , mCapsToClear(0)
   , mCallbacks(callbacks)
   , mConnectionInfo(ci)
   , mRequestHead(nullptr)
@@ -76,7 +77,14 @@ NullHttpTransaction::Status()
 uint32_t
 NullHttpTransaction::Caps()
 {
-  return mCaps;
+  return mCaps & ~mCapsToClear;
+}
+
+void
+NullHttpTransaction::SetDNSWasRefreshed()
+{
+  MOZ_ASSERT(NS_IsMainThread(), "SetDNSWasRefreshed on main thread only!");
+  mCapsToClear |= NS_HTTP_REFRESH_DNS;
 }
 
 uint64_t

netwerk/protocol/http/NullHttpTransaction.h

@@ -41,6 +41,12 @@ private:
 
   nsresult mStatus;
   uint32_t mCaps;
+  // mCapsToClear holds flags that should be cleared in mCaps, e.g. unset
+  // NS_HTTP_REFRESH_DNS when DNS refresh request has completed to avoid
+  // redundant requests on the network. To deal with raciness, only unsetting
+  // bitfields should be allowed: 'lost races' will thus err on the
+  // conservative side, e.g. by going ahead with a 2nd DNS refresh.
+  uint32_t mCapsToClear;
   nsRefPtr<nsAHttpConnection> mConnection;
   nsCOMPtr<nsIInterfaceRequestor> mCallbacks;
   nsRefPtr<nsHttpConnectionInfo> mConnectionInfo;

netwerk/protocol/http/SpdyPush3.cpp

@@ -227,6 +227,11 @@ SpdyPush3TransactionBuffer::Caps()
   return 0;
 }
 
+void
+SpdyPush3TransactionBuffer::SetDNSWasRefreshed()
+{
+}
+
 uint64_t
 SpdyPush3TransactionBuffer::Available()
 {

netwerk/protocol/http/SpdyPush31.cpp

@@ -225,6 +225,11 @@ SpdyPush31TransactionBuffer::Caps()
   return 0;
 }
 
+void
+SpdyPush31TransactionBuffer::SetDNSWasRefreshed()
+{
+}
+
 uint64_t
 SpdyPush31TransactionBuffer::Available()
 {

netwerk/protocol/http/SpdySession3.cpp

@@ -2578,6 +2578,11 @@ SpdySession3::Caps()
   return 0;
 }
 
+void
+SpdySession3::SetDNSWasRefreshed()
+{
+}
+
 uint64_t
 SpdySession3::Available()
 {

netwerk/protocol/http/SpdySession31.cpp

@@ -2702,6 +2702,11 @@ SpdySession31::Caps()
   return 0;
 }
 
+void
+SpdySession31::SetDNSWasRefreshed()
+{
+}
+
 uint64_t
 SpdySession31::Available()
 {

netwerk/protocol/http/nsAHttpTransaction.h

@@ -50,6 +50,9 @@ public:
     virtual nsresult Status() = 0;
     virtual uint32_t Caps() = 0;
 
+    // called to notify that a requested DNS cache entry was refreshed.
+    virtual void     SetDNSWasRefreshed() = 0;
+
     // called to find out how much request data is available for writing.
     virtual uint64_t Available() = 0;
 
@@ -154,6 +157,7 @@ public:
     bool     IsDone(); \
     nsresult Status(); \
     uint32_t Caps();   \
+    void     SetDNSWasRefreshed(); \
     uint64_t Available(); \
     nsresult ReadSegments(nsAHttpSegmentReader *, uint32_t, uint32_t *); \
     nsresult WriteSegments(nsAHttpSegmentWriter *, uint32_t, uint32_t *); \

netwerk/protocol/http/nsHttpChannel.cpp

@@ -5950,6 +5950,9 @@ nsHttpChannel::OnLookupComplete(nsICancelable *request,
     // Unset DNS cache refresh if it was requested,
     if (mCaps & NS_HTTP_REFRESH_DNS) {
         mCaps &= ~NS_HTTP_REFRESH_DNS;
+        if (mTransaction) {
+            mTransaction->SetDNSWasRefreshed();
+        }
     }
 
     return NS_OK;

netwerk/protocol/http/nsHttpPipeline.cpp

@@ -558,6 +558,17 @@ nsHttpPipeline::Caps()
     return trans ? trans->Caps() : 0;
 }
 
+void
+nsHttpPipeline::SetDNSWasRefreshed()
+{
+    nsAHttpTransaction *trans = Request(0);
+    if (!trans)
+        trans = Response(0);
+
+    if (trans)
+      trans->SetDNSWasRefreshed();
+}
+
 uint64_t
 nsHttpPipeline::Available()
 {

netwerk/protocol/http/nsHttpTransaction.cpp

@@ -98,6 +98,7 @@ nsHttpTransaction::nsHttpTransaction()
     , mPriority(0)
     , mRestartCount(0)
     , mCaps(0)
+    , mCapsToClear(0)
     , mClassification(CLASS_GENERAL)
     , mPipelinePosition(0)
     , mHttpVersion(NS_HTTP_VERSION_UNKNOWN)
@@ -552,7 +553,14 @@ nsHttpTransaction::Status()
 uint32_t
 nsHttpTransaction::Caps()
 {
-    return mCaps;
+    return mCaps & ~mCapsToClear;
+}
+
+void
+nsHttpTransaction::SetDNSWasRefreshed()
+{
+    MOZ_ASSERT(NS_IsMainThread(), "SetDNSWasRefreshed on main thread only!");
+    mCapsToClear |= NS_HTTP_REFRESH_DNS;
 }
 
 uint64_t

netwerk/protocol/http/nsHttpTransaction.h

@@ -210,6 +210,12 @@ private:
 
     uint16_t                        mRestartCount;        // the number of times this transaction has been restarted
     uint32_t                        mCaps;
+    // mCapsToClear holds flags that should be cleared in mCaps, e.g. unset
+    // NS_HTTP_REFRESH_DNS when DNS refresh request has completed to avoid
+    // redundant requests on the network. To deal with raciness, only unsetting
+    // bitfields should be allowed: 'lost races' will thus err on the
+    // conservative side, e.g. by going ahead with a 2nd DNS refresh.
+    uint32_t                        mCapsToClear;
     enum Classifier                 mClassification;
     int32_t                         mPipelinePosition;
     int64_t                         mMaxPipelineObjectSize;