Bug 939318 - Introduce the "network.notify.changed" prefs. r=mcmanus

Makes it possible to disable 'changed' events.

Disable the network changed event in test_ping_aboutnetworking.js

modules/libpref/init/all.js

@@ -1017,6 +1017,10 @@ pref("security.fileuri.strict_origin_policy", true);
 // the results
 pref("network.allow-experiments", true);
 
+// Allow the network changed event to get sent when a network topology or
+// setup change is noticed while running.
+pref("network.notify.changed", true);
+
 // Transmit UDP busy-work to the LAN when anticipating low latency
 // network reads and on wifi to mitigate 802.11 Power Save Polling delays
 pref("network.tickle-wifi.enabled", false);

netwerk/base/src/nsIOService.cpp

@@ -55,6 +55,7 @@ using namespace mozilla;
 // but the old names are still used to preserve backward compatibility.
 #define NECKO_BUFFER_CACHE_COUNT_PREF "network.buffer.cache.count"
 #define NECKO_BUFFER_CACHE_SIZE_PREF  "network.buffer.cache.size"
+#define NETWORK_NOTIFY_CHANGED_PREF   "network.notify.changed"
 
 #define MAX_RECURSION_COUNT 50
 
@@ -149,6 +150,7 @@ nsIOService::nsIOService()
     , mNetworkLinkServiceInitialized(false)
     , mChannelEventSinks(NS_CHANNEL_EVENT_SINK_CATEGORY)
     , mAutoDialEnabled(false)
+    , mNetworkNotifyChanged(true)
 {
 }
 
@@ -188,6 +190,7 @@ nsIOService::Init()
         prefBranch->AddObserver(MANAGE_OFFLINE_STATUS_PREF, this, true);
         prefBranch->AddObserver(NECKO_BUFFER_CACHE_COUNT_PREF, this, true);
         prefBranch->AddObserver(NECKO_BUFFER_CACHE_SIZE_PREF, this, true);
+        prefBranch->AddObserver(NETWORK_NOTIFY_CHANGED_PREF, this, true);
         PrefsChanged(prefBranch);
     }
     
@@ -852,6 +855,14 @@ nsIOService::PrefsChanged(nsIPrefBranch *prefs, const char *pref)
                 gDefaultSegmentSize = size;
         NS_WARN_IF_FALSE( (!(size & (size - 1))) , "network segment size is not a power of 2!");
     }
+
+    if (!pref || strcmp(pref, NETWORK_NOTIFY_CHANGED_PREF) == 0) {
+        bool allow;
+        nsresult rv = prefs->GetBoolPref(NETWORK_NOTIFY_CHANGED_PREF, &allow);
+        if (NS_SUCCEEDED(rv)) {
+            mNetworkNotifyChanged = allow;
+        }
+    }
 }
 
 void
@@ -958,7 +969,7 @@ nsIOService::Observe(nsISupports *subject,
 
         NS_ASSERTION(observerService, "The observer service should not be null");
 
-        if (observerService) {
+        if (observerService && mNetworkNotifyChanged) {
             (void)observerService->
                 NotifyObservers(nullptr,
                                 NS_NETWORK_LINK_TOPIC,

netwerk/base/src/nsIOService.h

@@ -129,6 +129,7 @@ private:
     nsTArray<int32_t>                    mRestrictedPortList;
 
     bool                                 mAutoDialEnabled;
+    bool                                 mNetworkNotifyChanged;
 public:
     // Used for all default buffer sizes that necko allocates.
     static uint32_t   gDefaultSegmentSize;

netwerk/system/win32/nsNotifyAddrListener.cpp

@@ -27,10 +27,13 @@
 #include "nsAutoPtr.h"
 #include "mozilla/Services.h"
 #include "nsCRT.h"
+#include "mozilla/Preferences.h"
 
 #include <iptypes.h>
 #include <iphlpapi.h>
 
+using namespace mozilla;
+
 static HMODULE sNetshell;
 static decltype(NcFreeNetconProperties)* sNcFreeNetconProperties;
 
@@ -38,6 +41,8 @@ static HMODULE sIphlpapi;
 static decltype(NotifyIpInterfaceChange)* sNotifyIpInterfaceChange;
 static decltype(CancelMibChangeNotify2)* sCancelMibChangeNotify2;
 
+#define NETWORK_NOTIFY_CHANGED_PREF "network.notify.changed"
+
 static void InitIphlpapi(void)
 {
     if (!sIphlpapi) {
@@ -91,6 +96,7 @@ nsNotifyAddrListener::nsNotifyAddrListener()
     , mCheckAttempted(false)
     , mShutdownEvent(nullptr)
     , mIPInterfaceChecksum(0)
+    , mAllowChangedEvent(true)
 {
     InitIphlpapi();
 }
@@ -215,6 +221,9 @@ nsNotifyAddrListener::Init(void)
                                                false);
     NS_ENSURE_SUCCESS(rv, rv);
 
+    Preferences::AddBoolVarCache(&mAllowChangedEvent,
+                                 NETWORK_NOTIFY_CHANGED_PREF, true);
+
     mShutdownEvent = CreateEvent(nullptr, FALSE, FALSE, nullptr);
     NS_ENSURE_TRUE(mShutdownEvent, NS_ERROR_OUT_OF_MEMORY);
 
@@ -500,8 +509,8 @@ nsNotifyAddrListener::CheckLinkStatus(void)
             TimeDuration since = TimeStamp::Now() - mChangedTime;
 
             // Network is online. Topology has changed. Always send CHANGED
-            // before UP - after having cooled down.
-            if (since.ToMilliseconds() > 2000) {
+            // before UP - if allowed to and having cooled down.
+            if (mAllowChangedEvent && (since.ToMilliseconds() > 2000)) {
                 SendEvent(NS_NETWORK_LINK_DATA_CHANGED);
             }
         }

netwerk/system/win32/nsNotifyAddrListener.h

@@ -69,6 +69,9 @@ private:
 
     // time of the last sent changed event
     mozilla::TimeStamp mChangedTime;
+
+    // Network changed events are enabled
+    bool mAllowChangedEvent;
 };
 
 #endif /* NSNOTIFYADDRLISTENER_H_ */

netwerk/test/unit/test_ping_aboutnetworking.js

@@ -42,6 +42,16 @@ function test_sockets(serverSocket) {
 }
 
 function run_test() {
+  var ps = Cc["@mozilla.org/preferences-service;1"]
+    .getService(Ci.nsIPrefBranch);
+  // disable network changed events to avoid the the risk of having the dns
+  // cache getting flushed behind our back
+  ps.setBoolPref("network.notify.changed", false);
+
+  do_register_cleanup(function() {
+    ps.clearUserPref("network.notify.changed");
+  });
+
   let serverSocket = Components.classes["@mozilla.org/network/server-socket;1"]
     .createInstance(Ci.nsIServerSocket);
   serverSocket.init(-1, true, -1);