[net] Add DNS-related signals and NetLog to NetworkChangeNotifier.

net/base/network_change_notifier_mac.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/base/network_change_notifier_mac.h"
 
 #include <netinet/in.h>
+#include <resolv.h>
+
+#include "base/threading/thread.h"
+
+#ifndef _PATH_RESCONF  // Normally defined in <resolv.h>
+#define _PATH_RESCONF "/etc/resolv.conf"
+#endif
 
 namespace net {
 
 static bool CalculateReachability(SCNetworkConnectionFlags flags) {
   bool reachable = flags & kSCNetworkFlagsReachable;
   bool connection_required = flags & kSCNetworkFlagsConnectionRequired;
   return reachable && !connection_required;
 }
 
+class NetworkChangeNotifierMac::DNSWatcher : public base::Thread {
+ public:
+  DNSWatcher() : watching_dns_(false) {}
+
+  virtual void Init() OVERRIDE {
+    base::AutoLock lock(watching_dns_lock_);
+    watching_dns_ = true;
+    if (!resolv_watcher_.Watch(
+          FilePath(FILE_PATH_LITERAL(_PATH_RESCONF)),
+          base::Bind(&DNSWatcher::OnDNSFileChanged,
+                     base::Unretained(this),
+                     static_cast<unsigned>(CHANGE_DNS_SETTINGS)))) {
+      LOG(ERROR) << "Failed to setup watch for /etc/resolv.conf";
+      watching_dns_ = false;
+    }
+    if (!hosts_watcher_.Watch(
+            FilePath(FILE_PATH_LITERAL("/etc/hosts")),
+            base::Bind(&DNSWatcher::OnDNSFileChanged,
+                       base::Unretained(this),
+                       static_cast<unsigned>(CHANGE_DNS_HOSTS)))) {
+      LOG(ERROR) << "Failed to setup watch for /etc/hosts";
+      watching_dns_ = false;
+    }
+  }
+
+  virtual void CleanUp() OVERRIDE {
+    base::AutoLock lock(watching_dns_lock_);
+    watching_dns_ = false;
+    resolv_watcher_.Cancel();
+    hosts_watcher_.Cancel();
+  }
+
+  bool IsWatching() const {
+    base::AutoLock lock(watching_dns_lock_);
+    return watching_dns_;
+  }
+
+ private:
+  // Called from FilePathWatcherCallback.
+  void OnDNSFileChanged(unsigned detail, bool watch_success) {
+    if (!watch_success) {
+      LOG(ERROR) << "DNS watch failed.";
+      base::AutoLock lock(watching_dns_lock_);
+      watching_dns_ = false;
+    }
+    // Always notify observers so that they can check IsWatchingDNS().
+    NetworkChangeNotifier::NotifyObserversOfDNSChange(detail);
+  }
+
+  FilePathWatcherCallback resolv_watcher_;
+  FilePathWatcherCallback hosts_watcher_;
+
+  bool watching_dns_;
+  mutable base::Lock watching_dns_lock_;
+};
+
 NetworkChangeNotifierMac::NetworkChangeNotifierMac()
     : online_state_(UNINITIALIZED),
       initial_state_cv_(&online_state_lock_),
       forwarder_(this) {
   // Must be initialized after the rest of this object, as it may call back into
   // SetInitialState().
   config_watcher_.reset(new NetworkConfigWatcherMac(&forwarder_));
+
+  dns_watcher_.reset(new DNSWatcher());
+  dns_watcher_->StartWithOptions(
+      base::Thread::Options(MessageLoop::TYPE_IO, 0));
 }
 
 NetworkChangeNotifierMac::~NetworkChangeNotifierMac() {
   // Delete the ConfigWatcher to join the notifier thread, ensuring that
   // StartReachabilityNotifications() has an opportunity to run to completion.
   config_watcher_.reset();
 
   // Now that StartReachabilityNotifications() has either run to completion or
   // never run at all, unschedule reachability_ if it was previously scheduled.
   if (reachability_.get() && run_loop_.get()) {
     SCNetworkReachabilityUnscheduleFromRunLoop(reachability_.get(),
                                                run_loop_.get(),
                                                kCFRunLoopCommonModes);
   }
 }
 
 bool NetworkChangeNotifierMac::IsCurrentlyOffline() const {
   base::AutoLock lock(online_state_lock_);
   // Make sure the initial state is set before returning.
   while (online_state_ == UNINITIALIZED) {
     initial_state_cv_.Wait();
   }
   return online_state_ == OFFLINE;
 }
 
+bool NetworkChangeNotifierMac::IsCurrentlyWatchingDNS() const {
+  return dns_watcher_->IsWatching();
+}
+
 void NetworkChangeNotifierMac::SetInitialState() {
   // Called on notifier thread.
 
   // Try to reach 0.0.0.0. This is the approach taken by Firefox:
   //
   // http://mxr.mozilla.org/mozilla2.0/source/netwerk/system/mac/nsNetworkLinkService.mm
   //
   // From my (adamk) testing on Snow Leopard, 0.0.0.0
   // seems to be reachable if any network connection is available.
   struct sockaddr_in addr = {0};
@@ skipping 99 matching lines @@
   {
     base::AutoLock lock(notifier_mac->online_state_lock_);
     old_state = notifier_mac->online_state_;
     notifier_mac->online_state_ = new_state;
   }
   if (old_state != new_state)
     NotifyObserversOfOnlineStateChange();
 }
 
 }  // namespace net