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

net/base/network_change_notifier_mac.cc

Index: net/base/network_change_notifier_mac.cc
diff --git a/net/base/network_change_notifier_mac.cc b/net/base/network_change_notifier_mac.cc
index ca314a199f9f6343b105a034bde290f5c55d3e72..20cbda7933aae29fef2cac4040919a06050e3bc3 100644
--- a/net/base/network_change_notifier_mac.cc
+++ b/net/base/network_change_notifier_mac.cc
@@ -5,6 +5,11 @@
 #include "net/base/network_change_notifier_mac.h"
 
 #include <netinet/in.h>
+#include <resolv.h>
+
+#ifndef _PATH_RESCONF  // Normally defined in <resolv.h>
+#define _PATH_RESCONF "/etc/resolv.conf"
+#endif
 
 namespace net {
 
@@ -17,10 +22,30 @@ static bool CalculateReachability(SCNetworkConnectionFlags flags) {
 NetworkChangeNotifierMac::NetworkChangeNotifierMac()
     : online_state_(UNINITIALIZED),
       initial_state_cv_(&online_state_lock_),
-      forwarder_(this) {
+      forwarder_(this),
+      watching_dns_(false) {
   // Must be initialized after the rest of this object, as it may call back into
   // SetInitialState().
   config_watcher_.reset(new NetworkConfigWatcherMac(&forwarder_));
+
+  base::AutoLock lock(watching_dns_lock_);
+  watching_dns_ = true;
+  if (!resolv_watcher_.Watch(
+        FilePath(FILE_PATH_LITERAL(_PATH_RESCONF)),
+        base::Bind(&NetworkChangeNotifierMac::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(&NetworkChangeNotifierMac::OnDNSFileChanged,
+                     base::Unretained(this),
+                     static_cast<unsigned>(CHANGE_DNS_HOSTS)))) {
+    LOG(ERROR) << "Failed to setup watch for /etc/hosts";
+    watching_dns_ = false;
+  }
 }
 
 NetworkChangeNotifierMac::~NetworkChangeNotifierMac() {
@@ -46,6 +71,11 @@ bool NetworkChangeNotifierMac::IsCurrentlyOffline() const {
   return online_state_ == OFFLINE;
 }
 
+bool NetworkChangeNotifierMac::IsCurrentlyWatchingDNS() const {
+  base::AutoLock lock(watching_dns_lock_);
+  return watching_dns_ == OFFLINE;
+}
+
 void NetworkChangeNotifierMac::SetInitialState() {
   // Called on notifier thread.
 
@@ -143,6 +173,17 @@ void NetworkChangeNotifierMac::OnNetworkConfigChange(CFArrayRef changed_keys) {
   }
 }
 
+void NetworkChangeNotifierMac::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);
+}
+
 // static
 void NetworkChangeNotifierMac::ReachabilityCallback(
     SCNetworkReachabilityRef target,