Adding non-tracking mode support to AddressTracker.

net/base/address_tracker_linux.h

 // 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.
 
 #ifndef NET_BASE_ADDRESS_TRACKER_LINUX_H_
 #define NET_BASE_ADDRESS_TRACKER_LINUX_H_
 
 #include <sys/socket.h>  // Needed to include netlink.
 // Mask superfluous definition of |struct net|. This is fixed in Linux 2.6.38.
 #define net net_kernel
 #include <linux/rtnetlink.h>
 #undef net
 
 #include <map>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/containers/hash_tables.h"
 #include "base/message_loop/message_loop.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/synchronization/lock.h"
+#include "base/threading/thread_checker.h"
+#include "base/threading/thread_restrictions.h"
 #include "net/base/net_util.h"
 #include "net/base/network_change_notifier.h"
 
 namespace net {
 namespace internal {
 
 // Keeps track of network interface addresses using rtnetlink. Used by
 // NetworkChangeNotifier to provide signals to registered IPAddressObservers.
 class NET_EXPORT_PRIVATE AddressTrackerLinux :
     public base::MessageLoopForIO::Watcher {
  public:
   typedef std::map<IPAddressNumber, struct ifaddrmsg> AddressMap;
 
-  // Will run |address_callback| when the AddressMap changes, |link_callback|
-  // when the list of online links changes, and |tunnel_callback| when the list
-  // of online tunnels changes.
+  // Non-tracking version constructor: When AddressTrackerLinux is
+  // constructed without callbacks, it takes a snapshot of current
+  // system configuration once Init() returns. The configuration is
+  // available through GetOnlineLinks() and GetAddressMap (). Note
+  // that the thread creating |AddressTrackerLinux| must be the one
+  // calling Init(). Otherwise, the |thread_checker_| will fail the
+  // assert on CalledOnValidThread().
+  AddressTrackerLinux();
+
+  // Tracking version constructor: it will run |address_callback| when
+  // the AddressMap changes, |link_callback| when the list of online
+  // links changes, and |tunnel_callback| when the list of online
+  // tunnels changes.
   AddressTrackerLinux(const base::Closure& address_callback,
                       const base::Closure& link_callback,
                       const base::Closure& tunnel_callback);
   virtual ~AddressTrackerLinux();
 
-  // Starts watching system configuration for changes. The current thread must
-  // have a MessageLoopForIO.
+  // In tracking mode, it starts watching system configuration for
+  // changes. The current thread must have a MessageLoopForIO. For
+  // non-tracking mode, the |AddressMap| and |online_links_| will be a
+  // one time snapshot of current system configuration after Init()
+  // returns.
   void Init();
 
   AddressMap GetAddressMap() const;
+  base::hash_set<int> GetOnlineLinks() const;
 
   // Implementation of NetworkChangeNotifierLinux::GetCurrentConnectionType().
   // Safe to call from any thread, but will block until Init() has completed.
   NetworkChangeNotifier::ConnectionType GetCurrentConnectionType();
 
  private:
   friend class AddressTrackerLinuxTest;
 
+  // A private nested class to facilitate different locking behaviors
+  // depending on whether the |AddressTrackerLinux| is in tracking
+  // mode or not. Lock will only be taken in the tracking mode.
+  class AddressTrackerAutoLock {

[pauljensen, 2014/09/19 18:39:42]

Please move all this code into address_tracker_linux.cc; the declaration can
stay here.

[guoweis2, 2014/09/19 18:48:30]

Done.

+   public:
+    AddressTrackerAutoLock(const AddressTrackerLinux& tracker, base::Lock& lock)
+        : tracker_(tracker), lock_(lock) {
+      if (tracker_.tracking_)
+        lock_.Acquire();
+    }
+
+    ~AddressTrackerAutoLock() {
+      if (tracker_.tracking_) {
+        lock_.AssertAcquired();
+        lock_.Release();
+      } else {
+        DCHECK(tracker_.thread_checker_.CalledOnValidThread());

[pauljensen, 2014/09/19 18:39:42]

let's move this to the constructor so it's a little more obvious when the check
is hit (i.e. rather than a hidden call to the destructor).

[guoweis2, 2014/09/19 18:48:30]

Done.

+      }
+    }
+
+   private:
+    const AddressTrackerLinux& tracker_;
+    base::Lock& lock_;
+    DISALLOW_COPY_AND_ASSIGN(AddressTrackerAutoLock);
+  };
+
   // A function that returns the name of an interface given the interface index
   // in |interface_index|.
   typedef const char* (*GetInterfaceNameFunction)(int interface_index);
 
   // Sets |*address_changed| to indicate whether |address_map_| changed and
   // sets |*link_changed| to indicate if |online_links_| changed and sets
   // |*tunnel_changed| to indicate if |online_links_| changed with regards to a
   // tunnel interface while reading messages from |netlink_fd_|.
   void ReadMessages(bool* address_changed,
                     bool* link_changed,
@@ skipping 31 matching lines @@
   base::Closure link_callback_;
   base::Closure tunnel_callback_;
 
   int netlink_fd_;
   base::MessageLoopForIO::FileDescriptorWatcher watcher_;
 
   mutable base::Lock address_map_lock_;
   AddressMap address_map_;
 
   // Set of interface indices for links that are currently online.
+  mutable base::Lock online_links_lock_;
   base::hash_set<int> online_links_;
 
   base::Lock is_offline_lock_;
   bool is_offline_;
   bool is_offline_initialized_;
   base::ConditionVariable is_offline_initialized_cv_;
+  bool tracking_;
+
+  // A |ThreadChecker| to validate that in the non-tracking mode, the

[pauljensen, 2014/09/19 18:39:42]

Eh how about something like "Used to verify single-threaded access in
non-tracking mode."

[guoweis2, 2014/09/19 18:48:30]

Done.

+  // thread destructing a |AddressTrackerAutoLock| is the same as the
+  // one which created it. This is to catch any unexpected callback
+  // happening in the non-tracking mode.
+  base::ThreadChecker thread_checker_;
 };
 
 }  // namespace internal
 }  // namespace net
 
 #endif  // NET_BASE_ADDRESS_TRACKER_LINUX_H_