[net] Adds AddressTrackerLinux which keeps track of interface addresses using rtnetlink.

net/base/address_tracker_linux.h

Index: net/base/address_tracker_linux.h
diff --git a/net/base/address_tracker_linux.h b/net/base/address_tracker_linux.h
new file mode 100644
index 0000000000000000000000000000000000000000..a70a14ccd3258e8e724e1fcb2c8982b7471d5938
--- /dev/null
+++ b/net/base/address_tracker_linux.h
@@ -0,0 +1,68 @@
+// 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/message_loop.h"
+#include "base/synchronization/lock.h"
+#include "net/base/net_util.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 MessageLoopForIO::Watcher {
+ public:
+  typedef std::map<IPAddressNumber, struct ifaddrmsg> AddressMap;
+
+  // Will run |callback| when the AddressMap changes.
+  explicit AddressTrackerLinux(const base::Closure& callback);
+  virtual ~AddressTrackerLinux();
+
+  // Starts watching system configuration for changes. The current thread must
+  // have a MessageLoopForIO.
+  void Init();
+
+  AddressMap GetAddressMap() const;
+
+ private:
+  friend class AddressTrackerLinuxTest;
+
+  // Returns true if |map_| changed while reading messages from |netlink_fd_|.
+  bool ReadMessages();
+
+  // Returns true if |map_| changed while reading the message from |buffer|.
+  bool HandleMessage(const char* buffer, size_t length);
+
+  // MessageLoopForIO::Watcher:
+  virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
+  virtual void OnFileCanWriteWithoutBlocking(int /* fd */) OVERRIDE;
+
+  base::Closure callback_;
+
+  int netlink_fd_;
+  MessageLoopForIO::FileDescriptorWatcher watcher_;
+
+  mutable base::Lock lock_;
+  AddressMap map_;
+};
+
+}  // namespace internal
+}  // namespace net
+
+#endif  // NET_BASE_ADDRESS_TRACKER_LINUX_H_