diff --git a/p2p_manager.h b/p2p_manager.h
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+++ b/p2p_manager.h
@@ -0,0 +1,164 @@
+// Copyright (c) 2013 The Chromium OS 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 CHROMEOS_PLATFORM_UPDATE_ENGINE_P2P_MANAGER_H__
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_P2P_MANAGER_H__
+
+#include <string>
+#include <vector>
+
+#include <base/callback.h>
+#include <base/file_path.h>
+#include <base/memory/ref_counted.h>
+#include <base/time.h>
+
+#include "update_engine/prefs_interface.h"
+
+namespace chromeos_update_engine {
+
+// Interface for sharing and discovering files via p2p.
+class P2PManager {
+public:
+  // Interface used for P2PManager implementations. The sole reason
+  // for this interface is unit testing.
+  class Configuration {
+  public:
+    virtual ~Configuration() {}
+
+    // Gets the path to the p2p dir being used, e.g. /var/cache/p2p.
+    virtual base::FilePath GetP2PDir() = 0;
+
+    // Gets the argument vector for starting (if |is_start| is True)
+    // resp. stopping (if |is_start| is False) the p2p service
+    // e.g. ["initctl", "start", "p2p"] or ["initctl", "stop", "p2p"].
+    virtual std::vector<std::string> GetInitctlArgs(bool is_start) = 0;
+
+    // Gets the argument vector for invoking p2p-client, e.g.
+    // "p2p-client --get-url=file_id_we_want --minimum-size=42123".
+    virtual std::vector<std::string> GetP2PClientArgs(
+        const std::string& file_id, size_t minimum_size) = 0;
+  };
+
+  virtual ~P2PManager() {}
+
+  // The type for the callback used in LookupUrlForFile().
+  // If the lookup failed, |url| is empty.
+  typedef base::Callback<void(const std::string& url)> LookupCallback;
+
+  // Returns true if - and only if - P2P should be used on this
+  // device. This value is derived from a variety of sources including
+  // enterprise policy.
+  virtual bool IsP2PEnabled() = 0;
+
+  // Ensures that the p2p subsystem is running (e.g. starts it if it's
+  // not already running) and blocks until this is so. Returns false
+  // if an error occurred.
+  virtual bool EnsureP2PRunning() = 0;
+
+  // Ensures that the p2p subsystem is not running (e.g. stops it if
+  // it's running) and blocks until this is so. Returns false if an
+  // error occurred.
+  virtual bool EnsureP2PNotRunning() = 0;
+
+  // Cleans up files in /var/cache/p2p owned by this application as
+  // per the |file_extension| and |num_files_to_keep| values passed
+  // when the object was constructed. This may be called even if
+  // the p2p subsystem is not running.
+  virtual bool PerformHousekeeping() = 0;
+
+  // Asynchronously finds a peer that serves the file identified by
+  // |file_id|. If |minimum_size| is non-zero, will find a peer that
+  // has at least that many bytes. When the result is ready |callback|
+  // is called from the default GLib mainloop.
+  //
+  // This operation may take a very long time to complete because part
+  // of the p2p protocol involves waiting for the LAN-wide sum of all
+  // num-connections to drop below a given threshold. However, if
+  // |max_time_to_wait| is non-zero, the operation is guaranteed to
+  // not exceed this duration.
+  //
+  // If the file is not available on the LAN (or if mDNS/DNS-SD is
+  // filtered), this is guaranteed to not take longer than 5 seconds.
+  virtual void LookupUrlForFile(const std::string& file_id,
+                                size_t minimum_size,
+                                base::TimeDelta max_time_to_wait,
+                                LookupCallback callback) = 0;
+
+  // Shares a file identified by |file_id| in the directory
+  // /var/cache/p2p. Initially the file will not be visible, that is,
+  // it will have a .tmp extension and not be shared via p2p. Use the
+  // FileMakeVisible() method to change this.
+  //
+  // If you know the final size of the file, pass it in the
+  // |expected_size| parameter. Otherwise pass zero. If non-zero, the
+  // amount of free space in /var/cache/p2p is checked and if there is
+  // less than twice the amount of space available, this method
+  // fails. Additionally, disk space will be reserved via fallocate(2)
+  // and |expected_size| is written to the user.cros-p2p-filesize
+  // xattr of the created file.
+  //
+  // If the file already exists, true is returned. Any on-disk xattr
+  // is not updated.
+  virtual bool FileShare(const std::string& file_id,
+                         size_t expected_size) = 0;
+
+  // Gets a fully qualified path for the file identified by |file_id|.
+  // If the file has not been shared already using the FileShare()
+  // method, an empty FilePath is returned - use FilePath::empty() to
+  // find out.
+  virtual base::FilePath FileGetPath(const std::string& file_id) = 0;
+
+  // Gets the actual size of the file identified by |file_id|. This is
+  // equivalent to reading the value of the st_size field of the
+  // struct stat on the file given by FileGetPath(). Returns -1 if an
+  // error occurs.
+  //
+  // For a file just created with FileShare() this will return 0.
+  virtual ssize_t FileGetSize(const std::string& file_id) = 0;
+
+  // Gets the expected size of the file identified by |file_id|. This
+  // is equivalent to reading the value of the user.cros-p2p-filesize
+  // xattr on the file given by FileGetPath(). Returns -1 if an error
+  // occurs.
+  //
+  // For a file just created with FileShare() this will return the
+  // value of the |expected_size| parameter passed to that method.
+  virtual ssize_t FileGetExpectedSize(const std::string& file_id) = 0;
+
+  // Gets whether the file identified by |file_id| is publicly
+  // visible. If |out_result| is not NULL, the result is returned
+  // there. Returns false if an error occurs.
+  virtual bool FileGetVisible(const std::string& file_id,
+                              bool *out_result) = 0;
+
+  // Makes the file identified by |file_id| publicly visible
+  // (e.g. removes the .tmp extension). If the file is already
+  // visible, this method does nothing. Returns False if
+  // the method fails or there is no file for |file_id|.
+  virtual bool FileMakeVisible(const std::string& file_id) = 0;
+
+  // Counts the number of shared files used by this application
+  // (cf. the |file_extension parameter|. Returns -1 if an error
+  // occurred.
+  virtual int CountSharedFiles() = 0;
+
+  // Creates a suitable P2PManager instance and initializes the object
+  // so it's ready for use. The |file_extension| parameter is used to
+  // identify your application, use e.g. "cros_au".  If
+  // |configuration| is non-NULL, the P2PManager will take ownership
+  // of the Configuration object and use it (hence, it must be
+  // heap-allocated).
+  //
+  // The |num_files_to_keep| parameter specifies how many files to
+  // keep after performing housekeeping (cf. the PerformHousekeeping()
+  // method). If zero is passed, no files will be deleted.
+  static P2PManager* Construct(Configuration *configuration,
+                               PrefsInterface *prefs,
+                               const std::string& file_extension,
+                               const int num_files_to_keep);
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_P2P_MANAGER_H__