vpn-manager: Add l2tp/ipsec vpn manager

service_manager.h

+// Copyright (c) 2011 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 _VPN_MANAGER_SERVICE_MANAGER_H_
+#define _VPN_MANAGER_SERVICE_MANAGER_H_
+
+#include <string>
+
+#include "base/file_path.h"
+#include "gtest/gtest_prod.h"  // for FRIEND_TEST
+
+// Generic code to manage setting up and stopping a set of layered
+// tunnel services.  This object contains the code to manage a single
+// layer.  Services are meant to be started from outermost to innermost.
+// Services are meant to be stopped from the innermost out.  To
+// stop the entire set of services, call Stop on the innermost.
+// Services go from not-yet-started to started to in_running to
+// was_stopped.
+class ServiceManager {
+ public:
+  ServiceManager(const std::string& service_name);
+  virtual ~ServiceManager();
+
+  // Initialize directories used by services.
+  static void InitializeDirectories();
+
+  // Call to initiate this service.  If starting fails immediately this
+  // returns false.  If something fails after this returns, OnStopped
+  // will be called.  Code outside of the service manager stack
+  // must only call Start on the outermost function.
+  virtual bool Start() = 0;
+
+  // Callback when this service has successfully started.
+  virtual void OnStarted();
+
+  // Call to stop this service.  Must not be called on a separate
+  // thread from Start().  Code outside of the service manager stack
+  // must only call Stop on the innermost service.  It is ok to
+  // stop an already stopped service.
+  virtual void Stop() = 0;
+
+  // Returns the maximum amount of time to wait before this call should be
+  // called again in milliseconds.
+  virtual int Poll() = 0;
+
+  // Process output from child process.
+  virtual void ProcessOutput() = 0;
+
+  // Returns if |pid| is a child process of this service.
+  virtual bool IsChild(pid_t pid) = 0;
+
+  // Callback when this service has stopped after having started
+  // successfully.  |was_error| indicates if an error occurred.
+  virtual void OnStopped(bool was_error);
+
+  // Queries if this service is currently running.
+  bool is_running() {
+    return is_running_;
+  }
+
+  // Queries if this service was once running and is now stopped.
+  bool was_stopped() {
+    return was_stopped_;
+  }
+
+  // Set up layering between two service managers |outer| and |inner|.
+  static void SetLayerOrder(ServiceManager* outer,

[Will Drewry, 2011/03/05 04:06:39]

So is this currently limited to two managers for a given service?

(I'd almost prefer two lines versus a static func. E.g., 
  ipsec->Requires(l2tp);
  l2tp->Helps(ipsec);
Especially since it could let you arbitrarily layer in the future.

Ignoring that, I like the violation of encapsulation for consistency, but it
could still cause weird if someone assumes this supports an arbitrary number of
services and tries to SetLayerOrder beyond 2.  But that really doesn't matter
now I suspect.)

[kmixter1, 2011/03/11 01:34:27]

No, it's not limited to two.  This would work:
ServiceTurkey tuckey;
ServiceDuck duck;
ServiceChicken chicken;

ServiceManager::SetLayerOrder(&turkey, &duck);
ServiceManager::SetLayerOrder(&duck, &chicken);

It creates a linked list two elements at a time.

Added comments for clarification.

If this abstraction becomes generalizable I'd probably create a ServiceStack
class which takes push_back operators to avoid this kind of interface.

+                            ServiceManager* inner) {
+    outer->inner_service_ = inner;
+    inner->outer_service_ = outer;
+  }
+
+  const std::string& service_name() {
+    return service_name_;
+  }
+
+  // Repeat data from the given |fd| which is assumed to be ready
+  // and send it out to syslog, placing |prefix| before each line
+  // of output.
+  static void WriteFdToSyslog(int fd, const std::string& prefix);
+
+ protected:
+  friend class IpsecManagerTest;
+  friend class ServiceManagerTest;
+  FRIEND_TEST(ServiceManagerTest, InitializeDirectories);
+  FRIEND_TEST(ServiceManagerTest, OnStoppedFromFailure);
+  FRIEND_TEST(ServiceManagerTest, OnStoppedFromSuccess);
+
+  // Removes temporary directory.
+  static void DeleteTemp();
+
+  // Indicates if this service is currently running.
+  bool is_running_;
+
+  // Indicates if this service was running and is now stopped.
+  bool was_stopped_;
+
+  // Pointer to the next layer or NULL if innermost.
+  ServiceManager* inner_service_;
+
+  // Pointer to the outer layer or NULL if outermost.
+  ServiceManager* outer_service_;

[Will Drewry, 2011/03/05 04:06:39]

nit: Is there any reason these are protected instead of private with public or
protected accessors?   (applies to the other files in the cl too)

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Inheri...

[kmixter1, 2011/03/11 01:34:27]

I don't think I've ever seen that one before.  Done.

+
+  // Name of this service.
+  std::string service_name_;
+
+  // Path to temporary directory on cryptohome.
+  static FilePath* temp_path_;
+};
+
+#endif  // _VPN_MANAGER_SERVICE_MANAGER_H_