ppapi: PPB_VpnProvider: Define API

ppapi/api/ppb_vpn_provider.idl

+/* Copyright 2016 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.
+ */
+
+/**
+ * This file defines the <code>PPB_VpnProvider</code> interface.
+ */
+
+[generate_thunk]
+
+label Chrome {
+  [channel=dev] M52 = 0.1
+};
+
+/**
+ * Use the <code>PPB_VpnProvider</code> interface to implement a VPN client.
+ * Important: This API is available only on Chrome OS.
+ *
+ * This interface enhances the <code>chrome.vpnProvider</code> JavaScript API by
+ * providing a high performance path for packet handling.
+ *
+ * Permissions: Apps permission <code>vpnProvider</code> is required for
+ * <code>PPB_VpnProvider.Bind()</code>.
+ *
+ * Typical usage:
+ * - Create a <code>PPB_VpnProvider</code> instance.
+ * - Register callbacks via <code>PPB_VpnProvider.GetUnbindEvent()</code> and
+ *   <code>PPB_VpnProvider.ReceivePacket()</code>.
+ * - In the extension follow the usual workflow for configuring a VPN connection
+ *   via the <code>chrome.vpnProvider</code> API until the step for notifying
+ *   the connection state as "connected".
+ * - Bind to the previously created connection using
+ *   <code>PPB_VpnProvider.Bind()</code>.
+ * - Notify the connection state as "connected" from JavaScript using
+ *   <code>chrome.vpnProvider.notifyConnectionStateChanged</code>.
+ * - When the steps above are completed without errors, a virtual tunnel is
+ *   created to the network stack of Chrome OS. IP packets can be sent through
+ *   the tunnel using <code>PPB_VpnProvider.SendPacket()</code> and any packets
+ *   originating on the Chrome OS device will be received using the callback
+ *   registered for <code>PPB_VpnProvider.ReceivePacket()</code>.
+ * - When the user disconnects from the VPN configuration or there is an error
+ *   the callback registered using <code>PPB_VpnProvider.GetUnbindEvent()</code>
+ *   will be called.
+ */
+interface PPB_VpnProvider {
+  /**
+   * Create() creates a VpnProvider instance.
+   *
+   * @param[in] instance A <code>PP_Instance</code> identifying the instance
+   * with the VpnProvider.
+   *
+   * @return A <code>PP_Resource</code> corresponding to a VpnProvider if
+   * successful.
+   */
+  PP_Resource Create([in] PP_Instance instance);
+
+  /**
+   * IsVpnProvider() determines if the provided <code>resource</code> is a
+   * VpnProvider instance.
+   *
+   * @param[in] resource A <code>PP_Resource</code> corresponding to a
+   * VpnProvider.
+   *
+   * @return Returns <code>PP_TRUE</code> if <code>resource</code> is a
+   * <code>PPB_VpnProvider</code>, <code>PP_FALSE</code> if the
+   * <code>resource</code> is invalid or some type other than
+   * <code>PPB_VpnProvider</code>.
+   */
+  PP_Bool IsVpnProvider([in] PP_Resource resource);
+
+  /**
+   * Bind() binds to an existing configuration created from JavaScript by
+   * <code>chrome.vpnProvider.createConfig</code>. All packets will be routed
+   * via <code>SendPacket</code> and <code>ReceivePacket</code>. The user should
+   * register callbacks via <code>GetUnbindEvent</code> and
+   * <code>ReceivePacket</code> before calling <code>Bind()</code>.
+   *
+   * @param[in] vpn_provider A <code>PP_Resource</code> corresponding to a
+   * VpnProvider.
+   *
+   * @param[in] configuration_id A <code>PP_VARTYPE_STRING</code> representing
+   * the configuration id from the callback of
+   * <code>chrome.vpnProvider.createConfig</code>.
+   *
+   * @param[in] configuration_name A <code>PP_VARTYPE_STRING</code> representing
+   * the configuration name as defined by the user when calling
+   * <code>chrome.vpnProvider.createConfig</code>.
+   *
+   * @param[in] callback A <code>PP_CompletionCallback</code> called on
+   * completion.
+   *
+   * @return An int32_t containing an error code from <code>pp_errors.h</code>.
+   * Returns <code>PP_ERROR_INPROGRESS</code> if a previous call to
+   * <code>Bind()</code> has not completed.
+   * Returns <code>PP_ERROR_BADARGUMENT</code> if either
+   * <code>configuration_id</code> or <code>configuration_name</code> are not of
+   * type <code>PP_VARTYPE_STRING</code>.
+   * Returns <code>PP_ERROR_NOACCESS</code> if the caller does the have the
+   * required "vpnProvider" permission.
+   * Returns <code>PP_ERROR_FAILED</code> if <code>connection_id</code> and
+   * <code>connection_name</code> could not be matched with the existing
+   * connection, or if the plugin originates from a different extension than the
+   * one that created the connection.
+   */
+  int32_t Bind([in] PP_Resource vpn_provider,
+               [in] PP_Var configuration_id,
+               [in] PP_Var configuration_name,
+               [in] PP_CompletionCallback callback);
+
+  /**
+   * GetUnbindEvent() registers a callback that will be called when the current
+   * configuration gets unbound. The callback should be registered before
+   * calling <code>Bind()</code>.
+   *
+   * @param[in] vpn_provider A <code>PP_Resource</code> corresponding to a
+   * VpnProvider.
+   *
+   * @param[in] callback A <code>PP_CompletionCallback</code> called when
+   * the current configuration gets unbound.
+   *
+   * @return An int32_t containing an error code from <code>pp_errors.h</code>.
+   * Returns <code>PP_ERROR_INPROGRESS</code> if a previous call to
+   * <code>GetUnbindEvent()</code> has not completed.
+   */
+  int32_t GetUnbindEvent([in]  PP_Resource vpn_provider,
+                         [in]  PP_CompletionCallback callback);

[bbudge, 2016/05/05 21:45:50]

I forgot to bring this up before, but it might be simpler to just pass this
callback in as a parameter to Bind and eliminate this function. Are there any
use cases where a plugin wouldn't call GetUnbindEvent?

[adrian.belgun, 2016/05/06 02:40:01]

I've thought about this use case also. The issue is that I haven't seen the
pattern of having a PPAPI method with two callbacks, so I've concluded that it
wasn't an acceptable pattern.

Bind will then look like:
+  int32_t Bind([in] PP_Resource vpn_provider,
+               [in] PP_Var configuration_id,
+               [in] PP_Var configuration_name,
+               [in] PP_CompletionCallback unbind_callback,
+               [in] PP_CompletionCallback callback);
Is this acceptable?

Regarding the GetUnbindEvent, it gets called when the connection gets unbound,
that is when VpnService issues a vpnProvider.onPlatformMessage. The plugin could
actually rely only on this JS API to track the state of the connection. Actually
my demo application does this and GetUnbindEvent is just for logging purposes. 

What would be best?
- Change Bind to add a second callback?
- Remove GetUnbindEvent completely and just expect the plugin to rely only on
vpnProvider.onPlatformMessage?
- Leave it as is?

Please let me know and I will send a new patch set.

[bbudge, 2016/05/06 17:06:30]

I think if it's possible to simplify the Pepper API by having the web page do
more, that's a good thing. So I'd be in favor of removing the GetUnbindEvent
function.

[adrian.belgun, 2016/05/06 20:08:48]

Done.

+
+  /**
+   * SendPacket() sends an IP packet through the tunnel created for the VPN
+   * session. This will succeed only when the VPN session is owned by the
+   * module and the connection is bound.
+   *
+   * @param[in] vpn_provider A <code>PP_Resource</code> corresponding to a
+   * VpnProvider.
+   *
+   * @param[in] packet A <code>PP_VARTYPE_ARRAY_BUFFER</code> corresponding to
+   * an IP packet to be sent to the platform.
+   *
+   * @param[in] callback A <code>PP_CompletionCallback</code> called on
+   * completion.
+   *
+   * @return An int32_t containing an error code from <code>pp_errors.h</code>.
+   * Returns <code>PP_ERROR_FAILED</code> if the connection is not bound.
+   * Returns <code>PP_ERROR_INPROGRESS</code> if a previous call to
+   * <code>SendPacket()</code> has not completed.
+   * Returns <code>PP_ERROR_BADARGUMENT</code> if <code>packet</code> is not of
+   * type <code>PP_VARTYPE_ARRAY_BUFFER</code>.
+   */
+  int32_t SendPacket([in] PP_Resource vpn_provider,
+                     [in] PP_Var packet,
+                     [in] PP_CompletionCallback callback);
+
+  /**
+   * ReceivePacket() receives an IP packet from the tunnel for the VPN session.
+   * This function only returns a single packet. This function must be called at
+   * least N times to receive N packets, no matter the size of each packet. The
+   * callback should be registered before calling <code>Bind()</code>.
+   *
+   * @param[in] vpn_provider A <code>PP_Resource</code> corresponding to a
+   * VpnProvider.
+   *
+   * @param[out] packet The received packet is copied to provided
+   * <code>packet</code>. The <code>packet</code> must remain valid until
+   * ReceivePacket() completes. Its received <code>PP_VarType</code> will be
+   * <code>PP_VARTYPE_ARRAY_BUFFER</code>.
+   *
+   * @param[in] callback A <code>PP_CompletionCallback</code> called on
+   * completion.
+   *
+   * @return An int32_t containing an error code from <code>pp_errors.h</code>.
+   * Returns <code>PP_ERROR_INPROGRESS</code> if a previous call to
+   * <code>ReceivePacket()</code> has not completed.
+   */
+  int32_t ReceivePacket([in]  PP_Resource vpn_provider,
+                        [out] PP_Var packet,
+                        [in]  PP_CompletionCallback callback);
+};