/*
   * An implementation of file copy service.
   *
   * Copyright (C) 2014, Microsoft, Inc.
   *
   * Author : K. Y. Srinivasan <ksrinivasan@novell.com>
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 as published
   * by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
   * NON INFRINGEMENT.  See the GNU General Public License for more
   * details.
   *
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/nls.h>
  #include <linux/workqueue.h>

  #include <linux/hyperv.h>
  #include <linux/sched.h>

  
  #include "hyperv_vmbus.h"

  #include "hv_utils_transport.h"

  
  #define WIN8_SRV_MAJOR		1
  #define WIN8_SRV_MINOR		1
  #define WIN8_SRV_VERSION	(WIN8_SRV_MAJOR << 16 | WIN8_SRV_MINOR)

  #define FCOPY_VER_COUNT 1
  static const int fcopy_versions[] = {
  	WIN8_SRV_VERSION
  };
  
  #define FW_VER_COUNT 1
  static const int fw_versions[] = {
  	UTIL_FW_VERSION
  };

  /*
   * Global state maintained for transaction that is being processed.
   * For a class of integration services, including the "file copy service",
   * the specified protocol is a "request/response" protocol which means that
   * there can only be single outstanding transaction from the host at any
   * given point in time. We use this to simplify memory management in this
   * driver - we cache and process only one message at a time.
   *
   * While the request/response protocol is guaranteed by the host, we further
   * ensure this by serializing packet processing in this driver - we do not
   * read additional packets from the VMBUs until the current packet is fully
   * handled.

   */
  
  static struct {

  	int state;   /* hvutil_device_state */

  	int recv_len; /* number of bytes received. */
  	struct hv_fcopy_hdr  *fcopy_msg; /* current message */

  	struct vmbus_channel *recv_channel; /* chn we got the request */
  	u64 recv_req_id; /* request ID. */

  } fcopy_transaction;

  static void fcopy_respond_to_host(int error);

  static void fcopy_send_data(struct work_struct *dummy);

  static void fcopy_timeout_func(struct work_struct *dummy);
  static DECLARE_DELAYED_WORK(fcopy_timeout_work, fcopy_timeout_func);

  static DECLARE_WORK(fcopy_send_work, fcopy_send_data);
  static const char fcopy_devname[] = "vmbus/hv_fcopy";

  static u8 *recv_buffer;

  static struct hvutil_transport *hvt;

  /*
   * This state maintains the version number registered by the daemon.
   */
  static int dm_reg_value;

  static void fcopy_poll_wrapper(void *channel)
  {
  	/* Transaction is finished, reset the state here to avoid races. */
  	fcopy_transaction.state = HVUTIL_READY;
  	hv_fcopy_onchannelcallback(channel);
  }

  static void fcopy_timeout_func(struct work_struct *dummy)

  {
  	/*
  	 * If the timer fires, the user-mode component has not responded;
  	 * process the pending transaction.
  	 */
  	fcopy_respond_to_host(HV_E_FAIL);

  	hv_poll_channel(fcopy_transaction.recv_channel, fcopy_poll_wrapper);

  }

  static void fcopy_register_done(void)
  {
  	pr_debug("FCP: userspace daemon registered
  ");
  	hv_poll_channel(fcopy_transaction.recv_channel, fcopy_poll_wrapper);
  }

  static int fcopy_handle_handshake(u32 version)
  {

  	u32 our_ver = FCOPY_CURRENT_VERSION;

  	switch (version) {

  	case FCOPY_VERSION_0:
  		/* Daemon doesn't expect us to reply */
  		dm_reg_value = version;
  		break;
  	case FCOPY_VERSION_1:
  		/* Daemon expects us to reply with our own version */

  		if (hvutil_transport_send(hvt, &our_ver, sizeof(our_ver),
  		    fcopy_register_done))

  			return -EFAULT;
  		dm_reg_value = version;

  		break;
  	default:
  		/*
  		 * For now we will fail the registration.
  		 * If and when we have multiple versions to
  		 * deal with, we will be backward compatible.
  		 * We will add this code when needed.
  		 */
  		return -EINVAL;
  	}

  	pr_debug("FCP: userspace daemon ver. %d connected
  ", version);

  	return 0;
  }

  static void fcopy_send_data(struct work_struct *dummy)

  {

  	struct hv_start_fcopy *smsg_out = NULL;

  	int operation = fcopy_transaction.fcopy_msg->operation;
  	struct hv_start_fcopy *smsg_in;

  	void *out_src;
  	int rc, out_len;

  
  	/*
  	 * The  strings sent from the host are encoded in
  	 * in utf16; convert it to utf8 strings.
  	 * The host assures us that the utf16 strings will not exceed
  	 * the max lengths specified. We will however, reserve room
  	 * for the string terminating character - in the utf16s_utf8s()
  	 * function we limit the size of the buffer where the converted
  	 * string is placed to W_MAX_PATH -1 to guarantee
  	 * that the strings can be properly terminated!
  	 */
  
  	switch (operation) {
  	case START_FILE_COPY:

  		out_len = sizeof(struct hv_start_fcopy);

  		smsg_out = kzalloc(sizeof(*smsg_out), GFP_KERNEL);
  		if (!smsg_out)
  			return;
  
  		smsg_out->hdr.operation = operation;

  		smsg_in = (struct hv_start_fcopy *)fcopy_transaction.fcopy_msg;
  
  		utf16s_to_utf8s((wchar_t *)smsg_in->file_name, W_MAX_PATH,
  				UTF16_LITTLE_ENDIAN,

  				(__u8 *)&smsg_out->file_name, W_MAX_PATH - 1);

  
  		utf16s_to_utf8s((wchar_t *)smsg_in->path_name, W_MAX_PATH,
  				UTF16_LITTLE_ENDIAN,

  				(__u8 *)&smsg_out->path_name, W_MAX_PATH - 1);

  		smsg_out->copy_flags = smsg_in->copy_flags;
  		smsg_out->file_size = smsg_in->file_size;
  		out_src = smsg_out;

  		break;

  	case WRITE_TO_FILE:
  		out_src = fcopy_transaction.fcopy_msg;
  		out_len = sizeof(struct hv_do_fcopy);
  		break;

  	default:

  		out_src = fcopy_transaction.fcopy_msg;
  		out_len = fcopy_transaction.recv_len;

  		break;
  	}

  
  	fcopy_transaction.state = HVUTIL_USERSPACE_REQ;

  	rc = hvutil_transport_send(hvt, out_src, out_len, NULL);

  	if (rc) {
  		pr_debug("FCP: failed to communicate to the daemon: %d
  ", rc);
  		if (cancel_delayed_work_sync(&fcopy_timeout_work)) {
  			fcopy_respond_to_host(HV_E_FAIL);
  			fcopy_transaction.state = HVUTIL_READY;
  		}
  	}

  	kfree(smsg_out);

  }
  
  /*
   * Send a response back to the host.
   */
  
  static void
  fcopy_respond_to_host(int error)
  {
  	struct icmsg_hdr *icmsghdr;
  	u32 buf_len;
  	struct vmbus_channel *channel;
  	u64 req_id;
  
  	/*
  	 * Copy the global state for completing the transaction. Note that
  	 * only one transaction can be active at a time. This is guaranteed
  	 * by the file copy protocol implemented by the host. Furthermore,
  	 * the "transaction active" state we maintain ensures that there can
  	 * only be one active transaction at a time.
  	 */
  
  	buf_len = fcopy_transaction.recv_len;
  	channel = fcopy_transaction.recv_channel;
  	req_id = fcopy_transaction.recv_req_id;

  	icmsghdr = (struct icmsg_hdr *)
  			&recv_buffer[sizeof(struct vmbuspipe_hdr)];
  
  	if (channel->onchannel_callback == NULL)
  		/*
  		 * We have raced with util driver being unloaded;
  		 * silently return.
  		 */
  		return;
  
  	icmsghdr->status = error;
  	icmsghdr->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
  	vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
  				VM_PKT_DATA_INBAND, 0);
  }
  
  void hv_fcopy_onchannelcallback(void *context)
  {
  	struct vmbus_channel *channel = context;
  	u32 recvlen;
  	u64 requestid;
  	struct hv_fcopy_hdr *fcopy_msg;
  	struct icmsg_hdr *icmsghdr;

  	int fcopy_srv_version;

  	if (fcopy_transaction.state > HVUTIL_READY)

  		return;

  
  	vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 2, &recvlen,
  			 &requestid);
  	if (recvlen <= 0)
  		return;
  
  	icmsghdr = (struct icmsg_hdr *)&recv_buffer[
  			sizeof(struct vmbuspipe_hdr)];
  	if (icmsghdr->icmsgtype == ICMSGTYPE_NEGOTIATE) {

  		if (vmbus_prep_negotiate_resp(icmsghdr, recv_buffer,

  				fw_versions, FW_VER_COUNT,
  				fcopy_versions, FCOPY_VER_COUNT,

  				NULL, &fcopy_srv_version)) {
  
  			pr_info("FCopy IC version %d.%d
  ",
  				fcopy_srv_version >> 16,
  				fcopy_srv_version & 0xFFFF);
  		}

  	} else {
  		fcopy_msg = (struct hv_fcopy_hdr *)&recv_buffer[
  				sizeof(struct vmbuspipe_hdr) +
  				sizeof(struct icmsg_hdr)];
  
  		/*
  		 * Stash away this global state for completing the
  		 * transaction; note transactions are serialized.
  		 */

  		fcopy_transaction.recv_len = recvlen;

  		fcopy_transaction.recv_req_id = requestid;
  		fcopy_transaction.fcopy_msg = fcopy_msg;

  		if (fcopy_transaction.state < HVUTIL_READY) {
  			/* Userspace is not registered yet */
  			fcopy_respond_to_host(HV_E_FAIL);
  			return;
  		}
  		fcopy_transaction.state = HVUTIL_HOSTMSG_RECEIVED;

  		/*
  		 * Send the information to the user-level daemon.
  		 */

  		schedule_work(&fcopy_send_work);

  		schedule_delayed_work(&fcopy_timeout_work,
  				      HV_UTIL_TIMEOUT * HZ);

  		return;
  	}
  	icmsghdr->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
  	vmbus_sendpacket(channel, recv_buffer, recvlen, requestid,
  			VM_PKT_DATA_INBAND, 0);
  }

  /* Callback when data is received from userspace */
  static int fcopy_on_msg(void *msg, int len)

  {

  	int *val = (int *)msg;

  	if (len != sizeof(int))

  		return -EINVAL;

  	if (fcopy_transaction.state == HVUTIL_DEVICE_INIT)
  		return fcopy_handle_handshake(*val);

  	if (fcopy_transaction.state != HVUTIL_USERSPACE_REQ)
  		return -EINVAL;

  	/*
  	 * Complete the transaction by forwarding the result
  	 * to the host. But first, cancel the timeout.
  	 */

  	if (cancel_delayed_work_sync(&fcopy_timeout_work)) {
  		fcopy_transaction.state = HVUTIL_USERSPACE_RECV;

  		fcopy_respond_to_host(*val);

  		hv_poll_channel(fcopy_transaction.recv_channel,
  				fcopy_poll_wrapper);

  	}

  	return 0;
  }

  static void fcopy_on_reset(void)

  {
  	/*
  	 * The daemon has exited; reset the state.
  	 */

  	fcopy_transaction.state = HVUTIL_DEVICE_INIT;

  	if (cancel_delayed_work_sync(&fcopy_timeout_work))

  		fcopy_respond_to_host(HV_E_FAIL);

  }
  
  int hv_fcopy_init(struct hv_util_service *srv)
  {
  	recv_buffer = srv->recv_buffer;

  	fcopy_transaction.recv_channel = srv->channel;

  
  	/*
  	 * When this driver loads, the user level daemon that
  	 * processes the host requests may not yet be running.
  	 * Defer processing channel callbacks until the daemon
  	 * has registered.
  	 */

  	fcopy_transaction.state = HVUTIL_DEVICE_INIT;

  	hvt = hvutil_transport_init(fcopy_devname, 0, 0,
  				    fcopy_on_msg, fcopy_on_reset);
  	if (!hvt)
  		return -EFAULT;
  
  	return 0;

  }
  
  void hv_fcopy_deinit(void)
  {

  	fcopy_transaction.state = HVUTIL_DEVICE_DYING;

  	cancel_delayed_work_sync(&fcopy_timeout_work);

  	hvutil_transport_destroy(hvt);

  }