/*
   * Linux WiMAX
   * Generic messaging interface between userspace and driver/device
   *
   *
   * Copyright (C) 2007-2008 Intel Corporation <linux-wimax@intel.com>
   * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.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.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
   * 02110-1301, USA.
   *
   *
   * This implements a direct communication channel between user space and
   * the driver/device, by which free form messages can be sent back and
   * forth.
   *
   * This is intended for device-specific features, vendor quirks, etc.
   *
   * See include/net/wimax.h
   *
   * GENERIC NETLINK ENCODING AND CAPACITY
   *
   * A destination "pipe name" is added to each message; it is up to the
   * drivers to assign or use those names (if using them at all).
   *
   * Messages are encoded as a binary netlink attribute using nla_put()
   * using type NLA_UNSPEC (as some versions of libnl still in
   * deployment don't yet understand NLA_BINARY).
   *
   * The maximum capacity of this transport is PAGESIZE per message (so
   * the actual payload will be bit smaller depending on the
   * netlink/generic netlink attributes and headers).
   *
   * RECEPTION OF MESSAGES
   *
   * When a message is received from user space, it is passed verbatim
   * to the driver calling wimax_dev->op_msg_from_user(). The return
   * value from this function is passed back to user space as an ack
   * over the generic netlink protocol.
   *
   * The stack doesn't do any processing or interpretation of these
   * messages.
   *
   * SENDING MESSAGES
   *
   * Messages can be sent with wimax_msg().
   *
   * If the message delivery needs to happen on a different context to
   * that of its creation, wimax_msg_alloc() can be used to get a
   * pointer to the message that can be delivered later on with
   * wimax_msg_send().
   *
   * ROADMAP
   *
   * wimax_gnl_doit_msg_from_user()    Process a message from user space
   *   wimax_dev_get_by_genl_info()
   *   wimax_dev->op_msg_from_user()   Delivery of message to the driver
   *
   * wimax_msg()                       Send a message to user space
   *   wimax_msg_alloc()
   *   wimax_msg_send()
   */
  #include <linux/device.h>
  #include <linux/slab.h>
  #include <net/genetlink.h>
  #include <linux/netdevice.h>
  #include <linux/wimax.h>
  #include <linux/security.h>
  #include <linux/export.h>
  #include "wimax-internal.h"
  
  
  #define D_SUBMODULE op_msg
  #include "debug-levels.h"
  
  
  /**
   * wimax_msg_alloc - Create a new skb for sending a message to userspace
   *
   * @wimax_dev: WiMAX device descriptor
   * @pipe_name: "named pipe" the message will be sent to
   * @msg: pointer to the message data to send
   * @size: size of the message to send (in bytes), including the header.
   * @gfp_flags: flags for memory allocation.
   *
   * Returns: %0 if ok, negative errno code on error
   *
   * Description:
   *
   * Allocates an skb that will contain the message to send to user
   * space over the messaging pipe and initializes it, copying the
   * payload.
   *
   * Once this call is done, you can deliver it with
   * wimax_msg_send().
   *
   * IMPORTANT:
   *
   * Don't use skb_push()/skb_pull()/skb_reserve() on the skb, as
   * wimax_msg_send() depends on skb->data being placed at the
   * beginning of the user message.
   *
   * Unlike other WiMAX stack calls, this call can be used way early,
   * even before wimax_dev_add() is called, as long as the
   * wimax_dev->net_dev pointer is set to point to a proper
   * net_dev. This is so that drivers can use it early in case they need
   * to send stuff around or communicate with user space.
   */
  struct sk_buff *wimax_msg_alloc(struct wimax_dev *wimax_dev,
  				const char *pipe_name,
  				const void *msg, size_t size,
  				gfp_t gfp_flags)
  {
  	int result;
  	struct device *dev = wimax_dev_to_dev(wimax_dev);
  	size_t msg_size;
  	void *genl_msg;
  	struct sk_buff *skb;
  
  	msg_size = nla_total_size(size)
  		+ nla_total_size(sizeof(u32))
  		+ (pipe_name ? nla_total_size(strlen(pipe_name)) : 0);
  	result = -ENOMEM;
  	skb = genlmsg_new(msg_size, gfp_flags);
  	if (skb == NULL)
  		goto error_new;
  	genl_msg = genlmsg_put(skb, 0, 0, &wimax_gnl_family,
  			       0, WIMAX_GNL_OP_MSG_TO_USER);
  	if (genl_msg == NULL) {
  		dev_err(dev, "no memory to create generic netlink message
  ");
  		goto error_genlmsg_put;
  	}
  	result = nla_put_u32(skb, WIMAX_GNL_MSG_IFIDX,
  			     wimax_dev->net_dev->ifindex);
  	if (result < 0) {
  		dev_err(dev, "no memory to add ifindex attribute
  ");
  		goto error_nla_put;
  	}
  	if (pipe_name) {
  		result = nla_put_string(skb, WIMAX_GNL_MSG_PIPE_NAME,
  					pipe_name);
  		if (result < 0) {
  			dev_err(dev, "no memory to add pipe_name attribute
  ");
  			goto error_nla_put;
  		}
  	}
  	result = nla_put(skb, WIMAX_GNL_MSG_DATA, size, msg);
  	if (result < 0) {
  		dev_err(dev, "no memory to add payload (msg %p size %zu) in "
  			"attribute: %d
  ", msg, size, result);
  		goto error_nla_put;
  	}
  	genlmsg_end(skb, genl_msg);
  	return skb;
  
  error_nla_put:
  error_genlmsg_put:
  error_new:
  	nlmsg_free(skb);
  	return ERR_PTR(result);
  }
  EXPORT_SYMBOL_GPL(wimax_msg_alloc);
  
  
  /**
   * wimax_msg_data_len - Return a pointer and size of a message's payload
   *
   * @msg: Pointer to a message created with wimax_msg_alloc()
   * @size: Pointer to where to store the message's size
   *
   * Returns the pointer to the message data.
   */
  const void *wimax_msg_data_len(struct sk_buff *msg, size_t *size)
  {
  	struct nlmsghdr *nlh = (void *) msg->head;
  	struct nlattr *nla;
  
  	nla = nlmsg_find_attr(nlh, sizeof(struct genlmsghdr),
  			      WIMAX_GNL_MSG_DATA);
  	if (nla == NULL) {
  		printk(KERN_ERR "Cannot find attribute WIMAX_GNL_MSG_DATA
  ");
  		return NULL;
  	}
  	*size = nla_len(nla);
  	return nla_data(nla);
  }
  EXPORT_SYMBOL_GPL(wimax_msg_data_len);
  
  
  /**
   * wimax_msg_data - Return a pointer to a message's payload
   *
   * @msg: Pointer to a message created with wimax_msg_alloc()
   */
  const void *wimax_msg_data(struct sk_buff *msg)
  {
  	struct nlmsghdr *nlh = (void *) msg->head;
  	struct nlattr *nla;
  
  	nla = nlmsg_find_attr(nlh, sizeof(struct genlmsghdr),
  			      WIMAX_GNL_MSG_DATA);
  	if (nla == NULL) {
  		printk(KERN_ERR "Cannot find attribute WIMAX_GNL_MSG_DATA
  ");
  		return NULL;
  	}
  	return nla_data(nla);
  }
  EXPORT_SYMBOL_GPL(wimax_msg_data);
  
  
  /**
   * wimax_msg_len - Return a message's payload length
   *
   * @msg: Pointer to a message created with wimax_msg_alloc()
   */
  ssize_t wimax_msg_len(struct sk_buff *msg)
  {
  	struct nlmsghdr *nlh = (void *) msg->head;
  	struct nlattr *nla;
  
  	nla = nlmsg_find_attr(nlh, sizeof(struct genlmsghdr),
  			      WIMAX_GNL_MSG_DATA);
  	if (nla == NULL) {
  		printk(KERN_ERR "Cannot find attribute WIMAX_GNL_MSG_DATA
  ");
  		return -EINVAL;
  	}
  	return nla_len(nla);
  }
  EXPORT_SYMBOL_GPL(wimax_msg_len);
  
  
  /**
   * wimax_msg_send - Send a pre-allocated message to user space
   *
   * @wimax_dev: WiMAX device descriptor
   *
   * @skb: &struct sk_buff returned by wimax_msg_alloc(). Note the
   *     ownership of @skb is transferred to this function.
   *
   * Returns: 0 if ok, < 0 errno code on error
   *
   * Description:
   *
   * Sends a free-form message that was preallocated with
   * wimax_msg_alloc() and filled up.
   *
   * Assumes that once you pass an skb to this function for sending, it
   * owns it and will release it when done (on success).
   *
   * IMPORTANT:
   *
   * Don't use skb_push()/skb_pull()/skb_reserve() on the skb, as
   * wimax_msg_send() depends on skb->data being placed at the
   * beginning of the user message.
   *
   * Unlike other WiMAX stack calls, this call can be used way early,
   * even before wimax_dev_add() is called, as long as the
   * wimax_dev->net_dev pointer is set to point to a proper
   * net_dev. This is so that drivers can use it early in case they need
   * to send stuff around or communicate with user space.
   */
  int wimax_msg_send(struct wimax_dev *wimax_dev, struct sk_buff *skb)
  {
  	struct device *dev = wimax_dev_to_dev(wimax_dev);
  	void *msg = skb->data;
  	size_t size = skb->len;
  	might_sleep();
  
  	d_printf(1, dev, "CTX: wimax msg, %zu bytes
  ", size);
  	d_dump(2, dev, msg, size);
  	genlmsg_multicast(&wimax_gnl_family, skb, 0, 0, GFP_KERNEL);
  	d_printf(1, dev, "CTX: genl multicast done
  ");
  	return 0;
  }
  EXPORT_SYMBOL_GPL(wimax_msg_send);
  
  
  /**
   * wimax_msg - Send a message to user space
   *
   * @wimax_dev: WiMAX device descriptor (properly referenced)
   * @pipe_name: "named pipe" the message will be sent to
   * @buf: pointer to the message to send.
   * @size: size of the buffer pointed to by @buf (in bytes).
   * @gfp_flags: flags for memory allocation.
   *
   * Returns: %0 if ok, negative errno code on error.
   *
   * Description:
   *
   * Sends a free-form message to user space on the device @wimax_dev.
   *
   * NOTES:
   *
   * Once the @skb is given to this function, who will own it and will
   * release it when done (unless it returns error).
   */
  int wimax_msg(struct wimax_dev *wimax_dev, const char *pipe_name,
  	      const void *buf, size_t size, gfp_t gfp_flags)
  {
  	int result = -ENOMEM;
  	struct sk_buff *skb;
  
  	skb = wimax_msg_alloc(wimax_dev, pipe_name, buf, size, gfp_flags);
  	if (IS_ERR(skb))
  		result = PTR_ERR(skb);
  	else
  		result = wimax_msg_send(wimax_dev, skb);
  	return result;
  }
  EXPORT_SYMBOL_GPL(wimax_msg);
  
  /*
   * Relays a message from user space to the driver
   *
   * The skb is passed to the driver-specific function with the netlink
   * and generic netlink headers already stripped.
   *
   * This call will block while handling/relaying the message.
   */
  int wimax_gnl_doit_msg_from_user(struct sk_buff *skb, struct genl_info *info)
  {
  	int result, ifindex;
  	struct wimax_dev *wimax_dev;
  	struct device *dev;
  	struct nlmsghdr *nlh = info->nlhdr;
  	char *pipe_name;
  	void *msg_buf;
  	size_t msg_len;
  
  	might_sleep();
  	d_fnstart(3, NULL, "(skb %p info %p)
  ", skb, info);
  	result = -ENODEV;
  	if (info->attrs[WIMAX_GNL_MSG_IFIDX] == NULL) {
  		printk(KERN_ERR "WIMAX_GNL_MSG_FROM_USER: can't find IFIDX "
  		       "attribute
  ");
  		goto error_no_wimax_dev;
  	}
  	ifindex = nla_get_u32(info->attrs[WIMAX_GNL_MSG_IFIDX]);
  	wimax_dev = wimax_dev_get_by_genl_info(info, ifindex);
  	if (wimax_dev == NULL)
  		goto error_no_wimax_dev;
  	dev = wimax_dev_to_dev(wimax_dev);
  
  	/* Unpack arguments */
  	result = -EINVAL;
  	if (info->attrs[WIMAX_GNL_MSG_DATA] == NULL) {
  		dev_err(dev, "WIMAX_GNL_MSG_FROM_USER: can't find MSG_DATA "
  			"attribute
  ");
  		goto error_no_data;
  	}
  	msg_buf = nla_data(info->attrs[WIMAX_GNL_MSG_DATA]);
  	msg_len = nla_len(info->attrs[WIMAX_GNL_MSG_DATA]);
  
  	if (info->attrs[WIMAX_GNL_MSG_PIPE_NAME] == NULL)
  		pipe_name = NULL;
  	else {
  		struct nlattr *attr = info->attrs[WIMAX_GNL_MSG_PIPE_NAME];
  		size_t attr_len = nla_len(attr);
  		/* libnl-1.1 does not yet support NLA_NUL_STRING */
  		result = -ENOMEM;
  		pipe_name = kstrndup(nla_data(attr), attr_len + 1, GFP_KERNEL);
  		if (pipe_name == NULL)
  			goto error_alloc;
  		pipe_name[attr_len] = 0;
  	}
  	mutex_lock(&wimax_dev->mutex);
  	result = wimax_dev_is_ready(wimax_dev);
  	if (result == -ENOMEDIUM)
  		result = 0;
  	if (result < 0)
  		goto error_not_ready;
  	result = -ENOSYS;
  	if (wimax_dev->op_msg_from_user == NULL)
  		goto error_noop;
  
  	d_printf(1, dev,
  		 "CRX: nlmsghdr len %u type %u flags 0x%04x seq 0x%x pid %u
  ",
  		 nlh->nlmsg_len, nlh->nlmsg_type, nlh->nlmsg_flags,
  		 nlh->nlmsg_seq, nlh->nlmsg_pid);
  	d_printf(1, dev, "CRX: wimax message %zu bytes
  ", msg_len);
  	d_dump(2, dev, msg_buf, msg_len);
  
  	result = wimax_dev->op_msg_from_user(wimax_dev, pipe_name,
  					     msg_buf, msg_len, info);
  error_noop:
  error_not_ready:
  	mutex_unlock(&wimax_dev->mutex);
  error_alloc:
  	kfree(pipe_name);
  error_no_data:
  	dev_put(wimax_dev->net_dev);
  error_no_wimax_dev:
  	d_fnend(3, NULL, "(skb %p info %p) = %d
  ", skb, info, result);
  	return result;
  }