/*
   * 	connector.c
   * 
   * 2004-2005 Copyright (c) Evgeniy Polyakov <johnpol@2ka.mipt.ru>
   * All rights reserved.
   * 
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/list.h>
  #include <linux/skbuff.h>
  #include <linux/netlink.h>
  #include <linux/moduleparam.h>
  #include <linux/connector.h>

  #include <linux/mutex.h>

  
  #include <net/sock.h>
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
  MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
  
  static u32 cn_idx = CN_IDX_CONNECTOR;
  static u32 cn_val = CN_VAL_CONNECTOR;
  
  module_param(cn_idx, uint, 0);
  module_param(cn_val, uint, 0);
  MODULE_PARM_DESC(cn_idx, "Connector's main device idx.");
  MODULE_PARM_DESC(cn_val, "Connector's main device val.");

  static DEFINE_MUTEX(notify_lock);

  static LIST_HEAD(notify_list);
  
  static struct cn_dev cdev;

  static int cn_already_initialized;

  
  /*
   * msg->seq and msg->ack are used to determine message genealogy.
   * When someone sends message it puts there locally unique sequence
   * and random acknowledge numbers.  Sequence number may be copied into
   * nlmsghdr->nlmsg_seq too.
   *
   * Sequence number is incremented with each message to be sent.
   *
   * If we expect reply to our message then the sequence number in
   * received message MUST be the same as in original message, and
   * acknowledge number MUST be the same + 1.
   *
   * If we receive a message and its sequence number is not equal to the
   * one we are expecting then it is a new message.
   *
   * If we receive a message and its sequence number is the same as one
   * we are expecting but it's acknowledgement number is not equal to
   * the acknowledgement number in the original message + 1, then it is
   * a new message.
   *
   */

  int cn_netlink_send(struct cn_msg *msg, u32 __group, gfp_t gfp_mask)

  {
  	struct cn_callback_entry *__cbq;
  	unsigned int size;
  	struct sk_buff *skb;
  	struct nlmsghdr *nlh;
  	struct cn_msg *data;
  	struct cn_dev *dev = &cdev;
  	u32 group = 0;
  	int found = 0;
  
  	if (!__group) {
  		spin_lock_bh(&dev->cbdev->queue_lock);
  		list_for_each_entry(__cbq, &dev->cbdev->queue_list,
  				    callback_entry) {

  			if (cn_cb_equal(&__cbq->id.id, &msg->id)) {

  				found = 1;
  				group = __cbq->group;

  				break;

  			}
  		}
  		spin_unlock_bh(&dev->cbdev->queue_lock);
  
  		if (!found)
  			return -ENODEV;
  	} else {
  		group = __group;
  	}

  	if (!netlink_has_listeners(dev->nls, group))
  		return -ESRCH;

  	size = NLMSG_SPACE(sizeof(*msg) + msg->len);
  
  	skb = alloc_skb(size, gfp_mask);
  	if (!skb)
  		return -ENOMEM;
  
  	nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));
  
  	data = NLMSG_DATA(nlh);
  
  	memcpy(data, msg, sizeof(*data) + msg->len);
  
  	NETLINK_CB(skb).dst_group = group;

  	return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);

  
  nlmsg_failure:
  	kfree_skb(skb);
  	return -EINVAL;
  }

  EXPORT_SYMBOL_GPL(cn_netlink_send);

  
  /*
   * Callback helper - queues work and setup destructor for given data.
   */
  static int cn_call_callback(struct cn_msg *msg, void (*destruct_data)(void *), void *data)
  {

  	struct cn_callback_entry *__cbq, *__new_cbq;

  	struct cn_dev *dev = &cdev;

  	int err = -ENODEV;

  
  	spin_lock_bh(&dev->cbdev->queue_lock);
  	list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {

  		if (cn_cb_equal(&__cbq->id.id, &msg->id)) {

  			if (likely(!work_pending(&__cbq->work) &&

  					__cbq->data.ddata == NULL)) {
  				__cbq->data.callback_priv = msg;

  				__cbq->data.ddata = data;
  				__cbq->data.destruct_data = destruct_data;

  				if (queue_work(dev->cbdev->cn_queue,
  							&__cbq->work))

  					err = 0;

  				else
  					err = -EINVAL;

  			} else {

  				struct cn_callback_data *d;
  				

  				err = -ENOMEM;
  				__new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
  				if (__new_cbq) {
  					d = &__new_cbq->data;

  					d->callback_priv = msg;
  					d->callback = __cbq->data.callback;
  					d->ddata = data;
  					d->destruct_data = destruct_data;

  					d->free = __new_cbq;

  					INIT_WORK(&__new_cbq->work,

  							&cn_queue_wrapper);

  					if (queue_work(dev->cbdev->cn_queue,

  						    &__new_cbq->work))

  						err = 0;
  					else {

  						kfree(__new_cbq);

  						err = -EINVAL;
  					}

  				}

  			}
  			break;
  		}
  	}
  	spin_unlock_bh(&dev->cbdev->queue_lock);

  	return err;

  }
  
  /*

   * Main netlink receiving function.
   *

   * It checks skb, netlink header and msg sizes, and calls callback helper.

   */
  static void cn_rx_skb(struct sk_buff *__skb)
  {

  	struct cn_msg *msg;

  	struct nlmsghdr *nlh;

  	int err;
  	struct sk_buff *skb;
  
  	skb = skb_get(__skb);
  
  	if (skb->len >= NLMSG_SPACE(0)) {

  		nlh = nlmsg_hdr(skb);

  
  		if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
  		    skb->len < nlh->nlmsg_len ||
  		    nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
  			kfree_skb(skb);

  			return;

  		}

  		msg = NLMSG_DATA(nlh);
  		err = cn_call_callback(msg, (void (*)(void *))kfree_skb, skb);

  		if (err < 0)
  			kfree_skb(skb);
  	}

  }
  
  /*

   * Notification routing.
   *
   * Gets id and checks if there are notification request for it's idx
   * and val.  If there are such requests notify the listeners with the
   * given notify event.
   *
   */
  static void cn_notify(struct cb_id *id, u32 notify_event)
  {
  	struct cn_ctl_entry *ent;

  	mutex_lock(&notify_lock);

  	list_for_each_entry(ent, &notify_list, notify_entry) {
  		int i;
  		struct cn_notify_req *req;
  		struct cn_ctl_msg *ctl = ent->msg;
  		int idx_found, val_found;
  
  		idx_found = val_found = 0;
  
  		req = (struct cn_notify_req *)ctl->data;
  		for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
  			if (id->idx >= req->first && 
  					id->idx < req->first + req->range) {
  				idx_found = 1;
  				break;
  			}
  		}
  
  		for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
  			if (id->val >= req->first && 
  					id->val < req->first + req->range) {
  				val_found = 1;
  				break;
  			}
  		}
  
  		if (idx_found && val_found) {
  			struct cn_msg m = { .ack = notify_event, };
  
  			memcpy(&m.id, id, sizeof(m.id));
  			cn_netlink_send(&m, ctl->group, GFP_KERNEL);
  		}
  	}

  	mutex_unlock(&notify_lock);

  }
  
  /*
   * Callback add routing - adds callback with given ID and name.
   * If there is registered callback with the same ID it will not be added.
   *
   * May sleep.
   */
  int cn_add_callback(struct cb_id *id, char *name, void (*callback)(void *))
  {
  	int err;
  	struct cn_dev *dev = &cdev;

  	if (!cn_already_initialized)
  		return -EAGAIN;

  	err = cn_queue_add_callback(dev->cbdev, name, id, callback);
  	if (err)

  		return err;

  
  	cn_notify(id, 0);
  
  	return 0;
  }

  EXPORT_SYMBOL_GPL(cn_add_callback);

  
  /*
   * Callback remove routing - removes callback
   * with given ID.
   * If there is no registered callback with given
   * ID nothing happens.
   *
   * May sleep while waiting for reference counter to become zero.
   */
  void cn_del_callback(struct cb_id *id)
  {
  	struct cn_dev *dev = &cdev;
  
  	cn_queue_del_callback(dev->cbdev, id);
  	cn_notify(id, 1);
  }

  EXPORT_SYMBOL_GPL(cn_del_callback);

  
  /*
   * Checks two connector's control messages to be the same.
   * Returns 1 if they are the same or if the first one is corrupted.
   */
  static int cn_ctl_msg_equals(struct cn_ctl_msg *m1, struct cn_ctl_msg *m2)
  {
  	int i;
  	struct cn_notify_req *req1, *req2;
  
  	if (m1->idx_notify_num != m2->idx_notify_num)
  		return 0;
  
  	if (m1->val_notify_num != m2->val_notify_num)
  		return 0;
  
  	if (m1->len != m2->len)
  		return 0;
  
  	if ((m1->idx_notify_num + m1->val_notify_num) * sizeof(*req1) !=
  	    m1->len)
  		return 1;
  
  	req1 = (struct cn_notify_req *)m1->data;
  	req2 = (struct cn_notify_req *)m2->data;
  
  	for (i = 0; i < m1->idx_notify_num; ++i) {
  		if (req1->first != req2->first || req1->range != req2->range)
  			return 0;
  		req1++;
  		req2++;
  	}
  
  	for (i = 0; i < m1->val_notify_num; ++i) {
  		if (req1->first != req2->first || req1->range != req2->range)
  			return 0;
  		req1++;
  		req2++;
  	}
  
  	return 1;
  }
  
  /*
   * Main connector device's callback.
   *
   * Used for notification of a request's processing.
   */
  static void cn_callback(void *data)
  {
  	struct cn_msg *msg = data;
  	struct cn_ctl_msg *ctl;
  	struct cn_ctl_entry *ent;
  	u32 size;
  
  	if (msg->len < sizeof(*ctl))
  		return;
  
  	ctl = (struct cn_ctl_msg *)msg->data;
  
  	size = (sizeof(*ctl) + ((ctl->idx_notify_num +
  				 ctl->val_notify_num) *
  				sizeof(struct cn_notify_req)));
  
  	if (msg->len != size)
  		return;
  
  	if (ctl->len + sizeof(*ctl) != msg->len)
  		return;
  
  	/*
  	 * Remove notification.
  	 */
  	if (ctl->group == 0) {
  		struct cn_ctl_entry *n;

  		mutex_lock(&notify_lock);

  		list_for_each_entry_safe(ent, n, &notify_list, notify_entry) {
  			if (cn_ctl_msg_equals(ent->msg, ctl)) {
  				list_del(&ent->notify_entry);
  				kfree(ent);
  			}
  		}

  		mutex_unlock(&notify_lock);

  
  		return;
  	}
  
  	size += sizeof(*ent);
  
  	ent = kzalloc(size, GFP_KERNEL);
  	if (!ent)
  		return;
  
  	ent->msg = (struct cn_ctl_msg *)(ent + 1);
  
  	memcpy(ent->msg, ctl, size - sizeof(*ent));

  	mutex_lock(&notify_lock);

  	list_add(&ent->notify_entry, &notify_list);

  	mutex_unlock(&notify_lock);

  }

  static int __devinit cn_init(void)

  {
  	struct cn_dev *dev = &cdev;
  	int err;

  	dev->input = cn_rx_skb;

  	dev->id.idx = cn_idx;
  	dev->id.val = cn_val;

  	dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR,

  					 CN_NETLINK_USERS + 0xf,

  					 dev->input, NULL, THIS_MODULE);

  	if (!dev->nls)
  		return -EIO;
  
  	dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
  	if (!dev->cbdev) {

  		netlink_kernel_release(dev->nls);

  		return -EINVAL;
  	}

  	
  	cn_already_initialized = 1;

  
  	err = cn_add_callback(&dev->id, "connector", &cn_callback);
  	if (err) {

  		cn_already_initialized = 0;

  		cn_queue_free_dev(dev->cbdev);

  		netlink_kernel_release(dev->nls);

  		return -EINVAL;
  	}

  	return 0;
  }

  static void __devexit cn_fini(void)

  {
  	struct cn_dev *dev = &cdev;
  
  	cn_already_initialized = 0;
  
  	cn_del_callback(&dev->id);
  	cn_queue_free_dev(dev->cbdev);

  	netlink_kernel_release(dev->nls);

  }

  subsys_initcall(cn_init);

  module_exit(cn_fini);