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connector.c

/*
 *    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;

int cn_already_initialized = 0;

/*
 * 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;
                  }
            }
            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;
}

/*
 * Skb receive helper - checks skb and msg size and calls callback
 * helper.
 */
static int __cn_rx_skb(struct sk_buff *skb, struct nlmsghdr *nlh)
{
      u32 pid, uid, seq, group;
      struct cn_msg *msg;

      pid = NETLINK_CREDS(skb)->pid;
      uid = NETLINK_CREDS(skb)->uid;
      seq = nlh->nlmsg_seq;
      group = NETLINK_CB((skb)).dst_group;
      msg = NLMSG_DATA(nlh);

      return cn_call_callback(msg, (void (*)(void *))kfree_skb, skb);
}

/*
 * Main netlink receiving function.
 *
 * It checks skb and netlink header sizes and calls the skb receive
 * helper with a shared skb.
 */
static void cn_rx_skb(struct sk_buff *__skb)
{
      struct nlmsghdr *nlh;
      u32 len;
      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;
            }

            len = NLMSG_ALIGN(nlh->nlmsg_len);
            if (len > skb->len)
                  len = skb->len;

            err = __cn_rx_skb(skb, nlh);
            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) {
            if (dev->nls->sk_socket)
                  sock_release(dev->nls->sk_socket);
            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);
            if (dev->nls->sk_socket)
                  sock_release(dev->nls->sk_socket);
            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);
      if (dev->nls->sk_socket)
            sock_release(dev->nls->sk_socket);
}

subsys_initcall(cn_init);
module_exit(cn_fini);

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