/*
   *  scsi_netlink.c  - SCSI Transport Netlink Interface
   *
   *  Copyright (C) 2006   James Smart, Emulex Corporation
   *
   *  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/time.h>
  #include <linux/jiffies.h>
  #include <linux/security.h>

  #include <linux/delay.h>

  #include <linux/slab.h>

  #include <linux/export.h>

  #include <net/sock.h>
  #include <net/netlink.h>
  
  #include <scsi/scsi_netlink.h>
  #include "scsi_priv.h"
  
  struct sock *scsi_nl_sock = NULL;
  EXPORT_SYMBOL_GPL(scsi_nl_sock);

  static DEFINE_SPINLOCK(scsi_nl_lock);
  static struct list_head scsi_nl_drivers;
  
  static u32	scsi_nl_state;
  #define STATE_EHANDLER_BSY		0x00000001
  
  struct scsi_nl_transport {
  	int (*msg_handler)(struct sk_buff *);
  	void (*event_handler)(struct notifier_block *, unsigned long, void *);
  	unsigned int refcnt;
  	int flags;
  };
  
  /* flags values (bit flags) */
  #define HANDLER_DELETING		0x1
  
  static struct scsi_nl_transport transports[SCSI_NL_MAX_TRANSPORTS] =
  	{ {NULL, }, };
  
  
  struct scsi_nl_drvr {
  	struct list_head next;
  	int (*dmsg_handler)(struct Scsi_Host *shost, void *payload,
  				 u32 len, u32 pid);
  	void (*devt_handler)(struct notifier_block *nb,
  				 unsigned long event, void *notify_ptr);
  	struct scsi_host_template *hostt;
  	u64 vendor_id;
  	unsigned int refcnt;
  	int flags;
  };

  
  /**

   * scsi_nl_rcv_msg - Receive message handler.
   * @skb:		socket receive buffer
   *
   * Description: Extracts message from a receive buffer.

   *    Validates message header and calls appropriate transport message handler
   *

   *
   **/
  static void
  scsi_nl_rcv_msg(struct sk_buff *skb)
  {
  	struct nlmsghdr *nlh;
  	struct scsi_nl_hdr *hdr;

  	unsigned long flags;
  	u32 rlen;
  	int err, tport;

  
  	while (skb->len >= NLMSG_SPACE(0)) {
  		err = 0;

  		nlh = nlmsg_hdr(skb);

  		if ((nlh->nlmsg_len < (sizeof(*nlh) + sizeof(*hdr))) ||
  		    (skb->len < nlh->nlmsg_len)) {
  			printk(KERN_WARNING "%s: discarding partial skb
  ",

  				 __func__);

  			return;
  		}
  
  		rlen = NLMSG_ALIGN(nlh->nlmsg_len);
  		if (rlen > skb->len)
  			rlen = skb->len;
  
  		if (nlh->nlmsg_type != SCSI_TRANSPORT_MSG) {
  			err = -EBADMSG;

  			goto next_msg;

  		}
  
  		hdr = NLMSG_DATA(nlh);
  		if ((hdr->version != SCSI_NL_VERSION) ||
  		    (hdr->magic != SCSI_NL_MAGIC)) {
  			err = -EPROTOTYPE;
  			goto next_msg;
  		}

  		if (!capable(CAP_SYS_ADMIN)) {

  			err = -EPERM;
  			goto next_msg;
  		}
  
  		if (nlh->nlmsg_len < (sizeof(*nlh) + hdr->msglen)) {
  			printk(KERN_WARNING "%s: discarding partial message
  ",

  				 __func__);

  			goto next_msg;

  		}
  
  		/*

  		 * Deliver message to the appropriate transport

  		 */

  		spin_lock_irqsave(&scsi_nl_lock, flags);
  
  		tport = hdr->transport;
  		if ((tport < SCSI_NL_MAX_TRANSPORTS) &&
  		    !(transports[tport].flags & HANDLER_DELETING) &&
  		    (transports[tport].msg_handler)) {
  			transports[tport].refcnt++;
  			spin_unlock_irqrestore(&scsi_nl_lock, flags);
  			err = transports[tport].msg_handler(skb);
  			spin_lock_irqsave(&scsi_nl_lock, flags);
  			transports[tport].refcnt--;
  		} else
  			err = -ENOENT;
  
  		spin_unlock_irqrestore(&scsi_nl_lock, flags);

  
  next_msg:
  		if ((err) || (nlh->nlmsg_flags & NLM_F_ACK))
  			netlink_ack(skb, nlh, err);
  
  		skb_pull(skb, rlen);
  	}
  }
  
  
  /**

   * scsi_nl_rcv_event - Event handler for a netlink socket.

   * @this:		event notifier block
   * @event:		event type
   * @ptr:		event payload
   *
   **/
  static int
  scsi_nl_rcv_event(struct notifier_block *this, unsigned long event, void *ptr)
  {
  	struct netlink_notify *n = ptr;

  	struct scsi_nl_drvr *driver;
  	unsigned long flags;
  	int tport;

  
  	if (n->protocol != NETLINK_SCSITRANSPORT)
  		return NOTIFY_DONE;

  	spin_lock_irqsave(&scsi_nl_lock, flags);
  	scsi_nl_state |= STATE_EHANDLER_BSY;

  	/*

  	 * Pass event on to any transports that may be listening

  	 */

  	for (tport = 0; tport < SCSI_NL_MAX_TRANSPORTS; tport++) {
  		if (!(transports[tport].flags & HANDLER_DELETING) &&
  		    (transports[tport].event_handler)) {
  			spin_unlock_irqrestore(&scsi_nl_lock, flags);
  			transports[tport].event_handler(this, event, ptr);
  			spin_lock_irqsave(&scsi_nl_lock, flags);
  		}
  	}
  
  	/*
  	 * Pass event on to any drivers that may be listening
  	 */
  	list_for_each_entry(driver, &scsi_nl_drivers, next) {
  		if (!(driver->flags & HANDLER_DELETING) &&
  		    (driver->devt_handler)) {
  			spin_unlock_irqrestore(&scsi_nl_lock, flags);
  			driver->devt_handler(this, event, ptr);
  			spin_lock_irqsave(&scsi_nl_lock, flags);
  		}
  	}
  
  	scsi_nl_state &= ~STATE_EHANDLER_BSY;
  	spin_unlock_irqrestore(&scsi_nl_lock, flags);

  
  	return NOTIFY_DONE;
  }
  
  static struct notifier_block scsi_netlink_notifier = {
  	.notifier_call  = scsi_nl_rcv_event,
  };

  /*

   * GENERIC SCSI transport receive and event handlers

   */

  
  /**

   * scsi_generic_msg_handler - receive message handler for GENERIC transport messages

   * @skb:		socket receive buffer

   **/
  static int
  scsi_generic_msg_handler(struct sk_buff *skb)
  {
  	struct nlmsghdr *nlh = nlmsg_hdr(skb);
  	struct scsi_nl_hdr *snlh = NLMSG_DATA(nlh);
  	struct scsi_nl_drvr *driver;
  	struct Scsi_Host *shost;
  	unsigned long flags;
  	int err = 0, match, pid;
  
  	pid = NETLINK_CREDS(skb)->pid;
  
  	switch (snlh->msgtype) {
  	case SCSI_NL_SHOST_VENDOR:
  		{
  		struct scsi_nl_host_vendor_msg *msg = NLMSG_DATA(nlh);
  
  		/* Locate the driver that corresponds to the message */
  		spin_lock_irqsave(&scsi_nl_lock, flags);
  		match = 0;
  		list_for_each_entry(driver, &scsi_nl_drivers, next) {
  			if (driver->vendor_id == msg->vendor_id) {
  				match = 1;
  				break;
  			}
  		}
  
  		if ((!match) || (!driver->dmsg_handler)) {
  			spin_unlock_irqrestore(&scsi_nl_lock, flags);
  			err = -ESRCH;
  			goto rcv_exit;
  		}
  
  		if (driver->flags & HANDLER_DELETING) {
  			spin_unlock_irqrestore(&scsi_nl_lock, flags);
  			err = -ESHUTDOWN;
  			goto rcv_exit;
  		}
  
  		driver->refcnt++;
  		spin_unlock_irqrestore(&scsi_nl_lock, flags);
  
  
  		/* if successful, scsi_host_lookup takes a shost reference */
  		shost = scsi_host_lookup(msg->host_no);
  		if (!shost) {
  			err = -ENODEV;
  			goto driver_exit;
  		}
  
  		/* is this host owned by the vendor ? */
  		if (shost->hostt != driver->hostt) {
  			err = -EINVAL;
  			goto vendormsg_put;
  		}
  
  		/* pass message on to the driver */
  		err = driver->dmsg_handler(shost, (void *)&msg[1],
  					 msg->vmsg_datalen, pid);
  
  vendormsg_put:
  		/* release reference by scsi_host_lookup */
  		scsi_host_put(shost);
  
  driver_exit:
  		/* release our own reference on the registration object */
  		spin_lock_irqsave(&scsi_nl_lock, flags);
  		driver->refcnt--;
  		spin_unlock_irqrestore(&scsi_nl_lock, flags);
  		break;
  		}
  
  	default:
  		err = -EBADR;
  		break;
  	}
  
  rcv_exit:
  	if (err)
  		printk(KERN_WARNING "%s: Msgtype %d failed - err %d
  ",
  			 __func__, snlh->msgtype, err);
  	return err;
  }
  
  
  /**
   * scsi_nl_add_transport -
   *    Registers message and event handlers for a transport. Enables
   *    receipt of netlink messages and events to a transport.
   *
   * @tport:		transport registering handlers
   * @msg_handler:	receive message handler callback
   * @event_handler:	receive event handler callback
   **/
  int
  scsi_nl_add_transport(u8 tport,
  	int (*msg_handler)(struct sk_buff *),
  	void (*event_handler)(struct notifier_block *, unsigned long, void *))
  {
  	unsigned long flags;
  	int err = 0;
  
  	if (tport >= SCSI_NL_MAX_TRANSPORTS)
  		return -EINVAL;
  
  	spin_lock_irqsave(&scsi_nl_lock, flags);
  
  	if (scsi_nl_state & STATE_EHANDLER_BSY) {
  		spin_unlock_irqrestore(&scsi_nl_lock, flags);
  		msleep(1);
  		spin_lock_irqsave(&scsi_nl_lock, flags);
  	}
  
  	if (transports[tport].msg_handler || transports[tport].event_handler) {
  		err = -EALREADY;
  		goto register_out;
  	}
  
  	transports[tport].msg_handler = msg_handler;
  	transports[tport].event_handler = event_handler;
  	transports[tport].flags = 0;
  	transports[tport].refcnt = 0;
  
  register_out:
  	spin_unlock_irqrestore(&scsi_nl_lock, flags);
  
  	return err;
  }
  EXPORT_SYMBOL_GPL(scsi_nl_add_transport);
  
  
  /**
   * scsi_nl_remove_transport -
   *    Disable transport receiption of messages and events
   *
   * @tport:		transport deregistering handlers
   *
   **/
  void
  scsi_nl_remove_transport(u8 tport)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&scsi_nl_lock, flags);
  	if (scsi_nl_state & STATE_EHANDLER_BSY) {
  		spin_unlock_irqrestore(&scsi_nl_lock, flags);
  		msleep(1);
  		spin_lock_irqsave(&scsi_nl_lock, flags);
  	}
  
  	if (tport < SCSI_NL_MAX_TRANSPORTS) {
  		transports[tport].flags |= HANDLER_DELETING;
  
  		while (transports[tport].refcnt != 0) {
  			spin_unlock_irqrestore(&scsi_nl_lock, flags);
  			schedule_timeout_uninterruptible(HZ/4);
  			spin_lock_irqsave(&scsi_nl_lock, flags);
  		}
  		transports[tport].msg_handler = NULL;
  		transports[tport].event_handler = NULL;
  		transports[tport].flags = 0;
  	}
  
  	spin_unlock_irqrestore(&scsi_nl_lock, flags);
  
  	return;
  }
  EXPORT_SYMBOL_GPL(scsi_nl_remove_transport);
  
  
  /**
   * scsi_nl_add_driver -
   *    A driver is registering its interfaces for SCSI netlink messages
   *
   * @vendor_id:          A unique identification value for the driver.
   * @hostt:		address of the driver's host template. Used
   *			to verify an shost is bound to the driver
   * @nlmsg_handler:	receive message handler callback
   * @nlevt_handler:	receive event handler callback
   *
   * Returns:
   *   0 on Success
   *   error result otherwise
   **/
  int
  scsi_nl_add_driver(u64 vendor_id, struct scsi_host_template *hostt,
  	int (*nlmsg_handler)(struct Scsi_Host *shost, void *payload,
  				 u32 len, u32 pid),
  	void (*nlevt_handler)(struct notifier_block *nb,
  				 unsigned long event, void *notify_ptr))
  {
  	struct scsi_nl_drvr *driver;
  	unsigned long flags;
  
  	driver = kzalloc(sizeof(*driver), GFP_KERNEL);
  	if (unlikely(!driver)) {
  		printk(KERN_ERR "%s: allocation failure
  ", __func__);
  		return -ENOMEM;
  	}
  
  	driver->dmsg_handler = nlmsg_handler;
  	driver->devt_handler = nlevt_handler;
  	driver->hostt = hostt;
  	driver->vendor_id = vendor_id;
  
  	spin_lock_irqsave(&scsi_nl_lock, flags);
  	if (scsi_nl_state & STATE_EHANDLER_BSY) {
  		spin_unlock_irqrestore(&scsi_nl_lock, flags);
  		msleep(1);
  		spin_lock_irqsave(&scsi_nl_lock, flags);
  	}
  	list_add_tail(&driver->next, &scsi_nl_drivers);
  	spin_unlock_irqrestore(&scsi_nl_lock, flags);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(scsi_nl_add_driver);
  
  
  /**
   * scsi_nl_remove_driver -
   *    An driver is unregistering with the SCSI netlink messages
   *
   * @vendor_id:          The unique identification value for the driver.
   **/
  void
  scsi_nl_remove_driver(u64 vendor_id)
  {
  	struct scsi_nl_drvr *driver;
  	unsigned long flags;
  
  	spin_lock_irqsave(&scsi_nl_lock, flags);
  	if (scsi_nl_state & STATE_EHANDLER_BSY) {
  		spin_unlock_irqrestore(&scsi_nl_lock, flags);
  		msleep(1);
  		spin_lock_irqsave(&scsi_nl_lock, flags);
  	}
  
  	list_for_each_entry(driver, &scsi_nl_drivers, next) {
  		if (driver->vendor_id == vendor_id) {
  			driver->flags |= HANDLER_DELETING;
  			while (driver->refcnt != 0) {
  				spin_unlock_irqrestore(&scsi_nl_lock, flags);
  				schedule_timeout_uninterruptible(HZ/4);
  				spin_lock_irqsave(&scsi_nl_lock, flags);
  			}
  			list_del(&driver->next);
  			kfree(driver);
  			spin_unlock_irqrestore(&scsi_nl_lock, flags);
  			return;
  		}
  	}
  
  	spin_unlock_irqrestore(&scsi_nl_lock, flags);
  
  	printk(KERN_ERR "%s: removal of driver failed - vendor_id 0x%llx
  ",
  	       __func__, (unsigned long long)vendor_id);
  	return;
  }
  EXPORT_SYMBOL_GPL(scsi_nl_remove_driver);
  
  
  /**

   * scsi_netlink_init - Called by SCSI subsystem to initialize

   * 	the SCSI transport netlink interface

   *
   **/
  void
  scsi_netlink_init(void)
  {
  	int error;

  	INIT_LIST_HEAD(&scsi_nl_drivers);

  	error = netlink_register_notifier(&scsi_netlink_notifier);
  	if (error) {
  		printk(KERN_ERR "%s: register of event handler failed - %d
  ",

  				__func__, error);

  		return;
  	}

  	scsi_nl_sock = netlink_kernel_create(&init_net, NETLINK_SCSITRANSPORT,

  				SCSI_NL_GRP_CNT, scsi_nl_rcv_msg, NULL,

  				THIS_MODULE);

  	if (!scsi_nl_sock) {

  		printk(KERN_ERR "%s: register of receive handler failed
  ",

  				__func__);

  		netlink_unregister_notifier(&scsi_netlink_notifier);

  		return;

  	}

  	/* Register the entry points for the generic SCSI transport */
  	error = scsi_nl_add_transport(SCSI_NL_TRANSPORT,
  				scsi_generic_msg_handler, NULL);
  	if (error)
  		printk(KERN_ERR "%s: register of GENERIC transport handler"
  				"  failed - %d
  ", __func__, error);

  	return;
  }
  
  
  /**

   * scsi_netlink_exit - Called by SCSI subsystem to disable the SCSI transport netlink interface

   *
   **/
  void
  scsi_netlink_exit(void)
  {

  	scsi_nl_remove_transport(SCSI_NL_TRANSPORT);

  	if (scsi_nl_sock) {

  		netlink_kernel_release(scsi_nl_sock);

  		netlink_unregister_notifier(&scsi_netlink_notifier);
  	}
  
  	return;
  }

  /*
   * Exported Interfaces
   */
  
  /**
   * scsi_nl_send_transport_msg -
   *    Generic function to send a single message from a SCSI transport to
   *    a single process
   *
   * @pid:		receiving pid
   * @hdr:		message payload
   *
   **/
  void
  scsi_nl_send_transport_msg(u32 pid, struct scsi_nl_hdr *hdr)
  {
  	struct sk_buff *skb;
  	struct nlmsghdr	*nlh;
  	const char *fn;
  	char *datab;
  	u32 len, skblen;
  	int err;
  
  	if (!scsi_nl_sock) {
  		err = -ENOENT;
  		fn = "netlink socket";
  		goto msg_fail;
  	}
  
  	len = NLMSG_SPACE(hdr->msglen);
  	skblen = NLMSG_SPACE(len);
  
  	skb = alloc_skb(skblen, GFP_KERNEL);
  	if (!skb) {
  		err = -ENOBUFS;
  		fn = "alloc_skb";
  		goto msg_fail;
  	}
  
  	nlh = nlmsg_put(skb, pid, 0, SCSI_TRANSPORT_MSG, len - sizeof(*nlh), 0);
  	if (!nlh) {
  		err = -ENOBUFS;
  		fn = "nlmsg_put";
  		goto msg_fail_skb;
  	}
  	datab = NLMSG_DATA(nlh);
  	memcpy(datab, hdr, hdr->msglen);
  
  	err = nlmsg_unicast(scsi_nl_sock, skb, pid);
  	if (err < 0) {
  		fn = "nlmsg_unicast";
  		/* nlmsg_unicast already kfree_skb'd */
  		goto msg_fail;
  	}
  
  	return;
  
  msg_fail_skb:
  	kfree_skb(skb);
  msg_fail:
  	printk(KERN_WARNING
  		"%s: Dropped Message : pid %d Transport %d, msgtype x%x, "
  		"msglen %d: %s : err %d
  ",
  		__func__, pid, hdr->transport, hdr->msgtype, hdr->msglen,
  		fn, err);
  	return;
  }
  EXPORT_SYMBOL_GPL(scsi_nl_send_transport_msg);
  
  
  /**
   * scsi_nl_send_vendor_msg - called to send a shost vendor unique message
   *                      to a specific process id.
   *
   * @pid:		process id of the receiver
   * @host_no:		host # sending the message
   * @vendor_id:		unique identifier for the driver's vendor
   * @data_len:		amount, in bytes, of vendor unique payload data
   * @data_buf:		pointer to vendor unique data buffer
   *
   * Returns:

   *   0 on successful return

   *   otherwise, failing error code
   *
   * Notes:
   *	This routine assumes no locks are held on entry.
   */
  int
  scsi_nl_send_vendor_msg(u32 pid, unsigned short host_no, u64 vendor_id,
  			 char *data_buf, u32 data_len)
  {
  	struct sk_buff *skb;
  	struct nlmsghdr	*nlh;
  	struct scsi_nl_host_vendor_msg *msg;
  	u32 len, skblen;
  	int err;
  
  	if (!scsi_nl_sock) {
  		err = -ENOENT;
  		goto send_vendor_fail;
  	}
  
  	len = SCSI_NL_MSGALIGN(sizeof(*msg) + data_len);
  	skblen = NLMSG_SPACE(len);
  
  	skb = alloc_skb(skblen, GFP_KERNEL);
  	if (!skb) {
  		err = -ENOBUFS;
  		goto send_vendor_fail;
  	}
  
  	nlh = nlmsg_put(skb, 0, 0, SCSI_TRANSPORT_MSG,
  				skblen - sizeof(*nlh), 0);
  	if (!nlh) {
  		err = -ENOBUFS;
  		goto send_vendor_fail_skb;
  	}
  	msg = NLMSG_DATA(nlh);
  
  	INIT_SCSI_NL_HDR(&msg->snlh, SCSI_NL_TRANSPORT,
  				SCSI_NL_SHOST_VENDOR, len);
  	msg->vendor_id = vendor_id;
  	msg->host_no = host_no;
  	msg->vmsg_datalen = data_len;	/* bytes */
  	memcpy(&msg[1], data_buf, data_len);
  
  	err = nlmsg_unicast(scsi_nl_sock, skb, pid);
  	if (err)
  		/* nlmsg_multicast already kfree_skb'd */
  		goto send_vendor_fail;
  
  	return 0;
  
  send_vendor_fail_skb:
  	kfree_skb(skb);
  send_vendor_fail:
  	printk(KERN_WARNING
  		"%s: Dropped SCSI Msg : host %d vendor_unique - err %d
  ",
  		__func__, host_no, err);
  	return err;
  }
  EXPORT_SYMBOL(scsi_nl_send_vendor_msg);