drivers/scsi/scsi_transport_iscsi.c

/*
 * iSCSI transport class definitions
 *
 * Copyright (C) IBM Corporation, 2004
 * Copyright (C) Mike Christie, 2004 - 2005
 * Copyright (C) Dmitry Yusupov, 2004 - 2005
 * Copyright (C) Alex Aizman, 2004 - 2005
 *
 * 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/module.h>
#include <linux/mempool.h>
#include <linux/mutex.h>
#include <net/tcp.h>
#include <scsi/scsi.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_transport.h>
#include <scsi/scsi_transport_iscsi.h>
#include <scsi/iscsi_if.h>

#define ISCSI_SESSION_ATTRS 8
#define ISCSI_CONN_ATTRS 6

struct iscsi_internal {
	struct scsi_transport_template t;
	struct iscsi_transport *iscsi_transport;
	struct list_head list;
	/*
	 * based on transport capabilities, at register time we set these
	 * bits to tell the transport class it wants attributes displayed
	 * in sysfs or that it can support different iSCSI Data-Path
	 * capabilities
	 */
	uint32_t param_mask;

	struct class_device cdev;
	/*
	 * We do not have any private or other attrs.
	 */
	struct transport_container conn_cont;
	struct class_device_attribute *conn_attrs[ISCSI_CONN_ATTRS + 1];
	struct transport_container session_cont;
	struct class_device_attribute *session_attrs[ISCSI_SESSION_ATTRS + 1];
};

static int iscsi_session_nr;	/* sysfs session id for next new session */

/*
 * list of registered transports and lock that must
 * be held while accessing list. The iscsi_transport_lock must
 * be acquired after the rx_queue_mutex.
 */
static LIST_HEAD(iscsi_transports);
static DEFINE_SPINLOCK(iscsi_transport_lock);

#define to_iscsi_internal(tmpl) \
	container_of(tmpl, struct iscsi_internal, t)

#define cdev_to_iscsi_internal(_cdev) \
	container_of(_cdev, struct iscsi_internal, cdev)

static void iscsi_transport_release(struct class_device *cdev)
{
	struct iscsi_internal *priv = cdev_to_iscsi_internal(cdev);
	kfree(priv);
}

/*
 * iscsi_transport_class represents the iscsi_transports that are
 * registered.
 */
static struct class iscsi_transport_class = {
	.name = "iscsi_transport",
	.release = iscsi_transport_release,
};

static ssize_t
show_transport_handle(struct class_device *cdev, char *buf)
{
	struct iscsi_internal *priv = cdev_to_iscsi_internal(cdev);
	return sprintf(buf, "%llu\n", (unsigned long long)iscsi_handle(priv->iscsi_transport));
}
static CLASS_DEVICE_ATTR(handle, S_IRUGO, show_transport_handle, NULL);

#define show_transport_attr(name, format)				\
static ssize_t								\
show_transport_##name(struct class_device *cdev, char *buf)		\
{									\
	struct iscsi_internal *priv = cdev_to_iscsi_internal(cdev);	\
	return sprintf(buf, format"\n", priv->iscsi_transport->name);	\
}									\
static CLASS_DEVICE_ATTR(name, S_IRUGO, show_transport_##name, NULL);

show_transport_attr(caps, "0x%x");
show_transport_attr(max_lun, "%d");
show_transport_attr(max_conn, "%d");
show_transport_attr(max_cmd_len, "%d");

static struct attribute *iscsi_transport_attrs[] = {
	&class_device_attr_handle.attr,
	&class_device_attr_caps.attr,
	&class_device_attr_max_lun.attr,
	&class_device_attr_max_conn.attr,
	&class_device_attr_max_cmd_len.attr,
	NULL,
};

static struct attribute_group iscsi_transport_group = {
	.attrs = iscsi_transport_attrs,
};

static DECLARE_TRANSPORT_CLASS(iscsi_session_class,
			       "iscsi_session",
			       NULL,
			       NULL,
			       NULL);

static DECLARE_TRANSPORT_CLASS(iscsi_connection_class,
			       "iscsi_connection",
			       NULL,
			       NULL,
			       NULL);

static struct sock *nls;
static int daemon_pid;
static DEFINE_MUTEX(rx_queue_mutex);

struct mempool_zone {
	mempool_t *pool;
	atomic_t allocated;
	int size;
	int hiwat;
	struct list_head freequeue;
	spinlock_t freelock;
};

static struct mempool_zone *z_reply;

/*
 * Z_MAX_* - actual mempool size allocated at the mempool_zone_init() time
 * Z_HIWAT_* - zone's high watermark when if_error bit will be set to -ENOMEM
 *             so daemon will notice OOM on NETLINK tranposrt level and will
 *             be able to predict or change operational behavior
 */
#define Z_MAX_REPLY	8
#define Z_HIWAT_REPLY	6
#define Z_MAX_PDU	8
#define Z_HIWAT_PDU	6
#define Z_MAX_ERROR	16
#define Z_HIWAT_ERROR	12

static LIST_HEAD(sesslist);
static DEFINE_SPINLOCK(sesslock);
static LIST_HEAD(connlist);
static DEFINE_SPINLOCK(connlock);

static uint32_t iscsi_conn_get_sid(struct iscsi_cls_conn *conn)
{
	struct iscsi_cls_session *sess = iscsi_dev_to_session(conn->dev.parent);
	return sess->sid;
}

/*
 * Returns the matching session to a given sid
 */
static struct iscsi_cls_session *iscsi_session_lookup(uint32_t sid)
{
	unsigned long flags;
	struct iscsi_cls_session *sess;

	spin_lock_irqsave(&sesslock, flags);
	list_for_each_entry(sess, &sesslist, sess_list) {
		if (sess->sid == sid) {
			spin_unlock_irqrestore(&sesslock, flags);
			return sess;
		}
	}
	spin_unlock_irqrestore(&sesslock, flags);
	return NULL;
}

/*
 * Returns the matching connection to a given sid / cid tuple
 */
static struct iscsi_cls_conn *iscsi_conn_lookup(uint32_t sid, uint32_t cid)
{
	unsigned long flags;
	struct iscsi_cls_conn *conn;

	spin_lock_irqsave(&connlock, flags);
	list_for_each_entry(conn, &connlist, conn_list) {
		if ((conn->cid == cid) && (iscsi_conn_get_sid(conn) == sid)) {
			spin_unlock_irqrestore(&connlock, flags);
			return conn;
		}
	}
	spin_unlock_irqrestore(&connlock, flags);
	return NULL;
}

/*
 * The following functions can be used by LLDs that allocate
 * their own scsi_hosts or by software iscsi LLDs
 */
static void iscsi_session_release(struct device *dev)
{
	struct iscsi_cls_session *session = iscsi_dev_to_session(dev);
	struct iscsi_transport *transport = session->transport;
	struct Scsi_Host *shost;

	shost = iscsi_session_to_shost(session);
	scsi_host_put(shost);
	kfree(session);
	module_put(transport->owner);
}

static int iscsi_is_session_dev(const struct device *dev)
{
	return dev->release == iscsi_session_release;
}

/**
 * iscsi_create_session - create iscsi class session
 * @shost: scsi host
 * @transport: iscsi transport
 *
 * This can be called from a LLD or iscsi_transport.
 **/
struct iscsi_cls_session *
iscsi_create_session(struct Scsi_Host *shost, struct iscsi_transport *transport)
{
	struct iscsi_cls_session *session;
	int err;

	if (!try_module_get(transport->owner))
		return NULL;

	session = kzalloc(sizeof(*session) + transport->sessiondata_size,
			  GFP_KERNEL);
	if (!session)
		goto module_put;
	session->transport = transport;

	if (transport->sessiondata_size)
		session->dd_data = &session[1];

	/* this is released in the dev's release function */
	scsi_host_get(shost);
	session->sid = iscsi_session_nr++;
	snprintf(session->dev.bus_id, BUS_ID_SIZE, "session%u",
		 session->sid);
	session->dev.parent = &shost->shost_gendev;
	session->dev.release = iscsi_session_release;
	err = device_register(&session->dev);
	if (err) {
		dev_printk(KERN_ERR, &session->dev, "iscsi: could not "
			   "register session's dev\n");
		goto free_session;
	}
	transport_register_device(&session->dev);

	return session;

free_session:
	kfree(session);
module_put:
	module_put(transport->owner);
	return NULL;
}

EXPORT_SYMBOL_GPL(iscsi_create_session);

/**
 * iscsi_destroy_session - destroy iscsi session
 * @session: iscsi_session
 *
 * Can be called by a LLD or iscsi_transport. There must not be
 * any running connections.
 **/
int iscsi_destroy_session(struct iscsi_cls_session *session)
{
	transport_unregister_device(&session->dev);
	device_unregister(&session->dev);
	return 0;
}

EXPORT_SYMBOL_GPL(iscsi_destroy_session);

static void iscsi_conn_release(struct device *dev)
{
	struct iscsi_cls_conn *conn = iscsi_dev_to_conn(dev);
	struct device *parent = conn->dev.parent;

	kfree(conn);
	put_device(parent);
}

static int iscsi_is_conn_dev(const struct device *dev)
{
	return dev->release == iscsi_conn_release;
}

/**
 * iscsi_create_conn - create iscsi class connection
 * @session: iscsi cls session
 * @cid: connection id
 *
 * This can be called from a LLD or iscsi_transport. The connection
 * is child of the session so cid must be unique for all connections
 * on the session.
 *
 * Since we do not support MCS, cid will normally be zero. In some cases
 * for software iscsi we could be trying to preallocate a connection struct
 * in which case there could be two connection structs and cid would be
 * non-zero.
 **/
struct iscsi_cls_conn *
iscsi_create_conn(struct iscsi_cls_session *session, uint32_t cid)
{
	struct iscsi_transport *transport = session->transport;
	struct iscsi_cls_conn *conn;
	int err;

	conn = kzalloc(sizeof(*conn) + transport->conndata_size, GFP_KERNEL);
	if (!conn)
		return NULL;

	if (transport->conndata_size)
		conn->dd_data = &conn[1];

	INIT_LIST_HEAD(&conn->conn_list);
	conn->transport = transport;
	conn->cid = cid;

	/* this is released in the dev's release function */
	if (!get_device(&session->dev))
		goto free_conn;

	snprintf(conn->dev.bus_id, BUS_ID_SIZE, "connection%d:%u",
		 session->sid, cid);
	conn->dev.parent = &session->dev;
	conn->dev.release = iscsi_conn_release;
	err = device_register(&conn->dev);
	if (err) {
		dev_printk(KERN_ERR, &conn->dev, "iscsi: could not register "
			   "connection's dev\n");
		goto release_parent_ref;
	}
	transport_register_device(&conn->dev);
	return conn;

release_parent_ref:
	put_device(&session->dev);
free_conn:
	kfree(conn);
	return NULL;
}

EXPORT_SYMBOL_GPL(iscsi_create_conn);

/**
 * iscsi_destroy_conn - destroy iscsi class connection
 * @session: iscsi cls session
 *
 * This can be called from a LLD or iscsi_transport.
 **/
int iscsi_destroy_conn(struct iscsi_cls_conn *conn)
{
	transport_unregister_device(&conn->dev);
	device_unregister(&conn->dev);
	return 0;
}

EXPORT_SYMBOL_GPL(iscsi_destroy_conn);

/*
 * These functions are used only by software iscsi_transports
 * which do not allocate and more their scsi_hosts since this
 * is initiated from userspace.
 */

/*
 * iSCSI Session's hostdata organization:
 *
 *    *------------------* <== hostdata_session(host->hostdata)
 *    | ptr to class sess|
 *    |------------------| <== iscsi_hostdata(host->hostdata)
 *    | transport's data |
 *    *------------------*
 */

#define hostdata_privsize(_t)	(sizeof(unsigned long) + _t->hostdata_size + \
				 _t->hostdata_size % sizeof(unsigned long))

#define hostdata_session(_hostdata) (iscsi_ptr(*(unsigned long *)_hostdata))

/**
 * iscsi_transport_create_session - create iscsi cls session and host
 * scsit: scsi transport template
 * transport: iscsi transport template
 *
 * This can be used by software iscsi_transports that allocate
 * a session per scsi host.
 **/
struct Scsi_Host *
iscsi_transport_create_session(struct scsi_transport_template *scsit,
			       struct iscsi_transport *transport)
{
	struct iscsi_cls_session *session;
	struct Scsi_Host *shost;
	unsigned long flags;

	shost = scsi_host_alloc(transport->host_template,
				hostdata_privsize(transport));
	if (!shost) {
		printk(KERN_ERR "iscsi: can not allocate SCSI host for "
			"session\n");
		return NULL;
	}

	shost->max_id = 1;
	shost->max_channel = 0;
	shost->max_lun = transport->max_lun;
	shost->max_cmd_len = transport->max_cmd_len;
	shost->transportt = scsit;
	shost->transportt->create_work_queue = 1;

	if (scsi_add_host(shost, NULL))
		goto free_host;

	session = iscsi_create_session(shost, transport);
	if (!session)
		goto remove_host;

	*(unsigned long*)shost->hostdata = (unsigned long)session;
	spin_lock_irqsave(&sesslock, flags);
	list_add(&session->sess_list, &sesslist);
	spin_unlock_irqrestore(&sesslock, flags);
	return shost;

remove_host:
	scsi_remove_host(shost);
free_host:
	scsi_host_put(shost);
	return NULL;
}

EXPORT_SYMBOL_GPL(iscsi_transport_create_session);

/**
 * iscsi_transport_destroy_session - destroy session and scsi host
 * shost: scsi host
 *
 * This can be used by software iscsi_transports that allocate
 * a session per scsi host.
 **/
int iscsi_transport_destroy_session(struct Scsi_Host *shost)
{
	struct iscsi_cls_session *session;
	unsigned long flags;

	scsi_remove_host(shost);
	session = hostdata_session(shost->hostdata);
	spin_lock_irqsave(&sesslock, flags);
	list_del(&session->sess_list);
	spin_unlock_irqrestore(&sesslock, flags);
	iscsi_destroy_session(session);
	/* ref from host alloc */
	scsi_host_put(shost);
	return 0;
}

EXPORT_SYMBOL_GPL(iscsi_transport_destroy_session);

/*
 * iscsi interface functions
 */
static struct iscsi_internal *
iscsi_if_transport_lookup(struct iscsi_transport *tt)
{
	struct iscsi_internal *priv;
	unsigned long flags;

	spin_lock_irqsave(&iscsi_transport_lock, flags);
	list_for_each_entry(priv, &iscsi_transports, list) {
		if (tt == priv->iscsi_transport) {
			spin_unlock_irqrestore(&iscsi_transport_lock, flags);
			return priv;
		}
	}
	spin_unlock_irqrestore(&iscsi_transport_lock, flags);
	return NULL;
}

static inline struct list_head *skb_to_lh(struct sk_buff *skb)
{
	return (struct list_head *)&skb->cb;
}

static void*
mempool_zone_alloc_skb(gfp_t gfp_mask, void *pool_data)
{
	struct mempool_zone *zone = pool_data;

	return alloc_skb(zone->size, gfp_mask);
}

static void
mempool_zone_free_skb(void *element, void *pool_data)
{
	kfree_skb(element);
}

static void
mempool_zone_complete(struct mempool_zone *zone)
{
	unsigned long flags;
	struct list_head *lh, *n;

	spin_lock_irqsave(&zone->freelock, flags);
	list_for_each_safe(lh, n, &zone->freequeue) {
		struct sk_buff *skb = (struct sk_buff *)((char *)lh -
				offsetof(struct sk_buff, cb));
		if (!skb_shared(skb)) {
			list_del(skb_to_lh(skb));
			mempool_free(skb, zone->pool);
			atomic_dec(&zone->allocated);
		}
	}
	spin_unlock_irqrestore(&zone->freelock, flags);
}

static struct mempool_zone *
mempool_zone_init(unsigned max, unsigned size, unsigned hiwat)
{
	struct mempool_zone *zp;

	zp = kzalloc(sizeof(*zp), GFP_KERNEL);
	if (!zp)
		return NULL;

	zp->size = size;
	zp->hiwat = hiwat;
	INIT_LIST_HEAD(&zp->freequeue);
	spin_lock_init(&zp->freelock);
	atomic_set(&zp->allocated, 0);

	zp->pool = mempool_create(max, mempool_zone_alloc_skb,
				  mempool_zone_free_skb, zp);
	if (!zp->pool) {
		kfree(zp);
		return NULL;
	}

	return zp;
}

static void mempool_zone_destroy(struct mempool_zone *zp)
{
	mempool_destroy(zp->pool);
	kfree(zp);
}

static struct sk_buff*
mempool_zone_get_skb(struct mempool_zone *zone)
{
	struct sk_buff *skb;

	skb = mempool_alloc(zone->pool, GFP_ATOMIC);
	if (skb)
		atomic_inc(&zone->allocated);
	return skb;
}

static int
iscsi_unicast_skb(struct mempool_zone *zone, struct sk_buff *skb)
{
	unsigned long flags;
	int rc;

	skb_get(skb);
	rc = netlink_unicast(nls, skb, daemon_pid, MSG_DONTWAIT);
	if (rc < 0) {
		mempool_free(skb, zone->pool);
		printk(KERN_ERR "iscsi: can not unicast skb (%d)\n", rc);
		return rc;
	}

	spin_lock_irqsave(&zone->freelock, flags);
	list_add(skb_to_lh(skb), &zone->freequeue);
	spin_unlock_irqrestore(&zone->freelock, flags);

	return 0;
}

int iscsi_recv_pdu(struct iscsi_cls_conn *conn, struct iscsi_hdr *hdr,
		   char *data, uint32_t data_size)
{
	struct nlmsghdr	*nlh;
	struct sk_buff *skb;
	struct iscsi_uevent *ev;
	char *pdu;
	int len = NLMSG_SPACE(sizeof(*ev) + sizeof(struct iscsi_hdr) +
			      data_size);

	mempool_zone_complete(conn->z_pdu);

	skb = mempool_zone_get_skb(conn->z_pdu);
	if (!skb) {
		iscsi_conn_error(conn, ISCSI_ERR_CONN_FAILED);
		dev_printk(KERN_ERR, &conn->dev, "iscsi: can not deliver "
			   "control PDU: OOM\n");
		return -ENOMEM;
	}

	nlh = __nlmsg_put(skb, daemon_pid, 0, 0, (len - sizeof(*nlh)), 0);
	ev = NLMSG_DATA(nlh);
	memset(ev, 0, sizeof(*ev));
	ev->transport_handle = iscsi_handle(conn->transport);
	ev->type = ISCSI_KEVENT_RECV_PDU;
	if (atomic_read(&conn->z_pdu->allocated) >= conn->z_pdu->hiwat)
		ev->iferror = -ENOMEM;
	ev->r.recv_req.cid = conn->cid;
	ev->r.recv_req.sid = iscsi_conn_get_sid(conn);
	pdu = (char*)ev + sizeof(*ev);
	memcpy(pdu, hdr, sizeof(struct iscsi_hdr));
	memcpy(pdu + sizeof(struct iscsi_hdr), data, data_size);

	return iscsi_unicast_skb(conn->z_pdu, skb);
}
EXPORT_SYMBOL_GPL(iscsi_recv_pdu);

void iscsi_conn_error(struct iscsi_cls_conn *conn, enum iscsi_err error)
{
	struct nlmsghdr	*nlh;
	struct sk_buff	*skb;
	struct iscsi_uevent *ev;
	int len = NLMSG_SPACE(sizeof(*ev));

	mempool_zone_complete(conn->z_error);

	skb = mempool_zone_get_skb(conn->z_error);
	if (!skb) {
		dev_printk(KERN_ERR, &conn->dev, "iscsi: gracefully ignored "
			  "conn error (%d)\n", error);
		return;
	}

	nlh = __nlmsg_put(skb, daemon_pid, 0, 0, (len - sizeof(*nlh)), 0);
	ev = NLMSG_DATA(nlh);
	ev->transport_handle = iscsi_handle(conn->transport);
	ev->type = ISCSI_KEVENT_CONN_ERROR;
	if (atomic_read(&conn->z_error->allocated) >= conn->z_error->hiwat)
		ev->iferror = -ENOMEM;
	ev->r.connerror.error = error;
	ev->r.connerror.cid = conn->cid;
	ev->r.connerror.sid = iscsi_conn_get_sid(conn);

	iscsi_unicast_skb(conn->z_error, skb);

	dev_printk(KERN_INFO, &conn->dev, "iscsi: detected conn error (%d)\n",
		   error);
}
EXPORT_SYMBOL_GPL(iscsi_conn_error);

static int
iscsi_if_send_reply(int pid, int seq, int type, int done, int multi,
		      void *payload, int size)
{
	struct sk_buff	*skb;
	struct nlmsghdr	*nlh;
	int len = NLMSG_SPACE(size);
	int flags = multi ? NLM_F_MULTI : 0;
	int t = done ? NLMSG_DONE : type;

	mempool_zone_complete(z_reply);

	skb = mempool_zone_get_skb(z_reply);
	/*
	 * FIXME:
	 * user is supposed to react on iferror == -ENOMEM;
	 * see iscsi_if_rx().
	 */
	BUG_ON(!skb);

	nlh = __nlmsg_put(skb, pid, seq, t, (len - sizeof(*nlh)), 0);
	nlh->nlmsg_flags = flags;
	memcpy(NLMSG_DATA(nlh), payload, size);
	return iscsi_unicast_skb(z_reply, skb);
}

static int
iscsi_if_get_stats(struct iscsi_transport *transport, struct nlmsghdr *nlh)
{
	struct iscsi_uevent *ev = NLMSG_DATA(nlh);
	struct iscsi_stats *stats;
	struct sk_buff *skbstat;
	struct iscsi_cls_conn *conn;
	struct nlmsghdr	*nlhstat;
	struct iscsi_uevent *evstat;
	int len = NLMSG_SPACE(sizeof(*ev) +
			      sizeof(struct iscsi_stats) +
			      sizeof(struct iscsi_stats_custom) *
			      ISCSI_STATS_CUSTOM_MAX);
	int err = 0;

	conn = iscsi_conn_lookup(ev->u.get_stats.sid, ev->u.get_stats.cid);
	if (!conn)
		return -EEXIST;

	do {
		int actual_size;

		mempool_zone_complete(conn->z_pdu);

		skbstat = mempool_zone_get_skb(conn->z_pdu);
		if (!skbstat) {
			dev_printk(KERN_ERR, &conn->dev, "iscsi: can not "
				   "deliver stats: OOM\n");
			return -ENOMEM;
		}

		nlhstat = __nlmsg_put(skbstat, daemon_pid, 0, 0,
				      (len - sizeof(*nlhstat)), 0);
		evstat = NLMSG_DATA(nlhstat);
		memset(evstat, 0, sizeof(*evstat));
		evstat->transport_handle = iscsi_handle(conn->transport);
		evstat->type = nlh->nlmsg_type;
		if (atomic_read(&conn->z_pdu->allocated) >= conn->z_pdu->hiwat)
			evstat->iferror = -ENOMEM;
		evstat->u.get_stats.cid =
			ev->u.get_stats.cid;
		evstat->u.get_stats.sid =
			ev->u.get_stats.sid;
		stats = (struct iscsi_stats *)
			((char*)evstat + sizeof(*evstat));
		memset(stats, 0, sizeof(*stats));

		transport->get_stats(conn, stats);
		actual_size = NLMSG_SPACE(sizeof(struct iscsi_uevent) +
					  sizeof(struct iscsi_stats) +
					  sizeof(struct iscsi_stats_custom) *
					  stats->custom_length);
		actual_size -= sizeof(*nlhstat);
		actual_size = NLMSG_LENGTH(actual_size);
		skb_trim(skbstat, NLMSG_ALIGN(actual_size));
		nlhstat->nlmsg_len = actual_size;

		err = iscsi_unicast_skb(conn->z_pdu, skbstat);
	} while (err < 0 && err != -ECONNREFUSED);

	return err;
}

static int
iscsi_if_create_session(struct iscsi_internal *priv, struct iscsi_uevent *ev)
{
	struct iscsi_transport *transport = priv->iscsi_transport;
	struct iscsi_cls_session *session;
	uint32_t hostno;

	session = transport->create_session(&priv->t,
					    ev->u.c_session.initial_cmdsn,
					    &hostno);
	if (!session)
		return -ENOMEM;

	ev->r.c_session_ret.host_no = hostno;
	ev->r.c_session_ret.sid = session->sid;
	return 0;
}

static int
iscsi_if_create_conn(struct iscsi_transport *transport, struct iscsi_uevent *ev)
{
	struct iscsi_cls_conn *conn;
	struct iscsi_cls_session *session;
	unsigned long flags;

	session = iscsi_session_lookup(ev->u.c_conn.sid);
	if (!session) {
		printk(KERN_ERR "iscsi: invalid session %d\n",
		       ev->u.c_conn.sid);
		return -EINVAL;
	}

	conn = transport->create_conn(session, ev->u.c_conn.cid);
	if (!conn) {
		printk(KERN_ERR "iscsi: couldn't create a new "
			   "connection for session %d\n",
			   session->sid);
		return -ENOMEM;
	}

	conn->z_pdu = mempool_zone_init(Z_MAX_PDU,
			NLMSG_SPACE(sizeof(struct iscsi_uevent) +
				    sizeof(struct iscsi_hdr) +
				    DEFAULT_MAX_RECV_DATA_SEGMENT_LENGTH),
			Z_HIWAT_PDU);
	if (!conn->z_pdu) {
		dev_printk(KERN_ERR, &conn->dev, "iscsi: can not allocate "
			   "pdu zone for new conn\n");
		goto destroy_conn;
	}

	conn->z_error = mempool_zone_init(Z_MAX_ERROR,
			NLMSG_SPACE(sizeof(struct iscsi_uevent)),
			Z_HIWAT_ERROR);
	if (!conn->z_error) {
		dev_printk(KERN_ERR, &conn->dev, "iscsi: can not allocate "
			   "error zone for new conn\n");
		goto free_pdu_pool;
	}

	ev->r.c_conn_ret.sid = session->sid;
	ev->r.c_conn_ret.cid = conn->cid;

	spin_lock_irqsave(&connlock, flags);
	list_add(&conn->conn_list, &connlist);
	conn->active = 1;
	spin_unlock_irqrestore(&connlock, flags);

	return 0;

free_pdu_pool:
	mempool_zone_destroy(conn->z_pdu);
destroy_conn:
	if (transport->destroy_conn)
		transport->destroy_conn(conn->dd_data);
	return -ENOMEM;
}

static int
iscsi_if_destroy_conn(struct iscsi_transport *transport, struct iscsi_uevent *ev)
{
	unsigned long flags;
	struct iscsi_cls_conn *conn;
	struct mempool_zone *z_error, *z_pdu;

	conn = iscsi_conn_lookup(ev->u.d_conn.sid, ev->u.d_conn.cid);
	if (!conn)
		return -EINVAL;
	spin_lock_irqsave(&connlock, flags);
	conn->active = 0;
	list_del(&conn->conn_list);
	spin_unlock_irqrestore(&connlock, flags);

	z_pdu = conn->z_pdu;
	z_error = conn->z_error;

	if (transport->destroy_conn)
		transport->destroy_conn(conn);

	mempool_zone_destroy(z_pdu);
	mempool_zone_destroy(z_error);

	return 0;
}

static int
iscsi_if_recv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
{
	int err = 0;
	struct iscsi_uevent *ev = NLMSG_DATA(nlh);
	struct iscsi_transport *transport = NULL;
	struct iscsi_internal *priv;
	struct iscsi_cls_session *session;
	struct iscsi_cls_conn *conn;

	priv = iscsi_if_transport_lookup(iscsi_ptr(ev->transport_handle));
	if (!priv)
		return -EINVAL;
	transport = priv->iscsi_transport;

	if (!try_module_get(transport->owner))
		return -EINVAL;

	switch (nlh->nlmsg_type) {
	case ISCSI_UEVENT_CREATE_SESSION:
		err = iscsi_if_create_session(priv, ev);
		break;
	case ISCSI_UEVENT_DESTROY_SESSION:
		session = iscsi_session_lookup(ev->u.d_session.sid);
		if (session)
			transport->destroy_session(session);
		else
			err = -EINVAL;
		break;
	case ISCSI_UEVENT_CREATE_CONN:
		err = iscsi_if_create_conn(transport, ev);
		break;
	case ISCSI_UEVENT_DESTROY_CONN:
		err = iscsi_if_destroy_conn(transport, ev);
		break;
	case ISCSI_UEVENT_BIND_CONN:
		session = iscsi_session_lookup(ev->u.b_conn.sid);
		conn = iscsi_conn_lookup(ev->u.b_conn.sid, ev->u.b_conn.cid);

		if (session && conn)
			ev->r.retcode =	transport->bind_conn(session, conn,
					ev->u.b_conn.transport_fd,
					ev->u.b_conn.is_leading);
		else
			err = -EINVAL;
		break;
	case ISCSI_UEVENT_SET_PARAM:
		conn = iscsi_conn_lookup(ev->u.set_param.sid, ev->u.set_param.cid);
		if (conn)
			ev->r.retcode =	transport->set_param(conn,
				ev->u.set_param.param, ev->u.set_param.value);
		else
			err = -EINVAL;
		break;
	case ISCSI_UEVENT_START_CONN:
		conn = iscsi_conn_lookup(ev->u.start_conn.sid, ev->u.start_conn.cid);
		if (conn)
			ev->r.retcode = transport->start_conn(conn);
		else
			err = -EINVAL;

		break;
	case ISCSI_UEVENT_STOP_CONN:
		conn = iscsi_conn_lookup(ev->u.stop_conn.sid, ev->u.stop_conn.cid);
		if (conn)
			transport->stop_conn(conn, ev->u.stop_conn.flag);
		else
			err = -EINVAL;
		break;
	case ISCSI_UEVENT_SEND_PDU:
		conn = iscsi_conn_lookup(ev->u.send_pdu.sid, ev->u.send_pdu.cid);
		if (conn)
			ev->r.retcode =	transport->send_pdu(conn,
				(struct iscsi_hdr*)((char*)ev + sizeof(*ev)),
				(char*)ev + sizeof(*ev) + ev->u.send_pdu.hdr_size,
				ev->u.send_pdu.data_size);
		else
			err = -EINVAL;
		break;
	case ISCSI_UEVENT_GET_STATS:
		err = iscsi_if_get_stats(transport, nlh);
		break;
	default:
		err = -EINVAL;
		break;
	}

	module_put(transport->owner);
	return err;
}

/*
 * Get message from skb (based on rtnetlink_rcv_skb).  Each message is
 * processed by iscsi_if_recv_msg.  Malformed skbs with wrong lengths or
 * invalid creds are discarded silently.
 */
static void
iscsi_if_rx(struct sock *sk, int len)
{
	struct sk_buff *skb;

	mutex_lock(&rx_queue_mutex);
	while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
		if (NETLINK_CREDS(skb)->uid) {
			skb_pull(skb, skb->len);
			goto free_skb;
		}
		daemon_pid = NETLINK_CREDS(skb)->pid;

		while (skb->len >= NLMSG_SPACE(0)) {
			int err;
			uint32_t rlen;
			struct nlmsghdr	*nlh;
			struct iscsi_uevent *ev;

			nlh = (struct nlmsghdr *)skb->data;
			if (nlh->nlmsg_len < sizeof(*nlh) ||
			    skb->len < nlh->nlmsg_len) {
				break;
			}

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

			err = iscsi_if_recv_msg(skb, nlh);
			if (err) {
				ev->type = ISCSI_KEVENT_IF_ERROR;
				ev->iferror = err;
			}
			do {
				/*
				 * special case for GET_STATS:
				 * on success - sending reply and stats from
				 * inside of if_recv_msg(),
				 * on error - fall through.
				 */
				if (ev->type == ISCSI_UEVENT_GET_STATS && !err)
					break;
				err = iscsi_if_send_reply(
					NETLINK_CREDS(skb)->pid, nlh->nlmsg_seq,
					nlh->nlmsg_type, 0, 0, ev, sizeof(*ev));
				if (atomic_read(&z_reply->allocated) >=
						z_reply->hiwat)
					ev->iferror = -ENOMEM;
			} while (err < 0 && err != -ECONNREFUSED);
			skb_pull(skb, rlen);
		}
free_skb:
		kfree_skb(skb);
	}
	mutex_unlock(&rx_queue_mutex);
}

#define iscsi_cdev_to_conn(_cdev) \
	iscsi_dev_to_conn(_cdev->dev)

/*
 * iSCSI connection attrs
 */
#define iscsi_conn_int_attr_show(param, format)				\
static ssize_t								\
show_conn_int_param_##param(struct class_device *cdev, char *buf)	\
{									\
	uint32_t value = 0;						\
	struct iscsi_cls_conn *conn = iscsi_cdev_to_conn(cdev);		\
	struct iscsi_transport *t = conn->transport;			\
									\
	t->get_conn_param(conn, param, &value);				\
	return snprintf(buf, 20, format"\n", value);			\
}

#define iscsi_conn_int_attr(field, param, format)			\
	iscsi_conn_int_attr_show(param, format)				\
static CLASS_DEVICE_ATTR(field, S_IRUGO, show_conn_int_param_##param, NULL);

iscsi_conn_int_attr(max_recv_dlength, ISCSI_PARAM_MAX_RECV_DLENGTH, "%u");
iscsi_conn_int_attr(max_xmit_dlength, ISCSI_PARAM_MAX_XMIT_DLENGTH, "%u");
iscsi_conn_int_attr(header_digest, ISCSI_PARAM_HDRDGST_EN, "%d");
iscsi_conn_int_attr(data_digest, ISCSI_PARAM_DATADGST_EN, "%d");
iscsi_conn_int_attr(ifmarker, ISCSI_PARAM_IFMARKER_EN, "%d");
iscsi_conn_int_attr(ofmarker, ISCSI_PARAM_OFMARKER_EN, "%d");

#define iscsi_cdev_to_session(_cdev) \
	iscsi_dev_to_session(_cdev->dev)

/*
 * iSCSI session attrs
 */
#define iscsi_session_int_attr_show(param, format)			\
static ssize_t								\
show_session_int_param_##param(struct class_device *cdev, char *buf)	\
{									\
	uint32_t value = 0;						\
	struct iscsi_cls_session *session = iscsi_cdev_to_session(cdev);	\
	struct iscsi_transport *t = session->transport;			\
									\
	t->get_session_param(session, param, &value);			\
	return snprintf(buf, 20, format"\n", value);			\
}

#define iscsi_session_int_attr(field, param, format)			\
	iscsi_session_int_attr_show(param, format)			\
static CLASS_DEVICE_ATTR(field, S_IRUGO, show_session_int_param_##param, NULL);

iscsi_session_int_attr(initial_r2t, ISCSI_PARAM_INITIAL_R2T_EN, "%d");
iscsi_session_int_attr(max_outstanding_r2t, ISCSI_PARAM_MAX_R2T, "%hu");
iscsi_session_int_attr(immediate_data, ISCSI_PARAM_IMM_DATA_EN, "%d");
iscsi_session_int_attr(first_burst_len, ISCSI_PARAM_FIRST_BURST, "%u");
iscsi_session_int_attr(max_burst_len, ISCSI_PARAM_MAX_BURST, "%u");
iscsi_session_int_attr(data_pdu_in_order, ISCSI_PARAM_PDU_INORDER_EN, "%d");
iscsi_session_int_attr(data_seq_in_order, ISCSI_PARAM_DATASEQ_INORDER_EN, "%d");
iscsi_session_int_attr(erl, ISCSI_PARAM_ERL, "%d");

#define SETUP_SESSION_RD_ATTR(field, param)				\
	if (priv->param_mask & (1 << param)) {				\
		priv->session_attrs[count] = &class_device_attr_##field;\
		count++;						\
	}

#define SETUP_CONN_RD_ATTR(field, param)				\
	if (priv->param_mask & (1 << param)) {				\
		priv->conn_attrs[count] = &class_device_attr_##field;	\
		count++;						\
	}

static int iscsi_session_match(struct attribute_container *cont,
			   struct device *dev)
{
	struct iscsi_cls_session *session;
	struct Scsi_Host *shost;
	struct iscsi_internal *priv;

	if (!iscsi_is_session_dev(dev))
		return 0;

	session = iscsi_dev_to_session(dev);
	shost = iscsi_session_to_shost(session);
	if (!shost->transportt)
		return 0;

	priv = to_iscsi_internal(shost->transportt);
	if (priv->session_cont.ac.class != &iscsi_session_class.class)
		return 0;

	return &priv->session_cont.ac == cont;
}

static int iscsi_conn_match(struct attribute_container *cont,
			   struct device *dev)
{
	struct iscsi_cls_session *session;
	struct iscsi_cls_conn *conn;
	struct Scsi_Host *shost;
	struct iscsi_internal *priv;

	if (!iscsi_is_conn_dev(dev))
		return 0;

	conn = iscsi_dev_to_conn(dev);
	session = iscsi_dev_to_session(conn->dev.parent);
	shost = iscsi_session_to_shost(session);

	if (!shost->transportt)
		return 0;

	priv = to_iscsi_internal(shost->transportt);
	if (priv->conn_cont.ac.class != &iscsi_connection_class.class)
		return 0;

	return &priv->conn_cont.ac == cont;
}

struct scsi_transport_template *
iscsi_register_transport(struct iscsi_transport *tt)
{
	struct iscsi_internal *priv;
	unsigned long flags;
	int count = 0, err;

	BUG_ON(!tt);

	priv = iscsi_if_transport_lookup(tt);
	if (priv)
		return NULL;

	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return NULL;
	INIT_LIST_HEAD(&priv->list);
	priv->iscsi_transport = tt;

	priv->cdev.class = &iscsi_transport_class;
	snprintf(priv->cdev.class_id, BUS_ID_SIZE, "%s", tt->name);
	err = class_device_register(&priv->cdev);
	if (err)
		goto free_priv;

	err = sysfs_create_group(&priv->cdev.kobj, &iscsi_transport_group);
	if (err)
		goto unregister_cdev;

	/* setup parameters mask */
	priv->param_mask = 0xFFFFFFFF;
	if (!(tt->caps & CAP_MULTI_R2T))
		priv->param_mask &= ~(1 << ISCSI_PARAM_MAX_R2T);
	if (!(tt->caps & CAP_HDRDGST))
		priv->param_mask &= ~(1 << ISCSI_PARAM_HDRDGST_EN);
	if (!(tt->caps & CAP_DATADGST))
		priv->param_mask &= ~(1 << ISCSI_PARAM_DATADGST_EN);
	if (!(tt->caps & CAP_MARKERS)) {
		priv->param_mask &= ~(1 << ISCSI_PARAM_IFMARKER_EN);
		priv->param_mask &= ~(1 << ISCSI_PARAM_OFMARKER_EN);
	}

	/* connection parameters */
	priv->conn_cont.ac.attrs = &priv->conn_attrs[0];
	priv->conn_cont.ac.class = &iscsi_connection_class.class;
	priv->conn_cont.ac.match = iscsi_conn_match;
	transport_container_register(&priv->conn_cont);

	SETUP_CONN_RD_ATTR(max_recv_dlength, ISCSI_PARAM_MAX_RECV_DLENGTH);
	SETUP_CONN_RD_ATTR(max_xmit_dlength, ISCSI_PARAM_MAX_XMIT_DLENGTH);
	SETUP_CONN_RD_ATTR(header_digest, ISCSI_PARAM_HDRDGST_EN);
	SETUP_CONN_RD_ATTR(data_digest, ISCSI_PARAM_DATADGST_EN);
	SETUP_CONN_RD_ATTR(ifmarker, ISCSI_PARAM_IFMARKER_EN);
	SETUP_CONN_RD_ATTR(ofmarker, ISCSI_PARAM_OFMARKER_EN);

	BUG_ON(count > ISCSI_CONN_ATTRS);
	priv->conn_attrs[count] = NULL;
	count = 0;

	/* session parameters */
	priv->session_cont.ac.attrs = &priv->session_attrs[0];
	priv->session_cont.ac.class = &iscsi_session_class.class;
	priv->session_cont.ac.match = iscsi_session_match;
	transport_container_register(&priv->session_cont);

	SETUP_SESSION_RD_ATTR(initial_r2t, ISCSI_PARAM_INITIAL_R2T_EN);
	SETUP_SESSION_RD_ATTR(max_outstanding_r2t, ISCSI_PARAM_MAX_R2T);
	SETUP_SESSION_RD_ATTR(immediate_data, ISCSI_PARAM_IMM_DATA_EN);
	SETUP_SESSION_RD_ATTR(first_burst_len, ISCSI_PARAM_FIRST_BURST);
	SETUP_SESSION_RD_ATTR(max_burst_len, ISCSI_PARAM_MAX_BURST);
	SETUP_SESSION_RD_ATTR(data_pdu_in_order, ISCSI_PARAM_PDU_INORDER_EN);
	SETUP_SESSION_RD_ATTR(data_seq_in_order,ISCSI_PARAM_DATASEQ_INORDER_EN)
	SETUP_SESSION_RD_ATTR(erl, ISCSI_PARAM_ERL);

	BUG_ON(count > ISCSI_SESSION_ATTRS);
	priv->session_attrs[count] = NULL;

	spin_lock_irqsave(&iscsi_transport_lock, flags);
	list_add(&priv->list, &iscsi_transports);
	spin_unlock_irqrestore(&iscsi_transport_lock, flags);

	printk(KERN_NOTICE "iscsi: registered transport (%s)\n", tt->name);
	return &priv->t;

unregister_cdev:
	class_device_unregister(&priv->cdev);
free_priv:
	kfree(priv);
	return NULL;
}
EXPORT_SYMBOL_GPL(iscsi_register_transport);

int iscsi_unregister_transport(struct iscsi_transport *tt)
{
	struct iscsi_internal *priv;
	unsigned long flags;

	BUG_ON(!tt);

	mutex_lock(&rx_queue_mutex);

	priv = iscsi_if_transport_lookup(tt);
	BUG_ON (!priv);

	spin_lock_irqsave(&iscsi_transport_lock, flags);
	list_del(&priv->list);
	spin_unlock_irqrestore(&iscsi_transport_lock, flags);

	transport_container_unregister(&priv->conn_cont);
	transport_container_unregister(&priv->session_cont);

	sysfs_remove_group(&priv->cdev.kobj, &iscsi_transport_group);
	class_device_unregister(&priv->cdev);
	mutex_unlock(&rx_queue_mutex);

	return 0;
}
EXPORT_SYMBOL_GPL(iscsi_unregister_transport);

static int
iscsi_rcv_nl_event(struct notifier_block *this, unsigned long event, void *ptr)
{
	struct netlink_notify *n = ptr;

	if (event == NETLINK_URELEASE &&
	    n->protocol == NETLINK_ISCSI && n->pid) {
		struct iscsi_cls_conn *conn;
		unsigned long flags;

		mempool_zone_complete(z_reply);
		spin_lock_irqsave(&connlock, flags);
		list_for_each_entry(conn, &connlist, conn_list) {
			mempool_zone_complete(conn->z_error);
			mempool_zone_complete(conn->z_pdu);
		}
		spin_unlock_irqrestore(&connlock, flags);
	}

	return NOTIFY_DONE;
}

static struct notifier_block iscsi_nl_notifier = {
	.notifier_call	= iscsi_rcv_nl_event,
};

static __init int iscsi_transport_init(void)
{
	int err;

	err = class_register(&iscsi_transport_class);
	if (err)
		return err;

	err = transport_class_register(&iscsi_connection_class);
	if (err)
		goto unregister_transport_class;

	err = transport_class_register(&iscsi_session_class);
	if (err)
		goto unregister_conn_class;

	err = netlink_register_notifier(&iscsi_nl_notifier);
	if (err)
		goto unregister_session_class;

	nls = netlink_kernel_create(NETLINK_ISCSI, 1, iscsi_if_rx,
			THIS_MODULE);
	if (!nls) {
		err = -ENOBUFS;
		goto unregister_notifier;
	}

	z_reply = mempool_zone_init(Z_MAX_REPLY,
		NLMSG_SPACE(sizeof(struct iscsi_uevent)), Z_HIWAT_REPLY);
	if (z_reply)
		return 0;

	sock_release(nls->sk_socket);
unregister_notifier:
	netlink_unregister_notifier(&iscsi_nl_notifier);
unregister_session_class:
	transport_class_unregister(&iscsi_session_class);
unregister_conn_class:
	transport_class_unregister(&iscsi_connection_class);
unregister_transport_class:
	class_unregister(&iscsi_transport_class);
	return err;
}

static void __exit iscsi_transport_exit(void)
{
	mempool_zone_destroy(z_reply);
	sock_release(nls->sk_socket);
	netlink_unregister_notifier(&iscsi_nl_notifier);
	transport_class_unregister(&iscsi_connection_class);
	transport_class_unregister(&iscsi_session_class);
	class_unregister(&iscsi_transport_class);
}

module_init(iscsi_transport_init);
module_exit(iscsi_transport_exit);

MODULE_AUTHOR("Mike Christie <michaelc@cs.wisc.edu>, "
	      "Dmitry Yusupov <dmitry_yus@yahoo.com>, "
	      "Alex Aizman <itn780@yahoo.com>");
MODULE_DESCRIPTION("iSCSI Transport Interface");
MODULE_LICENSE("GPL");