/*
   * iSCSI Initiator over TCP/IP Data-Path
   *
   * Copyright (C) 2004 Dmitry Yusupov
   * Copyright (C) 2004 Alex Aizman

   * Copyright (C) 2005 - 2006 Mike Christie
   * Copyright (C) 2006 Red Hat, Inc.  All rights reserved.

   * maintained by open-iscsi@googlegroups.com
   *
   * 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.
   *
   * See the file COPYING included with this distribution for more details.
   *
   * Credits:
   *	Christoph Hellwig
   *	FUJITA Tomonori
   *	Arne Redlich
   *	Zhenyu Wang
   */
  
  #include <linux/types.h>

  #include <linux/inet.h>

  #include <linux/slab.h>

  #include <linux/file.h>

  #include <linux/blkdev.h>
  #include <linux/crypto.h>
  #include <linux/delay.h>
  #include <linux/kfifo.h>
  #include <linux/scatterlist.h>

  #include <linux/module.h>

  #include <net/tcp.h>
  #include <scsi/scsi_cmnd.h>

  #include <scsi/scsi_device.h>

  #include <scsi/scsi_host.h>
  #include <scsi/scsi.h>
  #include <scsi/scsi_transport_iscsi.h>
  
  #include "iscsi_tcp.h"

  MODULE_AUTHOR("Mike Christie <michaelc@cs.wisc.edu>, "
  	      "Dmitry Yusupov <dmitry_yus@yahoo.com>, "

  	      "Alex Aizman <itn780@yahoo.com>");
  MODULE_DESCRIPTION("iSCSI/TCP data-path");
  MODULE_LICENSE("GPL");

  static struct scsi_transport_template *iscsi_sw_tcp_scsi_transport;
  static struct scsi_host_template iscsi_sw_tcp_sht;
  static struct iscsi_transport iscsi_sw_tcp_transport;

  static unsigned int iscsi_max_lun = 512;
  module_param_named(max_lun, iscsi_max_lun, uint, S_IRUGO);

  static int iscsi_sw_tcp_dbg;
  module_param_named(debug_iscsi_tcp, iscsi_sw_tcp_dbg, int,
  		   S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(debug_iscsi_tcp, "Turn on debugging for iscsi_tcp module "
  		 "Set to 1 to turn on, and zero to turn off. Default is off.");
  
  #define ISCSI_SW_TCP_DBG(_conn, dbg_fmt, arg...)		\
  	do {							\
  		if (iscsi_sw_tcp_dbg)				\
  			iscsi_conn_printk(KERN_INFO, _conn,	\
  					     "%s " dbg_fmt,	\
  					     __func__, ##arg);	\
  	} while (0);

  /**

   * iscsi_sw_tcp_recv - TCP receive in sendfile fashion

   * @rd_desc: read descriptor
   * @skb: socket buffer
   * @offset: offset in skb
   * @len: skb->len - offset

   */
  static int iscsi_sw_tcp_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
  			     unsigned int offset, size_t len)

  {
  	struct iscsi_conn *conn = rd_desc->arg.data;
  	unsigned int consumed, total_consumed = 0;
  	int status;

  	ISCSI_SW_TCP_DBG(conn, "in %d bytes
  ", skb->len - offset);

  
  	do {
  		status = 0;
  		consumed = iscsi_tcp_recv_skb(conn, skb, offset, 0, &status);
  		offset += consumed;
  		total_consumed += consumed;
  	} while (consumed != 0 && status != ISCSI_TCP_SKB_DONE);

  	ISCSI_SW_TCP_DBG(conn, "read %d bytes status %d
  ",
  			 skb->len - offset, status);

  	return total_consumed;

  }

  /**
   * iscsi_sw_sk_state_check - check socket state
   * @sk: socket
   *
   * If the socket is in CLOSE or CLOSE_WAIT we should
   * not close the connection if there is still some
   * data pending.

   *
   * Must be called with sk_callback_lock.

   */
  static inline int iscsi_sw_sk_state_check(struct sock *sk)
  {

  	struct iscsi_conn *conn = sk->sk_user_data;

  	if ((sk->sk_state == TCP_CLOSE_WAIT || sk->sk_state == TCP_CLOSE) &&
  	    !atomic_read(&sk->sk_rmem_alloc)) {
  		ISCSI_SW_TCP_DBG(conn, "TCP_CLOSE|TCP_CLOSE_WAIT
  ");
  		iscsi_conn_failure(conn, ISCSI_ERR_TCP_CONN_CLOSE);
  		return -ECONNRESET;
  	}

  	return 0;
  }

  static void iscsi_sw_tcp_data_ready(struct sock *sk, int flag)

  {

  	struct iscsi_conn *conn;
  	struct iscsi_tcp_conn *tcp_conn;

  	read_descriptor_t rd_desc;
  
  	read_lock(&sk->sk_callback_lock);

  	conn = sk->sk_user_data;
  	if (!conn) {
  		read_unlock(&sk->sk_callback_lock);
  		return;
  	}
  	tcp_conn = conn->dd_data;

  	/*

  	 * Use rd_desc to pass 'conn' to iscsi_tcp_recv.

  	 * We set count to 1 because we want the network layer to

  	 * hand us all the skbs that are available. iscsi_tcp_recv

  	 * handled pdus that cross buffers or pdus that still need data.
  	 */

  	rd_desc.arg.data = conn;

  	rd_desc.count = 1;

  	tcp_read_sock(sk, &rd_desc, iscsi_sw_tcp_recv);

  	iscsi_sw_sk_state_check(sk);

  	/* If we had to (atomically) map a highmem page,
  	 * unmap it now. */

  	iscsi_tcp_segment_unmap(&tcp_conn->in.segment);

  	read_unlock(&sk->sk_callback_lock);

  }

  static void iscsi_sw_tcp_state_change(struct sock *sk)

  {

  	struct iscsi_tcp_conn *tcp_conn;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn;

  	struct iscsi_conn *conn;
  	struct iscsi_session *session;
  	void (*old_state_change)(struct sock *);
  
  	read_lock(&sk->sk_callback_lock);

  	conn = sk->sk_user_data;
  	if (!conn) {
  		read_unlock(&sk->sk_callback_lock);
  		return;
  	}

  	session = conn->session;

  	iscsi_sw_sk_state_check(sk);

  	tcp_conn = conn->dd_data;

  	tcp_sw_conn = tcp_conn->dd_data;
  	old_state_change = tcp_sw_conn->old_state_change;

  
  	read_unlock(&sk->sk_callback_lock);
  
  	old_state_change(sk);
  }
  
  /**
   * iscsi_write_space - Called when more output buffer space is available
   * @sk: socket space is available for
   **/

  static void iscsi_sw_tcp_write_space(struct sock *sk)

  {

  	struct iscsi_conn *conn;
  	struct iscsi_tcp_conn *tcp_conn;
  	struct iscsi_sw_tcp_conn *tcp_sw_conn;
  	void (*old_write_space)(struct sock *);
  
  	read_lock_bh(&sk->sk_callback_lock);
  	conn = sk->sk_user_data;
  	if (!conn) {
  		read_unlock_bh(&sk->sk_callback_lock);
  		return;
  	}
  
  	tcp_conn = conn->dd_data;
  	tcp_sw_conn = tcp_conn->dd_data;
  	old_write_space = tcp_sw_conn->old_write_space;
  	read_unlock_bh(&sk->sk_callback_lock);
  
  	old_write_space(sk);

  	ISCSI_SW_TCP_DBG(conn, "iscsi_write_space
  ");

  	iscsi_conn_queue_work(conn);

  }

  static void iscsi_sw_tcp_conn_set_callbacks(struct iscsi_conn *conn)

  {

  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
  	struct sock *sk = tcp_sw_conn->sock->sk;

  
  	/* assign new callbacks */
  	write_lock_bh(&sk->sk_callback_lock);
  	sk->sk_user_data = conn;

  	tcp_sw_conn->old_data_ready = sk->sk_data_ready;
  	tcp_sw_conn->old_state_change = sk->sk_state_change;
  	tcp_sw_conn->old_write_space = sk->sk_write_space;
  	sk->sk_data_ready = iscsi_sw_tcp_data_ready;
  	sk->sk_state_change = iscsi_sw_tcp_state_change;
  	sk->sk_write_space = iscsi_sw_tcp_write_space;

  	write_unlock_bh(&sk->sk_callback_lock);
  }

  static void

  iscsi_sw_tcp_conn_restore_callbacks(struct iscsi_conn *conn)

  {

  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

  	struct sock *sk = tcp_sw_conn->sock->sk;

  
  	/* restore socket callbacks, see also: iscsi_conn_set_callbacks() */
  	write_lock_bh(&sk->sk_callback_lock);
  	sk->sk_user_data    = NULL;

  	sk->sk_data_ready   = tcp_sw_conn->old_data_ready;
  	sk->sk_state_change = tcp_sw_conn->old_state_change;
  	sk->sk_write_space  = tcp_sw_conn->old_write_space;

  	sk->sk_no_check	 = 0;
  	write_unlock_bh(&sk->sk_callback_lock);
  }
  
  /**

   * iscsi_sw_tcp_xmit_segment - transmit segment

   * @tcp_conn: the iSCSI TCP connection

   * @segment: the buffer to transmnit
   *
   * This function transmits as much of the buffer as
   * the network layer will accept, and returns the number of
   * bytes transmitted.
   *
   * If CRC hashing is enabled, the function will compute the
   * hash as it goes. When the entire segment has been transmitted,
   * it will retrieve the hash value and send it as well.
   */

  static int iscsi_sw_tcp_xmit_segment(struct iscsi_tcp_conn *tcp_conn,

  				     struct iscsi_segment *segment)
  {

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

  	struct socket *sk = tcp_sw_conn->sock;
  	unsigned int copied = 0;
  	int r = 0;

  	while (!iscsi_tcp_segment_done(tcp_conn, segment, 0, r)) {

  		struct scatterlist *sg;
  		unsigned int offset, copy;
  		int flags = 0;
  
  		r = 0;
  		offset = segment->copied;
  		copy = segment->size - offset;
  
  		if (segment->total_copied + segment->size < segment->total_size)
  			flags |= MSG_MORE;
  
  		/* Use sendpage if we can; else fall back to sendmsg */
  		if (!segment->data) {
  			sg = segment->sg;
  			offset += segment->sg_offset + sg->offset;
  			r = tcp_sw_conn->sendpage(sk, sg_page(sg), offset,
  						  copy, flags);
  		} else {
  			struct msghdr msg = { .msg_flags = flags };
  			struct kvec iov = {
  				.iov_base = segment->data + offset,
  				.iov_len = copy
  			};
  
  			r = kernel_sendmsg(sk, &msg, &iov, 1, copy);
  		}
  
  		if (r < 0) {
  			iscsi_tcp_segment_unmap(segment);

  			return r;
  		}
  		copied += r;
  	}
  	return copied;
  }
  
  /**
   * iscsi_sw_tcp_xmit - TCP transmit

   **/

  static int iscsi_sw_tcp_xmit(struct iscsi_conn *conn)

  {

  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
  	struct iscsi_segment *segment = &tcp_sw_conn->out.segment;

  	unsigned int consumed = 0;
  	int rc = 0;

  	while (1) {

  		rc = iscsi_sw_tcp_xmit_segment(tcp_conn, segment);

  		/*
  		 * We may not have been able to send data because the conn

  		 * is getting stopped. libiscsi will know so propagate err

  		 * for it to do the right thing.
  		 */
  		if (rc == -EAGAIN)
  			return rc;
  		else if (rc < 0) {

  			rc = ISCSI_ERR_XMIT_FAILED;

  			goto error;

  		} else if (rc == 0)

  			break;
  
  		consumed += rc;
  
  		if (segment->total_copied >= segment->total_size) {
  			if (segment->done != NULL) {
  				rc = segment->done(tcp_conn, segment);

  				if (rc != 0)

  					goto error;
  			}
  		}

  	}

  	ISCSI_SW_TCP_DBG(conn, "xmit %d bytes
  ", consumed);

  
  	conn->txdata_octets += consumed;
  	return consumed;
  
  error:
  	/* Transmit error. We could initiate error recovery
  	 * here. */

  	ISCSI_SW_TCP_DBG(conn, "Error sending PDU, errno=%d
  ", rc);

  	iscsi_conn_failure(conn, rc);
  	return -EIO;

  }
  
  /**

   * iscsi_tcp_xmit_qlen - return the number of bytes queued for xmit
   */

  static inline int iscsi_sw_tcp_xmit_qlen(struct iscsi_conn *conn)

  {

  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
  	struct iscsi_segment *segment = &tcp_sw_conn->out.segment;

  	return segment->total_copied - segment->total_size;

  }

  static int iscsi_sw_tcp_pdu_xmit(struct iscsi_task *task)

  {

  	struct iscsi_conn *conn = task->conn;

  	int rc;

  	while (iscsi_sw_tcp_xmit_qlen(conn)) {
  		rc = iscsi_sw_tcp_xmit(conn);

  		if (rc == 0)

  			return -EAGAIN;

  		if (rc < 0)
  			return rc;

  	}

  	return 0;

  }

  /*
   * This is called when we're done sending the header.
   * Simply copy the data_segment to the send segment, and return.
   */

  static int iscsi_sw_tcp_send_hdr_done(struct iscsi_tcp_conn *tcp_conn,
  				      struct iscsi_segment *segment)

  {

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
  
  	tcp_sw_conn->out.segment = tcp_sw_conn->out.data_segment;

  	ISCSI_SW_TCP_DBG(tcp_conn->iscsi_conn,
  			 "Header done. Next segment size %u total_size %u
  ",
  			 tcp_sw_conn->out.segment.size,
  			 tcp_sw_conn->out.segment.total_size);

  	return 0;
  }

  static void iscsi_sw_tcp_send_hdr_prep(struct iscsi_conn *conn, void *hdr,
  				       size_t hdrlen)

  {
  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

  	ISCSI_SW_TCP_DBG(conn, "%s
  ", conn->hdrdgst_en ?
  			 "digest enabled" : "digest disabled");

  
  	/* Clear the data segment - needs to be filled in by the
  	 * caller using iscsi_tcp_send_data_prep() */

  	memset(&tcp_sw_conn->out.data_segment, 0,
  	       sizeof(struct iscsi_segment));

  
  	/* If header digest is enabled, compute the CRC and
  	 * place the digest into the same buffer. We make

  	 * sure that both iscsi_tcp_task and mtask have

  	 * sufficient room.
  	 */
  	if (conn->hdrdgst_en) {

  		iscsi_tcp_dgst_header(&tcp_sw_conn->tx_hash, hdr, hdrlen,

  				      hdr + hdrlen);
  		hdrlen += ISCSI_DIGEST_SIZE;
  	}
  
  	/* Remember header pointer for later, when we need
  	 * to decide whether there's a payload to go along
  	 * with the header. */

  	tcp_sw_conn->out.hdr = hdr;

  	iscsi_segment_init_linear(&tcp_sw_conn->out.segment, hdr, hdrlen,
  				  iscsi_sw_tcp_send_hdr_done, NULL);

  }
  
  /*
   * Prepare the send buffer for the payload data.
   * Padding and checksumming will all be taken care
   * of by the iscsi_segment routines.
   */
  static int

  iscsi_sw_tcp_send_data_prep(struct iscsi_conn *conn, struct scatterlist *sg,
  			    unsigned int count, unsigned int offset,
  			    unsigned int len)

  {
  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

  	struct hash_desc *tx_hash = NULL;
  	unsigned int hdr_spec_len;

  	ISCSI_SW_TCP_DBG(conn, "offset=%d, datalen=%d %s
  ", offset, len,
  			 conn->datadgst_en ?
  			 "digest enabled" : "digest disabled");

  
  	/* Make sure the datalen matches what the caller
  	   said he would send. */

  	hdr_spec_len = ntoh24(tcp_sw_conn->out.hdr->dlength);

  	WARN_ON(iscsi_padded(len) != iscsi_padded(hdr_spec_len));
  
  	if (conn->datadgst_en)

  		tx_hash = &tcp_sw_conn->tx_hash;

  	return iscsi_segment_seek_sg(&tcp_sw_conn->out.data_segment,
  				     sg, count, offset, len,
  				     NULL, tx_hash);

  }
  
  static void

  iscsi_sw_tcp_send_linear_data_prep(struct iscsi_conn *conn, void *data,

  				   size_t len)
  {
  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

  	struct hash_desc *tx_hash = NULL;
  	unsigned int hdr_spec_len;

  	ISCSI_SW_TCP_DBG(conn, "datalen=%zd %s
  ", len, conn->datadgst_en ?
  			 "digest enabled" : "digest disabled");

  
  	/* Make sure the datalen matches what the caller
  	   said he would send. */

  	hdr_spec_len = ntoh24(tcp_sw_conn->out.hdr->dlength);

  	WARN_ON(iscsi_padded(len) != iscsi_padded(hdr_spec_len));
  
  	if (conn->datadgst_en)

  		tx_hash = &tcp_sw_conn->tx_hash;

  	iscsi_segment_init_linear(&tcp_sw_conn->out.data_segment,

  				data, len, NULL, tx_hash);

  }

  static int iscsi_sw_tcp_pdu_init(struct iscsi_task *task,
  				 unsigned int offset, unsigned int count)

  {
  	struct iscsi_conn *conn = task->conn;
  	int err = 0;

  	iscsi_sw_tcp_send_hdr_prep(conn, task->hdr, task->hdr_len);

  
  	if (!count)
  		return 0;
  
  	if (!task->sc)

  		iscsi_sw_tcp_send_linear_data_prep(conn, task->data, count);

  	else {
  		struct scsi_data_buffer *sdb = scsi_out(task->sc);

  		err = iscsi_sw_tcp_send_data_prep(conn, sdb->table.sgl,
  						  sdb->table.nents, offset,
  						  count);

  	}
  
  	if (err) {

  		/* got invalid offset/len */

  		return -EIO;
  	}
  	return 0;
  }

  static int iscsi_sw_tcp_pdu_alloc(struct iscsi_task *task, uint8_t opcode)

  {

  	struct iscsi_tcp_task *tcp_task = task->dd_data;

  	task->hdr = task->dd_data + sizeof(*tcp_task);
  	task->hdr_max = sizeof(struct iscsi_sw_tcp_hdrbuf) - ISCSI_DIGEST_SIZE;

  	return 0;

  }

  static struct iscsi_cls_conn *

  iscsi_sw_tcp_conn_create(struct iscsi_cls_session *cls_session,
  			 uint32_t conn_idx)

  {

  	struct iscsi_conn *conn;
  	struct iscsi_cls_conn *cls_conn;
  	struct iscsi_tcp_conn *tcp_conn;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn;

  	cls_conn = iscsi_tcp_conn_setup(cls_session, sizeof(*tcp_sw_conn),
  					conn_idx);

  	if (!cls_conn)
  		return NULL;
  	conn = cls_conn->dd_data;

  	tcp_conn = conn->dd_data;

  	tcp_sw_conn = tcp_conn->dd_data;

  	tcp_sw_conn->tx_hash.tfm = crypto_alloc_hash("crc32c", 0,
  						     CRYPTO_ALG_ASYNC);
  	tcp_sw_conn->tx_hash.flags = 0;
  	if (IS_ERR(tcp_sw_conn->tx_hash.tfm))

  		goto free_conn;

  	tcp_sw_conn->rx_hash.tfm = crypto_alloc_hash("crc32c", 0,
  						     CRYPTO_ALG_ASYNC);
  	tcp_sw_conn->rx_hash.flags = 0;
  	if (IS_ERR(tcp_sw_conn->rx_hash.tfm))

  		goto free_tx_tfm;

  	tcp_conn->rx_hash = &tcp_sw_conn->rx_hash;

  	return cls_conn;

  free_tx_tfm:

  	crypto_free_hash(tcp_sw_conn->tx_hash.tfm);

  free_conn:

  	iscsi_conn_printk(KERN_ERR, conn,
  			  "Could not create connection due to crc32c "
  			  "loading error. Make sure the crc32c "
  			  "module is built as a module or into the "
  			  "kernel
  ");

  	iscsi_tcp_conn_teardown(cls_conn);

  	return NULL;

  }

  static void iscsi_sw_tcp_release_conn(struct iscsi_conn *conn)

  {

  	struct iscsi_session *session = conn->session;

  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
  	struct socket *sock = tcp_sw_conn->sock;

  	if (!sock)

  		return;

  	sock_hold(sock->sk);

  	iscsi_sw_tcp_conn_restore_callbacks(conn);

  	sock_put(sock->sk);

  	spin_lock_bh(&session->lock);

  	tcp_sw_conn->sock = NULL;

  	spin_unlock_bh(&session->lock);
  	sockfd_put(sock);

  }

  static void iscsi_sw_tcp_conn_destroy(struct iscsi_cls_conn *cls_conn)

  {

  	struct iscsi_conn *conn = cls_conn->dd_data;
  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

  	iscsi_sw_tcp_release_conn(conn);

  	if (tcp_sw_conn->tx_hash.tfm)
  		crypto_free_hash(tcp_sw_conn->tx_hash.tfm);
  	if (tcp_sw_conn->rx_hash.tfm)
  		crypto_free_hash(tcp_sw_conn->rx_hash.tfm);

  	iscsi_tcp_conn_teardown(cls_conn);

  }

  static void iscsi_sw_tcp_conn_stop(struct iscsi_cls_conn *cls_conn, int flag)

  {
  	struct iscsi_conn *conn = cls_conn->dd_data;

  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

  	struct socket *sock = tcp_sw_conn->sock;

  
  	/* userspace may have goofed up and not bound us */

  	if (!sock)

  		return;

  	sock->sk->sk_err = EIO;
  	wake_up_interruptible(sk_sleep(sock->sk));

  	/* stop xmit side */
  	iscsi_suspend_tx(conn);
  
  	/* stop recv side and release socket */

  	iscsi_sw_tcp_release_conn(conn);

  
  	iscsi_conn_stop(cls_conn, flag);

  }

  static int

  iscsi_sw_tcp_conn_bind(struct iscsi_cls_session *cls_session,
  		       struct iscsi_cls_conn *cls_conn, uint64_t transport_eph,
  		       int is_leading)

  {

  	struct iscsi_session *session = cls_session->dd_data;

  	struct iscsi_conn *conn = cls_conn->dd_data;
  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

  	struct sock *sk;
  	struct socket *sock;
  	int err;

  	/* lookup for existing socket */

  	sock = sockfd_lookup((int)transport_eph, &err);

  	if (!sock) {

  		iscsi_conn_printk(KERN_ERR, conn,
  				  "sockfd_lookup failed %d
  ", err);

  		return -EEXIST;

  	}

  	err = iscsi_conn_bind(cls_session, cls_conn, is_leading);
  	if (err)

  		goto free_socket;

  	spin_lock_bh(&session->lock);

  	/* bind iSCSI connection and socket */

  	tcp_sw_conn->sock = sock;

  	spin_unlock_bh(&session->lock);

  	/* setup Socket parameters */
  	sk = sock->sk;
  	sk->sk_reuse = 1;
  	sk->sk_sndtimeo = 15 * HZ; /* FIXME: make it configurable */
  	sk->sk_allocation = GFP_ATOMIC;

  	iscsi_sw_tcp_conn_set_callbacks(conn);
  	tcp_sw_conn->sendpage = tcp_sw_conn->sock->ops->sendpage;

  	/*
  	 * set receive state machine into initial state
  	 */

  	iscsi_tcp_hdr_recv_prep(tcp_conn);

  	return 0;

  
  free_socket:
  	sockfd_put(sock);
  	return err;

  }

  static int iscsi_sw_tcp_conn_set_param(struct iscsi_cls_conn *cls_conn,
  				       enum iscsi_param param, char *buf,
  				       int buflen)

  {

  	struct iscsi_conn *conn = cls_conn->dd_data;

  	struct iscsi_session *session = conn->session;

  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

  	int value;

  	switch(param) {

  	case ISCSI_PARAM_HDRDGST_EN:

  		iscsi_set_param(cls_conn, param, buf, buflen);

  		break;
  	case ISCSI_PARAM_DATADGST_EN:

  		iscsi_set_param(cls_conn, param, buf, buflen);

  		tcp_sw_conn->sendpage = conn->datadgst_en ?
  			sock_no_sendpage : tcp_sw_conn->sock->ops->sendpage;

  		break;

  	case ISCSI_PARAM_MAX_R2T:

  		sscanf(buf, "%d", &value);

  		if (value <= 0 || !is_power_of_2(value))
  			return -EINVAL;
  		if (session->max_r2t == value)

  			break;

  		iscsi_tcp_r2tpool_free(session);

  		iscsi_set_param(cls_conn, param, buf, buflen);

  		if (iscsi_tcp_r2tpool_alloc(session))

  			return -ENOMEM;
  		break;

  	default:

  		return iscsi_set_param(cls_conn, param, buf, buflen);

  	}
  
  	return 0;
  }

  static int iscsi_sw_tcp_conn_get_param(struct iscsi_cls_conn *cls_conn,
  				       enum iscsi_param param, char *buf)

  {

  	struct iscsi_conn *conn = cls_conn->dd_data;

  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
  	struct sockaddr_in6 addr;
  	int rc, len;

  
  	switch(param) {

  	case ISCSI_PARAM_CONN_PORT:

  	case ISCSI_PARAM_CONN_ADDRESS:

  		spin_lock_bh(&conn->session->lock);

  		if (!tcp_sw_conn || !tcp_sw_conn->sock) {
  			spin_unlock_bh(&conn->session->lock);
  			return -ENOTCONN;
  		}
  		rc = kernel_getpeername(tcp_sw_conn->sock,
  					(struct sockaddr *)&addr, &len);

  		spin_unlock_bh(&conn->session->lock);

  		if (rc)
  			return rc;
  
  		return iscsi_conn_get_addr_param((struct sockaddr_storage *)
  						 &addr, param, buf);

  	default:

  		return iscsi_conn_get_param(cls_conn, param, buf);

  	}

  	return 0;
  }
  
  static int iscsi_sw_tcp_host_get_param(struct Scsi_Host *shost,
  				       enum iscsi_host_param param, char *buf)
  {
  	struct iscsi_sw_tcp_host *tcp_sw_host = iscsi_host_priv(shost);
  	struct iscsi_session *session = tcp_sw_host->session;
  	struct iscsi_conn *conn;
  	struct iscsi_tcp_conn *tcp_conn;
  	struct iscsi_sw_tcp_conn *tcp_sw_conn;
  	struct sockaddr_in6 addr;
  	int rc, len;
  
  	switch (param) {
  	case ISCSI_HOST_PARAM_IPADDRESS:
  		spin_lock_bh(&session->lock);
  		conn = session->leadconn;
  		if (!conn) {
  			spin_unlock_bh(&session->lock);
  			return -ENOTCONN;
  		}
  		tcp_conn = conn->dd_data;
  
  		tcp_sw_conn = tcp_conn->dd_data;
  		if (!tcp_sw_conn->sock) {
  			spin_unlock_bh(&session->lock);
  			return -ENOTCONN;
  		}
  
  		rc = kernel_getsockname(tcp_sw_conn->sock,
  					(struct sockaddr *)&addr, &len);
  		spin_unlock_bh(&session->lock);
  		if (rc)
  			return rc;
  
  		return iscsi_conn_get_addr_param((struct sockaddr_storage *)
  						 &addr, param, buf);
  	default:
  		return iscsi_host_get_param(shost, param, buf);
  	}
  
  	return 0;

  }

  static void

  iscsi_sw_tcp_conn_get_stats(struct iscsi_cls_conn *cls_conn,
  			    struct iscsi_stats *stats)

  {

  	struct iscsi_conn *conn = cls_conn->dd_data;

  	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

  	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

  	stats->custom_length = 3;
  	strcpy(stats->custom[0].desc, "tx_sendpage_failures");

  	stats->custom[0].value = tcp_sw_conn->sendpage_failures_cnt;

  	strcpy(stats->custom[1].desc, "rx_discontiguous_hdr");

  	stats->custom[1].value = tcp_sw_conn->discontiguous_hdr_cnt;

  	strcpy(stats->custom[2].desc, "eh_abort_cnt");
  	stats->custom[2].value = conn->eh_abort_cnt;

  
  	iscsi_tcp_conn_get_stats(cls_conn, stats);

  }

  static struct iscsi_cls_session *

  iscsi_sw_tcp_session_create(struct iscsi_endpoint *ep, uint16_t cmds_max,

  			    uint16_t qdepth, uint32_t initial_cmdsn)

  {

  	struct iscsi_cls_session *cls_session;
  	struct iscsi_session *session;

  	struct iscsi_sw_tcp_host *tcp_sw_host;

  	struct Scsi_Host *shost;

  	if (ep) {
  		printk(KERN_ERR "iscsi_tcp: invalid ep %p.
  ", ep);

  		return NULL;
  	}

  	shost = iscsi_host_alloc(&iscsi_sw_tcp_sht,
  				 sizeof(struct iscsi_sw_tcp_host), 1);

  	if (!shost)

  		return NULL;

  	shost->transportt = iscsi_sw_tcp_scsi_transport;

  	shost->cmd_per_lun = qdepth;

  	shost->max_lun = iscsi_max_lun;
  	shost->max_id = 0;
  	shost->max_channel = 0;

  	shost->max_cmd_len = SCSI_MAX_VARLEN_CDB_SIZE;

  	if (iscsi_host_add(shost, NULL))

  		goto free_host;

  	cls_session = iscsi_session_setup(&iscsi_sw_tcp_transport, shost,

  					  cmds_max, 0,

  					  sizeof(struct iscsi_tcp_task) +
  					  sizeof(struct iscsi_sw_tcp_hdrbuf),

  					  initial_cmdsn, 0);

  	if (!cls_session)
  		goto remove_host;
  	session = cls_session->dd_data;

  	tcp_sw_host = iscsi_host_priv(shost);
  	tcp_sw_host->session = session;

  	shost->can_queue = session->scsi_cmds_max;

  	if (iscsi_tcp_r2tpool_alloc(session))

  		goto remove_session;

  	return cls_session;

  remove_session:

  	iscsi_session_teardown(cls_session);

  remove_host:

  	iscsi_host_remove(shost);

  free_host:

  	iscsi_host_free(shost);

  	return NULL;
  }

  static void iscsi_sw_tcp_session_destroy(struct iscsi_cls_session *cls_session)

  {

  	struct Scsi_Host *shost = iscsi_session_to_shost(cls_session);

  	iscsi_tcp_r2tpool_free(cls_session->dd_data);

  	iscsi_session_teardown(cls_session);

  	iscsi_host_remove(shost);
  	iscsi_host_free(shost);

  }

  static umode_t iscsi_sw_tcp_attr_is_visible(int param_type, int param)

  {
  	switch (param_type) {

  	case ISCSI_HOST_PARAM:
  		switch (param) {
  		case ISCSI_HOST_PARAM_NETDEV_NAME:
  		case ISCSI_HOST_PARAM_HWADDRESS:
  		case ISCSI_HOST_PARAM_IPADDRESS:
  		case ISCSI_HOST_PARAM_INITIATOR_NAME:
  			return S_IRUGO;
  		default:
  			return 0;
  		}

  	case ISCSI_PARAM:
  		switch (param) {
  		case ISCSI_PARAM_MAX_RECV_DLENGTH:
  		case ISCSI_PARAM_MAX_XMIT_DLENGTH:
  		case ISCSI_PARAM_HDRDGST_EN:
  		case ISCSI_PARAM_DATADGST_EN:
  		case ISCSI_PARAM_CONN_ADDRESS:
  		case ISCSI_PARAM_CONN_PORT:
  		case ISCSI_PARAM_EXP_STATSN:
  		case ISCSI_PARAM_PERSISTENT_ADDRESS:
  		case ISCSI_PARAM_PERSISTENT_PORT:
  		case ISCSI_PARAM_PING_TMO:
  		case ISCSI_PARAM_RECV_TMO:

  		case ISCSI_PARAM_INITIAL_R2T_EN:
  		case ISCSI_PARAM_MAX_R2T:
  		case ISCSI_PARAM_IMM_DATA_EN:
  		case ISCSI_PARAM_FIRST_BURST:
  		case ISCSI_PARAM_MAX_BURST:
  		case ISCSI_PARAM_PDU_INORDER_EN:
  		case ISCSI_PARAM_DATASEQ_INORDER_EN:
  		case ISCSI_PARAM_ERL:
  		case ISCSI_PARAM_TARGET_NAME:
  		case ISCSI_PARAM_TPGT:
  		case ISCSI_PARAM_USERNAME:
  		case ISCSI_PARAM_PASSWORD:
  		case ISCSI_PARAM_USERNAME_IN:
  		case ISCSI_PARAM_PASSWORD_IN:
  		case ISCSI_PARAM_FAST_ABORT:
  		case ISCSI_PARAM_ABORT_TMO:
  		case ISCSI_PARAM_LU_RESET_TMO:
  		case ISCSI_PARAM_TGT_RESET_TMO:
  		case ISCSI_PARAM_IFACE_NAME:
  		case ISCSI_PARAM_INITIATOR_NAME:

  			return S_IRUGO;
  		default:
  			return 0;
  		}
  	}
  
  	return 0;
  }

  static int iscsi_sw_tcp_slave_alloc(struct scsi_device *sdev)
  {
  	set_bit(QUEUE_FLAG_BIDI, &sdev->request_queue->queue_flags);
  	return 0;
  }

  static int iscsi_sw_tcp_slave_configure(struct scsi_device *sdev)

  {

  	blk_queue_bounce_limit(sdev->request_queue, BLK_BOUNCE_ANY);

  	blk_queue_dma_alignment(sdev->request_queue, 0);
  	return 0;
  }

  static struct scsi_host_template iscsi_sw_tcp_sht = {

  	.module			= THIS_MODULE,

  	.name			= "iSCSI Initiator over TCP/IP",

  	.queuecommand           = iscsi_queuecommand,
  	.change_queue_depth	= iscsi_change_queue_depth,

  	.can_queue		= ISCSI_DEF_XMIT_CMDS_MAX - 1,

  	.sg_tablesize		= 4096,

  	.max_sectors		= 0xFFFF,

  	.cmd_per_lun		= ISCSI_DEF_CMD_PER_LUN,
  	.eh_abort_handler       = iscsi_eh_abort,

  	.eh_device_reset_handler= iscsi_eh_device_reset,

  	.eh_target_reset_handler = iscsi_eh_recover_target,

  	.use_clustering         = DISABLE_CLUSTERING,

  	.slave_alloc            = iscsi_sw_tcp_slave_alloc,

  	.slave_configure        = iscsi_sw_tcp_slave_configure,

  	.target_alloc		= iscsi_target_alloc,

  	.proc_name		= "iscsi_tcp",
  	.this_id		= -1,
  };

  static struct iscsi_transport iscsi_sw_tcp_transport = {

  	.owner			= THIS_MODULE,
  	.name			= "tcp",
  	.caps			= CAP_RECOVERY_L0 | CAP_MULTI_R2T | CAP_HDRDGST
  				  | CAP_DATADGST,

  	/* session management */

  	.create_session		= iscsi_sw_tcp_session_create,
  	.destroy_session	= iscsi_sw_tcp_session_destroy,

  	/* connection management */

  	.create_conn		= iscsi_sw_tcp_conn_create,
  	.bind_conn		= iscsi_sw_tcp_conn_bind,
  	.destroy_conn		= iscsi_sw_tcp_conn_destroy,

  	.attr_is_visible	= iscsi_sw_tcp_attr_is_visible,

  	.set_param		= iscsi_sw_tcp_conn_set_param,
  	.get_conn_param		= iscsi_sw_tcp_conn_get_param,

  	.get_session_param	= iscsi_session_get_param,

  	.start_conn		= iscsi_conn_start,

  	.stop_conn		= iscsi_sw_tcp_conn_stop,

  	/* iscsi host params */

  	.get_host_param		= iscsi_sw_tcp_host_get_param,

  	.set_host_param		= iscsi_host_set_param,

  	/* IO */

  	.send_pdu		= iscsi_conn_send_pdu,

  	.get_stats		= iscsi_sw_tcp_conn_get_stats,

  	/* iscsi task/cmd helpers */

  	.init_task		= iscsi_tcp_task_init,
  	.xmit_task		= iscsi_tcp_task_xmit,
  	.cleanup_task		= iscsi_tcp_cleanup_task,

  	/* low level pdu helpers */

  	.xmit_pdu		= iscsi_sw_tcp_pdu_xmit,
  	.init_pdu		= iscsi_sw_tcp_pdu_init,
  	.alloc_pdu		= iscsi_sw_tcp_pdu_alloc,

  	/* recovery */

  	.session_recovery_timedout = iscsi_session_recovery_timedout,

  };

  static int __init iscsi_sw_tcp_init(void)

  {

  	if (iscsi_max_lun < 1) {

  		printk(KERN_ERR "iscsi_tcp: Invalid max_lun value of %u
  ",
  		       iscsi_max_lun);

  		return -EINVAL;
  	}

  	iscsi_sw_tcp_scsi_transport = iscsi_register_transport(
  						&iscsi_sw_tcp_transport);
  	if (!iscsi_sw_tcp_scsi_transport)

  		return -ENODEV;

  	return 0;

  }

  static void __exit iscsi_sw_tcp_exit(void)

  {

  	iscsi_unregister_transport(&iscsi_sw_tcp_transport);

  }

  module_init(iscsi_sw_tcp_init);
  module_exit(iscsi_sw_tcp_exit);