iscsi_tcp.c

Go to the documentation of this file.

/*
 * 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 [email protected]
 *
 * 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 <[email protected]>, "
          "Dmitry Yusupov <[email protected]>, "
          "Alex Aizman <[email protected]>");
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 = ~0;
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);


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\n", 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\n",
             skb->len - offset, status);
    return total_consumed;
}

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\n");
        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);
}

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\n");
    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);
}

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;
}

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\n", 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\n", rc);
    iscsi_conn_failure(conn, rc);
    return -EIO;
}

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\n",
             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\n", 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\n", 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\n", 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\n");
    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\n", 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 = SK_CAN_REUSE;
    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_tcp_conn *tcp_conn = conn->dd_data;
    struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;

    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:
        return iscsi_tcp_set_max_r2t(conn, buf);
    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.\n", 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\n",
               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);