libiscsi_tcp.c

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/*
 * iSCSI over TCP/IP Data-Path lib
 *
 * 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/list.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 int iscsi_dbg_libtcp;
module_param_named(debug_libiscsi_tcp, iscsi_dbg_libtcp, int,
           S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug_libiscsi_tcp, "Turn on debugging for libiscsi_tcp "
         "module. Set to 1 to turn on, and zero to turn off. Default "
         "is off.");

#define ISCSI_DBG_TCP(_conn, dbg_fmt, arg...)           \
    do {                            \
        if (iscsi_dbg_libtcp)               \
            iscsi_conn_printk(KERN_INFO, _conn, \
                         "%s " dbg_fmt, \
                         __func__, ##arg);  \
    } while (0);

static int iscsi_tcp_hdr_recv_done(struct iscsi_tcp_conn *tcp_conn,
                   struct iscsi_segment *segment);

/*
 * Scatterlist handling: inside the iscsi_segment, we
 * remember an index into the scatterlist, and set data/size
 * to the current scatterlist entry. For highmem pages, we
 * kmap as needed.
 *
 * Note that the page is unmapped when we return from
 * TCP's data_ready handler, so we may end up mapping and
 * unmapping the same page repeatedly. The whole reason
 * for this is that we shouldn't keep the page mapped
 * outside the softirq.
 */

static inline void
iscsi_tcp_segment_init_sg(struct iscsi_segment *segment,
              struct scatterlist *sg, unsigned int offset)
{
    segment->sg = sg;
    segment->sg_offset = offset;
    segment->size = min(sg->length - offset,
                segment->total_size - segment->total_copied);
    segment->data = NULL;
}

static void iscsi_tcp_segment_map(struct iscsi_segment *segment, int recv)
{
    struct scatterlist *sg;

    if (segment->data != NULL || !segment->sg)
        return;

    sg = segment->sg;
    BUG_ON(segment->sg_mapped);
    BUG_ON(sg->length == 0);

    /*
     * If the page count is greater than one it is ok to send
     * to the network layer's zero copy send path. If not we
     * have to go the slow sendmsg path. We always map for the
     * recv path.
     */
    if (page_count(sg_page(sg)) >= 1 && !recv)
        return;

    if (recv) {
        segment->atomic_mapped = true;
        segment->sg_mapped = kmap_atomic(sg_page(sg));
    } else {
        segment->atomic_mapped = false;
        /* the xmit path can sleep with the page mapped so use kmap */
        segment->sg_mapped = kmap(sg_page(sg));
    }

    segment->data = segment->sg_mapped + sg->offset + segment->sg_offset;
}

void iscsi_tcp_segment_unmap(struct iscsi_segment *segment)
{
    if (segment->sg_mapped) {
        if (segment->atomic_mapped)
            kunmap_atomic(segment->sg_mapped);
        else
            kunmap(sg_page(segment->sg));
        segment->sg_mapped = NULL;
        segment->data = NULL;
    }
}
EXPORT_SYMBOL_GPL(iscsi_tcp_segment_unmap);

/*
 * Splice the digest buffer into the buffer
 */
static inline void
iscsi_tcp_segment_splice_digest(struct iscsi_segment *segment, void *digest)
{
    segment->data = digest;
    segment->digest_len = ISCSI_DIGEST_SIZE;
    segment->total_size += ISCSI_DIGEST_SIZE;
    segment->size = ISCSI_DIGEST_SIZE;
    segment->copied = 0;
    segment->sg = NULL;
    segment->hash = NULL;
}

int iscsi_tcp_segment_done(struct iscsi_tcp_conn *tcp_conn,
               struct iscsi_segment *segment, int recv,
               unsigned copied)
{
    struct scatterlist sg;
    unsigned int pad;

    ISCSI_DBG_TCP(tcp_conn->iscsi_conn, "copied %u %u size %u %s\n",
              segment->copied, copied, segment->size,
              recv ? "recv" : "xmit");
    if (segment->hash && copied) {
        /*
         * If a segment is kmapd we must unmap it before sending
         * to the crypto layer since that will try to kmap it again.
         */
        iscsi_tcp_segment_unmap(segment);

        if (!segment->data) {
            sg_init_table(&sg, 1);
            sg_set_page(&sg, sg_page(segment->sg), copied,
                    segment->copied + segment->sg_offset +
                            segment->sg->offset);
        } else
            sg_init_one(&sg, segment->data + segment->copied,
                    copied);
        crypto_hash_update(segment->hash, &sg, copied);
    }

    segment->copied += copied;
    if (segment->copied < segment->size) {
        iscsi_tcp_segment_map(segment, recv);
        return 0;
    }

    segment->total_copied += segment->copied;
    segment->copied = 0;
    segment->size = 0;

    /* Unmap the current scatterlist page, if there is one. */
    iscsi_tcp_segment_unmap(segment);

    /* Do we have more scatterlist entries? */
    ISCSI_DBG_TCP(tcp_conn->iscsi_conn, "total copied %u total size %u\n",
              segment->total_copied, segment->total_size);
    if (segment->total_copied < segment->total_size) {
        /* Proceed to the next entry in the scatterlist. */
        iscsi_tcp_segment_init_sg(segment, sg_next(segment->sg),
                      0);
        iscsi_tcp_segment_map(segment, recv);
        BUG_ON(segment->size == 0);
        return 0;
    }

    /* Do we need to handle padding? */
    if (!(tcp_conn->iscsi_conn->session->tt->caps & CAP_PADDING_OFFLOAD)) {
        pad = iscsi_padding(segment->total_copied);
        if (pad != 0) {
            ISCSI_DBG_TCP(tcp_conn->iscsi_conn,
                      "consume %d pad bytes\n", pad);
            segment->total_size += pad;
            segment->size = pad;
            segment->data = segment->padbuf;
            return 0;
        }
    }

    /*
     * Set us up for transferring the data digest. hdr digest
     * is completely handled in hdr done function.
     */
    if (segment->hash) {
        crypto_hash_final(segment->hash, segment->digest);
        iscsi_tcp_segment_splice_digest(segment,
                 recv ? segment->recv_digest : segment->digest);
        return 0;
    }

    return 1;
}
EXPORT_SYMBOL_GPL(iscsi_tcp_segment_done);

static int
iscsi_tcp_segment_recv(struct iscsi_tcp_conn *tcp_conn,
               struct iscsi_segment *segment, const void *ptr,
               unsigned int len)
{
    unsigned int copy = 0, copied = 0;

    while (!iscsi_tcp_segment_done(tcp_conn, segment, 1, copy)) {
        if (copied == len) {
            ISCSI_DBG_TCP(tcp_conn->iscsi_conn,
                      "copied %d bytes\n", len);
            break;
        }

        copy = min(len - copied, segment->size - segment->copied);
        ISCSI_DBG_TCP(tcp_conn->iscsi_conn, "copying %d\n", copy);
        memcpy(segment->data + segment->copied, ptr + copied, copy);
        copied += copy;
    }
    return copied;
}

inline void
iscsi_tcp_dgst_header(struct hash_desc *hash, const void *hdr, size_t hdrlen,
              unsigned char digest[ISCSI_DIGEST_SIZE])
{
    struct scatterlist sg;

    sg_init_one(&sg, hdr, hdrlen);
    crypto_hash_digest(hash, &sg, hdrlen, digest);
}
EXPORT_SYMBOL_GPL(iscsi_tcp_dgst_header);

static inline int
iscsi_tcp_dgst_verify(struct iscsi_tcp_conn *tcp_conn,
              struct iscsi_segment *segment)
{
    if (!segment->digest_len)
        return 1;

    if (memcmp(segment->recv_digest, segment->digest,
           segment->digest_len)) {
        ISCSI_DBG_TCP(tcp_conn->iscsi_conn, "digest mismatch\n");
        return 0;
    }

    return 1;
}

/*
 * Helper function to set up segment buffer
 */
static inline void
__iscsi_segment_init(struct iscsi_segment *segment, size_t size,
             iscsi_segment_done_fn_t *done, struct hash_desc *hash)
{
    memset(segment, 0, sizeof(*segment));
    segment->total_size = size;
    segment->done = done;

    if (hash) {
        segment->hash = hash;
        crypto_hash_init(hash);
    }
}

inline void
iscsi_segment_init_linear(struct iscsi_segment *segment, void *data,
              size_t size, iscsi_segment_done_fn_t *done,
              struct hash_desc *hash)
{
    __iscsi_segment_init(segment, size, done, hash);
    segment->data = data;
    segment->size = size;
}
EXPORT_SYMBOL_GPL(iscsi_segment_init_linear);

inline int
iscsi_segment_seek_sg(struct iscsi_segment *segment,
              struct scatterlist *sg_list, unsigned int sg_count,
              unsigned int offset, size_t size,
              iscsi_segment_done_fn_t *done, struct hash_desc *hash)
{
    struct scatterlist *sg;
    unsigned int i;

    __iscsi_segment_init(segment, size, done, hash);
    for_each_sg(sg_list, sg, sg_count, i) {
        if (offset < sg->length) {
            iscsi_tcp_segment_init_sg(segment, sg, offset);
            return 0;
        }
        offset -= sg->length;
    }

    return ISCSI_ERR_DATA_OFFSET;
}
EXPORT_SYMBOL_GPL(iscsi_segment_seek_sg);

void iscsi_tcp_hdr_recv_prep(struct iscsi_tcp_conn *tcp_conn)
{
    ISCSI_DBG_TCP(tcp_conn->iscsi_conn,
              "(%s)\n", tcp_conn->iscsi_conn->hdrdgst_en ?
              "digest enabled" : "digest disabled");
    iscsi_segment_init_linear(&tcp_conn->in.segment,
                tcp_conn->in.hdr_buf, sizeof(struct iscsi_hdr),
                iscsi_tcp_hdr_recv_done, NULL);
}
EXPORT_SYMBOL_GPL(iscsi_tcp_hdr_recv_prep);

/*
 * Handle incoming reply to any other type of command
 */
static int
iscsi_tcp_data_recv_done(struct iscsi_tcp_conn *tcp_conn,
             struct iscsi_segment *segment)
{
    struct iscsi_conn *conn = tcp_conn->iscsi_conn;
    int rc = 0;

    if (!iscsi_tcp_dgst_verify(tcp_conn, segment))
        return ISCSI_ERR_DATA_DGST;

    rc = iscsi_complete_pdu(conn, tcp_conn->in.hdr,
            conn->data, tcp_conn->in.datalen);
    if (rc)
        return rc;

    iscsi_tcp_hdr_recv_prep(tcp_conn);
    return 0;
}

static void
iscsi_tcp_data_recv_prep(struct iscsi_tcp_conn *tcp_conn)
{
    struct iscsi_conn *conn = tcp_conn->iscsi_conn;
    struct hash_desc *rx_hash = NULL;

    if (conn->datadgst_en &&
        !(conn->session->tt->caps & CAP_DIGEST_OFFLOAD))
        rx_hash = tcp_conn->rx_hash;

    iscsi_segment_init_linear(&tcp_conn->in.segment,
                conn->data, tcp_conn->in.datalen,
                iscsi_tcp_data_recv_done, rx_hash);
}

void iscsi_tcp_cleanup_task(struct iscsi_task *task)
{
    struct iscsi_tcp_task *tcp_task = task->dd_data;
    struct iscsi_r2t_info *r2t;

    /* nothing to do for mgmt */
    if (!task->sc)
        return;

    /* flush task's r2t queues */
    while (kfifo_out(&tcp_task->r2tqueue, (void*)&r2t, sizeof(void*))) {
        kfifo_in(&tcp_task->r2tpool.queue, (void*)&r2t,
                sizeof(void*));
        ISCSI_DBG_TCP(task->conn, "pending r2t dropped\n");
    }

    r2t = tcp_task->r2t;
    if (r2t != NULL) {
        kfifo_in(&tcp_task->r2tpool.queue, (void*)&r2t,
                sizeof(void*));
        tcp_task->r2t = NULL;
    }
}
EXPORT_SYMBOL_GPL(iscsi_tcp_cleanup_task);

static int iscsi_tcp_data_in(struct iscsi_conn *conn, struct iscsi_task *task)
{
    struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
    struct iscsi_tcp_task *tcp_task = task->dd_data;
    struct iscsi_data_rsp *rhdr = (struct iscsi_data_rsp *)tcp_conn->in.hdr;
    int datasn = be32_to_cpu(rhdr->datasn);
    unsigned total_in_length = scsi_in(task->sc)->length;

    /*
     * lib iscsi will update this in the completion handling if there
     * is status.
     */
    if (!(rhdr->flags & ISCSI_FLAG_DATA_STATUS))
        iscsi_update_cmdsn(conn->session, (struct iscsi_nopin*)rhdr);

    if (tcp_conn->in.datalen == 0)
        return 0;

    if (tcp_task->exp_datasn != datasn) {
        ISCSI_DBG_TCP(conn, "task->exp_datasn(%d) != rhdr->datasn(%d)"
                  "\n", tcp_task->exp_datasn, datasn);
        return ISCSI_ERR_DATASN;
    }

    tcp_task->exp_datasn++;

    tcp_task->data_offset = be32_to_cpu(rhdr->offset);
    if (tcp_task->data_offset + tcp_conn->in.datalen > total_in_length) {
        ISCSI_DBG_TCP(conn, "data_offset(%d) + data_len(%d) > "
                  "total_length_in(%d)\n", tcp_task->data_offset,
                  tcp_conn->in.datalen, total_in_length);
        return ISCSI_ERR_DATA_OFFSET;
    }

    conn->datain_pdus_cnt++;
    return 0;
}

static int iscsi_tcp_r2t_rsp(struct iscsi_conn *conn, struct iscsi_task *task)
{
    struct iscsi_session *session = conn->session;
    struct iscsi_tcp_task *tcp_task = task->dd_data;
    struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
    struct iscsi_r2t_rsp *rhdr = (struct iscsi_r2t_rsp *)tcp_conn->in.hdr;
    struct iscsi_r2t_info *r2t;
    int r2tsn = be32_to_cpu(rhdr->r2tsn);
    int rc;

    if (tcp_conn->in.datalen) {
        iscsi_conn_printk(KERN_ERR, conn,
                  "invalid R2t with datalen %d\n",
                  tcp_conn->in.datalen);
        return ISCSI_ERR_DATALEN;
    }

    if (tcp_task->exp_datasn != r2tsn){
        ISCSI_DBG_TCP(conn, "task->exp_datasn(%d) != rhdr->r2tsn(%d)\n",
                  tcp_task->exp_datasn, r2tsn);
        return ISCSI_ERR_R2TSN;
    }

    /* fill-in new R2T associated with the task */
    iscsi_update_cmdsn(session, (struct iscsi_nopin*)rhdr);

    if (!task->sc || session->state != ISCSI_STATE_LOGGED_IN) {
        iscsi_conn_printk(KERN_INFO, conn,
                  "dropping R2T itt %d in recovery.\n",
                  task->itt);
        return 0;
    }

    rc = kfifo_out(&tcp_task->r2tpool.queue, (void*)&r2t, sizeof(void*));
    if (!rc) {
        iscsi_conn_printk(KERN_ERR, conn, "Could not allocate R2T. "
                  "Target has sent more R2Ts than it "
                  "negotiated for or driver has has leaked.\n");
        return ISCSI_ERR_PROTO;
    }

    r2t->exp_statsn = rhdr->statsn;
    r2t->data_length = be32_to_cpu(rhdr->data_length);
    if (r2t->data_length == 0) {
        iscsi_conn_printk(KERN_ERR, conn,
                  "invalid R2T with zero data len\n");
        kfifo_in(&tcp_task->r2tpool.queue, (void*)&r2t,
                sizeof(void*));
        return ISCSI_ERR_DATALEN;
    }

    if (r2t->data_length > session->max_burst)
        ISCSI_DBG_TCP(conn, "invalid R2T with data len %u and max "
                  "burst %u. Attempting to execute request.\n",
                  r2t->data_length, session->max_burst);

    r2t->data_offset = be32_to_cpu(rhdr->data_offset);
    if (r2t->data_offset + r2t->data_length > scsi_out(task->sc)->length) {
        iscsi_conn_printk(KERN_ERR, conn,
                  "invalid R2T with data len %u at offset %u "
                  "and total length %d\n", r2t->data_length,
                  r2t->data_offset, scsi_out(task->sc)->length);
        kfifo_in(&tcp_task->r2tpool.queue, (void*)&r2t,
                sizeof(void*));
        return ISCSI_ERR_DATALEN;
    }

    r2t->ttt = rhdr->ttt; /* no flip */
    r2t->datasn = 0;
    r2t->sent = 0;

    tcp_task->exp_datasn = r2tsn + 1;
    kfifo_in(&tcp_task->r2tqueue, (void*)&r2t, sizeof(void*));
    conn->r2t_pdus_cnt++;

    iscsi_requeue_task(task);
    return 0;
}

/*
 * Handle incoming reply to DataIn command
 */
static int
iscsi_tcp_process_data_in(struct iscsi_tcp_conn *tcp_conn,
              struct iscsi_segment *segment)
{
    struct iscsi_conn *conn = tcp_conn->iscsi_conn;
    struct iscsi_hdr *hdr = tcp_conn->in.hdr;
    int rc;

    if (!iscsi_tcp_dgst_verify(tcp_conn, segment))
        return ISCSI_ERR_DATA_DGST;

    /* check for non-exceptional status */
    if (hdr->flags & ISCSI_FLAG_DATA_STATUS) {
        rc = iscsi_complete_pdu(conn, tcp_conn->in.hdr, NULL, 0);
        if (rc)
            return rc;
    }

    iscsi_tcp_hdr_recv_prep(tcp_conn);
    return 0;
}

static int
iscsi_tcp_hdr_dissect(struct iscsi_conn *conn, struct iscsi_hdr *hdr)
{
    int rc = 0, opcode, ahslen;
    struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
    struct iscsi_task *task;

    /* verify PDU length */
    tcp_conn->in.datalen = ntoh24(hdr->dlength);
    if (tcp_conn->in.datalen > conn->max_recv_dlength) {
        iscsi_conn_printk(KERN_ERR, conn,
                  "iscsi_tcp: datalen %d > %d\n",
                  tcp_conn->in.datalen, conn->max_recv_dlength);
        return ISCSI_ERR_DATALEN;
    }

    /* Additional header segments. So far, we don't
     * process additional headers.
     */
    ahslen = hdr->hlength << 2;

    opcode = hdr->opcode & ISCSI_OPCODE_MASK;
    /* verify itt (itt encoding: age+cid+itt) */
    rc = iscsi_verify_itt(conn, hdr->itt);
    if (rc)
        return rc;

    ISCSI_DBG_TCP(conn, "opcode 0x%x ahslen %d datalen %d\n",
              opcode, ahslen, tcp_conn->in.datalen);

    switch(opcode) {
    case ISCSI_OP_SCSI_DATA_IN:
        spin_lock(&conn->session->lock);
        task = iscsi_itt_to_ctask(conn, hdr->itt);
        if (!task)
            rc = ISCSI_ERR_BAD_ITT;
        else
            rc = iscsi_tcp_data_in(conn, task);
        if (rc) {
            spin_unlock(&conn->session->lock);
            break;
        }

        if (tcp_conn->in.datalen) {
            struct iscsi_tcp_task *tcp_task = task->dd_data;
            struct hash_desc *rx_hash = NULL;
            struct scsi_data_buffer *sdb = scsi_in(task->sc);

            /*
             * Setup copy of Data-In into the Scsi_Cmnd
             * Scatterlist case:
             * We set up the iscsi_segment to point to the next
             * scatterlist entry to copy to. As we go along,
             * we move on to the next scatterlist entry and
             * update the digest per-entry.
             */
            if (conn->datadgst_en &&
                !(conn->session->tt->caps & CAP_DIGEST_OFFLOAD))
                rx_hash = tcp_conn->rx_hash;

            ISCSI_DBG_TCP(conn, "iscsi_tcp_begin_data_in( "
                     "offset=%d, datalen=%d)\n",
                      tcp_task->data_offset,
                      tcp_conn->in.datalen);
            task->last_xfer = jiffies;
            rc = iscsi_segment_seek_sg(&tcp_conn->in.segment,
                           sdb->table.sgl,
                           sdb->table.nents,
                           tcp_task->data_offset,
                           tcp_conn->in.datalen,
                           iscsi_tcp_process_data_in,
                           rx_hash);
            spin_unlock(&conn->session->lock);
            return rc;
        }
        rc = __iscsi_complete_pdu(conn, hdr, NULL, 0);
        spin_unlock(&conn->session->lock);
        break;
    case ISCSI_OP_SCSI_CMD_RSP:
        if (tcp_conn->in.datalen) {
            iscsi_tcp_data_recv_prep(tcp_conn);
            return 0;
        }
        rc = iscsi_complete_pdu(conn, hdr, NULL, 0);
        break;
    case ISCSI_OP_R2T:
        spin_lock(&conn->session->lock);
        task = iscsi_itt_to_ctask(conn, hdr->itt);
        if (!task)
            rc = ISCSI_ERR_BAD_ITT;
        else if (ahslen)
            rc = ISCSI_ERR_AHSLEN;
        else if (task->sc->sc_data_direction == DMA_TO_DEVICE) {
            task->last_xfer = jiffies;
            rc = iscsi_tcp_r2t_rsp(conn, task);
        } else
            rc = ISCSI_ERR_PROTO;
        spin_unlock(&conn->session->lock);
        break;
    case ISCSI_OP_LOGIN_RSP:
    case ISCSI_OP_TEXT_RSP:
    case ISCSI_OP_REJECT:
    case ISCSI_OP_ASYNC_EVENT:
        /*
         * It is possible that we could get a PDU with a buffer larger
         * than 8K, but there are no targets that currently do this.
         * For now we fail until we find a vendor that needs it
         */
        if (ISCSI_DEF_MAX_RECV_SEG_LEN < tcp_conn->in.datalen) {
            iscsi_conn_printk(KERN_ERR, conn,
                      "iscsi_tcp: received buffer of "
                      "len %u but conn buffer is only %u "
                      "(opcode %0x)\n",
                      tcp_conn->in.datalen,
                      ISCSI_DEF_MAX_RECV_SEG_LEN, opcode);
            rc = ISCSI_ERR_PROTO;
            break;
        }

        /* If there's data coming in with the response,
         * receive it to the connection's buffer.
         */
        if (tcp_conn->in.datalen) {
            iscsi_tcp_data_recv_prep(tcp_conn);
            return 0;
        }
    /* fall through */
    case ISCSI_OP_LOGOUT_RSP:
    case ISCSI_OP_NOOP_IN:
    case ISCSI_OP_SCSI_TMFUNC_RSP:
        rc = iscsi_complete_pdu(conn, hdr, NULL, 0);
        break;
    default:
        rc = ISCSI_ERR_BAD_OPCODE;
        break;
    }

    if (rc == 0) {
        /* Anything that comes with data should have
         * been handled above. */
        if (tcp_conn->in.datalen)
            return ISCSI_ERR_PROTO;
        iscsi_tcp_hdr_recv_prep(tcp_conn);
    }

    return rc;
}

static int
iscsi_tcp_hdr_recv_done(struct iscsi_tcp_conn *tcp_conn,
            struct iscsi_segment *segment)
{
    struct iscsi_conn *conn = tcp_conn->iscsi_conn;
    struct iscsi_hdr *hdr;

    /* Check if there are additional header segments
     * *prior* to computing the digest, because we
     * may need to go back to the caller for more.
     */
    hdr = (struct iscsi_hdr *) tcp_conn->in.hdr_buf;
    if (segment->copied == sizeof(struct iscsi_hdr) && hdr->hlength) {
        /* Bump the header length - the caller will
         * just loop around and get the AHS for us, and
         * call again. */
        unsigned int ahslen = hdr->hlength << 2;

        /* Make sure we don't overflow */
        if (sizeof(*hdr) + ahslen > sizeof(tcp_conn->in.hdr_buf))
            return ISCSI_ERR_AHSLEN;

        segment->total_size += ahslen;
        segment->size += ahslen;
        return 0;
    }

    /* We're done processing the header. See if we're doing
     * header digests; if so, set up the recv_digest buffer
     * and go back for more. */
    if (conn->hdrdgst_en &&
        !(conn->session->tt->caps & CAP_DIGEST_OFFLOAD)) {
        if (segment->digest_len == 0) {
            /*
             * Even if we offload the digest processing we
             * splice it in so we can increment the skb/segment
             * counters in preparation for the data segment.
             */
            iscsi_tcp_segment_splice_digest(segment,
                            segment->recv_digest);
            return 0;
        }

        iscsi_tcp_dgst_header(tcp_conn->rx_hash, hdr,
                      segment->total_copied - ISCSI_DIGEST_SIZE,
                      segment->digest);

        if (!iscsi_tcp_dgst_verify(tcp_conn, segment))
            return ISCSI_ERR_HDR_DGST;
    }

    tcp_conn->in.hdr = hdr;
    return iscsi_tcp_hdr_dissect(conn, hdr);
}

inline int iscsi_tcp_recv_segment_is_hdr(struct iscsi_tcp_conn *tcp_conn)
{
    return tcp_conn->in.segment.done == iscsi_tcp_hdr_recv_done;
}
EXPORT_SYMBOL_GPL(iscsi_tcp_recv_segment_is_hdr);

int iscsi_tcp_recv_skb(struct iscsi_conn *conn, struct sk_buff *skb,
               unsigned int offset, bool offloaded, int *status)
{
    struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
    struct iscsi_segment *segment = &tcp_conn->in.segment;
    struct skb_seq_state seq;
    unsigned int consumed = 0;
    int rc = 0;

    ISCSI_DBG_TCP(conn, "in %d bytes\n", skb->len - offset);
    /*
     * Update for each skb instead of pdu, because over slow networks a
     * data_in's data could take a while to read in. We also want to
     * account for r2ts.
     */
    conn->last_recv = jiffies;

    if (unlikely(conn->suspend_rx)) {
        ISCSI_DBG_TCP(conn, "Rx suspended!\n");
        *status = ISCSI_TCP_SUSPENDED;
        return 0;
    }

    if (offloaded) {
        segment->total_copied = segment->total_size;
        goto segment_done;
    }

    skb_prepare_seq_read(skb, offset, skb->len, &seq);
    while (1) {
        unsigned int avail;
        const u8 *ptr;

        avail = skb_seq_read(consumed, &ptr, &seq);
        if (avail == 0) {
            ISCSI_DBG_TCP(conn, "no more data avail. Consumed %d\n",
                      consumed);
            *status = ISCSI_TCP_SKB_DONE;
            skb_abort_seq_read(&seq);
            goto skb_done;
        }
        BUG_ON(segment->copied >= segment->size);

        ISCSI_DBG_TCP(conn, "skb %p ptr=%p avail=%u\n", skb, ptr,
                  avail);
        rc = iscsi_tcp_segment_recv(tcp_conn, segment, ptr, avail);
        BUG_ON(rc == 0);
        consumed += rc;

        if (segment->total_copied >= segment->total_size) {
            skb_abort_seq_read(&seq);
            goto segment_done;
        }
    }

segment_done:
    *status = ISCSI_TCP_SEGMENT_DONE;
    ISCSI_DBG_TCP(conn, "segment done\n");
    rc = segment->done(tcp_conn, segment);
    if (rc != 0) {
        *status = ISCSI_TCP_CONN_ERR;
        ISCSI_DBG_TCP(conn, "Error receiving PDU, errno=%d\n", rc);
        iscsi_conn_failure(conn, rc);
        return 0;
    }
    /* The done() functions sets up the next segment. */

skb_done:
    conn->rxdata_octets += consumed;
    return consumed;
}
EXPORT_SYMBOL_GPL(iscsi_tcp_recv_skb);

int iscsi_tcp_task_init(struct iscsi_task *task)
{
    struct iscsi_tcp_task *tcp_task = task->dd_data;
    struct iscsi_conn *conn = task->conn;
    struct scsi_cmnd *sc = task->sc;
    int err;

    if (!sc) {
        /*
         * mgmt tasks do not have a scatterlist since they come
         * in from the iscsi interface.
         */
        ISCSI_DBG_TCP(conn, "mtask deq [itt 0x%x]\n", task->itt);

        return conn->session->tt->init_pdu(task, 0, task->data_count);
    }

    BUG_ON(kfifo_len(&tcp_task->r2tqueue));
    tcp_task->exp_datasn = 0;

    /* Prepare PDU, optionally w/ immediate data */
    ISCSI_DBG_TCP(conn, "task deq [itt 0x%x imm %d unsol %d]\n",
              task->itt, task->imm_count, task->unsol_r2t.data_length);

    err = conn->session->tt->init_pdu(task, 0, task->imm_count);
    if (err)
        return err;
    task->imm_count = 0;
    return 0;
}
EXPORT_SYMBOL_GPL(iscsi_tcp_task_init);

static struct iscsi_r2t_info *iscsi_tcp_get_curr_r2t(struct iscsi_task *task)
{
    struct iscsi_session *session = task->conn->session;
    struct iscsi_tcp_task *tcp_task = task->dd_data;
    struct iscsi_r2t_info *r2t = NULL;

    if (iscsi_task_has_unsol_data(task))
        r2t = &task->unsol_r2t;
    else {
        spin_lock_bh(&session->lock);
        if (tcp_task->r2t) {
            r2t = tcp_task->r2t;
            /* Continue with this R2T? */
            if (r2t->data_length <= r2t->sent) {
                ISCSI_DBG_TCP(task->conn,
                          "  done with r2t %p\n", r2t);
                kfifo_in(&tcp_task->r2tpool.queue,
                        (void *)&tcp_task->r2t,
                        sizeof(void *));
                tcp_task->r2t = r2t = NULL;
            }
        }

        if (r2t == NULL) {
            if (kfifo_out(&tcp_task->r2tqueue,
                (void *)&tcp_task->r2t, sizeof(void *)) !=
                sizeof(void *))
                r2t = NULL;
            else
                r2t = tcp_task->r2t;
        }
        spin_unlock_bh(&session->lock);
    }

    return r2t;
}

int iscsi_tcp_task_xmit(struct iscsi_task *task)
{
    struct iscsi_conn *conn = task->conn;
    struct iscsi_session *session = conn->session;
    struct iscsi_r2t_info *r2t;
    int rc = 0;

flush:
    /* Flush any pending data first. */
    rc = session->tt->xmit_pdu(task);
    if (rc < 0)
        return rc;

    /* mgmt command */
    if (!task->sc) {
        if (task->hdr->itt == RESERVED_ITT)
            iscsi_put_task(task);
        return 0;
    }

    /* Are we done already? */
    if (task->sc->sc_data_direction != DMA_TO_DEVICE)
        return 0;

    r2t = iscsi_tcp_get_curr_r2t(task);
    if (r2t == NULL) {
        /* Waiting for more R2Ts to arrive. */
        ISCSI_DBG_TCP(conn, "no R2Ts yet\n");
        return 0;
    }

    rc = conn->session->tt->alloc_pdu(task, ISCSI_OP_SCSI_DATA_OUT);
    if (rc)
        return rc;
    iscsi_prep_data_out_pdu(task, r2t, (struct iscsi_data *) task->hdr);

    ISCSI_DBG_TCP(conn, "sol dout %p [dsn %d itt 0x%x doff %d dlen %d]\n",
              r2t, r2t->datasn - 1, task->hdr->itt,
              r2t->data_offset + r2t->sent, r2t->data_count);

    rc = conn->session->tt->init_pdu(task, r2t->data_offset + r2t->sent,
                     r2t->data_count);
    if (rc) {
        iscsi_conn_failure(conn, ISCSI_ERR_XMIT_FAILED);
        return rc;
    }

    r2t->sent += r2t->data_count;
    goto flush;
}
EXPORT_SYMBOL_GPL(iscsi_tcp_task_xmit);

struct iscsi_cls_conn *
iscsi_tcp_conn_setup(struct iscsi_cls_session *cls_session, int dd_data_size,
              uint32_t conn_idx)

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

    cls_conn = iscsi_conn_setup(cls_session,
                    sizeof(*tcp_conn) + dd_data_size, conn_idx);
    if (!cls_conn)
        return NULL;
    conn = cls_conn->dd_data;
    /*
     * due to strange issues with iser these are not set
     * in iscsi_conn_setup
     */
    conn->max_recv_dlength = ISCSI_DEF_MAX_RECV_SEG_LEN;

    tcp_conn = conn->dd_data;
    tcp_conn->iscsi_conn = conn;
    tcp_conn->dd_data = conn->dd_data + sizeof(*tcp_conn);
    return cls_conn;
}
EXPORT_SYMBOL_GPL(iscsi_tcp_conn_setup);

void iscsi_tcp_conn_teardown(struct iscsi_cls_conn *cls_conn)
{
    iscsi_conn_teardown(cls_conn);
}
EXPORT_SYMBOL_GPL(iscsi_tcp_conn_teardown);

int iscsi_tcp_r2tpool_alloc(struct iscsi_session *session)
{
    int i;
    int cmd_i;

    /*
     * initialize per-task: R2T pool and xmit queue
     */
    for (cmd_i = 0; cmd_i < session->cmds_max; cmd_i++) {
            struct iscsi_task *task = session->cmds[cmd_i];
        struct iscsi_tcp_task *tcp_task = task->dd_data;

        /*
         * pre-allocated x2 as much r2ts to handle race when
         * target acks DataOut faster than we data_xmit() queues
         * could replenish r2tqueue.
         */

        /* R2T pool */
        if (iscsi_pool_init(&tcp_task->r2tpool,
                    session->max_r2t * 2, NULL,
                    sizeof(struct iscsi_r2t_info))) {
            goto r2t_alloc_fail;
        }

        /* R2T xmit queue */
        if (kfifo_alloc(&tcp_task->r2tqueue,
              session->max_r2t * 4 * sizeof(void*), GFP_KERNEL)) {
            iscsi_pool_free(&tcp_task->r2tpool);
            goto r2t_alloc_fail;
        }
    }

    return 0;

r2t_alloc_fail:
    for (i = 0; i < cmd_i; i++) {
        struct iscsi_task *task = session->cmds[i];
        struct iscsi_tcp_task *tcp_task = task->dd_data;

        kfifo_free(&tcp_task->r2tqueue);
        iscsi_pool_free(&tcp_task->r2tpool);
    }
    return -ENOMEM;
}
EXPORT_SYMBOL_GPL(iscsi_tcp_r2tpool_alloc);

void iscsi_tcp_r2tpool_free(struct iscsi_session *session)
{
    int i;

    for (i = 0; i < session->cmds_max; i++) {
        struct iscsi_task *task = session->cmds[i];
        struct iscsi_tcp_task *tcp_task = task->dd_data;

        kfifo_free(&tcp_task->r2tqueue);
        iscsi_pool_free(&tcp_task->r2tpool);
    }
}
EXPORT_SYMBOL_GPL(iscsi_tcp_r2tpool_free);

int iscsi_tcp_set_max_r2t(struct iscsi_conn *conn, char *buf)
{
    struct iscsi_session *session = conn->session;
    unsigned short r2ts = 0;

    sscanf(buf, "%hu", &r2ts);
    if (session->max_r2t == r2ts)
        return 0;

    if (!r2ts || !is_power_of_2(r2ts))
        return -EINVAL;

    session->max_r2t = r2ts;
    iscsi_tcp_r2tpool_free(session);
    return iscsi_tcp_r2tpool_alloc(session);
}
EXPORT_SYMBOL_GPL(iscsi_tcp_set_max_r2t);

void iscsi_tcp_conn_get_stats(struct iscsi_cls_conn *cls_conn,
                  struct iscsi_stats *stats)
{
    struct iscsi_conn *conn = cls_conn->dd_data;

    stats->txdata_octets = conn->txdata_octets;
    stats->rxdata_octets = conn->rxdata_octets;
    stats->scsicmd_pdus = conn->scsicmd_pdus_cnt;
    stats->dataout_pdus = conn->dataout_pdus_cnt;
    stats->scsirsp_pdus = conn->scsirsp_pdus_cnt;
    stats->datain_pdus = conn->datain_pdus_cnt;
    stats->r2t_pdus = conn->r2t_pdus_cnt;
    stats->tmfcmd_pdus = conn->tmfcmd_pdus_cnt;
    stats->tmfrsp_pdus = conn->tmfrsp_pdus_cnt;
}
EXPORT_SYMBOL_GPL(iscsi_tcp_conn_get_stats);