Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1218 insertions, 0 deletions

diff --git a/drivers/scsi/libiscsi_tcp.c b/drivers/scsi/libiscsi_tcp.c
new file mode 100644
index 000000000..83f14b2c8
--- /dev/null
+++ b/drivers/scsi/libiscsi_tcp.c
@@ -0,0 +1,1218 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * 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 open-iscsi@googlegroups.com
+ *
+ * Credits:
+ *	Christoph Hellwig
+ *	FUJITA Tomonori
+ *	Arne Redlich
+ *	Zhenyu Wang
+ */
+
+#include <crypto/hash.h>
+#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/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 <trace/events/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 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);	\
+		iscsi_dbg_trace(trace_iscsi_dbg_tcp,		\
+				&(_conn)->cls_conn->dev,	\
+				"%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.
+ */
+
+/**
+ * iscsi_tcp_segment_init_sg - init indicated scatterlist entry
+ * @segment: the buffer object
+ * @sg: scatterlist
+ * @offset: byte offset into that sg entry
+ *
+ * This function sets up the segment so that subsequent
+ * data is copied to the indicated sg entry, at the given
+ * offset.
+ */
+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;
+}
+
+/**
+ * iscsi_tcp_segment_map - map the current S/G page
+ * @segment: iscsi_segment
+ * @recv: 1 if called from recv path
+ *
+ * We only need to possibly kmap data if scatter lists are being used,
+ * because the iscsi passthrough and internal IO paths will never use high
+ * mem pages.
+ */
+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);
+
+	/*
+	 * We always map for the recv path.
+	 *
+	 * 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.
+	 *
+	 * Same goes for slab pages: skb_can_coalesce() allows
+	 * coalescing neighboring slab objects into a single frag which
+	 * triggers one of hardened usercopy checks.
+	 */
+	if (!recv && sendpage_ok(sg_page(sg)))
+		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;
+}
+
+/**
+ * iscsi_tcp_segment_done - check whether the segment is complete
+ * @tcp_conn: iscsi tcp connection
+ * @segment: iscsi segment to check
+ * @recv: set to one of this is called from the recv path
+ * @copied: number of bytes copied
+ *
+ * Check if we're done receiving this segment. If the receive
+ * buffer is full but we expect more data, move on to the
+ * next entry in the scatterlist.
+ *
+ * If the amount of data we received isn't a multiple of 4,
+ * we will transparently receive the pad bytes, too.
+ *
+ * This function must be re-entrant.
+ */
+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);
+		ahash_request_set_crypt(segment->hash, &sg, NULL, copied);
+		crypto_ahash_update(segment->hash);
+	}
+
+	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) {
+		ahash_request_set_crypt(segment->hash, NULL,
+					segment->digest, 0);
+		crypto_ahash_final(segment->hash);
+		iscsi_tcp_segment_splice_digest(segment,
+				 recv ? segment->recv_digest : segment->digest);
+		return 0;
+	}
+
+	return 1;
+}
+EXPORT_SYMBOL_GPL(iscsi_tcp_segment_done);
+
+/**
+ * iscsi_tcp_segment_recv - copy data to segment
+ * @tcp_conn: the iSCSI TCP connection
+ * @segment: the buffer to copy to
+ * @ptr: data pointer
+ * @len: amount of data available
+ *
+ * This function copies up to @len bytes to the
+ * given buffer, and returns the number of bytes
+ * consumed, which can actually be less than @len.
+ *
+ * If hash digest is enabled, the function will update the
+ * hash while copying.
+ * Combining these two operations doesn't buy us a lot (yet),
+ * but in the future we could implement combined copy+crc,
+ * just way we do for network layer checksums.
+ */
+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 ahash_request *hash, const void *hdr,
+		      size_t hdrlen, unsigned char digest[ISCSI_DIGEST_SIZE])
+{
+	struct scatterlist sg;
+
+	sg_init_one(&sg, hdr, hdrlen);
+	ahash_request_set_crypt(hash, &sg, digest, hdrlen);
+	crypto_ahash_digest(hash);
+}
+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 ahash_request *hash)
+{
+	memset(segment, 0, sizeof(*segment));
+	segment->total_size = size;
+	segment->done = done;
+
+	if (hash) {
+		segment->hash = hash;
+		crypto_ahash_init(hash);
+	}
+}
+
+inline void
+iscsi_segment_init_linear(struct iscsi_segment *segment, void *data,
+			  size_t size, iscsi_segment_done_fn_t *done,
+			  struct ahash_request *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 ahash_request *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);
+
+/**
+ * iscsi_tcp_hdr_recv_prep - prep segment for hdr reception
+ * @tcp_conn: iscsi connection to prep for
+ *
+ * This function always passes NULL for the hash argument, because when this
+ * function is called we do not yet know the final size of the header and want
+ * to delay the digest processing until we know that.
+ */
+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 ahash_request *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);
+}
+
+/**
+ * iscsi_tcp_cleanup_task - free tcp_task resources
+ * @task: iscsi task
+ *
+ * must be called with session back_lock
+ */
+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;
+
+	spin_lock_bh(&tcp_task->queue2pool);
+	/* 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;
+	}
+	spin_unlock_bh(&tcp_task->queue2pool);
+}
+EXPORT_SYMBOL_GPL(iscsi_tcp_cleanup_task);
+
+/**
+ * iscsi_tcp_data_in - SCSI Data-In Response processing
+ * @conn: iscsi connection
+ * @task: scsi command 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 = task->sc->sdb.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;
+}
+
+/**
+ * iscsi_tcp_r2t_rsp - iSCSI R2T Response processing
+ * @conn: iscsi connection
+ * @task: scsi command task
+ */
+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);
+	u32 data_length;
+	u32 data_offset;
+	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;
+	}
+
+	data_length = be32_to_cpu(rhdr->data_length);
+	if (data_length == 0) {
+		iscsi_conn_printk(KERN_ERR, conn,
+				  "invalid R2T with zero data len\n");
+		return ISCSI_ERR_DATALEN;
+	}
+
+	if (data_length > session->max_burst)
+		ISCSI_DBG_TCP(conn, "invalid R2T with data len %u and max "
+			      "burst %u. Attempting to execute request.\n",
+			      data_length, session->max_burst);
+
+	data_offset = be32_to_cpu(rhdr->data_offset);
+	if (data_offset + data_length > task->sc->sdb.length) {
+		iscsi_conn_printk(KERN_ERR, conn,
+				  "invalid R2T with data len %u at offset %u "
+				  "and total length %d\n", data_length,
+				  data_offset, task->sc->sdb.length);
+		return ISCSI_ERR_DATALEN;
+	}
+
+	spin_lock(&tcp_task->pool2queue);
+	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 leaked.\n");
+		spin_unlock(&tcp_task->pool2queue);
+		return ISCSI_ERR_PROTO;
+	}
+
+	r2t->exp_statsn = rhdr->statsn;
+	r2t->data_length = data_length;
+	r2t->data_offset = data_offset;
+
+	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++;
+	spin_unlock(&tcp_task->pool2queue);
+
+	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;
+}
+
+/**
+ * iscsi_tcp_hdr_dissect - process PDU header
+ * @conn: iSCSI connection
+ * @hdr: PDU header
+ *
+ * This function analyzes the header of the PDU received,
+ * and performs several sanity checks. If the PDU is accompanied
+ * by data, the receive buffer is set up to copy the incoming data
+ * to the correct location.
+ */
+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->back_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->back_lock);
+			break;
+		}
+
+		if (tcp_conn->in.datalen) {
+			struct iscsi_tcp_task *tcp_task = task->dd_data;
+			struct ahash_request *rx_hash = NULL;
+			struct scsi_data_buffer *sdb = &task->sc->sdb;
+
+			/*
+			 * Setup copy of Data-In into the struct 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->back_lock);
+			return rc;
+		}
+		rc = __iscsi_complete_pdu(conn, hdr, NULL, 0);
+		spin_unlock(&conn->session->back_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->back_lock);
+		task = iscsi_itt_to_ctask(conn, hdr->itt);
+		spin_unlock(&conn->session->back_lock);
+		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;
+			spin_lock(&conn->session->frwd_lock);
+			rc = iscsi_tcp_r2t_rsp(conn, task);
+			spin_unlock(&conn->session->frwd_lock);
+		} else
+			rc = ISCSI_ERR_PROTO;
+		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;
+		}
+		fallthrough;
+	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;
+}
+
+/**
+ * iscsi_tcp_hdr_recv_done - process PDU header
+ * @tcp_conn: iSCSI TCP connection
+ * @segment: the buffer segment being processed
+ *
+ * This is the callback invoked when the PDU header has
+ * been received. If the header is followed by additional
+ * header segments, we go back for more data.
+ */
+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);
+}
+
+/**
+ * iscsi_tcp_recv_segment_is_hdr - tests if we are reading in a header
+ * @tcp_conn: iscsi tcp conn
+ *
+ * returns non zero if we are currently processing or setup to process
+ * a header.
+ */
+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);
+
+/**
+ * iscsi_tcp_recv_skb - Process skb
+ * @conn: iscsi connection
+ * @skb: network buffer with header and/or data segment
+ * @offset: offset in skb
+ * @offloaded: bool indicating if transfer was offloaded
+ * @status: iscsi TCP status result
+ *
+ * Will return status of transfer in @status. And will return
+ * number of bytes copied.
+ */
+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;
+			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);
+
+/**
+ * iscsi_tcp_task_init - Initialize iSCSI SCSI_READ or SCSI_WRITE commands
+ * @task: scsi command task
+ */
+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_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(&tcp_task->queue2pool);
+		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(&tcp_task->queue2pool);
+	}
+
+	return r2t;
+}
+
+/**
+ * iscsi_tcp_task_xmit - xmit normal PDU task
+ * @task: iscsi command task
+ *
+ * We're expected to return 0 when everything was transmitted successfully,
+ * -EAGAIN if there's still data in the queue, or != 0 for any other kind
+ * of error.
+ */
+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;
+		}
+		spin_lock_init(&tcp_task->pool2queue);
+		spin_lock_init(&tcp_task->queue2pool);
+	}
+
+	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);