kernel/drivers/usb/usbip/usbip_common.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2003-2008 Takahiro Hirofuchi
 * Copyright (C) 2015-2016 Samsung Electronics
 *               Krzysztof Opasiak <k.opasiak@samsung.com>
 */

#include <asm/byteorder.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <net/sock.h>

#include "usbip_common.h"

#define DRIVER_AUTHOR "Takahiro Hirofuchi <hirofuchi@users.sourceforge.net>"
#define DRIVER_DESC "USB/IP Core"

#ifdef CONFIG_USBIP_DEBUG
unsigned long usbip_debug_flag = 0xffffffff;
#else
unsigned long usbip_debug_flag;
#endif
EXPORT_SYMBOL_GPL(usbip_debug_flag);
module_param(usbip_debug_flag, ulong, S_IRUGO|S_IWUSR);
MODULE_PARM_DESC(usbip_debug_flag, "debug flags (defined in usbip_common.h)");

/* FIXME */
struct device_attribute dev_attr_usbip_debug;
EXPORT_SYMBOL_GPL(dev_attr_usbip_debug);

static ssize_t usbip_debug_show(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%lx\n", usbip_debug_flag);
}

static ssize_t usbip_debug_store(struct device *dev,
				 struct device_attribute *attr, const char *buf,
				 size_t count)
{
	if (sscanf(buf, "%lx", &usbip_debug_flag) != 1)
		return -EINVAL;
	return count;
}
DEVICE_ATTR_RW(usbip_debug);

static void usbip_dump_buffer(char *buff, int bufflen)
{
	print_hex_dump(KERN_DEBUG, "usbip-core", DUMP_PREFIX_OFFSET, 16, 4,
		       buff, bufflen, false);
}

static void usbip_dump_pipe(unsigned int p)
{
	unsigned char type = usb_pipetype(p);
	unsigned char ep   = usb_pipeendpoint(p);
	unsigned char dev  = usb_pipedevice(p);
	unsigned char dir  = usb_pipein(p);

	pr_debug("dev(%d) ep(%d) [%s] ", dev, ep, dir ? "IN" : "OUT");

	switch (type) {
	case PIPE_ISOCHRONOUS:
		pr_debug("ISO\n");
		break;
	case PIPE_INTERRUPT:
		pr_debug("INT\n");
		break;
	case PIPE_CONTROL:
		pr_debug("CTRL\n");
		break;
	case PIPE_BULK:
		pr_debug("BULK\n");
		break;
	default:
		pr_debug("ERR\n");
		break;
	}
}

static void usbip_dump_usb_device(struct usb_device *udev)
{
	struct device *dev = &udev->dev;
	int i;

	dev_dbg(dev, "       devnum(%d) devpath(%s) usb speed(%s)",
		udev->devnum, udev->devpath, usb_speed_string(udev->speed));

	pr_debug("tt hub ttport %d\n", udev->ttport);

	dev_dbg(dev, "                    ");
	for (i = 0; i < 16; i++)
		pr_debug(" %2u", i);
	pr_debug("\n");

	dev_dbg(dev, "       toggle0(IN) :");
	for (i = 0; i < 16; i++)
		pr_debug(" %2u", (udev->toggle[0] & (1 << i)) ? 1 : 0);
	pr_debug("\n");

	dev_dbg(dev, "       toggle1(OUT):");
	for (i = 0; i < 16; i++)
		pr_debug(" %2u", (udev->toggle[1] & (1 << i)) ? 1 : 0);
	pr_debug("\n");

	dev_dbg(dev, "       epmaxp_in   :");
	for (i = 0; i < 16; i++) {
		if (udev->ep_in[i])
			pr_debug(" %2u",
			    le16_to_cpu(udev->ep_in[i]->desc.wMaxPacketSize));
	}
	pr_debug("\n");

	dev_dbg(dev, "       epmaxp_out  :");
	for (i = 0; i < 16; i++) {
		if (udev->ep_out[i])
			pr_debug(" %2u",
			    le16_to_cpu(udev->ep_out[i]->desc.wMaxPacketSize));
	}
	pr_debug("\n");

	dev_dbg(dev, "parent %s, bus %s\n", dev_name(&udev->parent->dev),
		udev->bus->bus_name);

	dev_dbg(dev, "have_langid %d, string_langid %d\n",
		udev->have_langid, udev->string_langid);

	dev_dbg(dev, "maxchild %d\n", udev->maxchild);
}

static void usbip_dump_request_type(__u8 rt)
{
	switch (rt & USB_RECIP_MASK) {
	case USB_RECIP_DEVICE:
		pr_debug("DEVICE");
		break;
	case USB_RECIP_INTERFACE:
		pr_debug("INTERF");
		break;
	case USB_RECIP_ENDPOINT:
		pr_debug("ENDPOI");
		break;
	case USB_RECIP_OTHER:
		pr_debug("OTHER ");
		break;
	default:
		pr_debug("------");
		break;
	}
}

static void usbip_dump_usb_ctrlrequest(struct usb_ctrlrequest *cmd)
{
	if (!cmd) {
		pr_debug("       : null pointer\n");
		return;
	}

	pr_debug("       ");
	pr_debug("bRequestType(%02X) bRequest(%02X) wValue(%04X) wIndex(%04X) wLength(%04X) ",
		 cmd->bRequestType, cmd->bRequest,
		 cmd->wValue, cmd->wIndex, cmd->wLength);
	pr_debug("\n       ");

	if ((cmd->bRequestType & USB_TYPE_MASK) == USB_TYPE_STANDARD) {
		pr_debug("STANDARD ");
		switch (cmd->bRequest) {
		case USB_REQ_GET_STATUS:
			pr_debug("GET_STATUS\n");
			break;
		case USB_REQ_CLEAR_FEATURE:
			pr_debug("CLEAR_FEAT\n");
			break;
		case USB_REQ_SET_FEATURE:
			pr_debug("SET_FEAT\n");
			break;
		case USB_REQ_SET_ADDRESS:
			pr_debug("SET_ADDRRS\n");
			break;
		case USB_REQ_GET_DESCRIPTOR:
			pr_debug("GET_DESCRI\n");
			break;
		case USB_REQ_SET_DESCRIPTOR:
			pr_debug("SET_DESCRI\n");
			break;
		case USB_REQ_GET_CONFIGURATION:
			pr_debug("GET_CONFIG\n");
			break;
		case USB_REQ_SET_CONFIGURATION:
			pr_debug("SET_CONFIG\n");
			break;
		case USB_REQ_GET_INTERFACE:
			pr_debug("GET_INTERF\n");
			break;
		case USB_REQ_SET_INTERFACE:
			pr_debug("SET_INTERF\n");
			break;
		case USB_REQ_SYNCH_FRAME:
			pr_debug("SYNC_FRAME\n");
			break;
		default:
			pr_debug("REQ(%02X)\n", cmd->bRequest);
			break;
		}
		usbip_dump_request_type(cmd->bRequestType);
	} else if ((cmd->bRequestType & USB_TYPE_MASK) == USB_TYPE_CLASS) {
		pr_debug("CLASS\n");
	} else if ((cmd->bRequestType & USB_TYPE_MASK) == USB_TYPE_VENDOR) {
		pr_debug("VENDOR\n");
	} else if ((cmd->bRequestType & USB_TYPE_MASK) == USB_TYPE_RESERVED) {
		pr_debug("RESERVED\n");
	}
}

void usbip_dump_urb(struct urb *urb)
{
	struct device *dev;

	if (!urb) {
		pr_debug("urb: null pointer!!\n");
		return;
	}

	if (!urb->dev) {
		pr_debug("urb->dev: null pointer!!\n");
		return;
	}

	dev = &urb->dev->dev;

	usbip_dump_usb_device(urb->dev);

	dev_dbg(dev, "   pipe                  :%08x ", urb->pipe);

	usbip_dump_pipe(urb->pipe);

	dev_dbg(dev, "   status                :%d\n", urb->status);
	dev_dbg(dev, "   transfer_flags        :%08X\n", urb->transfer_flags);
	dev_dbg(dev, "   transfer_buffer_length:%d\n",
						urb->transfer_buffer_length);
	dev_dbg(dev, "   actual_length         :%d\n", urb->actual_length);

	if (urb->setup_packet && usb_pipetype(urb->pipe) == PIPE_CONTROL)
		usbip_dump_usb_ctrlrequest(
			(struct usb_ctrlrequest *)urb->setup_packet);

	dev_dbg(dev, "   start_frame           :%d\n", urb->start_frame);
	dev_dbg(dev, "   number_of_packets     :%d\n", urb->number_of_packets);
	dev_dbg(dev, "   interval              :%d\n", urb->interval);
	dev_dbg(dev, "   error_count           :%d\n", urb->error_count);
}
EXPORT_SYMBOL_GPL(usbip_dump_urb);

void usbip_dump_header(struct usbip_header *pdu)
{
	pr_debug("BASE: cmd %u seq %u devid %u dir %u ep %u\n",
		 pdu->base.command,
		 pdu->base.seqnum,
		 pdu->base.devid,
		 pdu->base.direction,
		 pdu->base.ep);

	switch (pdu->base.command) {
	case USBIP_CMD_SUBMIT:
		pr_debug("USBIP_CMD_SUBMIT: x_flags %u x_len %u sf %u #p %d iv %d\n",
			 pdu->u.cmd_submit.transfer_flags,
			 pdu->u.cmd_submit.transfer_buffer_length,
			 pdu->u.cmd_submit.start_frame,
			 pdu->u.cmd_submit.number_of_packets,
			 pdu->u.cmd_submit.interval);
		break;
	case USBIP_CMD_UNLINK:
		pr_debug("USBIP_CMD_UNLINK: seq %u\n",
			 pdu->u.cmd_unlink.seqnum);
		break;
	case USBIP_RET_SUBMIT:
		pr_debug("USBIP_RET_SUBMIT: st %d al %u sf %d #p %d ec %d\n",
			 pdu->u.ret_submit.status,
			 pdu->u.ret_submit.actual_length,
			 pdu->u.ret_submit.start_frame,
			 pdu->u.ret_submit.number_of_packets,
			 pdu->u.ret_submit.error_count);
		break;
	case USBIP_RET_UNLINK:
		pr_debug("USBIP_RET_UNLINK: status %d\n",
			 pdu->u.ret_unlink.status);
		break;
	default:
		/* NOT REACHED */
		pr_err("unknown command\n");
		break;
	}
}
EXPORT_SYMBOL_GPL(usbip_dump_header);

/* Receive data over TCP/IP. */
int usbip_recv(struct socket *sock, void *buf, int size)
{
	int result;
	struct kvec iov = {.iov_base = buf, .iov_len = size};
	struct msghdr msg = {.msg_flags = MSG_NOSIGNAL};
	int total = 0;

	if (!sock || !buf || !size)
		return -EINVAL;

	iov_iter_kvec(&msg.msg_iter, ITER_DEST, &iov, 1, size);

	usbip_dbg_xmit("enter\n");

	do {
		sock->sk->sk_allocation = GFP_NOIO;
		sock->sk->sk_use_task_frag = false;

		result = sock_recvmsg(sock, &msg, MSG_WAITALL);
		if (result <= 0)
			goto err;

		total += result;
	} while (msg_data_left(&msg));

	if (usbip_dbg_flag_xmit) {
		pr_debug("receiving....\n");
		usbip_dump_buffer(buf, size);
		pr_debug("received, osize %d ret %d size %zd total %d\n",
			 size, result, msg_data_left(&msg), total);
	}

	return total;

err:
	return result;
}
EXPORT_SYMBOL_GPL(usbip_recv);

/* there may be more cases to tweak the flags. */
static unsigned int tweak_transfer_flags(unsigned int flags)
{
	flags &= ~URB_NO_TRANSFER_DMA_MAP;
	return flags;
}

/*
 * USBIP driver packs URB transfer flags in PDUs that are exchanged
 * between Server (usbip_host) and Client (vhci_hcd). URB_* flags
 * are internal to kernel and could change. Where as USBIP URB flags
 * exchanged in PDUs are USBIP user API must not change.
 *
 * USBIP_URB* flags are exported as explicit API and client and server
 * do mapping from kernel flags to USBIP_URB*. Details as follows:
 *
 * Client tx path (USBIP_CMD_SUBMIT):
 * - Maps URB_* to USBIP_URB_* when it sends USBIP_CMD_SUBMIT packet.
 *
 * Server rx path (USBIP_CMD_SUBMIT):
 * - Maps USBIP_URB_* to URB_* when it receives USBIP_CMD_SUBMIT packet.
 *
 * Flags aren't included in USBIP_CMD_UNLINK and USBIP_RET_SUBMIT packets
 * and no special handling is needed for them in the following cases:
 * - Server rx path (USBIP_CMD_UNLINK)
 * - Client rx path & Server tx path (USBIP_RET_SUBMIT)
 *
 * Code paths:
 * usbip_pack_pdu() is the common routine that handles packing pdu from
 * urb and unpack pdu to an urb.
 *
 * usbip_pack_cmd_submit() and usbip_pack_ret_submit() handle
 * USBIP_CMD_SUBMIT and USBIP_RET_SUBMIT respectively.
 *
 * usbip_map_urb_to_usbip() and usbip_map_usbip_to_urb() are used
 * by usbip_pack_cmd_submit() and usbip_pack_ret_submit() to map
 * flags.
 */

struct urb_to_usbip_flags {
	u32 urb_flag;
	u32 usbip_flag;
};

#define NUM_USBIP_FLAGS	17

static const struct urb_to_usbip_flags flag_map[NUM_USBIP_FLAGS] = {
	{URB_SHORT_NOT_OK, USBIP_URB_SHORT_NOT_OK},
	{URB_ISO_ASAP, USBIP_URB_ISO_ASAP},
	{URB_NO_TRANSFER_DMA_MAP, USBIP_URB_NO_TRANSFER_DMA_MAP},
	{URB_ZERO_PACKET, USBIP_URB_ZERO_PACKET},
	{URB_NO_INTERRUPT, USBIP_URB_NO_INTERRUPT},
	{URB_FREE_BUFFER, USBIP_URB_FREE_BUFFER},
	{URB_DIR_IN, USBIP_URB_DIR_IN},
	{URB_DIR_OUT, USBIP_URB_DIR_OUT},
	{URB_DIR_MASK, USBIP_URB_DIR_MASK},
	{URB_DMA_MAP_SINGLE, USBIP_URB_DMA_MAP_SINGLE},
	{URB_DMA_MAP_PAGE, USBIP_URB_DMA_MAP_PAGE},
	{URB_DMA_MAP_SG, USBIP_URB_DMA_MAP_SG},
	{URB_MAP_LOCAL, USBIP_URB_MAP_LOCAL},
	{URB_SETUP_MAP_SINGLE, USBIP_URB_SETUP_MAP_SINGLE},
	{URB_SETUP_MAP_LOCAL, USBIP_URB_SETUP_MAP_LOCAL},
	{URB_DMA_SG_COMBINED, USBIP_URB_DMA_SG_COMBINED},
	{URB_ALIGNED_TEMP_BUFFER, USBIP_URB_ALIGNED_TEMP_BUFFER},
};

static unsigned int urb_to_usbip(unsigned int flags)
{
	unsigned int map_flags = 0;
	int loop;

	for (loop = 0; loop < NUM_USBIP_FLAGS; loop++) {
		if (flags & flag_map[loop].urb_flag)
			map_flags |= flag_map[loop].usbip_flag;
	}

	return map_flags;
}

static unsigned int usbip_to_urb(unsigned int flags)
{
	unsigned int map_flags = 0;
	int loop;

	for (loop = 0; loop < NUM_USBIP_FLAGS; loop++) {
		if (flags & flag_map[loop].usbip_flag)
			map_flags |= flag_map[loop].urb_flag;
	}

	return map_flags;
}

static void usbip_pack_cmd_submit(struct usbip_header *pdu, struct urb *urb,
				  int pack)
{
	struct usbip_header_cmd_submit *spdu = &pdu->u.cmd_submit;

	/*
	 * Some members are not still implemented in usbip. I hope this issue
	 * will be discussed when usbip is ported to other operating systems.
	 */
	if (pack) {
		/* map after tweaking the urb flags */
		spdu->transfer_flags = urb_to_usbip(tweak_transfer_flags(urb->transfer_flags));
		spdu->transfer_buffer_length	= urb->transfer_buffer_length;
		spdu->start_frame		= urb->start_frame;
		spdu->number_of_packets		= urb->number_of_packets;
		spdu->interval			= urb->interval;
	} else  {
		urb->transfer_flags         = usbip_to_urb(spdu->transfer_flags);
		urb->transfer_buffer_length = spdu->transfer_buffer_length;
		urb->start_frame            = spdu->start_frame;
		urb->number_of_packets      = spdu->number_of_packets;
		urb->interval               = spdu->interval;
	}
}

static void usbip_pack_ret_submit(struct usbip_header *pdu, struct urb *urb,
				  int pack)
{
	struct usbip_header_ret_submit *rpdu = &pdu->u.ret_submit;

	if (pack) {
		rpdu->status		= urb->status;
		rpdu->actual_length	= urb->actual_length;
		rpdu->start_frame	= urb->start_frame;
		rpdu->number_of_packets = urb->number_of_packets;
		rpdu->error_count	= urb->error_count;
	} else {
		urb->status		= rpdu->status;
		urb->actual_length	= rpdu->actual_length;
		urb->start_frame	= rpdu->start_frame;
		urb->number_of_packets = rpdu->number_of_packets;
		urb->error_count	= rpdu->error_count;
	}
}

void usbip_pack_pdu(struct usbip_header *pdu, struct urb *urb, int cmd,
		    int pack)
{
	switch (cmd) {
	case USBIP_CMD_SUBMIT:
		usbip_pack_cmd_submit(pdu, urb, pack);
		break;
	case USBIP_RET_SUBMIT:
		usbip_pack_ret_submit(pdu, urb, pack);
		break;
	default:
		/* NOT REACHED */
		pr_err("unknown command\n");
		break;
	}
}
EXPORT_SYMBOL_GPL(usbip_pack_pdu);

static void correct_endian_basic(struct usbip_header_basic *base, int send)
{
	if (send) {
		base->command	= cpu_to_be32(base->command);
		base->seqnum	= cpu_to_be32(base->seqnum);
		base->devid	= cpu_to_be32(base->devid);
		base->direction	= cpu_to_be32(base->direction);
		base->ep	= cpu_to_be32(base->ep);
	} else {
		base->command	= be32_to_cpu(base->command);
		base->seqnum	= be32_to_cpu(base->seqnum);
		base->devid	= be32_to_cpu(base->devid);
		base->direction	= be32_to_cpu(base->direction);
		base->ep	= be32_to_cpu(base->ep);
	}
}

static void correct_endian_cmd_submit(struct usbip_header_cmd_submit *pdu,
				      int send)
{
	if (send) {
		pdu->transfer_flags = cpu_to_be32(pdu->transfer_flags);

		cpu_to_be32s(&pdu->transfer_buffer_length);
		cpu_to_be32s(&pdu->start_frame);
		cpu_to_be32s(&pdu->number_of_packets);
		cpu_to_be32s(&pdu->interval);
	} else {
		pdu->transfer_flags = be32_to_cpu(pdu->transfer_flags);

		be32_to_cpus(&pdu->transfer_buffer_length);
		be32_to_cpus(&pdu->start_frame);
		be32_to_cpus(&pdu->number_of_packets);
		be32_to_cpus(&pdu->interval);
	}
}

static void correct_endian_ret_submit(struct usbip_header_ret_submit *pdu,
				      int send)
{
	if (send) {
		cpu_to_be32s(&pdu->status);
		cpu_to_be32s(&pdu->actual_length);
		cpu_to_be32s(&pdu->start_frame);
		cpu_to_be32s(&pdu->number_of_packets);
		cpu_to_be32s(&pdu->error_count);
	} else {
		be32_to_cpus(&pdu->status);
		be32_to_cpus(&pdu->actual_length);
		be32_to_cpus(&pdu->start_frame);
		be32_to_cpus(&pdu->number_of_packets);
		be32_to_cpus(&pdu->error_count);
	}
}

static void correct_endian_cmd_unlink(struct usbip_header_cmd_unlink *pdu,
				      int send)
{
	if (send)
		pdu->seqnum = cpu_to_be32(pdu->seqnum);
	else
		pdu->seqnum = be32_to_cpu(pdu->seqnum);
}

static void correct_endian_ret_unlink(struct usbip_header_ret_unlink *pdu,
				      int send)
{
	if (send)
		cpu_to_be32s(&pdu->status);
	else
		be32_to_cpus(&pdu->status);
}

void usbip_header_correct_endian(struct usbip_header *pdu, int send)
{
	__u32 cmd = 0;

	if (send)
		cmd = pdu->base.command;

	correct_endian_basic(&pdu->base, send);

	if (!send)
		cmd = pdu->base.command;

	switch (cmd) {
	case USBIP_CMD_SUBMIT:
		correct_endian_cmd_submit(&pdu->u.cmd_submit, send);
		break;
	case USBIP_RET_SUBMIT:
		correct_endian_ret_submit(&pdu->u.ret_submit, send);
		break;
	case USBIP_CMD_UNLINK:
		correct_endian_cmd_unlink(&pdu->u.cmd_unlink, send);
		break;
	case USBIP_RET_UNLINK:
		correct_endian_ret_unlink(&pdu->u.ret_unlink, send);
		break;
	default:
		/* NOT REACHED */
		pr_err("unknown command\n");
		break;
	}
}
EXPORT_SYMBOL_GPL(usbip_header_correct_endian);

static void usbip_iso_packet_correct_endian(
		struct usbip_iso_packet_descriptor *iso, int send)
{
	/* does not need all members. but copy all simply. */
	if (send) {
		iso->offset	= cpu_to_be32(iso->offset);
		iso->length	= cpu_to_be32(iso->length);
		iso->status	= cpu_to_be32(iso->status);
		iso->actual_length = cpu_to_be32(iso->actual_length);
	} else {
		iso->offset	= be32_to_cpu(iso->offset);
		iso->length	= be32_to_cpu(iso->length);
		iso->status	= be32_to_cpu(iso->status);
		iso->actual_length = be32_to_cpu(iso->actual_length);
	}
}

static void usbip_pack_iso(struct usbip_iso_packet_descriptor *iso,
			   struct usb_iso_packet_descriptor *uiso, int pack)
{
	if (pack) {
		iso->offset		= uiso->offset;
		iso->length		= uiso->length;
		iso->status		= uiso->status;
		iso->actual_length	= uiso->actual_length;
	} else {
		uiso->offset		= iso->offset;
		uiso->length		= iso->length;
		uiso->status		= iso->status;
		uiso->actual_length	= iso->actual_length;
	}
}

/* must free buffer */
struct usbip_iso_packet_descriptor*
usbip_alloc_iso_desc_pdu(struct urb *urb, ssize_t *bufflen)
{
	struct usbip_iso_packet_descriptor *iso;
	int np = urb->number_of_packets;
	ssize_t size = np * sizeof(*iso);
	int i;

	iso = kzalloc(size, GFP_KERNEL);
	if (!iso)
		return NULL;

	for (i = 0; i < np; i++) {
		usbip_pack_iso(&iso[i], &urb->iso_frame_desc[i], 1);
		usbip_iso_packet_correct_endian(&iso[i], 1);
	}

	*bufflen = size;

	return iso;
}
EXPORT_SYMBOL_GPL(usbip_alloc_iso_desc_pdu);

/* some members of urb must be substituted before. */
int usbip_recv_iso(struct usbip_device *ud, struct urb *urb)
{
	void *buff;
	struct usbip_iso_packet_descriptor *iso;
	int np = urb->number_of_packets;
	int size = np * sizeof(*iso);
	int i;
	int ret;
	int total_length = 0;

	if (!usb_pipeisoc(urb->pipe))
		return 0;

	/* my Bluetooth dongle gets ISO URBs which are np = 0 */
	if (np == 0)
		return 0;

	buff = kzalloc(size, GFP_KERNEL);
	if (!buff)
		return -ENOMEM;

	ret = usbip_recv(ud->tcp_socket, buff, size);
	if (ret != size) {
		dev_err(&urb->dev->dev, "recv iso_frame_descriptor, %d\n",
			ret);
		kfree(buff);

		if (ud->side == USBIP_STUB || ud->side == USBIP_VUDC)
			usbip_event_add(ud, SDEV_EVENT_ERROR_TCP);
		else
			usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);

		return -EPIPE;
	}

	iso = (struct usbip_iso_packet_descriptor *) buff;
	for (i = 0; i < np; i++) {
		usbip_iso_packet_correct_endian(&iso[i], 0);
		usbip_pack_iso(&iso[i], &urb->iso_frame_desc[i], 0);
		total_length += urb->iso_frame_desc[i].actual_length;
	}

	kfree(buff);

	if (total_length != urb->actual_length) {
		dev_err(&urb->dev->dev,
			"total length of iso packets %d not equal to actual length of buffer %d\n",
			total_length, urb->actual_length);

		if (ud->side == USBIP_STUB || ud->side == USBIP_VUDC)
			usbip_event_add(ud, SDEV_EVENT_ERROR_TCP);
		else
			usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);

		return -EPIPE;
	}

	return ret;
}
EXPORT_SYMBOL_GPL(usbip_recv_iso);

/*
 * This functions restores the padding which was removed for optimizing
 * the bandwidth during transfer over tcp/ip
 *
 * buffer and iso packets need to be stored and be in propeper endian in urb
 * before calling this function
 */
void usbip_pad_iso(struct usbip_device *ud, struct urb *urb)
{
	int np = urb->number_of_packets;
	int i;
	int actualoffset = urb->actual_length;

	if (!usb_pipeisoc(urb->pipe))
		return;

	/* if no packets or length of data is 0, then nothing to unpack */
	if (np == 0 || urb->actual_length == 0)
		return;

	/*
	 * if actual_length is transfer_buffer_length then no padding is
	 * present.
	 */
	if (urb->actual_length == urb->transfer_buffer_length)
		return;

	/*
	 * loop over all packets from last to first (to prevent overwriting
	 * memory when padding) and move them into the proper place
	 */
	for (i = np-1; i > 0; i--) {
		actualoffset -= urb->iso_frame_desc[i].actual_length;
		memmove(urb->transfer_buffer + urb->iso_frame_desc[i].offset,
			urb->transfer_buffer + actualoffset,
			urb->iso_frame_desc[i].actual_length);
	}
}
EXPORT_SYMBOL_GPL(usbip_pad_iso);

/* some members of urb must be substituted before. */
int usbip_recv_xbuff(struct usbip_device *ud, struct urb *urb)
{
	struct scatterlist *sg;
	int ret = 0;
	int recv;
	int size;
	int copy;
	int i;

	if (ud->side == USBIP_STUB || ud->side == USBIP_VUDC) {
		/* the direction of urb must be OUT. */
		if (usb_pipein(urb->pipe))
			return 0;

		size = urb->transfer_buffer_length;
	} else {
		/* the direction of urb must be IN. */
		if (usb_pipeout(urb->pipe))
			return 0;

		size = urb->actual_length;
	}

	/* no need to recv xbuff */
	if (!(size > 0))
		return 0;

	if (size > urb->transfer_buffer_length)
		/* should not happen, probably malicious packet */
		goto error;

	if (urb->num_sgs) {
		copy = size;
		for_each_sg(urb->sg, sg, urb->num_sgs, i) {
			int recv_size;

			if (copy < sg->length)
				recv_size = copy;
			else
				recv_size = sg->length;

			recv = usbip_recv(ud->tcp_socket, sg_virt(sg),
						recv_size);

			if (recv != recv_size)
				goto error;

			copy -= recv;
			ret += recv;

			if (!copy)
				break;
		}

		if (ret != size)
			goto error;
	} else {
		ret = usbip_recv(ud->tcp_socket, urb->transfer_buffer, size);
		if (ret != size)
			goto error;
	}

	return ret;

error:
	dev_err(&urb->dev->dev, "recv xbuf, %d\n", ret);
	if (ud->side == USBIP_STUB || ud->side == USBIP_VUDC)
		usbip_event_add(ud, SDEV_EVENT_ERROR_TCP);
	else
		usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);

	return -EPIPE;
}
EXPORT_SYMBOL_GPL(usbip_recv_xbuff);

static int __init usbip_core_init(void)
{
	return usbip_init_eh();
}

static void __exit usbip_core_exit(void)
{
	usbip_finish_eh();
	return;
}

module_init(usbip_core_init);
module_exit(usbip_core_exit);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");