text: /*
   * Host Side support for RNDIS Networking Links
   * Copyright (C) 2005 by David Brownell
   *
   * 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  // #define	DEBUG			// error path messages, extra info
  // #define	VERBOSE			// more; success messages
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/netdevice.h>
  #include <linux/etherdevice.h>
  #include <linux/ethtool.h>
  #include <linux/workqueue.h>
  #include <linux/mii.h>
  #include <linux/usb.h>
  #include <linux/usb/cdc.h>
  
  #include "usbnet.h"
  
  
  /*
   * RNDIS is NDIS remoted over USB.  It's a MSFT variant of CDC ACM ... of
   * course ACM was intended for modems, not Ethernet links!  USB's standard
   * for Ethernet links is "CDC Ethernet", which is significantly simpler.
   *
   * NOTE that Microsoft's "RNDIS 1.0" specification is incomplete.  Issues
   * include:
   *    - Power management in particular relies on information that's scattered
   *	through other documentation, and which is incomplete or incorrect even
   *	there.
   *    - There are various undocumented protocol requirements, such as the
   *	need to send unused garbage in control-OUT messages.
   *    - In some cases, MS-Windows will emit undocumented requests; this
   *	matters more to peripheral implementations than host ones.
   *
   * Moreover there's a no-open-specs variant of RNDIS called "ActiveSync".
   *
   * For these reasons and others, ** USE OF RNDIS IS STRONGLY DISCOURAGED ** in
   * favor of such non-proprietary alternatives as CDC Ethernet or the newer (and
   * currently rare) "Ethernet Emulation Model" (EEM).
   */
  
  /*
   * CONTROL uses CDC "encapsulated commands" with funky notifications.
   *  - control-out:  SEND_ENCAPSULATED
   *  - interrupt-in:  RESPONSE_AVAILABLE
   *  - control-in:  GET_ENCAPSULATED
   *
   * We'll try to ignore the RESPONSE_AVAILABLE notifications.
   *
   * REVISIT some RNDIS implementations seem to have curious issues still
   * to be resolved.
   */
  struct rndis_msg_hdr {
  	__le32	msg_type;			/* RNDIS_MSG_* */
  	__le32	msg_len;
  	// followed by data that varies between messages
  	__le32	request_id;
  	__le32	status;
  	// ... and more
  } __attribute__ ((packed));
  
  /* MS-Windows uses this strange size, but RNDIS spec says 1024 minimum */
  #define	CONTROL_BUFFER_SIZE		1025
  
  /* RNDIS defines an (absurdly huge) 10 second control timeout,
   * but ActiveSync seems to use a more usual 5 second timeout
   * (which matches the USB 2.0 spec).
   */
  #define	RNDIS_CONTROL_TIMEOUT_MS	(5 * 1000)
  
  
  #define ccpu2 __constant_cpu_to_le32
  
  #define RNDIS_MSG_COMPLETION	ccpu2(0x80000000)
  
  /* codes for "msg_type" field of rndis messages;
   * only the data channel uses packet messages (maybe batched);
   * everything else goes on the control channel.
   */
  #define RNDIS_MSG_PACKET	ccpu2(0x00000001)	/* 1-N packets */
  #define RNDIS_MSG_INIT		ccpu2(0x00000002)
  #define RNDIS_MSG_INIT_C	(RNDIS_MSG_INIT|RNDIS_MSG_COMPLETION)
  #define RNDIS_MSG_HALT		ccpu2(0x00000003)
  #define RNDIS_MSG_QUERY		ccpu2(0x00000004)
  #define RNDIS_MSG_QUERY_C	(RNDIS_MSG_QUERY|RNDIS_MSG_COMPLETION)
  #define RNDIS_MSG_SET		ccpu2(0x00000005)
  #define RNDIS_MSG_SET_C		(RNDIS_MSG_SET|RNDIS_MSG_COMPLETION)
  #define RNDIS_MSG_RESET		ccpu2(0x00000006)
  #define RNDIS_MSG_RESET_C	(RNDIS_MSG_RESET|RNDIS_MSG_COMPLETION)
  #define RNDIS_MSG_INDICATE	ccpu2(0x00000007)
  #define RNDIS_MSG_KEEPALIVE	ccpu2(0x00000008)
  #define RNDIS_MSG_KEEPALIVE_C	(RNDIS_MSG_KEEPALIVE|RNDIS_MSG_COMPLETION)
  
  /* codes for "status" field of completion messages */
  #define	RNDIS_STATUS_SUCCESS		ccpu2(0x00000000)
  #define	RNDIS_STATUS_FAILURE		ccpu2(0xc0000001)
  #define	RNDIS_STATUS_INVALID_DATA	ccpu2(0xc0010015)
  #define	RNDIS_STATUS_NOT_SUPPORTED	ccpu2(0xc00000bb)
  #define	RNDIS_STATUS_MEDIA_CONNECT	ccpu2(0x4001000b)
  #define	RNDIS_STATUS_MEDIA_DISCONNECT	ccpu2(0x4001000c)
  
  
  struct rndis_data_hdr {
  	__le32	msg_type;		/* RNDIS_MSG_PACKET */
  	__le32	msg_len;		// rndis_data_hdr + data_len + pad
  	__le32	data_offset;		// 36 -- right after header
  	__le32	data_len;		// ... real packet size
  
  	__le32	oob_data_offset;	// zero
  	__le32	oob_data_len;		// zero
  	__le32	num_oob;		// zero
  	__le32	packet_data_offset;	// zero
  
  	__le32	packet_data_len;	// zero
  	__le32	vc_handle;		// zero
  	__le32	reserved;		// zero
  } __attribute__ ((packed));
  
  struct rndis_init {		/* OUT */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_INIT */
  	__le32	msg_len;			// 24
  	__le32	request_id;
  	__le32	major_version;			// of rndis (1.0)
  	__le32	minor_version;
  	__le32	max_transfer_size;
  } __attribute__ ((packed));
  
  struct rndis_init_c {		/* IN */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_INIT_C */
  	__le32	msg_len;
  	__le32	request_id;
  	__le32	status;
  	__le32	major_version;			// of rndis (1.0)
  	__le32	minor_version;
  	__le32	device_flags;
  	__le32	medium;				// zero == 802.3
  	__le32	max_packets_per_message;
  	__le32	max_transfer_size;
  	__le32	packet_alignment;		// max 7; (1<<n) bytes
  	__le32	af_list_offset;			// zero
  	__le32	af_list_size;			// zero
  } __attribute__ ((packed));
  
  struct rndis_halt {		/* OUT (no reply) */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_HALT */
  	__le32	msg_len;
  	__le32	request_id;
  } __attribute__ ((packed));
  
  struct rndis_query {		/* OUT */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_QUERY */
  	__le32	msg_len;
  	__le32	request_id;
  	__le32	oid;
  	__le32	len;
  	__le32	offset;
  /*?*/	__le32	handle;				// zero
  } __attribute__ ((packed));
  
  struct rndis_query_c {		/* IN */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_QUERY_C */
  	__le32	msg_len;
  	__le32	request_id;
  	__le32	status;
  	__le32	len;
  	__le32	offset;
  } __attribute__ ((packed));
  
  struct rndis_set {		/* OUT */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_SET */
  	__le32	msg_len;
  	__le32	request_id;
  	__le32	oid;
  	__le32	len;
  	__le32	offset;
  /*?*/	__le32	handle;				// zero
  } __attribute__ ((packed));
  
  struct rndis_set_c {		/* IN */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_SET_C */
  	__le32	msg_len;
  	__le32	request_id;
  	__le32	status;
  } __attribute__ ((packed));
  
  struct rndis_reset {		/* IN */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_RESET */
  	__le32	msg_len;
  	__le32	reserved;
  } __attribute__ ((packed));
  
  struct rndis_reset_c {		/* OUT */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_RESET_C */
  	__le32	msg_len;
  	__le32	status;
  	__le32	addressing_lost;
  } __attribute__ ((packed));
  
  struct rndis_indicate {		/* IN (unrequested) */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_INDICATE */
  	__le32	msg_len;
  	__le32	status;
  	__le32	length;
  	__le32	offset;
  /**/	__le32	diag_status;
  	__le32	error_offset;
  /**/	__le32	message;
  } __attribute__ ((packed));
  
  struct rndis_keepalive {	/* OUT (optionally IN) */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_KEEPALIVE */
  	__le32	msg_len;
  	__le32	request_id;
  } __attribute__ ((packed));
  
  struct rndis_keepalive_c {	/* IN (optionally OUT) */
  	// header and:
  	__le32	msg_type;			/* RNDIS_MSG_KEEPALIVE_C */
  	__le32	msg_len;
  	__le32	request_id;
  	__le32	status;
  } __attribute__ ((packed));
  
  /* NOTE:  about 30 OIDs are "mandatory" for peripherals to support ... and
   * there are gobs more that may optionally be supported.  We'll avoid as much
   * of that mess as possible.
   */
  #define OID_802_3_PERMANENT_ADDRESS	ccpu2(0x01010101)
  #define OID_GEN_MAXIMUM_FRAME_SIZE	ccpu2(0x00010106)
  #define OID_GEN_CURRENT_PACKET_FILTER	ccpu2(0x0001010e)
  
  /*
   * RNDIS notifications from device: command completion; "reverse"
   * keepalives; etc
   */
  static void rndis_status(struct usbnet *dev, struct urb *urb)
  {
  	devdbg(dev, "rndis status urb, len %d stat %d",
  		urb->actual_length, urb->status);
  	// FIXME for keepalives, respond immediately (asynchronously)
  	// if not an RNDIS status, do like cdc_status(dev,urb) does
  }
  
  /*
   * RPC done RNDIS-style.  Caller guarantees:
   * - message is properly byteswapped
   * - there's no other request pending
   * - buf can hold up to 1KB response (required by RNDIS spec)
   * On return, the first few entries are already byteswapped.
   *
   * Call context is likely probe(), before interface name is known,
   * which is why we won't try to use it in the diagnostics.
   */
  static int rndis_command(struct usbnet *dev, struct rndis_msg_hdr *buf)
  {
  	struct cdc_state	*info = (void *) &dev->data;
  	int			master_ifnum;
  	int			retval;
  	unsigned		count;
  	__le32			rsp;
  	u32			xid = 0, msg_len, request_id;
  
  	/* REVISIT when this gets called from contexts other than probe() or
  	 * disconnect(): either serialize, or dispatch responses on xid
  	 */
  
  	/* Issue the request; xid is unique, don't bother byteswapping it */
  	if (likely(buf->msg_type != RNDIS_MSG_HALT
  			&& buf->msg_type != RNDIS_MSG_RESET)) {
  		xid = dev->xid++;
  		if (!xid)
  			xid = dev->xid++;
  		buf->request_id = (__force __le32) xid;
  	}
  	master_ifnum = info->control->cur_altsetting->desc.bInterfaceNumber;
  	retval = usb_control_msg(dev->udev,
  		usb_sndctrlpipe(dev->udev, 0),
  		USB_CDC_SEND_ENCAPSULATED_COMMAND,
  		USB_TYPE_CLASS | USB_RECIP_INTERFACE,
  		0, master_ifnum,
  		buf, le32_to_cpu(buf->msg_len),
  		RNDIS_CONTROL_TIMEOUT_MS);
  	if (unlikely(retval < 0 || xid == 0))
  		return retval;
  
  	// FIXME Seems like some devices discard responses when
  	// we time out and cancel our "get response" requests...
  	// so, this is fragile.  Probably need to poll for status.
  
  	/* ignore status endpoint, just poll the control channel;
  	 * the request probably completed immediately
  	 */
  	rsp = buf->msg_type | RNDIS_MSG_COMPLETION;
  	for (count = 0; count < 10; count++) {
  		memset(buf, 0, CONTROL_BUFFER_SIZE);
  		retval = usb_control_msg(dev->udev,
  			usb_rcvctrlpipe(dev->udev, 0),
  			USB_CDC_GET_ENCAPSULATED_RESPONSE,
  			USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
  			0, master_ifnum,
  			buf, CONTROL_BUFFER_SIZE,
  			RNDIS_CONTROL_TIMEOUT_MS);
  		if (likely(retval >= 8)) {
  			msg_len = le32_to_cpu(buf->msg_len);
  			request_id = (__force u32) buf->request_id;
  			if (likely(buf->msg_type == rsp)) {
  				if (likely(request_id == xid)) {
  					if (unlikely(rsp == RNDIS_MSG_RESET_C))
  						return 0;
  					if (likely(RNDIS_STATUS_SUCCESS
  							== buf->status))
  						return 0;
  					dev_dbg(&info->control->dev,
  						"rndis reply status %08x\n",
  						le32_to_cpu(buf->status));
  					return -EL3RST;
  				}
  				dev_dbg(&info->control->dev,
  					"rndis reply id %d expected %d\n",
  					request_id, xid);
  				/* then likely retry */
  			} else switch (buf->msg_type) {
  			case RNDIS_MSG_INDICATE: {	/* fault */
  				// struct rndis_indicate *msg = (void *)buf;
  				dev_info(&info->control->dev,
  					"rndis fault indication\n");
  				}
  				break;
  			case RNDIS_MSG_KEEPALIVE: {	/* ping */
  				struct rndis_keepalive_c *msg = (void *)buf;
  
  				msg->msg_type = RNDIS_MSG_KEEPALIVE_C;
  				msg->msg_len = ccpu2(sizeof *msg);
  				msg->status = RNDIS_STATUS_SUCCESS;
  				retval = usb_control_msg(dev->udev,
  					usb_sndctrlpipe(dev->udev, 0),
  					USB_CDC_SEND_ENCAPSULATED_COMMAND,
  					USB_TYPE_CLASS | USB_RECIP_INTERFACE,
  					0, master_ifnum,
  					msg, sizeof *msg,
  					RNDIS_CONTROL_TIMEOUT_MS);
  				if (unlikely(retval < 0))
  					dev_dbg(&info->control->dev,
  						"rndis keepalive err %d\n",
  						retval);
  				}
  				break;
  			default:
  				dev_dbg(&info->control->dev,
  					"unexpected rndis msg %08x len %d\n",
  					le32_to_cpu(buf->msg_type), msg_len);
  			}
  		} else {
  			/* device probably issued a protocol stall; ignore */
  			dev_dbg(&info->control->dev,
  				"rndis response error, code %d\n", retval);
  		}
  		msleep(2);
  	}
  	dev_dbg(&info->control->dev, "rndis response timeout\n");
  	return -ETIMEDOUT;
  }
  
  /*
   * rndis_query:
   *
   * Performs a query for @oid along with 0 or more bytes of payload as
   * specified by @in_len. If @reply_len is not set to -1 then the reply
   * length is checked against this value, resulting in an error if it
   * doesn't match.
   *
   * NOTE: Adding a payload exactly or greater than the size of the expected
   * response payload is an evident requirement MSFT added for ActiveSync.
   *
   * The only exception is for OIDs that return a variably sized response,
   * in which case no payload should be added.  This undocumented (and
   * nonsensical!) issue was found by sniffing protocol requests from the
   * ActiveSync 4.1 Windows driver.
   */
  static int rndis_query(struct usbnet *dev, struct usb_interface *intf,
  		void *buf, u32 oid, u32 in_len,
  		void **reply, int *reply_len)
  {
  	int retval;
  	union {
  		void			*buf;
  		struct rndis_msg_hdr	*header;
  		struct rndis_query	*get;
  		struct rndis_query_c	*get_c;
  	} u;
  	u32 off, len;
  
  	u.buf = buf;
  
  	memset(u.get, 0, sizeof *u.get + in_len);
  	u.get->msg_type = RNDIS_MSG_QUERY;
  	u.get->msg_len = cpu_to_le32(sizeof *u.get + in_len);
  	u.get->oid = oid;
  	u.get->len = cpu_to_le32(in_len);
  	u.get->offset = ccpu2(20);
  
  	retval = rndis_command(dev, u.header);
  	if (unlikely(retval < 0)) {
  		dev_err(&intf->dev, "RNDIS_MSG_QUERY(0x%08x) failed, %d\n",
  				oid, retval);
  		return retval;
  	}
  
  	off = le32_to_cpu(u.get_c->offset);
  	len = le32_to_cpu(u.get_c->len);
  	if (unlikely((8 + off + len) > CONTROL_BUFFER_SIZE))
  		goto response_error;
  
  	if (*reply_len != -1 && len != *reply_len)
  		goto response_error;
  
  	*reply = (unsigned char *) &u.get_c->request_id + off;
  	*reply_len = len;
  
  	return retval;
  
  response_error:
  	dev_err(&intf->dev, "RNDIS_MSG_QUERY(0x%08x) "
  			"invalid response - off %d len %d\n",
  		oid, off, len);
  	return -EDOM;
  }
  
  static int rndis_bind(struct usbnet *dev, struct usb_interface *intf)
  {
  	int			retval;
  	struct net_device	*net = dev->net;
  	struct cdc_state	*info = (void *) &dev->data;
  	union {
  		void			*buf;
  		struct rndis_msg_hdr	*header;
  		struct rndis_init	*init;
  		struct rndis_init_c	*init_c;
  		struct rndis_query	*get;
  		struct rndis_query_c	*get_c;
  		struct rndis_set	*set;
  		struct rndis_set_c	*set_c;
  	} u;
  	u32			tmp;
  	int			reply_len;
  	unsigned char		*bp;
  
  	/* we can't rely on i/o from stack working, or stack allocation */
  	u.buf = kmalloc(CONTROL_BUFFER_SIZE, GFP_KERNEL);
  	if (!u.buf)
  		return -ENOMEM;
  	retval = usbnet_generic_cdc_bind(dev, intf);
  	if (retval < 0)
  		goto fail;
  
  	u.init->msg_type = RNDIS_MSG_INIT;
  	u.init->msg_len = ccpu2(sizeof *u.init);
  	u.init->major_version = ccpu2(1);
  	u.init->minor_version = ccpu2(0);
  
  	/* max transfer (in spec) is 0x4000 at full speed, but for
  	 * TX we'll stick to one Ethernet packet plus RNDIS framing.
  	 * For RX we handle drivers that zero-pad to end-of-packet.
  	 * Don't let userspace change these settings.
  	 *
  	 * NOTE: there still seems to be wierdness here, as if we need
  	 * to do some more things to make sure WinCE targets accept this.
  	 * They default to jumbograms of 8KB or 16KB, which is absurd
  	 * for such low data rates and which is also more than Linux
  	 * can usually expect to allocate for SKB data...
  	 */
  	net->hard_header_len += sizeof (struct rndis_data_hdr);
  	dev->hard_mtu = net->mtu + net->hard_header_len;
  
  	dev->rx_urb_size = dev->hard_mtu + (dev->maxpacket + 1);
  	dev->rx_urb_size &= ~(dev->maxpacket - 1);
  	u.init->max_transfer_size = cpu_to_le32(dev->rx_urb_size);
  
  	net->change_mtu = NULL;
  	retval = rndis_command(dev, u.header);
  	if (unlikely(retval < 0)) {
  		/* it might not even be an RNDIS device!! */
  		dev_err(&intf->dev, "RNDIS init failed, %d\n", retval);
  		goto fail_and_release;
  	}
  	tmp = le32_to_cpu(u.init_c->max_transfer_size);
  	if (tmp < dev->hard_mtu) {
  		dev_err(&intf->dev,
  			"dev can't take %u byte packets (max %u)\n",
  			dev->hard_mtu, tmp);
  		retval = -EINVAL;
  		goto fail_and_release;
  	}
  
  	/* REVISIT:  peripheral "alignment" request is ignored ... */
  	dev_dbg(&intf->dev,
  		"hard mtu %u (%u from dev), rx buflen %Zu, align %d\n",
  		dev->hard_mtu, tmp, dev->rx_urb_size,
  		1 << le32_to_cpu(u.init_c->packet_alignment));
  
  	/* Get designated host ethernet address */
  	reply_len = ETH_ALEN;
  	retval = rndis_query(dev, intf, u.buf, OID_802_3_PERMANENT_ADDRESS,
  			48, (void **) &bp, &reply_len);
  	if (unlikely(retval< 0)) {
  		dev_err(&intf->dev, "rndis get ethaddr, %d\n", retval);
  		goto fail_and_release;
  	}
  	memcpy(net->dev_addr, bp, ETH_ALEN);
  
  	/* set a nonzero filter to enable data transfers */
  	memset(u.set, 0, sizeof *u.set);
  	u.set->msg_type = RNDIS_MSG_SET;
  	u.set->msg_len = ccpu2(4 + sizeof *u.set);
  	u.set->oid = OID_GEN_CURRENT_PACKET_FILTER;
  	u.set->len = ccpu2(4);
  	u.set->offset = ccpu2((sizeof *u.set) - 8);
  	*(__le32 *)(u.buf + sizeof *u.set) = ccpu2(DEFAULT_FILTER);
  
  	retval = rndis_command(dev, u.header);
  	if (unlikely(retval < 0)) {
  		dev_err(&intf->dev, "rndis set packet filter, %d\n", retval);
  		goto fail_and_release;
  	}
  
  	retval = 0;
  
  	kfree(u.buf);
  	return retval;
  
  fail_and_release:
  	usb_set_intfdata(info->data, NULL);
  	usb_driver_release_interface(driver_of(intf), info->data);
  	info->data = NULL;
  fail:
  	kfree(u.buf);
  	return retval;
  }
  
  static void rndis_unbind(struct usbnet *dev, struct usb_interface *intf)
  {
  	struct rndis_halt	*halt;
  
  	/* try to clear any rndis state/activity (no i/o from stack!) */
  	halt = kzalloc(sizeof *halt, GFP_KERNEL);
  	if (halt) {
  		halt->msg_type = RNDIS_MSG_HALT;
  		halt->msg_len = ccpu2(sizeof *halt);
  		(void) rndis_command(dev, (void *)halt);
  		kfree(halt);
  	}
  
  	return usbnet_cdc_unbind(dev, intf);
  }
  
  /*
   * DATA -- host must not write zlps
   */
  static int rndis_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
  {
  	/* peripheral may have batched packets to us... */
  	while (likely(skb->len)) {
  		struct rndis_data_hdr	*hdr = (void *)skb->data;
  		struct sk_buff		*skb2;
  		u32			msg_len, data_offset, data_len;
  
  		msg_len = le32_to_cpu(hdr->msg_len);
  		data_offset = le32_to_cpu(hdr->data_offset);
  		data_len = le32_to_cpu(hdr->data_len);
  
  		/* don't choke if we see oob, per-packet data, etc */
  		if (unlikely(hdr->msg_type != RNDIS_MSG_PACKET
  				|| skb->len < msg_len
  				|| (data_offset + data_len + 8) > msg_len)) {
  			dev->stats.rx_frame_errors++;
  			devdbg(dev, "bad rndis message %d/%d/%d/%d, len %d",
  				le32_to_cpu(hdr->msg_type),
  				msg_len, data_offset, data_len, skb->len);
  			return 0;
  		}
  		skb_pull(skb, 8 + data_offset);
  
  		/* at most one packet left? */
  		if (likely((data_len - skb->len) <= sizeof *hdr)) {
  			skb_trim(skb, data_len);
  			break;
  		}
  
  		/* try to return all the packets in the batch */
  		skb2 = skb_clone(skb, GFP_ATOMIC);
  		if (unlikely(!skb2))
  			break;
  		skb_pull(skb, msg_len - sizeof *hdr);
  		skb_trim(skb2, data_len);
  		usbnet_skb_return(dev, skb2);
  	}
  
  	/* caller will usbnet_skb_return the remaining packet */
  	return 1;
  }
  
  static struct sk_buff *
  rndis_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
  {
  	struct rndis_data_hdr	*hdr;
  	struct sk_buff		*skb2;
  	unsigned		len = skb->len;
  
  	if (likely(!skb_cloned(skb))) {
  		int	room = skb_headroom(skb);
  
  		/* enough head room as-is? */
  		if (unlikely((sizeof *hdr) <= room))
  			goto fill;
  
  		/* enough room, but needs to be readjusted? */
  		room += skb_tailroom(skb);
  		if (likely((sizeof *hdr) <= room)) {
  			skb->data = memmove(skb->head + sizeof *hdr,
  					    skb->data, len);
  			skb_set_tail_pointer(skb, len);
  			goto fill;
  		}
  	}
  
  	/* create a new skb, with the correct size (and tailpad) */
  	skb2 = skb_copy_expand(skb, sizeof *hdr, 1, flags);
  	dev_kfree_skb_any(skb);
  	if (unlikely(!skb2))
  		return skb2;
  	skb = skb2;
  
  	/* fill out the RNDIS header.  we won't bother trying to batch
  	 * packets; Linux minimizes wasted bandwidth through tx queues.
  	 */
  fill:
  	hdr = (void *) __skb_push(skb, sizeof *hdr);
  	memset(hdr, 0, sizeof *hdr);
  	hdr->msg_type = RNDIS_MSG_PACKET;
  	hdr->msg_len = cpu_to_le32(skb->len);
  	hdr->data_offset = ccpu2(sizeof(*hdr) - 8);
  	hdr->data_len = cpu_to_le32(len);
  
  	/* FIXME make the last packet always be short ... */
  	return skb;
  }
  
  
  static const struct driver_info	rndis_info = {
  	.description =	"RNDIS device",
  	.flags =	FLAG_ETHER | FLAG_FRAMING_RN | FLAG_NO_SETINT,
  	.bind =		rndis_bind,
  	.unbind =	rndis_unbind,
  	.status =	rndis_status,
  	.rx_fixup =	rndis_rx_fixup,
  	.tx_fixup =	rndis_tx_fixup,
  };
  
  #undef ccpu2
  
  
  /*-------------------------------------------------------------------------*/
  
  static const struct usb_device_id	products [] = {
  {
  	/* RNDIS is MSFT's un-official variant of CDC ACM */
  	USB_INTERFACE_INFO(USB_CLASS_COMM, 2 /* ACM */, 0x0ff),
  	.driver_info = (unsigned long) &rndis_info,
  }, {
  	/* "ActiveSync" is an undocumented variant of RNDIS, used in WM5 */
  	USB_INTERFACE_INFO(USB_CLASS_MISC, 1, 1),
  	.driver_info = (unsigned long) &rndis_info,
  },
  	{ },		// END
  };
  MODULE_DEVICE_TABLE(usb, products);
  
  static struct usb_driver rndis_driver = {
  	.name =		"rndis_host",
  	.id_table =	products,
  	.probe =	usbnet_probe,
  	.disconnect =	usbnet_disconnect,
  	.suspend =	usbnet_suspend,
  	.resume =	usbnet_resume,
  };
  
  static int __init rndis_init(void)
  {
  	return usb_register(&rndis_driver);
  }
  module_init(rndis_init);
  
  static void __exit rndis_exit(void)
  {
  	usb_deregister(&rndis_driver);
  }
  module_exit(rndis_exit);
  
  MODULE_AUTHOR("David Brownell");
  MODULE_DESCRIPTION("USB Host side RNDIS driver");
  MODULE_LICENSE("GPL");
  