Subject: USB: usbnet (8/9) module for RNDIS devices

From: David Brownell <[email-masked]>
Date: Wed, 31 Aug 2005 09:54:36 -0700

This adds host-side RNDIS support to the "usbnet" driver, so Linux can talk
to various devices (often based on WinCE) that otherwise only Windows could
talk to.

Tested with little-endian Linux talking to a Linux-USB Ethernet/RNDIS based
peripheral.  This also includes updates from Eddie C. Dost <[email-masked]>
for big-endian SPARC Linux talking to a Nokia 9500 Communicator.

It's still marked as EXPERIMENTAL because this code is so young.  This
ought to let Linux to work with various cable modems that previously
would have been "Windows Only".

Signed-off-by: David Brownell <[email-masked]>
Signed-off-by: Greg Kroah-Hartman <[email-masked]>

---
 drivers/usb/net/Kconfig      |   13 
 drivers/usb/net/Makefile     |    1 
 drivers/usb/net/rndis_host.c |  615 +++++++++++++++++++++++++++++++++++++++++++
 drivers/usb/net/usbnet.c     |    9 
 4 files changed, 630 insertions(+), 8 deletions(-)

--- gregkh-2.6.orig/drivers/usb/net/Makefile	2005-09-08 14:08:44.000000000 -0700
+++ gregkh-2.6/drivers/usb/net/Makefile	2005-09-08 14:08:45.000000000 -0700
@@ -10,6 +10,7 @@ obj-$(CONFIG_USB_NET_AX8817X)	+= asix.o
 obj-$(CONFIG_USB_NET_CDCETHER)	+= cdc_ether.o
 obj-$(CONFIG_USB_NET_GL620A)	+= gl620a.o
 obj-$(CONFIG_USB_NET_NET1080)	+= net1080.o
+obj-$(CONFIG_USB_NET_RNDIS_HOST)	+= rndis_host.o
 obj-$(CONFIG_USB_NET_CDC_SUBSET)	+= cdc_subset.o
 obj-$(CONFIG_USB_NET_ZAURUS)	+= zaurus.o
 obj-$(CONFIG_USB_USBNET)	+= usbnet.o
--- gregkh-2.6.orig/drivers/usb/net/Kconfig	2005-09-08 14:08:44.000000000 -0700
+++ gregkh-2.6/drivers/usb/net/Kconfig	2005-09-08 14:08:45.000000000 -0700
@@ -212,6 +212,19 @@ config USB_NET_NET1080
 	  on this design:  one NetChip 1080 chip and supporting logic,
 	  optionally with LEDs that indicate traffic
 
+config USB_NET_RNDIS_HOST
+	tristate "Host for RNDIS devices (EXPERIMENTAL)"
+	depends on USB_USBNET && EXPERIMENTAL
+	select USB_NET_CDCETHER
+	help
+	  This option enables hosting "Remote NDIS" USB networking links,
+	  as encouraged by Microsoft (instead of CDC Ethernet!) for use in
+	  various devices that may only support this protocol.
+
+	  Avoid using this protocol unless you have no better options.
+	  The protocol specification is incomplete, and is controlled by
+	  (and for) Microsoft; it isn't an "Open" ecosystem or market.
+
 config USB_NET_CDC_SUBSET
 	tristate "Simple USB Network Links (CDC Ethernet subset)"
 	depends on USB_USBNET
--- gregkh-2.6.orig/drivers/usb/net/usbnet.c	2005-09-08 14:08:44.000000000 -0700
+++ gregkh-2.6/drivers/usb/net/usbnet.c	2005-09-08 14:08:45.000000000 -0700
@@ -103,6 +103,7 @@
  * 		disconnect; other cleanups. (db)  Flush net1080 fifos
  * 		after several sequential framing errors. (Johannes Erdfelt)
  * 22-aug-2003	AX8817X support (Dave Hollis).
+ *
  * 14-jun-2004  Trivial patch for AX8817X based Buffalo LUA-U2-KTX in Japan
  *		(Neil Bortnak)
  * 03-nov-2004	Trivial patch for KC2190 (KC-190) chip. (Jonathan McDowell)
@@ -1375,14 +1376,6 @@ static const struct usb_device_id	produc
 	.driver_info =	(unsigned long) &prolific_info,
 },
 #endif
-
-#ifdef	CONFIG_USB_RNDIS
-{
-	/* 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,
-},
-#endif
 	{ },		// END
 };
 MODULE_DEVICE_TABLE (usb, products);
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ gregkh-2.6/drivers/usb/net/rndis_host.c	2005-09-08 14:08:45.000000000 -0700
@@ -0,0 +1,615 @@
+/*
+ * 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/config.h>
+#ifdef	CONFIG_USB_DEBUG
+#   define DEBUG
+#endif
+#include <linux/module.h>
+#include <linux/sched.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.
+ */
+
+/*
+ * 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.
+ */
+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));
+
+/* RNDIS defines this (absurdly huge) control timeout */
+#define	RNDIS_CONTROL_TIMEOUT_MS	(10 * 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_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			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; don't bother byteswapping our xid */
+	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;
+	}
+	retval = usb_control_msg(dev->udev,
+		usb_sndctrlpipe(dev->udev, 0),
+		USB_CDC_SEND_ENCAPSULATED_COMMAND,
+		USB_TYPE_CLASS | USB_RECIP_INTERFACE,
+		0, info->u->bMasterInterface0,
+		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, 1024);
+		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, info->u->bMasterInterface0,
+			buf, 1024,
+			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, info->u->bMasterInterface0,
+					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;
+}
+
+static int rndis_bind(struct usbnet *dev, struct usb_interface *intf)
+{
+	int			retval;
+	struct net_device	*net = dev->net;
+	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;
+
+	/* we can't rely on i/o from stack working, or stack allocation */
+	u.buf = kmalloc(1024, GFP_KERNEL);
+	if (!u.buf)
+		return -ENOMEM;
+	retval = usbnet_generic_cdc_bind(dev, intf);
+	if (retval < 0)
+		goto done;
+
+	net->hard_header_len += sizeof (struct rndis_data_hdr);
+
+	/* initialize; max transfer is 16KB at full speed */
+	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);
+	u.init->max_transfer_size = ccpu2(net->mtu + net->hard_header_len);
+
+	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);
+fail:
+		usb_driver_release_interface(driver_of(intf),
+			((struct cdc_state *)&(dev->data))->data);
+		goto done;
+	}
+	dev->hard_mtu = le32_to_cpu(u.init_c->max_transfer_size);
+	/* REVISIT:  peripheral "alignment" request is ignored ... */
+	dev_dbg(&intf->dev, "hard mtu %u, align %d\n", dev->hard_mtu,
+		1 << le32_to_cpu(u.init_c->packet_alignment));
+
+	/* get designated host ethernet address */
+	memset(u.get, 0, sizeof *u.get);
+	u.get->msg_type = RNDIS_MSG_QUERY;
+	u.get->msg_len = ccpu2(sizeof *u.get);
+	u.get->oid = OID_802_3_PERMANENT_ADDRESS;
+
+	retval = rndis_command(dev, u.header);
+	if (unlikely(retval < 0)) {
+		dev_err(&intf->dev, "rndis get ethaddr, %d\n", retval);
+		goto fail;
+	}
+	tmp = le32_to_cpu(u.get_c->offset);
+	if (unlikely((tmp + 8) > (1024 - ETH_ALEN)
+			|| u.get_c->len != ccpu2(ETH_ALEN))) {
+		dev_err(&intf->dev, "rndis ethaddr off %d len %d ?\n",
+			tmp, le32_to_cpu(u.get_c->len));
+		retval = -EDOM;
+		goto fail;
+	}
+	memcpy(net->dev_addr, tmp + (char *)&u.get_c->request_id, 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;
+	}
+
+	retval = 0;
+done:
+	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 = kcalloc(1, sizeof *halt, SLAB_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, unsigned 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->tail = skb->data + 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,
+	.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,
+},
+	{ },		// END
+};
+MODULE_DEVICE_TABLE(usb, products);
+
+static struct usb_driver rndis_driver = {
+	.owner =	THIS_MODULE,
+	.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");