Date:	Mon, 28 Mar 2011 00:04:33 +0200
From:	Andrzej Zaborowski <andrew.zaborowski@...el.com>
To:	netdev@...r.kernel.org
Cc:	Oliver Neukum <oliver@...kum.name>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	linux-kernel@...r.kernel.org, balrogg@...il.com
Subject: [PATCH] net/usb: Ethernet quirks for the LG-VL600 4G modem

This adds a driver for the CDC Ethernet part of this modem.  The
device's ID is blacklisted in cdc_ether.c and is white-listed in
this new driver because of the quirks needed to make it useful.
The modem's firmware exposes a CDC ACM port for modem control and a
CDC Ethernet port for network data.  The descriptors look fine but
both ports actually are some sort of multiplexers requiring non-
standard headers added/removed from every packet or else they're
ignored.  The CDC Ethernet port is not technically an ethernet
interface because the ethernet header is stripped away from packets
and only packets sent to/from the gateway IP are allowed.  But
treating it like an ethernet interface lets us to reuse a lot of
driver code and userspace code like DHCP.  All information is
based on a usb traffic log from a Windows machine.

Comments on how to improve the code are welcome.  Note that
usb_skb_return is used in tx_fixup without a bottom half, which
other drivers don't do.

On the Verizon 4G network I've seen speeds up to 1.1MB/s so far with
this driver, a speed-o-meter site reports 16.2Mbps/10.5Mbps.
Userspace scripts are required to talk to the CDC ACM port.

Signed-off-by: Andrzej Zaborowski <balrogg@...il.com>
---
 drivers/net/usb/Kconfig     |   15 ++
 drivers/net/usb/Makefile    |    1 +
 drivers/net/usb/cdc_ether.c |   21 ++-
 drivers/net/usb/lg-vl600.c  |  325 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/usb/usbnet.h  |    4 +-
 5 files changed, 356 insertions(+), 7 deletions(-)
 create mode 100644 drivers/net/usb/lg-vl600.c

diff --git a/drivers/net/usb/Kconfig b/drivers/net/usb/Kconfig
index 6f600cc..b849017 100644
--- a/drivers/net/usb/Kconfig
+++ b/drivers/net/usb/Kconfig
@@ -433,4 +433,19 @@ config USB_SIERRA_NET
 	  To compile this driver as a module, choose M here: the
 	  module will be called sierra_net.
 
+config USB_VL600
+	tristate "LG VL600 modem dongle"
+	depends on USB_NET_CDCETHER
+	select USB_ACM
+	help
+	  Select this if you want to use an LG Electronics 4G/LTE usb modem
+	  called VL600.  This driver only handles the ethernet
+	  interface exposed by the modem firmware.  To establish a connection
+	  you will first need a userspace program that sends the right
+	  command to the modem through its CDC ACM port, and most
+	  likely also a DHCP client.  See this thread about using the
+	  4G modem from Verizon:
+
+	  http://ubuntuforums.org/showpost.php?p=10589647&postcount=17
+
 endmenu
diff --git a/drivers/net/usb/Makefile b/drivers/net/usb/Makefile
index cac1703..c7ec8a5 100644
--- a/drivers/net/usb/Makefile
+++ b/drivers/net/usb/Makefile
@@ -27,4 +27,5 @@ obj-$(CONFIG_USB_IPHETH)	+= ipheth.o
 obj-$(CONFIG_USB_SIERRA_NET)	+= sierra_net.o
 obj-$(CONFIG_USB_NET_CX82310_ETH)	+= cx82310_eth.o
 obj-$(CONFIG_USB_NET_CDC_NCM)	+= cdc_ncm.o
+obj-$(CONFIG_USB_VL600)		+= lg-vl600.o
 
diff --git a/drivers/net/usb/cdc_ether.c b/drivers/net/usb/cdc_ether.c
index 9a60e41..8bcb3d9 100644
--- a/drivers/net/usb/cdc_ether.c
+++ b/drivers/net/usb/cdc_ether.c
@@ -378,7 +378,7 @@ static void dumpspeed(struct usbnet *dev, __le32 *speeds)
 		   __le32_to_cpu(speeds[1]) / 1000);
 }
 
-static void cdc_status(struct usbnet *dev, struct urb *urb)
+void usbnet_cdc_status(struct usbnet *dev, struct urb *urb)
 {
 	struct usb_cdc_notification	*event;
 
@@ -418,8 +418,9 @@ static void cdc_status(struct usbnet *dev, struct urb *urb)
 		break;
 	}
 }
+EXPORT_SYMBOL_GPL(usbnet_cdc_status);
 
-static int cdc_bind(struct usbnet *dev, struct usb_interface *intf)
+int usbnet_cdc_bind(struct usbnet *dev, struct usb_interface *intf)
 {
 	int				status;
 	struct cdc_state		*info = (void *) &dev->data;
@@ -441,6 +442,7 @@ static int cdc_bind(struct usbnet *dev, struct usb_interface *intf)
 	 */
 	return 0;
 }
+EXPORT_SYMBOL_GPL(usbnet_cdc_bind);
 
 static int cdc_manage_power(struct usbnet *dev, int on)
 {
@@ -452,18 +454,18 @@ static const struct driver_info	cdc_info = {
 	.description =	"CDC Ethernet Device",
 	.flags =	FLAG_ETHER,
 	// .check_connect = cdc_check_connect,
-	.bind =		cdc_bind,
+	.bind =		usbnet_cdc_bind,
 	.unbind =	usbnet_cdc_unbind,
-	.status =	cdc_status,
+	.status =	usbnet_cdc_status,
 	.manage_power =	cdc_manage_power,
 };
 
 static const struct driver_info mbm_info = {
 	.description =	"Mobile Broadband Network Device",
 	.flags =	FLAG_WWAN,
-	.bind = 	cdc_bind,
+	.bind =		usbnet_cdc_bind,
 	.unbind =	usbnet_cdc_unbind,
-	.status =	cdc_status,
+	.status =	usbnet_cdc_status,
 	.manage_power =	cdc_manage_power,
 };
 
@@ -560,6 +562,13 @@ static const struct usb_device_id	products [] = {
 	.driver_info		= 0,
 },
 
+/* LG Electronics VL600 wants additional headers on every frame */
+{
+	USB_DEVICE_AND_INTERFACE_INFO(0x1004, 0x61aa, USB_CLASS_COMM,
+			USB_CDC_SUBCLASS_ETHERNET, USB_CDC_PROTO_NONE),
+	.driver_info		= 0,
+},
+
 /*
  * WHITELIST!!!
  *
diff --git a/drivers/net/usb/lg-vl600.c b/drivers/net/usb/lg-vl600.c
new file mode 100644
index 0000000..4f54661
--- /dev/null
+++ b/drivers/net/usb/lg-vl600.c
@@ -0,0 +1,325 @@
+/*
+ * Ethernet interface part of the LG VL600 LTE modem (4G dongle)
+ *
+ * Copyright (C) 2011 Intel Corporation
+ * Author: Andrzej Zaborowski <balrogg@...il.com>
+ *
+ * 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
+ */
+#include <linux/etherdevice.h>
+#include <linux/ethtool.h>
+#include <linux/mii.h>
+#include <linux/usb.h>
+#include <linux/usb/cdc.h>
+#include <linux/usb/usbnet.h>
+#include <linux/if_ether.h>
+#include <linux/if_arp.h>
+#include <linux/inetdevice.h>
+
+/*
+ * The device has a CDC ACM port for modem control (it claims to be
+ * CDC ACM anyway) and a CDC Ethernet port for actual network data.
+ * It will however ignore data on both ports that is not encapsulated
+ * in a specific way, any data returned is also encapsulated the same
+ * way.  The headers don't seem to follow any popular standard.
+ *
+ * This driver adds and strips these headers from the ethernet frames
+ * sent/received from the CDC Ethernet port.  The proprietary header
+ * replaces the standard ethernet header in a packet so only actual
+ * ethernet frames are allowed.  The headers allow some form of
+ * multiplexing by using non standard values of the .h_proto field.
+ * Windows/Mac drivers do send a couple of such frames to the device
+ * during initialisation, with protocol set to 0x0906 or 0x0b06 and (what
+ * seems to be) a flag in the .dummy_flags.  This doesn't seem necessary
+ * for modem operation but can possibly be used for GPS or other funcitons.
+ */
+
+struct vl600_frame_hdr {
+	__le32 len;
+	__le32 serial;
+	__le32 pkt_cnt;
+	__le32 dummy_flags;
+	__le32 dummy;
+	__le32 magic;
+} __attribute__((packed));
+
+struct vl600_pkt_hdr {
+	__le32 dummy[2];
+	__le32 len;
+	__be16 h_proto;
+} __attribute__((packed));
+
+/* Note: Turbo-hack! The modem firmware (or someone on the Verizon
+ * network side) works as a DHCP server and gateway between us and
+ * the intarwebs.  It has a dynamically assigned IP address on the
+ * same subnet as our IP and all communications goes through it.
+ * Effectively the subnet can contain only exactly two hosts (local
+ * and remote) and thus hardware addresses have no meaning any more
+ * making the ARP layer useless.  The source and the destination of
+ * each packet on the IN and on the OUT endpoints are known and are
+ * not included in the usb frames unlike on real ethernet.
+ * Apparently someone has noticed that ARP is not needed and the
+ * remote host doesn't bother answering ARP requests.  So we look
+ * for ARP requests in vl600_tx_fixup and we fake a response from
+ * the remote side containing a fake hardware address.
+ */
+static int vl600_handle_arp(struct usbnet *dev, struct sk_buff *skb)
+{
+	struct sk_buff *resp;
+	struct ethhdr *eth_req, *eth_resp;
+	struct arphdr *arp_req, *arp_resp;
+	int arp_len = arp_hdr_len(dev->net);
+	struct in_device *in_dev = dev->net->ip_ptr;
+
+	if (skb->len < sizeof(*eth_resp) + arp_len)
+		return 0;
+
+	arp_req = (struct arphdr *) (skb->data + sizeof(*eth_req));
+	if (be16_to_cpup(&arp_req->ar_hrd) != ARPHRD_ETHER ||
+			be16_to_cpup(&arp_req->ar_pro) != ETH_P_IP ||
+			arp_req->ar_hln != ETH_ALEN ||
+			arp_req->ar_pln != 4 ||
+			be16_to_cpup(&arp_req->ar_op) != ARPOP_REQUEST)
+		return 0;
+
+	if (!in_dev || !in_dev->ifa_list)
+		return 0;
+
+	/* This is a poor check that this request is not just ourselves asking
+	 * if the address proposed to us by DHCP is taken.. */
+	if (!memcmp(skb->data + sizeof(*eth_req) + sizeof(*arp_req) + ETH_ALEN,
+				"\0\0\0\0", 4))
+		return 0;
+
+	/* Build response packet */
+	resp = dev_alloc_skb(sizeof(*eth_resp) + arp_len);
+
+	eth_req = (struct ethhdr *) skb->data;
+	eth_resp = (struct ethhdr *) skb_put(resp, sizeof(*eth_resp));
+	eth_resp->h_proto = eth_req->h_proto;
+	memcpy(&eth_resp->h_dest, eth_req->h_source, ETH_ALEN);
+	memset(&eth_resp->h_source, 0, ETH_ALEN);
+
+	arp_req = (struct arphdr *) (skb->data + sizeof(*eth_req));
+	arp_resp = (struct arphdr *) skb_put(resp, sizeof(*arp_resp));
+	arp_resp->ar_hrd = arp_req->ar_hrd;
+	arp_resp->ar_pro = arp_req->ar_pro;
+	arp_resp->ar_hln = arp_req->ar_hln;
+	arp_resp->ar_pln = arp_req->ar_pln;
+	arp_resp->ar_op = cpu_to_be16(ARPOP_REPLY);
+
+	memcpy(skb_put(resp, ETH_ALEN + 4),
+			skb->data + sizeof(*eth_req) + sizeof(*arp_req) +
+			ETH_ALEN + 4, ETH_ALEN + 4);
+	memcpy(skb_put(resp, ETH_ALEN + 4),
+			skb->data + sizeof(*eth_req) + sizeof(*arp_req),
+			ETH_ALEN + 4);
+
+	usbnet_skb_return(dev, resp);
+
+	return 1;
+}
+
+static int vl600_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
+{
+	struct vl600_frame_hdr *frame;
+	struct vl600_pkt_hdr *packet;
+	struct ethhdr *ethhdr;
+	int packet_len, count;
+	struct sk_buff *clone;
+
+	frame = (struct vl600_frame_hdr *) skb->data;
+	/* Frame lengths are generally 4B multiplies but every couple of
+	 * hours there's an odd number of bytes sized yet correct frame,
+	 * so don't check for this.  */
+	if (skb->len < sizeof(*frame) ||
+			skb->len != le32_to_cpup(&frame->len)) {
+		netif_err(dev, ifup, dev->net, "Invalid frame length");
+		dev->net->stats.rx_length_errors++;
+		return 0;
+	}
+
+	/* Should check that frame->magic == 0x53544448 or so? */
+
+	count = le32_to_cpup(&frame->pkt_cnt);
+
+	skb_pull(skb, sizeof(*frame));
+
+	while (count--) {
+		if (skb->len < sizeof(*packet)) {
+			netif_err(dev, ifup, dev->net, "Frame too short");
+			dev->net->stats.rx_errors++;
+			return 0;
+		}
+
+		packet = (struct vl600_pkt_hdr *) skb->data;
+		packet_len = sizeof(*packet) + le32_to_cpup(&packet->len);
+		if (packet_len > skb->len) {
+			netif_err(dev, ifup, dev->net,
+					"Bad packet length stored in header");
+			dev->net->stats.rx_errors++;
+			return 0;
+		}
+
+		/* Packet header is same size as ethernet packet header
+		 * (sizeof(*packet) == sizeof(*ethhdr)), additionally
+		 * the h_proto field is in the same place so we just leave it
+		 * alone and fill in the remaining fields.
+		 */
+		ethhdr = (struct ethhdr *) skb->data;
+		if (be16_to_cpup(&ethhdr->h_proto) == ETH_P_ARP &&
+				skb->len > 0x26) {
+			/* Copy the addresses from packet contents */
+			memcpy(ethhdr->h_source,
+					&skb->data[sizeof(*ethhdr) + 0x8],
+					ETH_ALEN);
+			memcpy(ethhdr->h_dest,
+					&skb->data[sizeof(*ethhdr) + 0x12],
+					ETH_ALEN);
+		} else {
+			memset(ethhdr->h_source, 0, ETH_ALEN);
+			memcpy(ethhdr->h_dest, &dev->net->dev_addr, ETH_ALEN);
+		}
+
+		if (count) {
+			/* Not the last packet in this batch */
+			clone = skb_clone(skb, GFP_ATOMIC);
+			skb_trim(clone, packet_len);
+			usbnet_skb_return(dev, clone);
+
+			skb_pull(skb, (packet_len + 3) & ~3);
+		} else {
+			skb_trim(skb, packet_len);
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+static struct sk_buff *vl600_tx_fixup(struct usbnet *dev,
+		struct sk_buff *skb, gfp_t flags)
+{
+	struct sk_buff *ret;
+	struct vl600_frame_hdr *frame;
+	struct vl600_pkt_hdr *packet;
+	static uint32_t serial = 1;
+	int orig_len = skb->len - sizeof(struct ethhdr);
+	int full_len = (skb->len + sizeof(struct vl600_frame_hdr) + 3) & ~3;
+
+	frame = (struct vl600_frame_hdr *) skb->data;
+	if (skb->len > sizeof(*frame) && skb->len == le32_to_cpup(&frame->len))
+		return skb; /* Already encapsulated? */
+
+	if (skb->len < sizeof(struct ethhdr))
+		/* Drop, device can only deal with ethernet packets */
+		return NULL;
+
+	packet = (struct vl600_pkt_hdr *) skb->data;
+	if (be16_to_cpup(&packet->h_proto) == ETH_P_ARP)
+		if (vl600_handle_arp(dev, skb))
+			/* Drop if response faked */
+			return NULL;
+
+	if (!skb_cloned(skb)) {
+		int headroom = skb_headroom(skb);
+		int tailroom = skb_tailroom(skb);
+
+		if (tailroom >= full_len - skb->len - sizeof(*frame) &&
+				headroom >= sizeof(*frame))
+			/* There's enough head and tail room */
+			goto encapsulate;
+
+		if (headroom + tailroom + skb->len >= full_len) {
+			/* There's enough total room, just readjust */
+			skb->data = memmove(skb->head + sizeof(*frame),
+					skb->data, skb->len);
+			skb_set_tail_pointer(skb, skb->len);
+			goto encapsulate;
+		}
+	}
+
+	/* Alloc a new skb with the required size */
+	ret = skb_copy_expand(skb, sizeof(struct vl600_frame_hdr), full_len -
+			skb->len - sizeof(struct vl600_frame_hdr), flags);
+	dev_kfree_skb_any(skb);
+	if (!ret)
+		return ret;
+	skb = ret;
+
+encapsulate:
+	/* Packet header is same size as ethernet packet header
+	 * (sizeof(*packet) == sizeof(struct ethhdr)), additionally the
+	 * h_proto field is in the same place so we just leave it alone and
+	 * overwrite the remaining fields.
+	 */
+	packet = (struct vl600_pkt_hdr *) skb->data;
+	memset(&packet->dummy, 0, sizeof(packet->dummy));
+	packet->len = cpu_to_le32(orig_len);
+
+	frame = (struct vl600_frame_hdr *) skb_push(skb, sizeof(*frame));
+	memset(frame, 0, sizeof(*frame));
+	frame->len = cpu_to_le32(full_len);
+	frame->serial = cpu_to_le32(serial++);
+	frame->pkt_cnt = cpu_to_le32(1);
+
+	if (skb->len < full_len) /* Pad */
+		skb_put(skb, full_len - skb->len);
+
+	return skb;
+}
+
+static const struct driver_info	vl600_info = {
+	.description	= "LG VL600 modem",
+	.flags		= FLAG_ETHER,
+	.bind		= usbnet_cdc_bind,
+	.unbind		= usbnet_cdc_unbind,
+	.status		= usbnet_cdc_status,
+	.rx_fixup	= vl600_rx_fixup,
+	.tx_fixup	= vl600_tx_fixup,
+};
+
+static const struct usb_device_id products[] = {
+	{
+		USB_DEVICE_AND_INTERFACE_INFO(0x1004, 0x61aa, USB_CLASS_COMM,
+				USB_CDC_SUBCLASS_ETHERNET, USB_CDC_PROTO_NONE),
+		.driver_info	= (unsigned long) &vl600_info,
+	},
+	{},	/* End */
+};
+MODULE_DEVICE_TABLE(usb, products);
+
+static struct usb_driver lg_vl600_driver = {
+	.name		= "lg-vl600",
+	.id_table	= products,
+	.probe		= usbnet_probe,
+	.disconnect	= usbnet_disconnect,
+	.suspend	= usbnet_suspend,
+	.resume		= usbnet_resume,
+};
+
+static int __init vl600_init(void)
+{
+	return usb_register(&lg_vl600_driver);
+}
+module_init(vl600_init);
+
+static void __exit vl600_exit(void)
+{
+	usb_deregister(&lg_vl600_driver);
+}
+module_exit(vl600_exit);
+
+MODULE_LICENSE("GPL");
diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index 44842c8..3bef970 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -172,7 +172,9 @@ struct cdc_state {
 };
 
 extern int usbnet_generic_cdc_bind(struct usbnet *, struct usb_interface *);
-extern void usbnet_cdc_unbind(struct usbnet *, struct usb_interface *);
+extern int usbnet_cdc_bind(struct usbnet *, struct usb_interface *);
+extern void usbnet_cdc_unbind(struct usbnet *, struct usb_interface *);
+extern void usbnet_cdc_status(struct usbnet *, struct urb *);
 
 /* CDC and RNDIS support the same host-chosen packet filters for IN transfers */
 #define	DEFAULT_FILTER	(USB_CDC_PACKET_TYPE_BROADCAST \
-- 
1.7.1.86.g0e460.dirty

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