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 they get
ignored.  All information is based on a usb traffic log from a
Windows machine.

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@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 346 insertions, 0 deletions

diff --git a/drivers/net/usb/lg-vl600.c b/drivers/net/usb/lg-vl600.c
new file mode 100644
index 000000000000..1d83ccfd7277
--- /dev/null
+++ b/drivers/net/usb/lg-vl600.c
@@ -0,0 +1,346 @@
+/*
+ * Ethernet interface part of the LG VL600 LTE modem (4G dongle)
+ *
+ * Copyright (C) 2011 Intel Corporation
+ * Author: Andrzej Zaborowski <balrogg@gmail.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));
+
+struct vl600_state {
+        struct sk_buff *current_rx_buf;
+};
+
+static int vl600_bind(struct usbnet *dev, struct usb_interface *intf)
+{
+        int ret;
+        struct vl600_state *s = kzalloc(sizeof(struct vl600_state), GFP_KERNEL);
+
+        if (!s)
+                return -ENOMEM;
+
+        ret = usbnet_cdc_bind(dev, intf);
+        if (ret) {
+                kfree(s);
+                return ret;
+        }
+
+        dev->driver_priv = s;
+
+        /* ARP packets don't go through, but they're also of no use.  The
+         * subnet has only two hosts anyway: us and the gateway / DHCP
+         * server (probably simulated by modem firmware or network operator)
+         * whose address changes everytime we connect to the intarwebz and
+         * who doesn't bother answering ARP requests either.  So hardware
+         * addresses have no meaning, the destination and the source of every
+         * packet depend only on whether it is on the IN or OUT endpoint.  */
+        dev->net->flags |= IFF_NOARP;
+
+        return ret;
+}
+
+static void vl600_unbind(struct usbnet *dev, struct usb_interface *intf)
+{
+        struct vl600_state *s = dev->driver_priv;
+
+        if (s->current_rx_buf)
+                dev_kfree_skb(s->current_rx_buf);
+
+        kfree(s);
+
+        return usbnet_cdc_unbind(dev, intf);
+}
+
+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 *buf = skb;
+        struct sk_buff *clone;
+        struct vl600_state *s = dev->driver_priv;
+
+        /* 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 require this.  */
+
+        /* Allow a packet (or multiple packets batched together) to be
+         * split across many frames.  We don't allow a new batch to
+         * begin in the same frame another one is ending however, and no
+         * leading or trailing pad bytes.  */
+        if (s->current_rx_buf) {
+                frame = (struct vl600_frame_hdr *) s->current_rx_buf->data;
+                if (skb->len + s->current_rx_buf->len >
+                                le32_to_cpup(&frame->len)) {
+                        netif_err(dev, ifup, dev->net, "Fragment too long\n");
+                        dev->net->stats.rx_length_errors++;
+                        goto error;
+                }
+
+                buf = s->current_rx_buf;
+                memcpy(skb_put(buf, skb->len), skb->data, skb->len);
+        } else if (skb->len < 4) {
+                netif_err(dev, ifup, dev->net, "Frame too short\n");
+                dev->net->stats.rx_length_errors++;
+                goto error;
+        }
+
+        frame = (struct vl600_frame_hdr *) buf->data;
+        /* NOTE: Should check that frame->magic == 0x53544448?
+         * Otherwise if we receive garbage at the beginning of the frame
+         * we may end up allocating a huge buffer and saving all the
+         * future incoming data into it.  */
+
+        if (buf->len < sizeof(*frame) ||
+                        buf->len != le32_to_cpup(&frame->len)) {
+                /* Save this fragment for later assembly */
+                if (s->current_rx_buf)
+                        return 0;
+
+                s->current_rx_buf = skb_copy_expand(skb, 0,
+                                le32_to_cpup(&frame->len), GFP_ATOMIC);
+                if (!s->current_rx_buf) {
+                        netif_err(dev, ifup, dev->net, "Reserving %i bytes "
+                                        "for packet assembly failed.\n",
+                                        le32_to_cpup(&frame->len));
+                        dev->net->stats.rx_errors++;
+                }
+
+                return 0;
+        }
+
+        count = le32_to_cpup(&frame->pkt_cnt);
+
+        skb_pull(buf, sizeof(*frame));
+
+        while (count--) {
+                if (buf->len < sizeof(*packet)) {
+                        netif_err(dev, ifup, dev->net, "Packet too short\n");
+                        goto error;
+                }
+
+                packet = (struct vl600_pkt_hdr *) buf->data;
+                packet_len = sizeof(*packet) + le32_to_cpup(&packet->len);
+                if (packet_len > buf->len) {
+                        netif_err(dev, ifup, dev->net,
+                                        "Bad packet length stored in header\n");
+                        goto error;
+                }
+
+                /* Packet header is same size as the ethernet 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 &&
+                                buf->len > 0x26) {
+                        /* Copy the addresses from packet contents */
+                        memcpy(ethhdr->h_source,
+                                        &buf->data[sizeof(*ethhdr) + 0x8],
+                                        ETH_ALEN);
+                        memcpy(ethhdr->h_dest,
+                                        &buf->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(buf, GFP_ATOMIC);
+                        if (!clone)
+                                goto error;
+
+                        skb_trim(clone, packet_len);
+                        usbnet_skb_return(dev, clone);
+
+                        skb_pull(buf, (packet_len + 3) & ~3);
+                } else {
+                        skb_trim(buf, packet_len);
+
+                        if (s->current_rx_buf) {
+                                usbnet_skb_return(dev, buf);
+                                s->current_rx_buf = NULL;
+                                return 0;
+                        }
+
+                        return 1;
+                }
+        }
+
+error:
+        if (s->current_rx_buf) {
+                dev_kfree_skb_any(s->current_rx_buf);
+                s->current_rx_buf = NULL;
+        }
+        dev->net->stats.rx_errors++;
+        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;
+
+        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 | FLAG_RX_ASSEMBLE,
+        .bind           = vl600_bind,
+        .unbind         = vl600_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_AUTHOR("Anrzej Zaborowski");
+MODULE_DESCRIPTION("LG-VL600 modem's ethernet link");
+MODULE_LICENSE("GPL");