lg-vl600.c

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/*
 * Ethernet interface part of the LG VL600 LTE modem (4G dongle)
 *
 * Copyright (C) 2011 Intel Corporation
 * Author: Andrzej Zaborowski <[email protected]>
 *
 * 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>
#include <linux/module.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;
    /* IPv6 NDP relies on multicast.  Enable it by default. */
    dev->net->flags |= IFF_MULTICAST;

    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;
    /* Yes, check that frame->magic == 0x53544448 (or 0x44544d48),
     * otherwise we may run out of memory w/a bad packet */
    if (ntohl(frame->magic) != 0x53544448 &&
            ntohl(frame->magic) != 0x44544d48)
        goto error;

    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);

            /* Inbound IPv6 packets have an IPv4 ethertype (0x800)
             * for some reason.  Peek at the L3 header to check
             * for IPv6 packets, and set the ethertype to IPv6
             * (0x86dd) so Linux can understand it.
             */
            if ((buf->data[sizeof(*ethhdr)] & 0xf0) == 0x60)
                ethhdr->h_proto = __constant_htons(ETH_P_IPV6);
        }

        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;
    /* The VL600 wants IPv6 packets to have an IPv4 ethertype
     * Since this modem only supports IPv4 and IPv6, just set all
     * frames to 0x0800 (ETH_P_IP)
     */
    packet->h_proto = htons(ETH_P_IP);
    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_RX_ASSEMBLE | FLAG_WWAN,
    .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,
    .disable_hub_initiated_lpm = 1,
};

module_usb_driver(lg_vl600_driver);

MODULE_AUTHOR("Anrzej Zaborowski");
MODULE_DESCRIPTION("LG-VL600 modem's ethernet link");
MODULE_LICENSE("GPL");