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* Ethernet interface part of the LG VL600 LTE modem (4G dongle)
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* Copyright (C) 2011 Intel Corporation
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* Author: Andrzej Zaborowski <balrogg@gmail.com>
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#include <linux/etherdevice.h>
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#include <linux/ethtool.h>
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#include <linux/mii.h>
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#include <linux/usb.h>
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#include <linux/usb/cdc.h>
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#include <linux/usb/usbnet.h>
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#include <linux/if_ether.h>
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#include <linux/if_arp.h>
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#include <linux/inetdevice.h>
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#include <linux/module.h>
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* The device has a CDC ACM port for modem control (it claims to be
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* CDC ACM anyway) and a CDC Ethernet port for actual network data.
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* It will however ignore data on both ports that is not encapsulated
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* in a specific way, any data returned is also encapsulated the same
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* way. The headers don't seem to follow any popular standard.
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* This driver adds and strips these headers from the ethernet frames
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* sent/received from the CDC Ethernet port. The proprietary header
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* replaces the standard ethernet header in a packet so only actual
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* ethernet frames are allowed. The headers allow some form of
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* multiplexing by using non standard values of the .h_proto field.
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* Windows/Mac drivers do send a couple of such frames to the device
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* during initialisation, with protocol set to 0x0906 or 0x0b06 and (what
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* seems to be) a flag in the .dummy_flags. This doesn't seem necessary
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* for modem operation but can possibly be used for GPS or other funcitons.
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struct vl600_frame_hdr {
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} __attribute__((packed));
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struct vl600_pkt_hdr {
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} __attribute__((packed));
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struct sk_buff *current_rx_buf;
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static int vl600_bind(struct usbnet *dev, struct usb_interface *intf)
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struct vl600_state *s = kzalloc(sizeof(struct vl600_state), GFP_KERNEL);
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ret = usbnet_cdc_bind(dev, intf);
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/* ARP packets don't go through, but they're also of no use. The
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* subnet has only two hosts anyway: us and the gateway / DHCP
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* server (probably simulated by modem firmware or network operator)
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* whose address changes everytime we connect to the intarwebz and
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* who doesn't bother answering ARP requests either. So hardware
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* addresses have no meaning, the destination and the source of every
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* packet depend only on whether it is on the IN or OUT endpoint. */
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dev->net->flags |= IFF_NOARP;
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/* IPv6 NDP relies on multicast. Enable it by default. */
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dev->net->flags |= IFF_MULTICAST;
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static void vl600_unbind(struct usbnet *dev, struct usb_interface *intf)
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struct vl600_state *s = dev->driver_priv;
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if (s->current_rx_buf)
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dev_kfree_skb(s->current_rx_buf);
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return usbnet_cdc_unbind(dev, intf);
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static int vl600_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
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struct vl600_frame_hdr *frame;
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struct vl600_pkt_hdr *packet;
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struct ethhdr *ethhdr;
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int packet_len, count;
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struct sk_buff *buf = skb;
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struct sk_buff *clone;
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struct vl600_state *s = dev->driver_priv;
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/* Frame lengths are generally 4B multiplies but every couple of
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* hours there's an odd number of bytes sized yet correct frame,
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* so don't require this. */
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/* Allow a packet (or multiple packets batched together) to be
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* split across many frames. We don't allow a new batch to
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* begin in the same frame another one is ending however, and no
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* leading or trailing pad bytes. */
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if (s->current_rx_buf) {
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frame = (struct vl600_frame_hdr *) s->current_rx_buf->data;
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if (skb->len + s->current_rx_buf->len >
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le32_to_cpup(&frame->len)) {
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netif_err(dev, ifup, dev->net, "Fragment too long\n");
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dev->net->stats.rx_length_errors++;
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buf = s->current_rx_buf;
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memcpy(skb_put(buf, skb->len), skb->data, skb->len);
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} else if (skb->len < 4) {
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netif_err(dev, ifup, dev->net, "Frame too short\n");
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dev->net->stats.rx_length_errors++;
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frame = (struct vl600_frame_hdr *) buf->data;
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/* Yes, check that frame->magic == 0x53544448 (or 0x44544d48),
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* otherwise we may run out of memory w/a bad packet */
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if (ntohl(frame->magic) != 0x53544448 &&
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ntohl(frame->magic) != 0x44544d48)
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if (buf->len < sizeof(*frame) ||
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buf->len != le32_to_cpup(&frame->len)) {
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/* Save this fragment for later assembly */
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if (s->current_rx_buf)
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s->current_rx_buf = skb_copy_expand(skb, 0,
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le32_to_cpup(&frame->len), GFP_ATOMIC);
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if (!s->current_rx_buf) {
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netif_err(dev, ifup, dev->net, "Reserving %i bytes "
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"for packet assembly failed.\n",
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le32_to_cpup(&frame->len));
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dev->net->stats.rx_errors++;
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count = le32_to_cpup(&frame->pkt_cnt);
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skb_pull(buf, sizeof(*frame));
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if (buf->len < sizeof(*packet)) {
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netif_err(dev, ifup, dev->net, "Packet too short\n");
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packet = (struct vl600_pkt_hdr *) buf->data;
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packet_len = sizeof(*packet) + le32_to_cpup(&packet->len);
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if (packet_len > buf->len) {
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netif_err(dev, ifup, dev->net,
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"Bad packet length stored in header\n");
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/* Packet header is same size as the ethernet header
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* (sizeof(*packet) == sizeof(*ethhdr)), additionally
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* the h_proto field is in the same place so we just leave it
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* alone and fill in the remaining fields.
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ethhdr = (struct ethhdr *) skb->data;
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if (be16_to_cpup(ðhdr->h_proto) == ETH_P_ARP &&
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/* Copy the addresses from packet contents */
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memcpy(ethhdr->h_source,
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&buf->data[sizeof(*ethhdr) + 0x8],
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memcpy(ethhdr->h_dest,
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&buf->data[sizeof(*ethhdr) + 0x12],
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memset(ethhdr->h_source, 0, ETH_ALEN);
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memcpy(ethhdr->h_dest, dev->net->dev_addr, ETH_ALEN);
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/* Inbound IPv6 packets have an IPv4 ethertype (0x800)
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* for some reason. Peek at the L3 header to check
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* for IPv6 packets, and set the ethertype to IPv6
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* (0x86dd) so Linux can understand it.
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if ((buf->data[sizeof(*ethhdr)] & 0xf0) == 0x60)
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ethhdr->h_proto = __constant_htons(ETH_P_IPV6);
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/* Not the last packet in this batch */
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clone = skb_clone(buf, GFP_ATOMIC);
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skb_trim(clone, packet_len);
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usbnet_skb_return(dev, clone);
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skb_pull(buf, (packet_len + 3) & ~3);
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skb_trim(buf, packet_len);
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if (s->current_rx_buf) {
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usbnet_skb_return(dev, buf);
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s->current_rx_buf = NULL;
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if (s->current_rx_buf) {
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dev_kfree_skb_any(s->current_rx_buf);
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s->current_rx_buf = NULL;
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dev->net->stats.rx_errors++;
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static struct sk_buff *vl600_tx_fixup(struct usbnet *dev,
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struct sk_buff *skb, gfp_t flags)
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struct vl600_frame_hdr *frame;
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struct vl600_pkt_hdr *packet;
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static uint32_t serial = 1;
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int orig_len = skb->len - sizeof(struct ethhdr);
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int full_len = (skb->len + sizeof(struct vl600_frame_hdr) + 3) & ~3;
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frame = (struct vl600_frame_hdr *) skb->data;
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if (skb->len > sizeof(*frame) && skb->len == le32_to_cpup(&frame->len))
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return skb; /* Already encapsulated? */
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if (skb->len < sizeof(struct ethhdr))
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/* Drop, device can only deal with ethernet packets */
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if (!skb_cloned(skb)) {
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int headroom = skb_headroom(skb);
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int tailroom = skb_tailroom(skb);
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if (tailroom >= full_len - skb->len - sizeof(*frame) &&
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headroom >= sizeof(*frame))
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/* There's enough head and tail room */
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if (headroom + tailroom + skb->len >= full_len) {
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/* There's enough total room, just readjust */
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skb->data = memmove(skb->head + sizeof(*frame),
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skb->data, skb->len);
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skb_set_tail_pointer(skb, skb->len);
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/* Alloc a new skb with the required size */
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ret = skb_copy_expand(skb, sizeof(struct vl600_frame_hdr), full_len -
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skb->len - sizeof(struct vl600_frame_hdr), flags);
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dev_kfree_skb_any(skb);
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/* Packet header is same size as ethernet packet header
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* (sizeof(*packet) == sizeof(struct ethhdr)), additionally the
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* h_proto field is in the same place so we just leave it alone and
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* overwrite the remaining fields.
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packet = (struct vl600_pkt_hdr *) skb->data;
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/* The VL600 wants IPv6 packets to have an IPv4 ethertype
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* Since this modem only supports IPv4 and IPv6, just set all
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* frames to 0x0800 (ETH_P_IP)
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packet->h_proto = htons(ETH_P_IP);
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memset(&packet->dummy, 0, sizeof(packet->dummy));
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packet->len = cpu_to_le32(orig_len);
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frame = (struct vl600_frame_hdr *) skb_push(skb, sizeof(*frame));
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memset(frame, 0, sizeof(*frame));
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frame->len = cpu_to_le32(full_len);
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frame->serial = cpu_to_le32(serial++);
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frame->pkt_cnt = cpu_to_le32(1);
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if (skb->len < full_len) /* Pad */
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skb_put(skb, full_len - skb->len);
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static const struct driver_info vl600_info = {
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.description = "LG VL600 modem",
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.flags = FLAG_RX_ASSEMBLE | FLAG_WWAN,
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.unbind = vl600_unbind,
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.status = usbnet_cdc_status,
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.rx_fixup = vl600_rx_fixup,
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.tx_fixup = vl600_tx_fixup,
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static const struct usb_device_id products[] = {
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USB_DEVICE_AND_INTERFACE_INFO(0x1004, 0x61aa, USB_CLASS_COMM,
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USB_CDC_SUBCLASS_ETHERNET, USB_CDC_PROTO_NONE),
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.driver_info = (unsigned long) &vl600_info,
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MODULE_DEVICE_TABLE(usb, products);
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static struct usb_driver lg_vl600_driver = {
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.id_table = products,
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.probe = usbnet_probe,
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.disconnect = usbnet_disconnect,
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.suspend = usbnet_suspend,
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.resume = usbnet_resume,
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static int __init vl600_init(void)
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return usb_register(&lg_vl600_driver);
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module_init(vl600_init);
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static void __exit vl600_exit(void)
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usb_deregister(&lg_vl600_driver);
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module_exit(vl600_exit);
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MODULE_AUTHOR("Anrzej Zaborowski");
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MODULE_DESCRIPTION("LG-VL600 modem's ethernet link");
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MODULE_LICENSE("GPL");