root/drivers/net/usb/lg-vl600.c

DEFINITIONS

1. vl600_bind
2. vl600_unbind
3. vl600_rx_fixup
4. vl600_tx_fixup

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Ethernet interface part of the LG VL600 LTE modem (4G dongle)
   4  *
   5  * Copyright (C) 2011 Intel Corporation
   6  * Author: Andrzej Zaborowski <balrogg@gmail.com>
   7  */
   8 #include <linux/etherdevice.h>
   9 #include <linux/ethtool.h>
  10 #include <linux/mii.h>
  11 #include <linux/usb.h>
  12 #include <linux/usb/cdc.h>
  13 #include <linux/usb/usbnet.h>
  14 #include <linux/if_ether.h>
  15 #include <linux/if_arp.h>
  16 #include <linux/inetdevice.h>
  17 #include <linux/module.h>
  18 
  19 /*
  20  * The device has a CDC ACM port for modem control (it claims to be
  21  * CDC ACM anyway) and a CDC Ethernet port for actual network data.
  22  * It will however ignore data on both ports that is not encapsulated
  23  * in a specific way, any data returned is also encapsulated the same
  24  * way.  The headers don't seem to follow any popular standard.
  25  *
  26  * This driver adds and strips these headers from the ethernet frames
  27  * sent/received from the CDC Ethernet port.  The proprietary header
  28  * replaces the standard ethernet header in a packet so only actual
  29  * ethernet frames are allowed.  The headers allow some form of
  30  * multiplexing by using non standard values of the .h_proto field.
  31  * Windows/Mac drivers do send a couple of such frames to the device
  32  * during initialisation, with protocol set to 0x0906 or 0x0b06 and (what
  33  * seems to be) a flag in the .dummy_flags.  This doesn't seem necessary
  34  * for modem operation but can possibly be used for GPS or other funcitons.
  35  */
  36 
  37 struct vl600_frame_hdr {
  38         __le32 len;
  39         __le32 serial;
  40         __le32 pkt_cnt;
  41         __le32 dummy_flags;
  42         __le32 dummy;
  43         __le32 magic;
  44 } __attribute__((packed));
  45 
  46 struct vl600_pkt_hdr {
  47         __le32 dummy[2];
  48         __le32 len;
  49         __be16 h_proto;
  50 } __attribute__((packed));
  51 
  52 struct vl600_state {
  53         struct sk_buff *current_rx_buf;
  54 };
  55 
  56 static int vl600_bind(struct usbnet *dev, struct usb_interface *intf)
  57 {
  58         int ret;
  59         struct vl600_state *s = kzalloc(sizeof(struct vl600_state), GFP_KERNEL);
  60 
  61         if (!s)
  62                 return -ENOMEM;
  63 
  64         ret = usbnet_cdc_bind(dev, intf);
  65         if (ret) {
  66                 kfree(s);
  67                 return ret;
  68         }
  69 
  70         dev->driver_priv = s;
  71 
  72         /* ARP packets don't go through, but they're also of no use.  The
  73          * subnet has only two hosts anyway: us and the gateway / DHCP
  74          * server (probably simulated by modem firmware or network operator)
  75          * whose address changes everytime we connect to the intarwebz and
  76          * who doesn't bother answering ARP requests either.  So hardware
  77          * addresses have no meaning, the destination and the source of every
  78          * packet depend only on whether it is on the IN or OUT endpoint.  */
  79         dev->net->flags |= IFF_NOARP;
  80         /* IPv6 NDP relies on multicast.  Enable it by default. */
  81         dev->net->flags |= IFF_MULTICAST;
  82 
  83         return ret;
  84 }
  85 
  86 static void vl600_unbind(struct usbnet *dev, struct usb_interface *intf)
  87 {
  88         struct vl600_state *s = dev->driver_priv;
  89 
  90         dev_kfree_skb(s->current_rx_buf);
  91         kfree(s);
  92 
  93         return usbnet_cdc_unbind(dev, intf);
  94 }
  95 
  96 static int vl600_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
  97 {
  98         struct vl600_frame_hdr *frame;
  99         struct vl600_pkt_hdr *packet;
 100         struct ethhdr *ethhdr;
 101         int packet_len, count;
 102         struct sk_buff *buf = skb;
 103         struct sk_buff *clone;
 104         struct vl600_state *s = dev->driver_priv;
 105 
 106         /* Frame lengths are generally 4B multiplies but every couple of
 107          * hours there's an odd number of bytes sized yet correct frame,
 108          * so don't require this.  */
 109 
 110         /* Allow a packet (or multiple packets batched together) to be
 111          * split across many frames.  We don't allow a new batch to
 112          * begin in the same frame another one is ending however, and no
 113          * leading or trailing pad bytes.  */
 114         if (s->current_rx_buf) {
 115                 frame = (struct vl600_frame_hdr *) s->current_rx_buf->data;
 116                 if (skb->len + s->current_rx_buf->len >
 117                                 le32_to_cpup(&frame->len)) {
 118                         netif_err(dev, ifup, dev->net, "Fragment too long\n");
 119                         dev->net->stats.rx_length_errors++;
 120                         goto error;
 121                 }
 122 
 123                 buf = s->current_rx_buf;
 124                 skb_put_data(buf, skb->data, skb->len);
 125         } else if (skb->len < 4) {
 126                 netif_err(dev, ifup, dev->net, "Frame too short\n");
 127                 dev->net->stats.rx_length_errors++;
 128                 goto error;
 129         }
 130 
 131         frame = (struct vl600_frame_hdr *) buf->data;
 132         /* Yes, check that frame->magic == 0x53544448 (or 0x44544d48),
 133          * otherwise we may run out of memory w/a bad packet */
 134         if (ntohl(frame->magic) != 0x53544448 &&
 135                         ntohl(frame->magic) != 0x44544d48)
 136                 goto error;
 137 
 138         if (buf->len < sizeof(*frame) ||
 139                         buf->len != le32_to_cpup(&frame->len)) {
 140                 /* Save this fragment for later assembly */
 141                 if (s->current_rx_buf)
 142                         return 0;
 143 
 144                 s->current_rx_buf = skb_copy_expand(skb, 0,
 145                                 le32_to_cpup(&frame->len), GFP_ATOMIC);
 146                 if (!s->current_rx_buf)
 147                         dev->net->stats.rx_errors++;
 148 
 149                 return 0;
 150         }
 151 
 152         count = le32_to_cpup(&frame->pkt_cnt);
 153 
 154         skb_pull(buf, sizeof(*frame));
 155 
 156         while (count--) {
 157                 if (buf->len < sizeof(*packet)) {
 158                         netif_err(dev, ifup, dev->net, "Packet too short\n");
 159                         goto error;
 160                 }
 161 
 162                 packet = (struct vl600_pkt_hdr *) buf->data;
 163                 packet_len = sizeof(*packet) + le32_to_cpup(&packet->len);
 164                 if (packet_len > buf->len) {
 165                         netif_err(dev, ifup, dev->net,
 166                                         "Bad packet length stored in header\n");
 167                         goto error;
 168                 }
 169 
 170                 /* Packet header is same size as the ethernet header
 171                  * (sizeof(*packet) == sizeof(*ethhdr)), additionally
 172                  * the h_proto field is in the same place so we just leave it
 173                  * alone and fill in the remaining fields.
 174                  */
 175                 ethhdr = (struct ethhdr *) skb->data;
 176                 if (be16_to_cpup(&ethhdr->h_proto) == ETH_P_ARP &&
 177                                 buf->len > 0x26) {
 178                         /* Copy the addresses from packet contents */
 179                         memcpy(ethhdr->h_source,
 180                                         &buf->data[sizeof(*ethhdr) + 0x8],
 181                                         ETH_ALEN);
 182                         memcpy(ethhdr->h_dest,
 183                                         &buf->data[sizeof(*ethhdr) + 0x12],
 184                                         ETH_ALEN);
 185                 } else {
 186                         eth_zero_addr(ethhdr->h_source);
 187                         memcpy(ethhdr->h_dest, dev->net->dev_addr, ETH_ALEN);
 188 
 189                         /* Inbound IPv6 packets have an IPv4 ethertype (0x800)
 190                          * for some reason.  Peek at the L3 header to check
 191                          * for IPv6 packets, and set the ethertype to IPv6
 192                          * (0x86dd) so Linux can understand it.
 193                          */
 194                         if ((buf->data[sizeof(*ethhdr)] & 0xf0) == 0x60)
 195                                 ethhdr->h_proto = htons(ETH_P_IPV6);
 196                 }
 197 
 198                 if (count) {
 199                         /* Not the last packet in this batch */
 200                         clone = skb_clone(buf, GFP_ATOMIC);
 201                         if (!clone)
 202                                 goto error;
 203 
 204                         skb_trim(clone, packet_len);
 205                         usbnet_skb_return(dev, clone);
 206 
 207                         skb_pull(buf, (packet_len + 3) & ~3);
 208                 } else {
 209                         skb_trim(buf, packet_len);
 210 
 211                         if (s->current_rx_buf) {
 212                                 usbnet_skb_return(dev, buf);
 213                                 s->current_rx_buf = NULL;
 214                                 return 0;
 215                         }
 216 
 217                         return 1;
 218                 }
 219         }
 220 
 221 error:
 222         if (s->current_rx_buf) {
 223                 dev_kfree_skb_any(s->current_rx_buf);
 224                 s->current_rx_buf = NULL;
 225         }
 226         dev->net->stats.rx_errors++;
 227         return 0;
 228 }
 229 
 230 static struct sk_buff *vl600_tx_fixup(struct usbnet *dev,
 231                 struct sk_buff *skb, gfp_t flags)
 232 {
 233         struct sk_buff *ret;
 234         struct vl600_frame_hdr *frame;
 235         struct vl600_pkt_hdr *packet;
 236         static uint32_t serial = 1;
 237         int orig_len = skb->len - sizeof(struct ethhdr);
 238         int full_len = (skb->len + sizeof(struct vl600_frame_hdr) + 3) & ~3;
 239 
 240         frame = (struct vl600_frame_hdr *) skb->data;
 241         if (skb->len > sizeof(*frame) && skb->len == le32_to_cpup(&frame->len))
 242                 return skb; /* Already encapsulated? */
 243 
 244         if (skb->len < sizeof(struct ethhdr))
 245                 /* Drop, device can only deal with ethernet packets */
 246                 return NULL;
 247 
 248         if (!skb_cloned(skb)) {
 249                 int headroom = skb_headroom(skb);
 250                 int tailroom = skb_tailroom(skb);
 251 
 252                 if (tailroom >= full_len - skb->len - sizeof(*frame) &&
 253                                 headroom >= sizeof(*frame))
 254                         /* There's enough head and tail room */
 255                         goto encapsulate;
 256 
 257                 if (headroom + tailroom + skb->len >= full_len) {
 258                         /* There's enough total room, just readjust */
 259                         skb->data = memmove(skb->head + sizeof(*frame),
 260                                         skb->data, skb->len);
 261                         skb_set_tail_pointer(skb, skb->len);
 262                         goto encapsulate;
 263                 }
 264         }
 265 
 266         /* Alloc a new skb with the required size */
 267         ret = skb_copy_expand(skb, sizeof(struct vl600_frame_hdr), full_len -
 268                         skb->len - sizeof(struct vl600_frame_hdr), flags);
 269         dev_kfree_skb_any(skb);
 270         if (!ret)
 271                 return ret;
 272         skb = ret;
 273 
 274 encapsulate:
 275         /* Packet header is same size as ethernet packet header
 276          * (sizeof(*packet) == sizeof(struct ethhdr)), additionally the
 277          * h_proto field is in the same place so we just leave it alone and
 278          * overwrite the remaining fields.
 279          */
 280         packet = (struct vl600_pkt_hdr *) skb->data;
 281         /* The VL600 wants IPv6 packets to have an IPv4 ethertype
 282          * Since this modem only supports IPv4 and IPv6, just set all
 283          * frames to 0x0800 (ETH_P_IP)
 284          */
 285         packet->h_proto = htons(ETH_P_IP);
 286         memset(&packet->dummy, 0, sizeof(packet->dummy));
 287         packet->len = cpu_to_le32(orig_len);
 288 
 289         frame = skb_push(skb, sizeof(*frame));
 290         memset(frame, 0, sizeof(*frame));
 291         frame->len = cpu_to_le32(full_len);
 292         frame->serial = cpu_to_le32(serial++);
 293         frame->pkt_cnt = cpu_to_le32(1);
 294 
 295         if (skb->len < full_len) /* Pad */
 296                 skb_put(skb, full_len - skb->len);
 297 
 298         return skb;
 299 }
 300 
 301 static const struct driver_info vl600_info = {
 302         .description    = "LG VL600 modem",
 303         .flags          = FLAG_RX_ASSEMBLE | FLAG_WWAN,
 304         .bind           = vl600_bind,
 305         .unbind         = vl600_unbind,
 306         .status         = usbnet_cdc_status,
 307         .rx_fixup       = vl600_rx_fixup,
 308         .tx_fixup       = vl600_tx_fixup,
 309 };
 310 
 311 static const struct usb_device_id products[] = {
 312         {
 313                 USB_DEVICE_AND_INTERFACE_INFO(0x1004, 0x61aa, USB_CLASS_COMM,
 314                                 USB_CDC_SUBCLASS_ETHERNET, USB_CDC_PROTO_NONE),
 315                 .driver_info    = (unsigned long) &vl600_info,
 316         },
 317         {},     /* End */
 318 };
 319 MODULE_DEVICE_TABLE(usb, products);
 320 
 321 static struct usb_driver lg_vl600_driver = {
 322         .name           = "lg-vl600",
 323         .id_table       = products,
 324         .probe          = usbnet_probe,
 325         .disconnect     = usbnet_disconnect,
 326         .suspend        = usbnet_suspend,
 327         .resume         = usbnet_resume,
 328         .disable_hub_initiated_lpm = 1,
 329 };
 330 
 331 module_usb_driver(lg_vl600_driver);
 332 
 333 MODULE_AUTHOR("Anrzej Zaborowski");
 334 MODULE_DESCRIPTION("LG-VL600 modem's ethernet link");
 335 MODULE_LICENSE("GPL");