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, 7 insertions, 3 deletions

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 95c41d56631c..cf58b7682565 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -387,8 +387,12 @@ static int rx_submit (struct usbnet *dev, struct urb *urb, gfp_t flags)
 static inline void rx_process (struct usbnet *dev, struct sk_buff *skb)
 {
         if (dev->driver_info->rx_fixup &&
-            !dev->driver_info->rx_fixup (dev, skb))
-                goto error;
+            !dev->driver_info->rx_fixup (dev, skb)) {
+                /* With RX_ASSEMBLE, rx_fixup() must update counters */
+                if (!(dev->driver_info->flags & FLAG_RX_ASSEMBLE))
+                        dev->net->stats.rx_errors++;
+                goto done;
+        }
         // else network stack removes extra byte if we forced a short packet
 
         if (skb->len) {
@@ -401,8 +405,8 @@ static inline void rx_process (struct usbnet *dev, struct sk_buff *skb)
         }
 
         netif_dbg(dev, rx_err, dev->net, "drop\n");
-error:
         dev->net->stats.rx_errors++;
+done:
         skb_queue_tail(&dev->done, skb);
 }