net: usbnet: fix tx_dropped statistics

It is normal for minidrivers accumulating frames to return NULL
from their tx_fixup function. We do not want to count this as a
drop, or log any debug messages.  A different exit path is
therefore chosen for such drivers, skipping the debug message
and the tx_dropped increment.

The test for accumulating drivers was however completely bogus,
making the exit path selection depend on whether the user had
enabled tx_err logging or not. This would arbitrarily mess up
accounting for both accumulating and non-accumulating minidrivers,
and would result in unwanted debug messages for the accumulating
drivers.

Fix by testing for FLAG_MULTI_PACKET instead, which probably was
the intention from the beginning.  This usage match the documented
behaviour of this flag:

 Indicates to usbnet, that USB driver accumulates multiple IP packets.
 Affects statistic (counters) and short packet handling.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 6 deletions

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 977837725726..5e33606c1366 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1125,13 +1125,11 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
         if (info->tx_fixup) {
                 skb = info->tx_fixup (dev, skb, GFP_ATOMIC);
                 if (!skb) {
-                        if (netif_msg_tx_err(dev)) {
-                                netif_dbg(dev, tx_err, dev->net, "can't tx_fixup skb\n");
-                                goto drop;
-                        } else {
-                                /* cdc_ncm collected packet; waits for more */
+                        /* packet collected; minidriver waiting for more */
+                        if (info->flags & FLAG_MULTI_PACKET)
                                 goto not_drop;
-                        }
+                        netif_dbg(dev, tx_err, dev->net, "can't tx_fixup skb\n");
+                        goto drop;
                 }
         }
         length = skb->len;