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usbnet: Fix tx_bytes statistic running backward in cdc_ncm

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cdc_ncm disagrees with usbnet about how much framing overhead should
be counted in the tx_bytes statistics, and tries 'fix' this by
decrementing tx_bytes on the transmit path.  But statistics must never
be decremented except due to roll-over; this will thoroughly confuse
user-space.  Also, tx_bytes is only incremented by usbnet in the
completion path.

Fix this by requiring drivers that set FLAG_MULTI_FRAME to set a
tx_bytes delta along with the tx_packets count.

Fixes: beeecd42c3 ("net: cdc_ncm/cdc_mbim: adding NCM protocol statistics")
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
This commit is contained in:
Ben Hutchings
2015-03-25 21:41:33 +01:00
committed by David S. Miller
parent 1e9e39f4a2
commit 7a1e890e21
5 changed files with 22 additions and 11 deletions
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16
drivers/net/usb/usbnet.c
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@@ -1346,9 +1346,19 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
} else
urb->transfer_flags |= URB_ZERO_PACKET;
}
entry->length = urb->transfer_buffer_length = length;
if (!(info->flags & FLAG_MULTI_PACKET))
usbnet_set_skb_tx_stats(skb, 1);
urb->transfer_buffer_length = length;
if (info->flags & FLAG_MULTI_PACKET) {
/* Driver has set number of packets and a length delta.
* Calculate the complete length and ensure that it's
* positive.
*/
entry->length += length;
if (WARN_ON_ONCE(entry->length <= 0))
entry->length = length;
} else {
usbnet_set_skb_tx_stats(skb, 1, length);
}
spin_lock_irqsave(&dev->txq.lock, flags);
retval = usb_autopm_get_interface_async(dev->intf);