usbnet: Fix tx_bytes statistic running backward in cdc_ncm

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: beeecd42c3b4 ("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>

diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
index 724a9b5..75d6f26 100644 (file)
--- a/drivers/net/usb/asix_common.c
+++ b/drivers/net/usb/asix_common.c
@@ -189,7 +189,7 @@ struct sk_buff *asix_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
                skb_put(skb, sizeof(padbytes));
        }
 
-       usbnet_set_skb_tx_stats(skb, 1);
+       usbnet_set_skb_tx_stats(skb, 1, 0);
        return skb;
 }
 

diff --cc drivers/net/usb/cdc_ncm.c
Simple merge

diff --cc drivers/net/usb/sr9800.c
Simple merge

diff --cc drivers/net/usb/usbnet.c
Simple merge

diff --cc include/linux/usb/usbnet.h
Simple merge