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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: 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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/net/usb/asix_common.c
View File

@ -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;
}

7
drivers/net/usb/cdc_ncm.c
View File

@ -1177,13 +1177,12 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
ctx->tx_overhead += skb_out->len - ctx->tx_curr_frame_payload;
ctx->tx_ntbs++;
/* usbnet has already counted all the framing overhead.
/* usbnet will count all the framing overhead by default.
* Adjust the stats so that the tx_bytes counter show real
* payload data instead.
*/
dev->net->stats.tx_bytes -= skb_out->len - ctx->tx_curr_frame_payload;
usbnet_set_skb_tx_stats(skb_out, n);
usbnet_set_skb_tx_stats(skb_out, n,
ctx->tx_curr_frame_payload - skb_out->len);
return skb_out;

2
drivers/net/usb/sr9800.c
View File

@ -144,7 +144,7 @@ static struct sk_buff *sr_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;
}

16
drivers/net/usb/usbnet.c
View File

@ -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);

6
include/linux/usb/usbnet.h
View File

@ -227,7 +227,7 @@ struct skb_data { /* skb->cb is one of these */
struct urb *urb;
struct usbnet *dev;
enum skb_state state;
size_t length;
long length;
unsigned long packets;
};
@ -235,11 +235,13 @@ struct skb_data { /* skb->cb is one of these */
* tx_fixup method before returning an skb.
*/
static inline void
usbnet_set_skb_tx_stats(struct sk_buff *skb, unsigned long packets)
usbnet_set_skb_tx_stats(struct sk_buff *skb,
unsigned long packets, long bytes_delta)
{
struct skb_data *entry = (struct skb_data *) skb->cb;
entry->packets = packets;
entry->length = bytes_delta;
}
extern int usbnet_open(struct net_device *net);