Commit 7a1e890e authored by Ben Hutchings's avatar Ben Hutchings Committed by David S. Miller
Browse files

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: beeecd42 ("net: cdc_ncm/cdc_mbim: adding NCM protocol statistics")
Signed-off-by: default avatarBen Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: default avatarBjørn Mork <bjorn@mork.no>
parent 1e9e39f4

drivers/net/usb/asix_common.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

}

drivers/net/usb/cdc_ncm.c

+3 −4
Original line number Diff line number Diff line
@@ -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;

drivers/net/usb/sr9800.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

}

drivers/net/usb/usbnet.c

+13 −3
Original line number Diff line number Diff line
@@ -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);

include/linux/usb/usbnet.h

+4 −2
Original line number Diff line number Diff line
@@ -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);

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