Annoying /proc/net/dev rollovers.

[Mark J Roberts <mjr@znex.org>]

The rolling-over of /proc/net/dev fields annoys me.

I read a couple threads about the issue and saw a lot of whimpering
about how locking would be such a pain to implement in lieu of
32-bit atomicity.

Alan Cox pointed out in one of them that accurate info could be
collected through "the firewalling facilities", which I take to mean
the ipt_counters structure. The caveat is that it only provides
packet and byte counts.

One alternative to throwing locks around everything accessing those
fields is to update a 64-bit counter asynchronously. Has this been
considered? It would entail atomically executing

	total_rx_bytes += rx_bytes;
	rx_bytes = 0;

and merely ensuring that rx_bytes does not roll over between calls.