Re: [RFC] net: usbnet: prevent buggy devices from killing us

On Thursday 24 January 2013 13:47:40 Bjørn Mork wrote:

Oliver Neukum [off-list ref] writes:

quoted

On Thursday 24 January 2013 12:22:54 Bjørn Mork wrote:

quoted

Sorry for being daft, but how do I code the "20 among the last 30" part
there?

Just by agreeing that you can live with false negatives but not false positives

if (++counter > 30) {
	counter = bogus = 0;
} else {
	if (is_bogus(packet)
		bogus++;
	if (bogus > counter/2)

Should probably be something like bogus > counter/2 + 10

quoted

		throttle();
}

So, add two new counters to struct usbnet for this?  That seems a little
overkill to me, but I don't see how else to implement anything like that.

Memory is cheap.
 

It is still not completely clear to me how the throttling/unthrottling
should be done.  It tested with static counters (to avoid having to
rebuild everything for this test) and a new EVENT_RX_THROTTLE flag.
Still on top of my previous patch just for safety while testing, as I am
fed up of having to reboot all the time :-)

Doing the flag test in rx_submit seems simpler than trying to track all
the places this is called.  Still checking the dev->done.qlen to be able
to unthrottle.

Ideally we would do some error handling. Does the device keep spewing
zero packets for all eternity?

	Regards
		Oliver

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