lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Tue, 10 Dec 2013 10:29:28 +0800
From:	Yang Yingliang <yangyingliang@...wei.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	<davem@...emloft.net>, <netdev@...r.kernel.org>,
	David Laight <David.Laight@...LAB.COM>, <brouer@...hat.com>,
	<jpirko@...hat.com>, <jbrouer@...hat.com>
Subject: Re: [PATCH RFC ] net: sched: tbf: fix the calculation of max_size

On 2013/12/9 23:12, Eric Dumazet wrote:
> On Mon, 2013-12-09 at 21:10 +0800, Yang Yingliang wrote:
>> From: Yang Yingliang <yangyingliang@...wei.com>
>>
>> Current max_size is caluated from rate table. Now, the rate table
>> has been replaced and it's wrong to caculate max_size based on this
>> rate table. It can lead wrong calculation of max_size.
>>
>> The burst in kernel may be lower than user asked, because burst may gets
>> some loss when transform it to buffer(E.g. "burst 40kb rate 30mbit/s")
>> and it seems we cannot avoid this loss. Burst's value(max_size) based on
>> rate table may be equal user asked. If a packet's length is max_size, this
>> packet will be stalled in tbf_dequeue() because its length is above the
>> burst in kernel so that it cannot get enough tokens. The max_size guards
>> against enqueuing packet sizes above q->buffer "time" in tbf_enqueue().
>>
>> To make consistent with the calculation of tokens, this patch add a helper
>> psched_ns_t2l() to calculate burst(max_size) directly to fix this problem.
>>
>> After this fix, we can support to using 64bit rates to calculate burst as well.
>>
>> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
>> ---
>>  net/sched/sch_tbf.c | 203 +++++++++++++++++++++++++++++++++++++++-------------
>>  1 file changed, 155 insertions(+), 48 deletions(-)
> 
> 
> There is no way I am going to study this patch.
> 
> There is no way 32bit * 32bit multiply can overflow 64bit.
> 
> If the user gave a stupid input, like a buffer bigger than 4 sec, just
> say no. Nobody ever did such stupid things in the past, and nobody will
> do in the future because it is so wrong and useless.
> 
> q->mtu = max_t(u64, ~0U, PSCHED_TICKS2NS(qopt->mtu));
> 
> q->buffer = max_t(u64, ~0U, PSCHED_TICKS2NS(qopt->buffer));
> 
> Could we keep this code understandable, please ?

Hmm, I cannot figure out why max_t, did you mean min_t?

> 
> 
> 
> 
> 


--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists