[dpdk-dev] [PATCH v2] lib/librte_meter: fix divide by zero for RFC4115 meter
Eelco Chaudron
echaudro at redhat.com
Tue Mar 19 12:00:04 CET 2019
On 28 Feb 2019, at 19:50, Dumitrescu, Cristian wrote:
> Hi Eelco,
>
> Sorry for my delayed reply
No problem I was OOO also so hence my late reply ;)
>> -----Original Message-----
>> From: Eelco Chaudron [mailto:echaudro at redhat.com]
>> Sent: Friday, February 1, 2019 4:07 PM
>> To: Dumitrescu, Cristian <cristian.dumitrescu at intel.com>
>> Cc: dev at dpdk.org
>> Subject: [PATCH v2] lib/librte_meter: fix divide by zero for RFC4115
>> meter
>>
>> RFC 4115 allows a meter with either cir and/or eir configured.
>> When only one is configured a divide by zero would occur.
>>
>> Fixes: 655796d2b5fb ("meter: support RFC4115 trTCM")
>> Cc: echaudro at redhat.com
>>
>> Signed-off-by: Eelco Chaudron <echaudro at redhat.com>
>> ---
>>
>> v2 - Removed configuration change that got included by accident
>>
>> lib/librte_meter/rte_meter.h | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/lib/librte_meter/rte_meter.h
>> b/lib/librte_meter/rte_meter.h
>> index 005e4eeee..56d85ecf0 100644
>> --- a/lib/librte_meter/rte_meter.h
>> +++ b/lib/librte_meter/rte_meter.h
>> @@ -597,8 +597,8 @@ rte_meter_trtcm_rfc4115_color_blind_check(
>> /* Bucket update */
>> time_diff_tc = time - m->time_tc;
>> time_diff_te = time - m->time_te;
>> - n_periods_tc = time_diff_tc / p->cir_period;
>> - n_periods_te = time_diff_te / p->eir_period;
>> + n_periods_tc = p->cir_period != 0 ? time_diff_tc / p->cir_period :
>> 0;
>> + n_periods_te = p->eir_period != 0 ? time_diff_te / p->eir_period :
>> 0;
>> m->time_tc += n_periods_tc * p->cir_period;
>> m->time_te += n_periods_te * p->eir_period;
>>
>> @@ -641,8 +641,8 @@ rte_meter_trtcm_rfc4115_color_aware_check(
>> /* Bucket update */
>> time_diff_tc = time - m->time_tc;
>> time_diff_te = time - m->time_te;
>> - n_periods_tc = time_diff_tc / p->cir_period;
>> - n_periods_te = time_diff_te / p->eir_period;
>> + n_periods_tc = p->cir_period != 0 ? time_diff_tc / p->cir_period :
>> 0;
>> + n_periods_te = p->eir_period != 0 ? time_diff_te / p->eir_period :
>> 0;
>> m->time_tc += n_periods_tc * p->cir_period;
>> m->time_te += n_periods_te * p->eir_period;
>>
>
> Yes, this is indeed an issue, good catch!
>
> For performance reasons, we'd like to avoid a test on the fast path
> (rte_meter_xyz_check) and replace it with more work done on the
> configuration stage (rte_meter_profile_xyz_config), if possible.
>
> We can intercept the null CIR or EIR cases very early in
> rte_meter_trtcm_rfc4115_profile_config() and deal with them separately
> by setting the CIR/EIR period and bytes_per_period to some neutral
> values and skipping the call to rte_meter_get_tb_params(): period =
> RTE_METER_TB_PERIOD_MIN, bytes_per_period = 0.
Excellent idea, will sent out a v3 soon, after some testing…
//Eelco
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