tc filter flow hash question

tc filter flow hash question

[Badalian Vyacheslav]

Hello all.
Sorry for mail to this maillist, but in internet i can't found any
information to understand this situation, lartc list is dead, function
do not documented and only developers understand how it works.

As i understand if i add flow hash i divide speed to KEYs (example to
dst) not for sessions right?

Why if i add simple example my traffic stop and i get DROP at parent class?

This my sample

tc qdisc add dev eth0 root handle 1 htb default 7
class add dev eth0 parent 1: classid 1:7 htb rate 500mbit ceil 1000mbit
prio 3
qdisc add dev eth0 parent 1:7 handle 10: sfq perturb 10
# all normal
tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys
src,dst
# all traffic drop

Thanks!
Best regals, Badalian Vyacheslav

Re: tc filter flow hash question

[Jarek Poplawski]

On 30-06-2009 10:12, Badalian Vyacheslav wrote:
> Hello all.
> Sorry for mail to this maillist, but in internet i can't found any
> information to understand this situation, lartc list is dead, function
> do not documented and only developers understand how it works.

They only pretend they understand how it works...

> 
> As i understand if i add flow hash i divide speed to KEYs (example to
> dst) not for sessions right?
> 
> Why if i add simple example my traffic stop and i get DROP at parent class?
> 
> This my sample
> 
> tc qdisc add dev eth0 root handle 1 htb default 7
> class add dev eth0 parent 1: classid 1:7 htb rate 500mbit ceil 1000mbit
> prio 3
> qdisc add dev eth0 parent 1:7 handle 10: sfq perturb 10
> # all normal
> tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys
> src,dst
> # all traffic drop
> 

Here are some hints (if we don't mention google ;-)
http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.29.y.git;a=commitdiff;h=e5dfb815181fcb186d6080ac3a091eadff2d98fe

Regards,
Jarek P.

Re: tc filter flow hash question

[Badalian Vyacheslav]

Jarek Poplawski пишет:
> On 30-06-2009 10:12, Badalian Vyacheslav wrote:
>   
>> Hello all.
>> Sorry for mail to this maillist, but in internet i can't found any
>> information to understand this situation, lartc list is dead, function
>> do not documented and only developers understand how it works.
>>     
>
> They only pretend they understand how it works...
>
>   
>> As i understand if i add flow hash i divide speed to KEYs (example to
>> dst) not for sessions right?
>>
>> Why if i add simple example my traffic stop and i get DROP at parent class?
>>
>> This my sample
>>
>> tc qdisc add dev eth0 root handle 1 htb default 7
>> class add dev eth0 parent 1: classid 1:7 htb rate 500mbit ceil 1000mbit
>> prio 3
>> qdisc add dev eth0 parent 1:7 handle 10: sfq perturb 10
>> # all normal
>> tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys
>> src,dst
>> # all traffic drop
>>
>>     
>
>   
Yep. I was read this commit and create example based on it.
My question why its drop all traffic after add flow filter? Its simple
must group traffic to sfq qidsc by HASH like equal cost routing by KEY
if i understand. I need balance traffic in class/qdisc by KEY, but not
by sessions.

Any worked example will be great. In commit i see only syntax :)

Thanks!

> Here are some hints (if we don't mention google ;-)
> http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.29.y.git;a=commitdiff;h=e5dfb815181fcb186d6080ac3a091eadff2d98fe
>
> Regards,
> Jarek P.
>
>
>   

Re: tc filter flow hash question

[Jarek Poplawski]

On Tue, Jun 30, 2009 at 01:18:42PM +0400, Badalian Vyacheslav wrote:
> Jarek Poplawski ??????????:
> > On 30-06-2009 10:12, Badalian Vyacheslav wrote:
...
> >> tc qdisc add dev eth0 root handle 1 htb default 7
> >> class add dev eth0 parent 1: classid 1:7 htb rate 500mbit ceil 1000mbit
> >> prio 3
> >> qdisc add dev eth0 parent 1:7 handle 10: sfq perturb 10
> >> # all normal
> >> tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys
> >> src,dst
> >> # all traffic drop
> >>
> >>     
> >
> >   
> Yep. I was read this commit and create example based on it.
> My question why its drop all traffic after add flow filter? Its simple
> must group traffic to sfq qidsc by HASH like equal cost routing by KEY
> if i understand. I need balance traffic in class/qdisc by KEY, but not
> by sessions.
> 
> Any worked example will be great. In commit i see only syntax :)

Any non-working example with this syntax? (divisor?)

Jarek P.
> 
> > Here are some hints (if we don't mention google ;-)
> > http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.29.y.git;a=commitdiff;h=e5dfb815181fcb186d6080ac3a091eadff2d98fe
> >
> > Regards,
> > Jarek P.
> >
> >
> >   
> 

Re: tc filter flow hash question

[Badalian Vyacheslav]

> On Tue, Jun 30, 2009 at 01:18:42PM +0400, Badalian Vyacheslav wrote:
>   
>> Jarek Poplawski ??????????:
>>     
>>> On 30-06-2009 10:12, Badalian Vyacheslav wrote:
>>>       
> ...
>   
>>>> tc qdisc add dev eth0 root handle 1 htb default 7
>>>> class add dev eth0 parent 1: classid 1:7 htb rate 500mbit ceil 1000mbit
>>>> prio 3
>>>> qdisc add dev eth0 parent 1:7 handle 10: sfq perturb 10
>>>> # all normal
>>>> tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys
>>>> src,dst
>>>> # all traffic drop
>>>>
>>>>     
>>>>         
>>>   
>>>       
>> Yep. I was read this commit and create example based on it.
>> My question why its drop all traffic after add flow filter? Its simple
>> must group traffic to sfq qidsc by HASH like equal cost routing by KEY
>> if i understand. I need balance traffic in class/qdisc by KEY, but not
>> by sessions.
>>
>> Any worked example will be great. In commit i see only syntax :)
>>     
>
> Any non-working example with this syntax? (divisor?)
>
>   

This example not approach? 

tc qdisc add dev eth0 root handle 1 htb default 7
tc class add dev eth0 parent 1: classid 1:7 htb rate 500mbit ceil 1000mbit prio 3
tc qdisc add dev eth0 parent 1:7 handle 10: sfq perturb 10

# all traffic go to class 1-7.

# Try group traffic by "src,dst" key

tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys src,dst

# all traffic dropped


> Jarek P.
>   
>>> Here are some hints (if we don't mention google ;-)
>>> http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.29.y.git;a=commitdiff;h=e5dfb815181fcb186d6080ac3a091eadff2d98fe
>>>
>>> Regards,
>>> Jarek P

Re: tc filter flow hash question

[Jarek Poplawski]

On Tue, Jun 30, 2009 at 01:49:11PM +0400, Badalian Vyacheslav wrote:
...
> This example not approach? 
> 
> tc qdisc add dev eth0 root handle 1 htb default 7
> tc class add dev eth0 parent 1: classid 1:7 htb rate 500mbit ceil 1000mbit prio 3
> tc qdisc add dev eth0 parent 1:7 handle 10: sfq perturb 10
> 
> # all traffic go to class 1-7.
> 
> # Try group traffic by "src,dst" key
> 
> tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys src,dst
> 
> # all traffic dropped

Try:
tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys src,dst divisor 1024

Jarek P.
> >   
> >>> Here are some hints (if we don't mention google ;-)
> >>> http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.29.y.git;a=commitdiff;h=e5dfb815181fcb186d6080ac3a091eadff2d98fe
> >>>
> >>> Regards,
> >>> Jarek P

Re: tc filter flow hash question

[Badalian Vyacheslav]

Jarek Poplawski пишет:
> On Tue, Jun 30, 2009 at 01:49:11PM +0400, Badalian Vyacheslav wrote:
> ...
>   
>> This example not approach? 
>>
>> tc qdisc add dev eth0 root handle 1 htb default 7
>> tc class add dev eth0 parent 1: classid 1:7 htb rate 500mbit ceil 1000mbit prio 3
>> tc qdisc add dev eth0 parent 1:7 handle 10: sfq perturb 10
>>
>> # all traffic go to class 1-7.
>>
>> # Try group traffic by "src,dst" key
>>
>> tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys src,dst
>>
>> # all traffic dropped
>>     
>
> Try:
> tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys src,dst divisor 1024
>
>   
Outh! Very thanks! I'm so stupid. its simple :(

Also i look in code and see in flow_classify function this lines:

if (f->divisor)
        classid %= f->divisor;

classid generated in up.
Also i see to SFQ code and see that SFQ create 1024 hashes.
If we do not add divisor when added filter rule we get classid > 1024
and its not go to hash of SFQ (my example).
Also divisor must be > 0 because = NaN as i understand.
I not sure that it must be <= 1024 because it may use not in SFQ and i
don't know MAX size of other qdiscs but if it use only in in SFQ i think
we need to check <= SFQ_HASH_DIVISOR also?

Maybe "if" code must be changed to

if (f->divisor && f->divisor > 0)
        classid %= f->divisor;
else
        classid %= 1024;


How you think?
Best regals, Slavon


> Jarek P.
>   
>>>   
>>>       
>>>>> Here are some hints (if we don't mention google ;-)
>>>>> http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.29.y.git;a=commitdiff;h=e5dfb815181fcb186d6080ac3a091eadff2d98fe
>>>>>
>>>>> Regards,
>>>>> Jarek P
>>>>>           
>
>
>   

Re: tc filter flow hash question

[Jarek Poplawski]

On Tue, Jun 30, 2009 at 02:30:38PM +0400, Badalian Vyacheslav wrote:
> Jarek Poplawski ??????????:
> > On Tue, Jun 30, 2009 at 01:49:11PM +0400, Badalian Vyacheslav wrote:
> > ...
> >   
> >> This example not approach? 
> >>
> >> tc qdisc add dev eth0 root handle 1 htb default 7
> >> tc class add dev eth0 parent 1: classid 1:7 htb rate 500mbit ceil 1000mbit prio 3
> >> tc qdisc add dev eth0 parent 1:7 handle 10: sfq perturb 10
> >>
> >> # all traffic go to class 1-7.
> >>
> >> # Try group traffic by "src,dst" key
> >>
> >> tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys src,dst
> >>
> >> # all traffic dropped
> >>     
> >
> > Try:
> > tc filter add dev eth0 protocol ip parent 10: handle 2 flow hash keys src,dst divisor 1024
> >
> >   
> Outh! Very thanks! I'm so stupid. its simple :(
> 
> Also i look in code and see in flow_classify function this lines:
> 
> if (f->divisor)
>         classid %= f->divisor;
> 
> classid generated in up.
> Also i see to SFQ code and see that SFQ create 1024 hashes.
> If we do not add divisor when added filter rule we get classid > 1024
> and its not go to hash of SFQ (my example).
> Also divisor must be > 0 because = NaN as i understand.
> I not sure that it must be <= 1024 because it may use not in SFQ and i
> don't know MAX size of other qdiscs but if it use only in in SFQ i think
> we need to check <= SFQ_HASH_DIVISOR also?
> 
> Maybe "if" code must be changed to
> 
> if (f->divisor && f->divisor > 0)
>         classid %= f->divisor;
> else
>         classid %= 1024;
> 
> 
> How you think?

I guess the author preferred to signal that something is misconfigured
with drops, but you could try to send a patch or ask him to make sure.

Btw., sfq isn't very useful with real 1024 or even much less flows, so
you should probably start looking for sch_drr with cls_flow examples
(there were a few of them on the list).

Best regards,
Jarek P.