netdev - Re: taprio testing

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Date:   Fri, 11 Oct 2019 16:56:51 -0400
From:   Murali Karicheri <m-karicheri2@...com>
To:     Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: taprio testing - Any help?

Hi Vinicius,

On 10/11/2019 04:12 PM, Vinicius Costa Gomes wrote:
> Hi Murali,
> 
> Murali Karicheri <m-karicheri2@...com> writes:
> 
>> Hi,
>>
>> I am testing the taprio (802.1Q Time Aware Shaper) as part of my
>> pre-work to implement taprio hw offload and test.
>>
>> I was able to configure tap prio on my board and looking to do
>> some traffic test and wondering how to play with the tc command
>> to direct traffic to a specfic queue. For example I have setup
>> taprio to create 5 traffic classes as shows below;-
>>
>> Now I plan to create iperf streams to pass through different
>> gates. Now how do I use tc filters to mark the packets to
>> go through these gates/queues? I heard about skbedit action
>> in tc filter to change the priority field of SKB to allow
>> the above mapping to happen. Any example that some one can
>> point me to?
> 
> What I have been using for testing these kinds of use cases (like iperf)
> is to use an iptables rule to set the priority for some kinds of traffic.
> 
> Something like this:
> 
> sudo iptables -t mangle -A POSTROUTING -p udp --dport 7788 -j CLASSIFY --set-class 0:3
Let me try this. Yes. This is what I was looking for. I was trying
something like this and I was getting an error

tc filter add  dev eth0 parent 100: protocol ip prio 10 u32 match ip 
dport 10000 0xffff flowid 100:3
RTNETLINK answers: Operation not supported
We have an error talking to the kernel, -1

Not sure why the above throws an error for me. If I understand it
right, match rule will add a filter to the parent to send packet to
100:3 which is for TC3 or Q3.

My taprio configuration is as follows:-

root@...7xx-evm:~# tc qdisc show  dev eth0
qdisc taprio 100: root refcnt 9 tc 5 map 0 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2
queues offset 0 count 1 offset 1 count 1 offset 2 count 1 offset 3 count 
1 offset 4 count 1
clockid TAI offload 0   base-time 0 cycle-time 0 cycle-time-extension 0 
base-time 1564536613194451433 cycle-time 20000000 cycle-
time-extension 0
         index 0 cmd S gatemask 0x1 interval 4000000
         index 1 cmd S gatemask 0x2 interval 4000000
         index 2 cmd S gatemask 0x4 interval 4000000
         index 3 cmd S gatemask 0x8 interval 4000000
         index 4 cmd S gatemask 0x10 interval 4000000

qdisc pfifo 0: parent 100:5 limit 1000p
qdisc pfifo 0: parent 100:4 limit 1000p
qdisc pfifo 0: parent 100:3 limit 1000p
qdisc pfifo 0: parent 100:2 limit 1000p
qdisc pfifo 0: parent 100:1 limit 1000p

Thanks for your response!
>  
> This will set the skb->priority of UDP packets matching that rule to 3.
> 
> Another alternative is to create a net_prio cgroup, and the sockets
> created under that hierarchy would have have that priority. I don't have
> an example handy for this right now, sorry.
> 
> Is this what you were looking for?
> 
> 
> Cheers,
> --
> Vinicius
>