netdev - Re: [PATCH net-next 2/3] net: ethernet: ti: cpsw_new: enable broadcast/multicast rate limit support

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Message-ID: <7c288b6d-f32f-c5a9-8e8c-ab377423d4a8@ti.com>
Date:   Mon, 16 Nov 2020 15:01:43 +0200
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Vladimir Oltean <olteanv@...il.com>
CC:     "David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Sekhar Nori <nsekhar@...com>, <linux-kernel@...r.kernel.org>,
        <linux-omap@...r.kernel.org>, Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH net-next 2/3] net: ethernet: ti: cpsw_new: enable
 broadcast/multicast rate limit support



On 14/11/2020 21:09, Vladimir Oltean wrote:
> On Sat, Nov 14, 2020 at 05:56:53AM +0200, Grygorii Strashko wrote:
>> This patch enables support for ingress broadcast(BC)/multicast(MC) rate limiting
>> in TI CPSW switchdev driver (the corresponding ALE support was added in previous
>> patch) by implementing HW offload for simple tc-flower policer with matches
>> on dst_mac:
>>   - ff:ff:ff:ff:ff:ff has to be used for BC rate limiting
>>   - 01:00:00:00:00:00 fixed value has to be used for MC rate limiting
>>
>> Hence tc policer defines rate limit in terms of bits per second, but the
>> ALE supports limiting in terms of packets per second - the rate limit
>> bits/sec is converted to number of packets per second assuming minimum
>> Ethernet packet size ETH_ZLEN=60 bytes.
>>
>> Examples:
>> - BC rate limit to 1000pps:
>>    tc qdisc add dev eth0 clsact
>>    tc filter add dev eth0 ingress flower skip_sw dst_mac ff:ff:ff:ff:ff:ff \
>>    action police rate 480kbit burst 64k
>>
>>    rate 480kbit - 1000pps * 60 bytes * 8, burst - not used.
>>
>> - MC rate limit to 20000pps:
>>    tc qdisc add dev eth0 clsact
>>    tc filter add dev eth0 ingress flower skip_sw dst_mac 01:00:00:00:00:00 \
>>    action police rate 9600kbit burst 64k
>>
>>    rate 9600kbit - 20000pps * 60 bytes * 8, burst - not used.
>>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
>> ---
> 
> Your example for multicast would actually be correct if you specified
> the mask as well. Like this:
> 
> tc filter add dev eth0 ingress flower skip_sw \
> 	dst_mac 01:00:00:00:00:00/01:00:00:00:00:00 \
> 	action police rate 9600kbit burst 64k
> 
> But as things stand, the flow rule would have a certain meaning in
> software (rate-limit only that particular multicast MAC address) and a
> different meaning in hardware. Please modify the driver code to also
> match on the mask.
> 

ok.

-- 
Best regards,
grygorii