Re: tc and IPv6 : any experiences ?

Linux Advanced Routing and Traffic Control

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On Fri, Jan 13, 2017 at 10:02 AM, Andy Furniss <adf.lists@xxxxxxxxx> wrote:
> Dave Taht wrote:
>>
>> On Fri, Jan 13, 2017 at 5:49 AM, Alan Goodman
>> <notifications@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>>>
>>> 'Just works' for me.
>>>
>>> TF + HFSC + FQ_Codel.  QoS categoriser written in iptables rules which
>>> mark
>>> the traffic was 'cloned' across using ip6tables. Slight adjustments
>>> needed.
>>
>>
>> I pointed to a common mistake folk tend to make when dealing with
>> ipv6, in writing a filter rule, or a default bin, here:
>>
>> https://www.bufferbloat.net/projects/cerowrt/wiki/Wondershaper_Must_Die/
>>
>> When I started that rant I was seeing in nearly every off the shelf
>> shaper a tc pattern match that looked like this:
>>
>> tc filter add dev $DEV parent ffff: protocol ip prio 50 u32 match ip src \
>>     0.0.0.0/0 police rate ${DOWNLINK}kbit burst 10k drop flowid :1
>>
>> Instead of
>>
>> tc filter add dev ${DEV} parent ffff: protocol all match u32 0 0 \
>> police rate ${DOWNLINK}kbit burst 100k drop flowid :1
>>
>>
>> Not matching protocol "all", thus ipv4 only - and thus the instant you
>> added ipv6 to a network, the shaper (or policer in this case),  failed
>> to shape successfully any traffic. Additional problems listed in the
>> link above. I went on a search-and-destroy mission on every shaper I
>> could find that was public to fix it a few years ago, but there's so
>> much copy/pasted tc code out there...
>
>
> I was about to post that ip is just v4, but would also add - be careful
> with protocol all as well. You may end up shaping/dropping "critical"
> packets like arp.

Not sure I understand, arp is matched with all? ip v4 is not?

We ended up adding an explicit arp prioritization to cake recently.

(see https://github.com/dtaht/sch_cake/commit/644b7efb2a552ba76871e65033c58275c15207f9
)

cake eliminates a whole raft of other oft-required tc magic, I hope we
get around to mainlining it this year.




-- 
Dave Täht
Let's go make home routers and wifi faster! With better software!
http://blog.cerowrt.org
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