On Apr 6, 2017, at 12:50 PM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:

Pete Heist <peteheist@gmail.com> writes:

The fq_codel qdisc does have support for arbitrary tc filters to replace
the default hashing, BTW. If you don't need the cake shaper, that might
be a solution?

I see, I found mention of it in Chapter 6 of a draft RFC that it looks
like you wrote, actually
(https://tools.ietf.org/html/draft-ietf-aqm-fq-codel-06#section-6). :)
To try it out, am I heading the right direction by looking at tc
filter’s skbedit action, or is that just for MQ devices?
(http://man7.org/linux/man-pages/man8/tc-skbedit.8.html)

I also saw this mention of “We are not aware of any deployments
utilising the custom classification feature"
https://tools.ietf.org/html/draft-ietf-aqm-fq-codel-02#section-5.1.1,
so not sure how often this has been tried. :)

Yeah, haven't actually heard of anyone using the feature in production.
It's basically this section from the 'classful qdiscs' section of 'man
tc':

      When a packet enters a classful qdisc it can be classified to one of the classes within. Three criteria are available, although not all qdiscs will use all three:

      tc filters
             If tc filters are attached to a class, they are consulted first for relevant instructions. Filters can match on all fields of a packet header, as well as on the firewall mark applied by ipchains or iptables.

So you can basically use the full capabilities of tc-filter in place of
the built-in hashing of fq_codel. The tc-u32 man page has some examples,
which is probably a good starting point.

If you do try this out and feel like writing up a small
example/tutorial, I'm happy to add a link (or the whole thing) somewhere
on bufferbloat.net :)