> On Apr 6, 2017, at 12:50 PM, Toke Høiland-Jørgensen wrote: > > Pete Heist > 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 :) Sure, if I get it working I’ll include an example in my paper, but I’m still a little confused. Is fq_codel actually a classful qdisc? I get the part about matching with tc-filter and the u32 selector (as intuitive as that is :), but am not sure of the action the filter needs to take. However, I do see the example towards the bottom of the tc-u32 man page where a hash table is created and filters move packets into the right buckets. Perhaps it will be eventually decipherable from this… :)