Re: rte_flow MARK + JUMP with mlx5

[Tom Barbette <tom.barbette@uclouvain.be>]

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Le 11-11-21 à 13:48, Daniel Romell a écrit :
> Hey all!
>
> A few questions about rte_flow, specifically the MARK + JUMP actions;
>
> What's the expected behavior of MARK + JUMP in the same flow? Is the 
> mark expected to survive to the target flow group? Is it driver 
> specific? Undefined? Unsupported?
>
> For example, when testing with the following flow setup in testpmd 
> (mlx CX6, DPDK 19.11.2 and latest mainline), none of the received 
> packets are marked:
>
> flow create 0 ingress pattern eth / end actions mark id 0x1337 / jump 
> group 1 / end
> flow create 0 ingress group 1 pattern eth / end actions queue index 0 
> / end
>
> A single flow with MARK + QUEUE works as expected.
I don't know about that, I would have expected it to work.
>
> What I want in the end is a set of simple RSS rules that would match 
> most of the traffic, and another set of rules that would mark a small 
> subset of the traffic before being processed by the RSS rule.
>
> I realize I *could* duplicate the RSS actions and have them in the 
> same rule as the MARK, but that just seems like the wrong thing to do 
> for a few different reasons;
> * It would require one flow for each combination of MARK and RSS 
> condition.
> * The MARK rules should be inserted and removed during runtime, while 
> the RSS rules should be long-lived and static.
> * The code inserting the MARK rule ideally shouldn't have be aware of 
> the RSS config (other than that it should continue to a new group for 
> further matching).


As far as I know, and from that discussion you mention, there is no "go 
back to the default global RSS action" action. Once you add a rule, you 
have to add the RSS fate action.


You can duplicate the "global" RSS using rte_eth_dev_rss_hash_conf_get 
only once with the new "shared action" API  (    
rte_flow_action_handle_create etc) precisely to avoid creating many RSS 
context as you mentioned.


Tom

>
> What's the right way of doing something like this with DPDK?
> I've already implemented the same thing with a custom/proprietary mlx 
> driver, so I know it should be doable. What I ended up doing there was 
> simply to have two flow tables. The root table (level 0) holds all 
> "mark" rules (flow tag), and forwards to everything (including misses) 
> to the next table. The table at level 1 contains the RSS rules, and 
> leaves all flows untagged so the tag set in the first level is 
> preserved. Is there a way to get to a similar setup through the 
> rte_flow API?
>
> Thanks,
> Daniel Romell
>
> (CCs as suggested by Thomas in slack + Tom as this seems somewhat 
> similar to https://www.mail-archive.com/users@dpdk.org/msg03900.html 
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