Messages in this thread | | | Date | Mon, 14 Nov 2022 13:55:59 +0200 | From | Vladimir Oltean <> | Subject | Re: [PATCH net-next v3 1/4] net: dsa: add support for DSA rx offloading via metadata dst |
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On Sat, Nov 12, 2022 at 12:13:15PM +0100, Felix Fietkau wrote: > On 12.11.22 05:40, Jakub Kicinski wrote: > I don't really see a valid use case in running generic XDP, TC and NFT on a > DSA master dealing with packets before the tag receive function has been > run. And after the tag has been processed, the metadata DST is cleared from > the skb.
Oh, there are potentially many use cases, the problem is that maybe there aren't as many actual implementations as ideas? At least XDP is, I think, expected to be able to deal with DSA tags if run on a DSA master (not sure how that applies when RX DSA tag is offloaded, but whatever). Marek Behun had a prototype with Marvell tags, not sure how far that went in the end: https://www.mail-archive.com/netdev@vger.kernel.org/msg381018.html In general, forwarding a packet to another switch port belonging to the same master via XDP_TX should be relatively efficient.
> How about this: I send a v4 which uses skb_dst_drop instead of skb_dst_set, > so that other drivers can use refcounting if it makes sense for them. For > mtk_eth_soc, I prefer to leave out refcounting for performance reasons. > Is that acceptable to you guys?
I don't think you can mix refcounting at consumer side with no-refcounting at producer side, no?
I suppose that we could leave refcounting out for now, and bug you if someone comes with a real need later and complains. Right now it's a bit hard for me to imagine all the possibilities. How does that sound?
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