On Thu, Dec 03, 2020 at 22:09, Andrew Lunn <and...@lunn.ch> wrote: >> One could argue that if Linus had received an error instead, adapted his >> teamd config and tried again, he would be a happier user and we might >> not have to compete with his OS. >> >> I am not sure which way is the correct one, but I do not think that it >> necessarily _always_ correct to silently fallback to a non-offloaded >> mode. > > This is an argument Mellanox makes, where falling back to software > would be a bad idea given the huge bandwidth of their hardware > accelerator, and the slow bandwidth of their CPU.
Yeah when you have 100G interfaces the choice becomes easier :) > If the switch has no hardware support for LAG at all, then falling > back to software is reasonable. It is less clear when there is some > support in the switch. If we do reject it, we should try to make use > of extack to give the user a useful error messages: Not supported, try > configuration XYZ. But i guess that needs some plumbing, getting > extack available in the place we make the decision. I do not think we need to add anything. Looking at mlxsw, the extack is available in the `struct netdev_notifier_changeupper_info`. I am leaning towards the behavior you just described: - If there is no offloading available, accept anything and let the software take care of it. The user wants a LAG and that is the best we can do. - If offloading is available, reject anything that can not be offloaded. My guess is that _any_ hardware offloaded setup will almost always yield a better solution for the user than a software fallback.
