On 06/08, Andrii Nakryiko wrote: > On Thu, Jun 8, 2023 at 4:55 PM Alexei Starovoitov > <alexei.starovoitov@xxxxxxxxx> wrote: > > > > On Thu, Jun 8, 2023 at 4:06 PM Stanislav Fomichev <sdf@xxxxxxxxxx> wrote: > > > > > > I'm not really concerned about our production environment. It's pretty > > > controlled and restricted and I'm pretty certain we can avoid doing > > > something stupid. Probably the same for your env. > > > > > > I'm mostly fantasizing about upstream world where different users don't > > > know about each other and start doing stupid things like F_FIRST where > > > they don't really have to be first. It's that "used judiciously" part > > > that I'm a bit skeptical about :-D > > > > > > Because even with this new ordering scheme, there still should be > > > some entity to do relative ordering (systemd-style, maybe CNI?). > > > And if it does the ordering, I don't really see why we need > > > F_FIRST/F_LAST. > > > > +1. > > I have the same concerns as expressed during lsfmmbpf. > > This first/last is a foot gun. > > It puts the whole API back into a single user situation. > > Without "first api" the users are forced to talk to each other > > and come up with an arbitration mechanism. A daemon to control > > the order or something like that. > > With "first api" there is no incentive to do so. > > If Cilium and some other company X both produce, say, anti-DDOS > solution which cannot co-exist with any other anti-DDOS program and > either of them needs to guarantee that their program runs first, then > FIRST is what would be used by both to prevent accidental breakage of > each other (which is basically what happened with Cilium and some > other networking solution, don't remember the name). It's better for > one of them to loudly fail to attach than silently break other > solution with end users struggling to understand what's going on. > > You and Stanislav keep insisting that any combination of any BPF > programs should co-exist, and I don't understand why we can or should > presume that. I think we are conflating generic API (and kernel *not* > making any assumptions about such API usage) with encouraging > collaborative BPF attachment policies. They are orthogonal and are not > in conflict with each other. > > But we lived without FIRST/LAST guarantees till now, that's fine, I'll > stop fighting this. I'm not saying this situation where there are several incompatible programs doesn't exist. All I'm saying is that imo this is a policy that doesn't belong to the kernel. Or maybe even let's put it that way: F_FIRST and F_LAST isn't flexible enough to express this policy. External systemd-like arbiter should express the dependencies/ordering/conflicts/etc. And F_BEFORE and F_AFTER is enough for that sysmted-like entity to do the rest.
