Quentin Deslandes <qde@xxxxxxxx> wrote: > Le 03/01/2023 à 12:45, Florian Westphal a écrit : > > You can't make this atomic from userspace perspective, the > > get/setsockopt API of iptables uses a read-modify-write model. > > This refers to updating the programs from bpfilter's side. It won't > be atomic from iptables point of view, but currently bpfilter will > remove the program associated to a table, before installing the new > one. This means packets received in between those operations are > not filtered. I assume a better solution is possible. Ah, I see, thanks. > > Tentatively I'd try to extend libnftnl and generate bpf code there, > > since its used by both iptables(-nft) and nftables we'd automatically > > get support for both. > > That's one of the option, this could also remain in the kernel > tree or in a dedicated git repository. I don't know which one would > be the best, I'm open to suggestions. I can imagine that this will see a flurry of activity in the early phase so I think a 'semi test repo' makes sense. Provideded license allows this, useable bits and pieces can then be grafted on to libnftnl (or iptables or whatever). > > I was planning to look into "attach bpf progs to raw netfilter hooks" > > in Q1 2023, once the initial nf-bpf-codegen is merged. > > Is there any plan to support non raw hooks? That's mainly out > of curiosity, I don't even know whether that would be a good thing > or not. Not sure what 'non raw hook' is. Idea was to expose 1. protcocol family 2. hook number (prerouting, input etc) 3. priority to userspace via bpf syscall/bpf link. userspace would then provide the above info to kernel via bpf(... BPF_LINK_CREATE ) which would then end up doing: -------------- h.hook = nf_hook_run_bpf; // wrapper to call BPF_PROG_RUN h.priv = prog; // the bpf program to run h.pf = attr->netfilter.pf; h.priority = attr->netfilter.priority; h.hooknum = attr->netfilter.hooknum; nf_register_net_hook(net, &h); -------------- After that nf_hook_slow() calls the bpf program just like any other of the netfilter hooks. Does that make sense or did you have something else in mind?
