Messages in this thread | | | Subject | Re: [PATCH bpf-next 3/5] libbpf: add low level TC-BPF API | From | Daniel Borkmann <> | Date | Tue, 30 Mar 2021 23:25:47 +0200 |
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On 3/30/21 10:39 PM, Andrii Nakryiko wrote: > On Sun, Mar 28, 2021 at 1:11 AM Kumar Kartikeya Dwivedi > <memxor@gmail.com> wrote: >> On Sun, Mar 28, 2021 at 10:12:40AM IST, Andrii Nakryiko wrote: >>> Is there some succinct but complete enough documentation/tutorial/etc >>> that I can reasonably read to understand kernel APIs provided by TC >>> (w.r.t. BPF, of course). I'm trying to wrap my head around this and >>> whether API makes sense or not. Please share links, if you have some. >> >> Hi Andrii, >> >> Unfortunately for the kernel API part, I couldn't find any when I was working >> on this. So I had to read the iproute2 tc code (tc_filter.c, f_bpf.c, >> m_action.c, m_bpf.c) and the kernel side bits (cls_api.c, cls_bpf.c, act_api.c, >> act_bpf.c) to grok anything I didn't understand. There's also similar code in >> libnl (lib/route/{act,cls}.c). >> >> Other than that, these resources were useful (perhaps you already went through >> some/all of them): >> >> https://docs.cilium.io/en/latest/bpf/#tc-traffic-control >> https://qmonnet.github.io/whirl-offload/2020/04/11/tc-bpf-direct-action/ >> tc(8), and tc-bpf(8) man pages >> >> I hope this is helpful! > > Thanks! I'll take a look. Sorry, I'm a bit behind with all the stuff, > trying to catch up. > > I was just wondering if it would be more natural instead of having > _dev _block variants and having to specify __u32 ifindex, __u32 > parent_id, __u32 protocol, to have some struct specifying TC > "destination"? Maybe not, but I thought I'd bring this up early. So > you'd have just bpf_tc_cls_attach(), and you'd so something like > > bpf_tc_cls_attach(prog_fd, TC_DEV(ifindex, parent_id, protocol)) > > or > > bpf_tc_cls_attach(prog_fd, TC_BLOCK(block_idx, protocol)) > > ? Or it's taking it too far? > > But even if not, I think detaching can be unified between _dev and > _block, can't it?
Do we even need the _block variant? I would rather prefer to take the chance and make it as simple as possible, and only iff really needed extend with other APIs, for example:
bpf_tc_attach(prog_fd, ifindex, {INGRESS,EGRESS});
Internally, this will create the sch_clsact qdisc & cls_bpf filter instance iff not present yet, and attach to a default prio 1 handle 1, and _always_ in direct-action mode. This is /as simple as it gets/ and we don't need to bother users with more complex tc/cls_bpf internals unless desired. For example, extended APIs could add prio/parent so that multi-prog can be attached to a single cls_bpf instance, but even that could be a second step, imho.
Thanks, Daniel
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