Andrii Nakryiko andrii.nakryiko@gmail.com writes:
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?
Hmm, that's not a bad idea, actually. An earlier version of the series did have only a single set of functions, but with way too many arguments, which is why we ended up agreeing to split them. But encapsulating the destination in a separate struct and combining it with some helper macros might just make this work! I like it! Kumar, WDYT?
-Toke