Daniel Borkmann [off-list ref] writes:

On 4/28/21 12:36 AM, Toke Høiland-Jørgensen wrote:

quoted

Daniel Borkmann [off-list ref] writes:

[...]

quoted

quoted

Small addendum:

      DECLARE_LIBBPF_OPTS(bpf_tc_hook, hook, .ifindex = 42, .which = BPF_TC_INGRESS|BPF_TC_EGRESS);

      err = bpf_tc_hook_create(&hook);
      [...]

... is also possible, of course, and then both bpf_tc_hook_{create,destroy}() are symmetric.

It should be allowed, but it wouldn't actually make any difference which
combination of TC_INGRESS and TC_EGRESS you specify, as long as one of
them is set, right? I.e., we just attach the clsact qdisc in both
cases...

Yes, that is correct, for the bpf_tc_hook_create() whether you pass in BPF_TC_INGRESS,
BPF_TC_EGRESS or BPF_TC_INGRESS|BPF_TC_EGRESS, you'll end up creating clsact qdisc in
either of the three cases. Only the bpf_tc_hook_destroy() differs
between all of them.

Right, just checking. Other than that, I like your proposal; it loses
the "automatic removal of qdisc if we added it" feature, but that's
probably OK: less magic is good. And as long as bpf_tc_hook_create()
returns EEXIST if the qdisc already exists, the caller can do the same
thing if they want.

-Toke