Re: [PATCHv11 bpf-next 2/5] xdp: add a new helper for dev map multicast support

Alexei Starovoitov
2020-09-10T15:43:04Z

On Thu, Sep 10, 2020 at 2:44 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:
>
> > On Wed, Sep 9, 2020 at 8:30 PM David Ahern <dsahern@gmail.com> wrote:
> >> >
> >> > I think the packets modification (edit dst mac, add vlan tag, etc) should be
> >> > done on egress, which rely on David's XDP egress support.
> >>
> >> agreed. The DEVMAP used for redirect can have programs attached that
> >> update the packet headers - assuming you want to update them.
> >
> > Then you folks have to submit them as one set.
> > As-is the programmer cannot achieve correct behavior.
>
> The ability to attach a program to devmaps is already there. See:
>
> fbee97feed9b ("bpf: Add support to attach bpf program to a devmap entry")

ahh. you meant that one.

> But now that you mention it, it does appear that this series is skipping
> the hook that will actually run such a program. Didn't realise that was
> in the caller of bq_enqueue() and not inside bq_enqueue() itself...
>
> Hangbin, you'll need to add the hook for dev_map_run_prog() before
> bq_enqueue(); see the existing dev_map_enqueue() function.

If that's the expected usage it should have been described in the commit log
and thoroughly exercised in the tests.