netdev - Re: [PATCH RFC v4 bpf-next 00/11] Add support for XDP in egress path

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Date:   Thu, 27 Feb 2020 08:22:48 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     David Ahern <dsahern@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Prashant Bhole <prashantbhole.linux@...il.com>,
        Jason Wang <jasowang@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Toshiaki Makita <toshiaki.makita1@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        David Ahern <dsahern@...il.com>
Subject: Re: [PATCH RFC v4 bpf-next 00/11] Add support for XDP in egress path

On Thu, Feb 27, 2020 at 3:55 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> However, my issue with this encoding is that it is write-only: You can't
> inspect a BPF program already loaded into the kernel and tell which type
> it is. So my proposal would be to make it explicit: Expose the
> expected_attach_type as a new field in bpf_prog_info so userspace can
> query it, and clearly document it as, essentially, a program subtype
> that can significantly affect how a program is treated by the kernel.

You had the same request for "freplace" target prog.
My answer to both is still the same:
Please take a look at drgn and the script that Andrey posted.
All this information is trivial to extract from the kernel
without introducing new uapi.