From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Björn Töpel" <bjorn.topel@intel.com>,
"Andrii Nakryiko" <andrii@kernel.org>
Cc: "Toke Høiland-Jørgensen" <toke@redhat.com>,
"Björn Töpel" <bjorn.topel@gmail.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Network Development" <netdev@vger.kernel.org>,
bpf <bpf@vger.kernel.org>,
"Karlsson, Magnus" <magnus.karlsson@intel.com>,
"Fijalkowski, Maciej" <maciej.fijalkowski@intel.com>,
"Jakub Kicinski" <kuba@kernel.org>,
"Jonathan Lemon" <jonathan.lemon@gmail.com>,
maximmi@nvidia.com, "David S. Miller" <davem@davemloft.net>,
"Jesper Dangaard Brouer" <hawk@kernel.org>,
"John Fastabend" <john.fastabend@gmail.com>,
"Ciara Loftus" <ciara.loftus@intel.com>,
weqaar.a.janjua@intel.com, "Marek Majtyka" <alardam@gmail.com>
Subject: Re: [PATCH bpf-next v2 5/8] libbpf, xsk: select AF_XDP BPF program based on kernel version
Date: Wed, 20 Jan 2021 10:25:40 -0800 [thread overview]
Message-ID: <CAADnVQK1vL307SmmUZyuEAmy9S_A2fJwyHryCHBavQ-QDNyxww@mail.gmail.com> (raw)
In-Reply-To: <2751bcd9-b3af-0366-32ee-a52d5919246c@intel.com>
On Wed, Jan 20, 2021 at 7:27 AM Björn Töpel <bjorn.topel@intel.com> wrote:
>
> >> Would it make sense with some kind of BPF-specific "supported
> >> features" mechanism? Something else with a bigger scope (whole
> >> kernel)?
> >
> > Heh, in my opinion, yeah. Seems like we'll finally get it for XDP, but
> > for BPF in general the approach has always been probing AFAICT.
> >
> > For the particular case of arguments to helpers, I suppose the verifier
> > could technically validate value ranges for flags arguments, say. That
> > would be nice as an early reject anyway, but I'm not sure if it is
> > possible to add after-the-fact without breaking existing programs
> > because the verifier can't prove the argument is within the valid range.
> > And of course it doesn't help you with compatibility with
> > already-released kernels.
> >
>
> Hmm, think I have a way forward. I'll use BPF_PROG_TEST_RUN.
>
> If the load fail for the new helper, fallback to bpf_redirect_map(). Use
> BPF_PROG_TEST_RUN to make sure that "action via flags" passes.
+1 to Toke's point. No version checks please.
One way to detect is to try prog_load. Search for FEAT_* in libbpf.
Another approach is to scan vmlinux BTF for necessary helpers.
Currently libbpf is relying on the former.
I think going forward would be good to detect features via BTF.
It's going to be much faster and won't create noise for audit that
could be looking at prog_load calls.
next prev parent reply other threads:[~2021-01-20 18:30 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 15:50 [PATCH bpf-next v2 0/8] Introduce bpf_redirect_xsk() helper Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 1/8] xdp: restructure redirect actions Björn Töpel
2021-01-20 12:44 ` Toke Høiland-Jørgensen
2021-01-20 13:40 ` Björn Töpel
2021-01-20 14:52 ` Toke Høiland-Jørgensen
2021-01-20 15:49 ` Björn Töpel
2021-01-20 16:30 ` Toke Høiland-Jørgensen
2021-01-20 17:26 ` Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 2/8] xsk: remove explicit_free parameter from __xsk_rcv() Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 3/8] xsk: fold xp_assign_dev and __xp_assign_dev Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 4/8] xsk: register XDP sockets at bind(), and add new AF_XDP BPF helper Björn Töpel
2021-01-20 8:25 ` kernel test robot
2021-01-20 8:41 ` Björn Töpel
2021-01-20 8:50 ` kernel test robot
2021-01-20 12:50 ` Toke Høiland-Jørgensen
2021-01-20 13:25 ` Björn Töpel
2021-01-20 14:54 ` Toke Høiland-Jørgensen
2021-01-20 15:18 ` Björn Töpel
2021-01-20 17:29 ` Toke Høiland-Jørgensen
2021-01-20 18:22 ` Björn Töpel
2021-01-20 20:26 ` Toke Høiland-Jørgensen
2021-01-20 21:15 ` Alexei Starovoitov
2021-01-21 8:18 ` Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 5/8] libbpf, xsk: select AF_XDP BPF program based on kernel version Björn Töpel
2021-01-20 12:52 ` Toke Høiland-Jørgensen
2021-01-20 13:25 ` Björn Töpel
2021-01-20 14:49 ` Björn Töpel
2021-01-20 15:11 ` Toke Høiland-Jørgensen
2021-01-20 15:27 ` Björn Töpel
2021-01-20 17:30 ` Toke Høiland-Jørgensen
2021-01-20 18:25 ` Alexei Starovoitov [this message]
2021-01-20 18:30 ` Björn Töpel
2021-01-20 14:56 ` Toke Høiland-Jørgensen
2021-01-19 15:50 ` [PATCH bpf-next v2 6/8] libbpf, xsk: select bpf_redirect_xsk(), if supported Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 7/8] selftest/bpf: add XDP socket tests for bpf_redirect_{xsk, map}() Björn Töpel
2021-01-21 7:39 ` Andrii Nakryiko
2021-01-21 12:31 ` Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 8/8] selftest/bpf: remove a lot of ifobject casting in xdpxceiver Björn Töpel
2021-01-20 13:15 ` [PATCH bpf-next v2 0/8] Introduce bpf_redirect_xsk() helper Maxim Mikityanskiy
2021-01-20 13:27 ` Björn Töpel
2021-01-20 15:57 ` Jesper Dangaard Brouer
2021-01-20 16:19 ` Maciej Fijalkowski
2021-01-21 17:01 ` Jesper Dangaard Brouer
2021-01-22 8:59 ` Magnus Karlsson
2021-01-22 9:45 ` Maciej Fijalkowski
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