From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Maciej Fijalkowski <maciejromanfijalkowski@gmail.com>
Cc: daniel@iogearbox.net, ast@kernel.org, netdev@vger.kernel.org,
jakub.kicinski@netronome.com, brouer@redhat.com
Subject: Re: [PATCH bpf-next v4 5/7] samples/bpf: Add a "force" flag to XDP samples
Date: Wed, 30 Jan 2019 20:08:59 +0100 [thread overview]
Message-ID: <20190130200859.16237d3f@redhat.com> (raw)
In-Reply-To: <20190130191248.00000167@gmail.com>
On Wed, 30 Jan 2019 19:12:48 +0100
Maciej Fijalkowski <maciejromanfijalkowski@gmail.com> wrote:
> On Tue, 29 Jan 2019 12:34:05 +0100
> Jesper Dangaard Brouer <brouer@redhat.com> wrote:
>
> > On Tue, 29 Jan 2019 09:00:00 +0100
> > Jesper Dangaard Brouer <brouer@redhat.com> wrote:
> >
> > > On Mon, 28 Jan 2019 20:16:11 +0100
> > > Maciej Fijalkowski <maciejromanfijalkowski@gmail.com> wrote:
> > >
> > > > From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> > > >
> > > > Make xdp samples consistent with iproute2 behavior and set the
> > > > XDP_FLAGS_UPDATE_IF_NOEXIST by default when setting the xdp program on
> > > > interface. Provide an option for user to force the program loading,
> > > > which as a result will not include the mentioned flag in
> > > > bpf_set_link_xdp_fd call.
> > >
> > > I like the idea, but what is the error message users get after this
> > > change?
> >
> > $ sudo ./xdp1 mlx5p1 &
> > [1] 9768
> >
> > $ sudo ./xdp1 mlx5p1
> > link set xdp fd failed
> >
> > This error message is a little too generic to be a good user experience.
> > The kernel (in dev_change_xdp_fd) will return errno -EBUSY (-16), but
> > we don't use or report the return value in these sample programs.
> >
> > If my QA see this error message, I will still get an error report
> > bugzilla that I need to spend time on investigating. Can we please
> > improve this error message?
> >
> > If you are really cool you get inspired by (or use) libbpf_strerror()
> > code avail in tools/lib/bpf/libbpf_errno.c. Default strerror(EBUSY)
> > will return "Device or resource busy", but maybe we can do slightly
> > better and report something more meaningful for this XDP context.
> >
> I'll post a v5 with libbpf_strerror() usage when bpf_set_link_xdp_fd failed in
> samples but at this point it will only give us a standard "device or resource
> busy" error
That is a good first iteration improvement. And if QA complains, I can
quickly diagnose and explain the issue, based on this generic message,
without digging further and wasting more time.
> , so if we need some more meaningful message that libbpf will give
> us then I guess we need to define a new libbpf_errno entry (as well as entry in
> libbpf_strerror_table for this new errno value) and set the errno in
> bpf_set_link_xdp_fd in case of a failure?
It likely require more work do provide more meaningful messages, and I
guess it is out-of-scope for your patchset.
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2019-01-30 19:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-28 19:16 [PATCH bpf-next v4 0/7] xdp: Avoid unloading xdp prog not attached by sample Maciej Fijalkowski
2019-01-28 19:16 ` [PATCH bpf-next v4 1/7] libbpf: Add a helper for retrieving a map fd for a given name Maciej Fijalkowski
2019-01-28 20:49 ` John Fastabend
2019-01-28 19:16 ` [PATCH bpf-next v4 2/7] samples/bpf: xdp_redirect_cpu have not need for read_trace_pipe Maciej Fijalkowski
2019-01-28 20:50 ` John Fastabend
2019-01-28 19:16 ` [PATCH bpf-next v4 3/7] samples/bpf: Convert XDP samples to libbpf usage Maciej Fijalkowski
2019-01-28 19:16 ` [PATCH bpf-next v4 4/7] samples/bpf: Extend RLIMIT_MEMLOCK for xdp_{sample_pkts, router_ipv4} Maciej Fijalkowski
2019-01-28 20:54 ` John Fastabend
2019-01-28 19:16 ` [PATCH bpf-next v4 5/7] samples/bpf: Add a "force" flag to XDP samples Maciej Fijalkowski
2019-01-28 20:57 ` John Fastabend
2019-01-29 8:00 ` Jesper Dangaard Brouer
2019-01-29 11:34 ` Jesper Dangaard Brouer
2019-01-30 18:12 ` Maciej Fijalkowski
2019-01-30 19:08 ` Jesper Dangaard Brouer [this message]
2019-01-31 2:26 ` Jakub Kicinski
2019-01-31 20:19 ` Jesper Dangaard Brouer
2019-01-28 19:16 ` [PATCH bpf-next v4 6/7] libbpf: Add a support for getting xdp prog id on ifindex Maciej Fijalkowski
2019-01-28 21:07 ` John Fastabend
2019-01-30 17:53 ` Maciej Fijalkowski
2019-01-28 19:16 ` [PATCH bpf-next v4 7/7] samples/bpf: Check the prog id before exiting Maciej Fijalkowski
2019-01-28 21:10 ` John Fastabend
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