dumpcap: weird failure with six IPv6 hosts in the filter

[Isaac Boukris]

Hi Konstantin

On Fri, Jun 28, 2024 at 7:42 PM Konstantin Ananyev
<konstantin.v.ananyev at yandex.ru> wrote:
>
>
> Hi Isaac,
>
> >
> > On Wed, Jun 19, 2024 at 2:06 AM Konstantin Ananyev
> > <konstantin.v.ananyev at yandex.ru> wrote:
> >>
> >> 17.06.2024 22:40, Stephen Hemminger пишет:
> >>> On Mon, 17 Jun 2024 23:43:19 +0300
> >>> Isaac Boukris <iboukris at gmail.com> wrote:
> >>>
> >>>> On Mon, Jun 17, 2024 at 10:37 PM Isaac Boukris <iboukris at gmail.com> wrote:
> >>>>>
> >>>>>> Just a quick update that I still see the issue in my env with the
> >>>>>> master branch (24.07.0-rc0), I'm now testing by adding the filter to
> >>>>>> 'sample_filters' in test_bpf.c and running:
> >>>>>> time sudo build/app/dpdk-test bpf_convert_autotest
> >>>>>>
> >>>>>> With 5 hosts it takes less than 2 secs, with 6 it takes about 25 secs,
> >>>>>> i'll try to strace it maybe.
> >>>>>
> >>>>> strace was useless, no syscalls for ~18 secs, not sure how to debug it
> >>>>> further, valgrind / callgrind don't work on dpdk..
> >>>>>
> >>>>> It doesn't seem to be about the size though, I was able to produce
> >>>>> larger bpf code with ipv4 addresses and it worked fine too.
> >>>>
> >>>> Debugged a bit further with gdb, it looks like it is stuck in a while
> >>>> loop in lib/bpf/bpf_validate.c:evaluate(), there is a comment saying
> >>>> "make sure we evaluate each node only once" but it seem to go back and
> >>>> forth on the same idx's afaict.
> >>>
> >>> No idea, only original author understands the verifier.
> >>> Having our own unique verifier may not be a good idea.
> >>> There some other userspace BPF projects, seems like a good place for
> >>> convergence.
> >>>
> >>>
> >>> https://lpc.events/event/17/contributions/1639/attachments/1280/2585/userspace-ebpf-bpftime-lpc.pdf
> >>
> >> hi Isaac,
> >> please create a bug report in DPDK bugzilla.
> >> Ideally with a clear and simple way to reproduce
> >> the bug you are facing in the description.
> >> I'll try to have a look when I'll have some free time.
> >> Thanks
> >> Konstantin
> >
> > Done:
> >
> > https://bugs.dpdk.org/show_bug.cgi?id=1465
>
>
> In case you didn't get update from the bugzilla,
> here is a patch to try, when you'll get a chance:
> http://patchwork.dpdk.org/project/dpdk/list/?series=32321

I tested it yesterday and it solves the bug for me, the whole test
takes less than a second now and dumpcap works just fine! I've posted
the feedback on the bug :)