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From:   Ian Kumlien <ian.kumlien@gmail.com>
Date:   Wed, 5 Jul 2023 15:58:43 +0200
Message-ID: <CAA85sZuZLg+L7Sr51PPaOkPKbbiywXbbKzhTyjaw12_S6CsZHQ@mail.gmail.com>
Subject: Re: [Intel-wired-lan] bug with rx-udp-gro-forwarding offloading?
To:     Paolo Abeni <pabeni@redhat.com>
Cc:     Alexander Lobakin <aleksander.lobakin@intel.com>,
        intel-wired-lan <intel-wired-lan@lists.osuosl.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Wed, Jul 5, 2023 at 3:29=E2=80=AFPM Paolo Abeni <pabeni@redhat.com> wrot=
e:
>
> On Wed, 2023-07-05 at 13:32 +0200, Ian Kumlien wrote:
> > On Wed, Jul 5, 2023 at 12:28=E2=80=AFPM Paolo Abeni <pabeni@redhat.com>=
 wrote:
> > >
> > > On Tue, 2023-07-04 at 16:27 +0200, Ian Kumlien wrote:
> > > > More stacktraces.. =3D)
> > > >
> > > > cat bug.txt | ./scripts/decode_stacktrace.sh vmlinux
> > > > [  411.413767] ------------[ cut here ]------------
> > > > [  411.413792] WARNING: CPU: 9 PID: 942 at include/net/ud     p.h:5=
09
> > > > udpv6_queue_rcv_skb (./include/net/udp.h:509 net/ipv6/udp.c:800
> > > > net/ipv6/udp.c:787)
> > >
> > > I'm really running out of ideas here...
> > >
> > > This is:
> > >
> > >         WARN_ON_ONCE(UDP_SKB_CB(skb)->partial_cov);
> > >
> > > sort of hint skb being shared (skb->users > 1) while enqueued in
> > > multiple places (bridge local input and br forward/flood to tun
> > > device). I audited the bridge mc flooding code, and I could not find
> > > how a shared skb could land into the local input path.
> > >
> > > Anyway the other splats reported here and in later emails are
> > > compatible with shared skbs.
> > >
> > > The above leads to another bunch of questions:
> > > * can you reproduce the issue after disabling 'rx-gro-list' on the
> > > ingress device? (while keeping 'rx-udp-gro-forwarding' on).
> >
> > With rx-gro-list off, as in never turned on, everything seems to run fi=
ne
> >
> > > * do you have by chance qdiscs on top of the VM tun devices?
> >
> > default qdisc is fq
>
> IIRC libvirt could reset the qdisc to noqueue for the owned tun
> devices.
>
> Could you please report the output of:
>
> tc -d -s qdisc show dev <tun dev name>

I don't have these set:
CONFIG_NET_SCH_INGRESS
CONFIG_NET_SCHED

so tc just gives an error...

> Thanks!
>
> /P
>