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Message-ID: <c6cf7b4c0a561700d2015c970d52fc9d92b114c7.camel@redhat.com>
Subject: Re: [Intel-wired-lan] bug with rx-udp-gro-forwarding offloading?
From:   Paolo Abeni <pabeni@redhat.com>
To:     Ian Kumlien <ian.kumlien@gmail.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>
Date:   Thu, 06 Jul 2023 10:42:38 +0200
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On Wed, 2023-07-05 at 15:58 +0200, Ian Kumlien wrote:
> On Wed, Jul 5, 2023 at 3:29=E2=80=AFPM Paolo Abeni <pabeni@redhat.com> wr=
ote:
> >=20
> > 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.co=
m> wrote:
> > > >=20
> > > > On Tue, 2023-07-04 at 16:27 +0200, Ian Kumlien wrote:
> > > > > More stacktraces.. =3D)
> > > > >=20
> > > > > 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=
:509
> > > > > udpv6_queue_rcv_skb (./include/net/udp.h:509 net/ipv6/udp.c:800
> > > > > net/ipv6/udp.c:787)
> > > >=20
> > > > I'm really running out of ideas here...
> > > >=20
> > > > This is:
> > > >=20
> > > >         WARN_ON_ONCE(UDP_SKB_CB(skb)->partial_cov);
> > > >=20
> > > > 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 fin=
d
> > > > how a shared skb could land into the local input path.
> > > >=20
> > > > Anyway the other splats reported here and in later emails are
> > > > compatible with shared skbs.
> > > >=20
> > > > 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).
> > >=20
> > > With rx-gro-list off, as in never turned on, everything seems to run =
fine
> > >=20
> > > > * do you have by chance qdiscs on top of the VM tun devices?
> > >=20
> > > default qdisc is fq
> >=20
> > IIRC libvirt could reset the qdisc to noqueue for the owned tun
> > devices.
> >=20
> > Could you please report the output of:
> >=20
> > tc -d -s qdisc show dev <tun dev name>
>=20
> I don't have these set:
> CONFIG_NET_SCH_INGRESS
> CONFIG_NET_SCHED
>=20
> so tc just gives an error...

The above is confusing. AS CONFIG_NET_SCH_DEFAULT depends on
CONFIG_NET_SCHED, you should not have a default qdisc, too ;)

Could you please share your kernel config?

Thanks!

/P