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Date:   Mon, 2 Nov 2020 08:27:20 +0000
From:   Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
To:     "dsahern@...il.com" <dsahern@...il.com>,
        "linyunsheng@...wei.com" <linyunsheng@...wei.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kuba@...nel.org" <kuba@...nel.org>
Subject: Re: arping stuck with ENOBUFS in 4.19.150

On Sat, 2020-10-31 at 09:48 +0800, Yunsheng Lin wrote:
> On 2020/10/30 19:50, Joakim Tjernlund wrote:
> > On Fri, 2020-10-30 at 09:36 +0800, Yunsheng Lin wrote:
> > > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
> > > 
> > > 
> > > On 2020/10/29 23:18, David Ahern wrote:
> > > > On 10/29/20 8:10 AM, Joakim Tjernlund wrote:
> > > > > OK, bisecting (was a bit of a bother since we merge upstream releases into our tree, is there a way to just bisect that?)
> > > > > 
> > > > > Result was commit "net: sch_generic: aviod concurrent reset and enqueue op for lockless qdisc"  (749cc0b0c7f3dcdfe5842f998c0274e54987384f)
> > > > > 
> > > > > Reverting that commit on top of our tree made it work again. How to fix?
> > > > 
> > > > Adding the author of that patch (linyunsheng@...wei.com) to take a look.
> > > > 
> > > > 
> > > > > 
> > > > >  Jocke
> > > > > 
> > > > > On Mon, 2020-10-26 at 12:31 -0600, David Ahern wrote:
> > > > > > 
> > > > > > On 10/26/20 6:58 AM, Joakim Tjernlund wrote:
> > > > > > > Ping  (maybe it should read "arping" instead :)
> > > > > > > 
> > > > > > >  Jocke
> > > > > > > 
> > > > > > > On Thu, 2020-10-22 at 17:19 +0200, Joakim Tjernlund wrote:
> > > > > > > > strace arping -q -c 1 -b -U  -I eth1 0.0.0.0
> > > > > > > > ...
> > > > > > > > sendto(3, "\0\1\10\0\6\4\0\1\0\6\234\v\6 \v\v\v\v\377\377\377\377\377\377\0\0\0\0", 28, 0, {sa_family=AF_PACKET, proto=0x806, if4, pkttype=PACKET_HOST, addr(6)={1, ffffffffffff},
> > > > > > > > 20) = -1 ENOBUFS (No buffer space available)
> > > > > > > > ....
> > > > > > > > and then arping loops.
> > > > > > > > 
> > > > > > > > in 4.19.127 it was:
> > > > > > > > sendto(3, "\0\1\10\0\6\4\0\1\0\6\234\5\271\362\n\322\212E\377\377\377\377\377\377\0\0\0\0", 28, 0, {​sa_family=AF_PACKET, proto=0x806, if4, pkttype=PACKET_HOST, addr(6)={​1,
> > > > > > > > ffffffffffff}​, 20) = 28
> > > > > > > > 
> > > > > > > > Seems like something has changed the IP behaviour between now and then ?
> > > > > > > > eth1 is UP but not RUNNING and has an IP address.
> > > 
> > > "eth1 is UP but not RUNNING" usually mean user has configure the netdev as up,
> > > but the hardware has not detected a linkup yet.
> > > 
> > > Also What is the output of "ethtool eth1"?
> > 
> > echo 1 >  /sys/class/net/eth1/carrier
> > cu3-jocke ~ # arping -q -c 1 -b -U  -I eth1 0.0.0.0
> > cu3-jocke ~ # echo 0 >  /sys/class/net/eth1/carrier
> > cu3-jocke ~ # arping -q -c 1 -b -U  -I eth1 0.0.0.0
> > ^Ccu3-jocke ~ # ethtool eth1
> > Settings for eth1:
> > 	Supported ports: [ MII ]
> > 	Supported link modes:   1000baseT/Full 
> > 	Supported pause frame use: Symmetric Receive-only
> > 	Supports auto-negotiation: Yes
> > 	Advertised link modes:  1000baseT/Full 
> > 	Advertised pause frame use: Symmetric Receive-only
> > 	Advertised auto-negotiation: Yes
> > 	Speed: 10Mb/s
> > 	Duplex: Half
> > 	Port: MII
> > 	PHYAD: 1
> > 	Transceiver: external
> > 	Auto-negotiation: on
> > 	Current message level: 0x00000037 (55)
> > 			       drv probe link ifdown ifup
> > 	Link detected: no
> > 
> > We have a writeable carrier since eth device is PHY less. Maybe that path is different ?
> > Check drivers/net/ethernet/freescale/dpaa/dpa_eth.c
> 
> The above difference does not seems to matter.
> 
> > 
> > > 
> > > It would be good to see the status of netdev before and after executing arping cmd
> > > too.
> > 
> > hmm, how do you mean?
> 
> I was trying to find out when the netdev' state became "eth1 is UP but not RUNNING".
> 
> Anyway, when I looked at the backported patch, I did find new qdisc assignment is
> missing from the upstream patch.
> 
> Please see if the below patch fix your problem, thanks:
> 
> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> index bd96fd2..4e15913 100644
> --- a/net/sched/sch_generic.c
> +++ b/net/sched/sch_generic.c
> @@ -1116,10 +1116,13 @@ static void dev_deactivate_queue(struct net_device *dev,
>                                  void *_qdisc_default)
>  {
>         struct Qdisc *qdisc = rtnl_dereference(dev_queue->qdisc);
> +       struct Qdisc *qdisc_default = _qdisc_default;
> 
>         if (qdisc) {
>                 if (!(qdisc->flags & TCQ_F_BUILTIN))
>                         set_bit(__QDISC_STATE_DEACTIVATED, &qdisc->state);
> +
> +               rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
>         }
>  }

This patch seem to have resolved the problem, thanks.
Please CC me on the formal patch for 4.19.x

 Jocke

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