linux-kernel - Re: [BUG] 4.10-rc8

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Message-ID: <20170216160806.GL582@shells.gnugeneration.com>
Date:   Thu, 16 Feb 2017 08:08:06 -0800
From:   lkml@...garu.com
To:     Soheil Hassas Yeganeh <soheil@...gle.com>
Cc:     netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: Re: [BUG] 4.10-rc8 - ping spinning?

On Thu, Feb 16, 2017 at 10:52:19AM -0500, Soheil Hassas Yeganeh wrote:
> On Thu, Feb 16, 2017 at 10:50 AM, Soheil Hassas Yeganeh
> <soheil@...gle.com> wrote:
> > Thank you Vito for the report.
> >
> > The patch you cited actually resolves a similar backward compatibility
> > problem for traceroute.
> >
> > I suspect the problem here is that there's a local error queued on the
> > error queue after an ICMP message. ping apparently expect the
> > sk->sk_err to be set for the local errors as well, and hence the
> > error. Ideally, ping should read the error queue if there an EPOLLERR,
> > because local errors never sk->sk_err on their own. That is, if we
> > have
> 
> [oops] That is, if we have only one local error on the error queue, we
> cannot rely on having an error on recvmsg (i.e., sk->sk_err being set)
> even in 4.9.
> 
> <snip>

Hi Soheil,

This doesn't appear to be trivially reproducible here by just running ping
as it were originally discovered.  I'll see if I can reliably cause the
malfunction somehow, but until then I can't meaningfully test patches.

Perhaps a form of fault injection would make more sense if there's a
reasonable idea of what this is stemming from?

I've opened an issue with iputils on github in the event that this is found
to be a ping bug.  Your input might be helpful there as well:
https://github.com/iputils/iputils/issues/74

Thanks,
Vito Caputo