[ovs-discuss] tnl arp causes infinite reentrant stack death.

David Evans davidjoshuaevans at gmail.com
Wed Sep 16 04:18:50 UTC 2015


Wow. - Thanks so much Jesse,
I will try this with a fresh coffee in the morning @ the office in the
morning. it's 11pm now. - can't think straight anymore.. :)

On Tue, Sep 15, 2015 at 10:54 PM, Jesse Gross <jesse at nicira.com> wrote:

> On Tue, Sep 15, 2015 at 7:38 PM, David Evans <davidjoshuaevans at gmail.com>
> wrote:
> > Thanks Jesse!
> > I think you may be close, but it is the ovs code that is re-entering it's
> > self, this isn't an arp storm from a circle of traffic path, as far as i
> can
> > tell. it is an attempt to transmit a single packet.. but never gets even
> the
> > arp out to the stack at all.
> > you can see build_tunnel_send 3 times as the stack trace goes in the
> > original post. but no packets make it out. the program call stack is
> 13000
> > frames deep - which is why it crashed.
>
> When tunneling is done in userspace (such as with DPDK), the Linux
> stack is not involved at all since the point of DPDK is to avoid the
> kernel for performance reasons. That's why you see OVS reentering
> itself repeatedly as it tries to forward and then generate more ARP
> frames.
>
> I just sent out a patch CC'd to you that should fix this issue. Can
> you test it? Note that in this case 'fix' means that it will prevent
> OVS from crashing. However, traffic won't flow until the loop in the
> configuration is resolved. Based on the stack trace, my guess is that
> you have one or more patch ports connecting the bridges.
>
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