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From: Tiwei Bie <tiwei.bie@intel.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: Maxime Coquelin <maxime.coquelin@redhat.com>,
	Zhihong Wang <zhihong.wang@intel.com>,
	dev@dpdk.org
Subject: Re: [dpdk-dev] vtap0 device creation (bug)?
Date: Mon, 11 Nov 2019 16:15:44 +0800	[thread overview]
Message-ID: <20191111081543.GA12998@___> (raw)
In-Reply-To: <20191108154407.0bd8734d@hermes.lan>

On Fri, Nov 08, 2019 at 03:44:07PM -0800, Stephen Hemminger wrote:
> When I create a virtio-user device with rte_hotplug it creates a kernel device (ie vtap0).
> This is normal an the device has ifindex N.
> 
> But later when device is configured an started the original vtap0 device is deleted
> and a new one is created (with ifindex N+1).  This seems like a bug, if nothing
> else it unnecessary overhead and link flapping for routing daemons.
> 
> Noticed only while tracking down a bug where after vtap was created the
> address was being set, but then disappearing.
> 
> Is this intentional? Is it documented?

Thanks for catching this.
I think it's caused by the fact that tapfds will be closed
each time when the queue pairs are disabled [1]. We may need
a way to keep tapfds open to fix it.

[1] https://github.com/DPDK/dpdk/blob/6bbc5a923625/drivers/net/virtio/virtio_user/vhost_kernel.c#L333-L338

Thanks,
Tiwei

      reply	other threads:[~2019-11-11  8:15 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08 23:44 [dpdk-dev] vtap0 device creation (bug)? Stephen Hemminger
2019-11-11  8:15 ` Tiwei Bie [this message]

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