netdev - Re: [PATCH net 1/2] macvlan: forbid L2 fowarding offload for macvtap

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Date:	Fri, 10 Jan 2014 11:40:51 -0500
From:	Vlad Yasevich <vyasevic@...hat.com>
To:	Jason Wang <jasowang@...hat.com>,
	Stephen Hemminger <stephen@...workplumber.org>
CC:	"Michael S. Tsirkin" <mst@...hat.com>,
	John Fastabend <john.fastabend@...il.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	Neil Horman <nhorman@...driver.com>, davem@...emloft.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/2] macvlan: forbid L2 fowarding offload for macvtap

On 01/10/2014 02:06 AM, Jason Wang wrote:
> On 01/10/2014 05:39 AM, Stephen Hemminger wrote:
>> On Thu, 09 Jan 2014 16:55:07 +0800
>> Jason Wang <jasowang@...hat.com> wrote:
>>
>>> What if use do want a qdisc and want to change the its queue length for
>>> tun/macvlan? And the the name tx_queue_length is misleading. For tun it
>>> may make sense since it was used in transmission path. For macvtap it
>>> was not. So maybe what we need is just a new ioctl for both tun/macvtap
>>> and a new feature flag. If user create the device with new feature flag,
>>> the socket receive queue length could be changed by ioctl instead of
>>> dev->tx_queue_length. If not, the old behaviour could be kept.
>> The overloading of tx_queue_len in macvtap was the original design mistake.
>> Can't this just be undone and expose rx_queue_len as sysfs attribute?
> 
> That works. But we current allow user to change the socket sndbuf
> through TUNSNDBUF. Maybe we need a similar one for receive.
> 

That would make sense.  Since the user interacts with tun fd almost as a
socket and there is actually a socket hiding in the kernel, it almost
begs for actual SO_SNDBUF/SO_RCVBUF support :)

-vlad
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