netdev - Re: [PATCH net] macvlan: allow to enqueue broadcast pkt on virtual device

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Message-ID: <1411162501.26859.39.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 19 Sep 2014 14:35:01 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Cong Wang <cwang@...pensource.com>
Cc:	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH net] macvlan: allow to enqueue broadcast pkt on virtual
 device

On Fri, 2014-09-19 at 14:24 -0700, Cong Wang wrote:
> On Wed, Sep 17, 2014 at 1:08 AM, Nicolas Dichtel
> <nicolas.dichtel@...nd.com> wrote:
> > Since commit 412ca1550cbe ("macvlan: Move broadcasts into a work queue"), the
> > driver uses tx_queue_len of the master device as the limit of packets enqueuing.
> > Problem is that virtual drivers have this value set to 0, thus all broadcast
> > packets were rejected.
> > Because tx_queue_len was arbitrarily chosen, I replace it with a static limit
> > of 1000 (also arbitrarily chosen).
> >
> 
> Hmm, why not manually set this tx_queue_len to fix it?
> 
> At least fifo qdisc also uses tx_queue_len, and when you bond
> you have to set it to non-zero.


This is not true. We usually leave virtual devices with tx_queue_len to
0, otherwise you get a qdisc on them for nothing...

Only when you want to have say HTB on the bonding, you might need to
change tx_queue_len

> 
> I am not saying using this tx_queue_len is absolutely correct,
> I am saying it may be expected to set tx_queue_len by yourself.

I disagree.


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