netdev - Re: [net-next 02/10] ixgbevf: Fix broken trunk vlan

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Message-ID: <CAEP_g=_DXCPHhWDptJ+WW-gxDCLM6pZtdaTnvFaxZ-NB3GULDg@mail.gmail.com>
Date:	Tue, 27 Sep 2011 09:49:06 -0700
From:	Jesse Gross <jesse@...ira.com>
To:	"Rose, Gregory V" <gregory.v.rose@...el.com>
Cc:	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...hat.com" <gospo@...hat.com>,
	Jiri Pirko <jpirko@...hat.com>
Subject: Re: [net-next 02/10] ixgbevf: Fix broken trunk vlan

On Tue, Sep 27, 2011 at 9:39 AM, Rose, Gregory V
<gregory.v.rose@...el.com> wrote:
>> -----Original Message-----
>> From: Jesse Gross [mailto:jesse@...ira.com]
>> Sent: Monday, September 26, 2011 5:54 PM
>> To: Rose, Gregory V
>> Cc: Kirsher, Jeffrey T; davem@...emloft.net; netdev@...r.kernel.org;
>> gospo@...hat.com; Jiri Pirko
>> Subject: Re: [net-next 02/10] ixgbevf: Fix broken trunk vlan
>>
>>
>> OK, maybe due to hardware limitations what I'm looking for just really
>> isn't possible.
>
> From what I can tell that is the case.
>
>>  However, what I'm trying to emphasize is that vconfig
>> is not the only way that vlans can be consumed by the network stack
>> and active_vlans is just an indication of whether a vlan filter was
>> set, nothing more (perhaps I should have picked a better name when I
>> originally designed this stuff).
>
> Understood.  The VF is incapable of receiving VLAN traffic unless a filter has been set.  It doesn't do promiscuous mode and any path that doesn't actually end up setting a VLAN filter won't receive any VLAN traffic.
>
>>  In particular, it is not intended to
>> determine whether a tag should be stripped off or not because
>> non-vconfig users don't necessarily know which vlans they care about
>> (think tcpdump or trunking over a bridge).  A major goal of the
>> existing vlan infrastructure is to avoid having drivers make
>> assumptions about the consumer of the tag and instead just hand all
>> information over to the network stack so it can behave in a consistent
>> manner.  That's why I was looking for alternate ways to get this
>> information without depending on active_vlans as this driver behaves
>> quite a bit differently from others, include the ixgbe PF driver.
>
> There are only two paths for the ixgbevf driver to receive VLAN traffic.  Either a VLAN filter has been set, which will result in a bit tag in active_vlans being set or the system administrator in the host VMM has put the VF device in trunk VLAN mode using the 'ip link set <dev> vf <n> <vlanid>' path.  There is no other way for it to receive VLAN traffic, so I think we're fine.  And keep in mind, once the system admin has put the VF device in trunk vlan mode, the VF is no longer allowed, as a policy implemented in the PF driver, to set any other VLAN filters.  Even if it did, it wouldn't work due to the operational characteristics of the VF device HW.
>
> The methods by which the ixgbe driver, as a fully featured Physical Function device, are quite a bit more varied.  I believe you're thinking of the VF device as a typical Ethernet device and that is just not the case.

Yes, I think you're right.  Thanks for the explanation.
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