netdev - Re: [patch net-next-2.6] forcedeth: fix vlans

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Date:	Tue, 26 Jul 2011 10:49:43 -0700
From:	Jesse Gross <jesse@...ira.com>
To:	Michał Mirosław <mirqus@...il.com>
Cc:	Jiri Pirko <jpirko@...hat.com>, netdev@...r.kernel.org,
	davem@...emloft.net, johnstul@...ibm.com, w41ter@...il.com
Subject: Re: [patch net-next-2.6] forcedeth: fix vlans

2011/7/26 Michał Mirosław <mirqus@...il.com>:
> 2011/7/26 Jiri Pirko <jpirko@...hat.com>:
>> For some reason, when rxaccel is disabled, NV_RX3_VLAN_TAG_PRESENT is
>> still set and some pseudorandom vids appear. So check for
>> NETIF_F_HW_VLAN_RX as well. Also set correctly hw_features and set vlan
>> mode on probe.
>>
>> Signed-off-by: Jiri Pirko <jpirko@...hat.com>
>> ---
>>  drivers/net/forcedeth.c |    8 ++++++--
>>  1 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/forcedeth.c b/drivers/net/forcedeth.c
>> index e64cd9c..256a272 100644
>> --- a/drivers/net/forcedeth.c
>> +++ b/drivers/net/forcedeth.c
>> @@ -2764,7 +2764,8 @@ static int nv_rx_process_optimized(struct net_device *dev, int limit)
>>                        prefetch(skb->data);
>>
>>                        vlanflags = le32_to_cpu(np->get_rx.ex->buflow);
>> -                       if (vlanflags & NV_RX3_VLAN_TAG_PRESENT) {
>> +                       if (dev->features & NETIF_F_HW_VLAN_RX &&
>> +                           vlanflags & NV_RX3_VLAN_TAG_PRESENT) {
>>                                u16 vid = vlanflags & NV_RX3_VLAN_TAG_MASK;
>
> Please add comment that resembles this patch's description. This is a
> bad idea to do in the general case as this will cause VLAN tagged
> packets that were in the queue before feature change to be
> misinterpreted.

It may be a bad idea but it's not that uncommon - frequently those
vlan status fields come from the parser and merely indicate the
presence of a tag in the original packet, not whether it was stripped.
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