netdev - Re: [PATCH 1/2] ixgb: Don't check for vlan group on transmit.

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Message-ID: <1288984304.3091.11.camel@jtkirshe-MOBL1>
Date:	Fri, 05 Nov 2010 12:11:44 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	Jesse Gross <jesse@...ira.com>
Cc:	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	"Duyck, Alexander H" <alexander.h.duyck@...el.com>
Subject: Re: [PATCH 1/2] ixgb: Don't check for vlan group on transmit.

On Sat, 2010-10-30 at 11:49 -0700, Jesse Gross wrote:
> On transmit, the ixgb driver will only use vlan acceleration if a
> vlan group is configured.  This can lead to tags getting dropped
> when bridging because the networking core assumes that a driver
> that claims vlan acceleration support can do it at all times.  This
> change should have been part of commit eab6d18d "vlan: Don't check for
> vlan group before vlan_tx_tag_present." but was missed.
> 
> Signed-off-by: Jesse Gross <jesse@...ira.com>
> CC: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> CC: Jesse Brandeburg <jesse.brandeburg@...el.com>
> CC: PJ Waskiewicz <peter.p.waskiewicz.jr@...el.com>
> ---
>  drivers/net/ixgb/ixgb_main.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/net/ixgb/ixgb_main.c b/drivers/net/ixgb/ixgb_main.c
> index caa8192..d18194e 100644
> --- a/drivers/net/ixgb/ixgb_main.c
> +++ b/drivers/net/ixgb/ixgb_main.c
> @@ -1498,7 +1498,7 @@ ixgb_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
>                       DESC_NEEDED)))
>  		return NETDEV_TX_BUSY;
>  
> -	if (adapter->vlgrp && vlan_tx_tag_present(skb)) {
> +	if (vlan_tx_tag_present(skb)) {
>  		tx_flags |= IXGB_TX_FLAGS_VLAN;
>  		vlan_id = vlan_tx_tag_get(skb);
>  	}

After further review, NAK because this will cause a bug.  With this
patch it would be possible to overrun the buffers, so the correct fix is
to increase max_frame_size by VLAN_TAG_SIZE in ixgb/igb_change_mtu.

Alex has said that he will generate the patches for the alternate fix.

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