Subject: Re: [PATCH 0/2] fix kernel crash with macvtap on top of LRO

From: "Michael S. Tsirkin" <[email-masked]>
Date: Thu, 7 Feb 2013 10:15:29 +0200

On Thu, Feb 07, 2013 at 11:25:13AM +0800, Cong Wang wrote:
> On 02/07/2013 07:02 AM, Michael S. Tsirkin wrote:
> >At the moment, macvtap crashes are observed if macvtap is attached
> >to an interface with LRO enabled.
> >The crash in question is BUG() in macvtap_skb_to_vnet_hdr.
> >This happens because several drivers set gso_size but not gso_type
> >in incoming skbs.
> >The following patches fix this for
> >Additionally, cbf1de72324a8105ddcc3d9ce9acbc613faea17e is required
> >to fix this for broadcom - would it make sense to cherry-pick
> >this patch into 3.8?
> 
> 
> Doesn't macvtap need to call skb_warn_if_lro() too like bridge and
> openvswitch? Something like...

This is what Ben proposed a year ago
http://thread.gmane.org/gmane.linux.network/221695
but apparently people really want LRO to work with macvtap.

> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index b181dfb..b2c6227 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -253,6 +253,9 @@ static int macvtap_forward(struct net_device
> *dev, struct sk_buff *skb)
>         if (!q)
>                 goto drop;
> 
> +       if (unlikely(skb_warn_if_lro(skb)))
> +               goto drop;
> +
>         if (skb_queue_len(&q->sk.sk_receive_queue) >= dev->tx_queue_len)
>                 goto drop;
> 
> 
> I am not saying these drivers don't need to fix, I am just saying if
> we need to fix LRO case.
> 
> Thanks.

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