netdev - Re: [PATCH v2 net 2/2] Revert "macvlan : fix checksums error when we are in bridge mode"

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Message-ID: <20140429132224.GB18119@redhat.com>
Date:	Tue, 29 Apr 2014 16:22:24 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Vlad Yasevich <vyasevic@...hat.com>
Cc:	netdev@...r.kernel.org, daniel.lezcano@...e.fr,
	nightnord@...il.com, kaber@...sh.net, eric.dumazet@...il.com,
	jasowang@...hat.com
Subject: Re: [PATCH v2 net 2/2] Revert "macvlan : fix checksums error when we
 are in bridge mode"

On Tue, Apr 29, 2014 at 10:09:51AM -0400, Vlad Yasevich wrote:
> This reverts commit 12a2856b604476c27d85a5f9a57ae1661fc46019.
> The commit above doesn't appear to be necessary any more as the
> checksums appear to be correctly computed/validated.
> 
> Additionally the above commit breaks kvm configurations where
> one VM is using a device that support checksum offload (virtio) and
> the other VM does not.
> In this case, packets leaving virtio device will have CHECKSUM_PARTIAL
> set.  The packets is forwarded to a macvtap that has offload features
> turned off.  Since we use CHECKSUM_UNNECESSARY, the host does does not
> update the checksum and thus a bad checksum is passed up to
> the guest.
> 
> CC: Daniel Lezcano <daniel.lezcano@...e.fr>
> CC: Patrick McHardy <kaber@...sh.net>
> CC: Andrian Nord <nightnord@...il.com>
> CC: Eric Dumazet <eric.dumazet@...il.com>
> CC: Michael S. Tsirkin <mst@...hat.com>
> CC: Jason Wang <jasowang@...hat.com>
> Signed-off-by: Vlad Yasevich <vyasevic@...hat.com>

Acked-by: Michael S. Tsirkin <mst@...hat.com>

> ---
>  drivers/net/macvlan.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> index 1831fb7..33b6cf8 100644
> --- a/drivers/net/macvlan.c
> +++ b/drivers/net/macvlan.c
> @@ -263,11 +263,9 @@ static int macvlan_queue_xmit(struct sk_buff *skb, struct net_device *dev)
>  	const struct macvlan_dev *vlan = netdev_priv(dev);
>  	const struct macvlan_port *port = vlan->port;
>  	const struct macvlan_dev *dest;
> -	__u8 ip_summed = skb->ip_summed;
>  
>  	if (vlan->mode == MACVLAN_MODE_BRIDGE) {
>  		const struct ethhdr *eth = (void *)skb->data;
> -		skb->ip_summed = CHECKSUM_UNNECESSARY;
>  
>  		/* send to other bridge ports directly */
>  		if (is_multicast_ether_addr(eth->h_dest)) {
> @@ -285,7 +283,6 @@ static int macvlan_queue_xmit(struct sk_buff *skb, struct net_device *dev)
>  	}
>  
>  xmit_world:
> -	skb->ip_summed = ip_summed;
>  	skb->dev = vlan->lowerdev;
>  	return dev_queue_xmit(skb);
>  }
> -- 
> 1.9.0
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