netdev - Re: [PATCH v2 net-next] ifb: support more features

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Date:	Sat, 07 May 2016 22:41:12 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>,
	Alexander Duyck <aduyck@...antis.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 net-next] ifb: support more features

On Fri, 2016-05-06 at 18:19 -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> When using ifb+netem on ingress on SIT/IPIP/GRE traffic,
> GRO packets are not properly processed.
> 
> Segmentation should not be forced, since ifb is already adding
> quite a performance hit.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
>  drivers/net/ifb.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
> index cc56fac3c3f8..66c0eeafcb5d 100644
> --- a/drivers/net/ifb.c
> +++ b/drivers/net/ifb.c
> @@ -196,6 +196,7 @@ static const struct net_device_ops ifb_netdev_ops = {
>  
>  #define IFB_FEATURES (NETIF_F_HW_CSUM | NETIF_F_SG  | NETIF_F_FRAGLIST	| \
>  		      NETIF_F_TSO_ECN | NETIF_F_TSO | NETIF_F_TSO6	| \
> +		      NETIF_F_GSO_ENCAP_ALL 				| \
>  		      NETIF_F_HIGHDMA | NETIF_F_HW_VLAN_CTAG_TX		| \
>  		      NETIF_F_HW_VLAN_STAG_TX)
>  
> @@ -224,6 +225,8 @@ static void ifb_setup(struct net_device *dev)
>  	dev->tx_queue_len = TX_Q_LIMIT;
>  
>  	dev->features |= IFB_FEATURES;
> +	dev->hw_features |= dev->features;
> +	dev->hw_enc_features |= dev->features;
>  	dev->vlan_features |= IFB_FEATURES & ~(NETIF_F_HW_VLAN_CTAG_TX |
>  					       NETIF_F_HW_VLAN_STAG_TX);
>  
> 


BTW, encapsulated GRO traffic going through mirred+ifb is dropped
because segments get an incorrect skb->mac_len 

(If TSO/GSO is disabled on ifb, as before the above patch)

SIT traffic for example : segments get mac_len set to 34 instead of 14

What do you think of :

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index e561f9f07d6d..bec5c32b2fe9 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3176,7 +3176,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 		__copy_skb_header(nskb, head_skb);
 
 		skb_headers_offset_update(nskb, skb_headroom(nskb) - headroom);
-		skb_reset_mac_len(nskb);
+		nskb->mac_len = head_skb->mac_len;
 
 		skb_copy_from_linear_data_offset(head_skb, -tnl_hlen,
 						 nskb->data - tnl_hlen,