netdev - Re: [RFC v2] ipvs: allow transmit of GRO aggregated skbs

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Date:	Mon, 8 Nov 2010 11:36:21 +0200 (EET)
From:	Julian Anastasov <ja@....bg>
To:	Simon Horman <horms@...ge.net.au>
cc:	lvs-devel@...r.kernel.org, netdev@...r.kernel.org,
	Herbert Xu <herbert@...dor.hengli.com.au>
Subject: Re: [RFC v2] ipvs: allow transmit of GRO aggregated skbs


 	Hello,

On Mon, 8 Nov 2010, Simon Horman wrote:

> [ CCing Herbet Xu ]
>
>>>> This is a first attempt at allowing LVS to transmit
>>>> skbs of greater than MTU length that have been aggregated by GRO.
>>>>
>>>> I have lightly tested the ip_vs_dr_xmit() portion of this patch and
>>>> although it seems to work I am unsure that netif_needs_gso() is the correct
>>>> test to use.
>>>
>>> 	ip_forward() uses !skb_is_gso(skb), so may be it is
>>> enough to check for GRO instead of using netif_needs_gso?
>>
>> Thanks, I'll look into that.
>
> Hi Julian,
>
> just to clarify, you think that !skb_is_gso(skb) should be
> used in ip_vs_xmit.c? If so, yes I think that makes sense
> and I'll re-spin my patch accordingly.

 	Yes, I think we should check for !skb_is_gso(skb)
as it looks as correct check to avoid FRAG_NEEDED after GRO
but lets wait for confirmation from Herbert Xu.
Also, !skb->local_df check should help for local IPVS clients
that set local_df.

 	If you prefer you can create such helper in ip_vs_xmit.c:

/* Check if packet exceeds MTU */
static inline int ip_vs_mtu_exceeded(struct sk_buff *skb, unsigned int mtu)
{
 	return skb->len > mtu && !skb_is_gso(skb) && !skb->local_df;
}

Regards

--
Julian Anastasov <ja@....bg>
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