netdev - Re: [PATCH] net: Handle gso packets in dev_forward

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Message-ID: <1300743744.2837.7.camel@edumazet-laptop>
Date:	Mon, 21 Mar 2011 22:42:24 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Ben Greear <greearb@...delatech.com>,
	Arnd Bergmann <arnd@...db.de>,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH] net: Handle gso packets in dev_forward_skb

Le lundi 21 mars 2011 à 14:25 -0700, Eric W. Biederman a écrit :
> Today when gso packets reach dev_forward_skb through the macvlan driver
> we drop them on the floor because they exceed the device mtu.  Ouch!
> 
> I don't undersand the subtelties of gso but I think it is sufficient to
> simply relax the checks and let gso packets through without an mtu
> check, and it works in my test case.
> 
> If needed we can split the gso packets into multiple packets here but
> that just seems like a wast of memory and time.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
> ---
>  net/core/dev.c |   16 ++++++++++------
>  1 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 0b88eba..2e26606 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -1527,17 +1527,21 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
>  	skb_orphan(skb);
>  	nf_reset(skb);
>  
> -	if (unlikely(!(dev->flags & IFF_UP) ||
> -		     (skb->len > (dev->mtu + dev->hard_header_len + VLAN_HLEN)))) {
> -		atomic_long_inc(&dev->rx_dropped);
> -		kfree_skb(skb);
> -		return NET_RX_DROP;
> -	}
> +	if (unlikely(!(dev->flags & IFF_UP)))
> +		goto kfree_skb;
> +	/* Don't check mtu on gso packets... */
> +	if (unlikely(!skb_is_gso(skb) &&
> +		     (skb->len > (dev->mtu + dev->hard_header_len + VLAN_HLEN))))
> +		goto kfree_skb;
>  	skb_set_dev(skb, dev);
>  	skb->tstamp.tv64 = 0;
>  	skb->pkt_type = PACKET_HOST;
>  	skb->protocol = eth_type_trans(skb, dev);
>  	return netif_rx(skb);
> +kfree_skb:
> +	atomic_long_inc(&dev->rx_dropped);
> +	kfree_skb(skb);
> +	return NET_RX_DROP;
>  }
>  EXPORT_SYMBOL_GPL(dev_forward_skb);
>  


Hmm, did you follow http://patchwork.ozlabs.org/patch/86815/
discussion ?



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