netdev - Re: [PATCH 2/2] network: Allow af_packet to transmit +4 bytes for VLAN packets.

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Message-ID: <1297407446.2493.5.camel@edumazet-laptop>
Date:	Fri, 11 Feb 2011 07:57:26 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	greearb@...delatech.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] network: Allow af_packet to transmit +4 bytes for
 VLAN packets.

Le jeudi 10 février 2011 à 13:59 -0800, greearb@...delatech.com a
écrit :
> From: Ben Greear <greearb@...delatech.com>
> 
> This allows user-space to send a '1500' MTU VLAN packet on a
> 1500 MTU ethernet frame.  The extra 4 bytes of a VLAN header is
> not usually charged against the MTU when other parts of the
> network stack is transmitting vlans...
> 
> Signed-off-by: Ben Greear <greearb@...delatech.com>
> ---
> :100644 100644 91cb1d7... ef7f378... M	net/packet/af_packet.c
>  net/packet/af_packet.c |   31 +++++++++++++++++++++++++++++--
>  1 files changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index 91cb1d7..ef7f378 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -466,7 +466,7 @@ retry:
>  	 */
>  
>  	err = -EMSGSIZE;
> -	if (len > dev->mtu + dev->hard_header_len)
> +	if (len > dev->mtu + dev->hard_header_len + VLAN_HLEN)
>  		goto out_unlock;
>  
>  	if (!skb) {
> @@ -497,6 +497,19 @@ retry:
>  		goto retry;
>  	}
>  
> +	if (len > (dev->mtu + dev->hard_header_len)) {
> +		/* Earlier code assumed this would be a VLAN pkt,
> +		 * double-check this now that we have the actual
> +		 * packet in hand.
> +		 */
> +		struct ethhdr *ehdr;
> +		skb_reset_mac_header(skb);
> +		ehdr = eth_hdr(skb);
> +		if (ehdr->h_proto != htons(ETH_P_8021Q)) {
> +			err = -EMSGSIZE;
> +			goto out_unlock;

This would leak skb.

> +		}
> +	}
>  
>  	skb->protocol = proto;
>  	skb->dev = dev;


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