netdev - Re: [PATCH net] net: fix wrong mac

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Date:	Wed, 28 May 2014 08:39:00 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Nikolay Aleksandrov <nikolay@...hat.com>
Cc:	netdev@...r.kernel.org, Vlad Yasevich <vyasevic@...hat.com>,
	Daniel Borkman <dborkman@...hat.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net] net: fix wrong mac_len calculation for vlans

On Wed, 2014-05-28 at 17:24 +0200, Nikolay Aleksandrov wrote:

> 
>  net/core/dev.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 9abc503b19b7..94167fc660b1 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2283,8 +2283,8 @@ EXPORT_SYMBOL(skb_checksum_help);
>  
>  __be16 skb_network_protocol(struct sk_buff *skb, int *depth)
>  {
> +	unsigned int vlan_depth = skb->mac_len;
>  	__be16 type = skb->protocol;
> -	int vlan_depth = skb->mac_len;
>  
>  	/* Tunnel gso handlers can set protocol to ethernet. */
>  	if (type == htons(ETH_P_TEB)) {
> @@ -2297,6 +2297,20 @@ __be16 skb_network_protocol(struct sk_buff *skb, int *depth)
>  		type = eth->h_proto;
>  	}
>  
> +	/* if skb->protocol is 802.1Q/AD then the header should already be
> +	 * present at mac_len - VLAN_HLEN (if mac_len > 0), or at
> +	 * ETH_HLEN otherwise
> +	 */
> +	if (type == htons(ETH_P_8021Q) || type == htons(ETH_P_8021AD)) {
> +		if (vlan_depth) {
> +			if (unlikely(WARN_ON(vlan_depth < VLAN_HLEN)))
> +				return 0;
> +			vlan_depth -= VLAN_HLEN;
> +		} else {
> +			vlan_depth = ETH_HLEN;
> +		}
> +	}

It would be nice not having 4 tests in fast path for non vlan traffic

> +
>  	while (type == htons(ETH_P_8021Q) || type == htons(ETH_P_8021AD)) {
>  		struct vlan_hdr *vh;
>  

Like :

       if (type == htons(ETH_P_8021Q) || type == htons(ETH_P_8021AD)) {
                if (vlan_depth) {
                       if (unlikely(WARN_ON(vlan_depth < VLAN_HLEN)))
                               return 0;
                       vlan_depth -= VLAN_HLEN;
                } else {
                       vlan_depth = ETH_HLEN;
                }
		do {
			struct vlan_hdr *vh;

			if (unlikely(!pskb_may_pull(skb, vlan_depth + VLAN_HLEN)))
 	                	return 0;

 	                vh = (struct vlan_hdr *)(skb->data + vlan_depth);
 	                type = vh->h_vlan_encapsulated_proto;
 	                vlan_depth += VLAN_HLEN;
		} while (type == htons(ETH_P_8021Q) || type == htons(ETH_P_8021AD));
        }
	


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