[4/6] batman-adv: Distributed ARP Table - add ARP parsing functions

  ARP messages are now parsed to make it possible to trigger special actions
depending on their types (snooping).

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
---
 arp.c |   43 +++++++++++++++++++++++++++++++++++++++++++
 arp.h |    7 +++++++
 2 files changed, 50 insertions(+), 0 deletions(-)
  

This patch is not checkpatch.pl --strict clean

On Sun, Oct 30, 2011 at 09:56:00AM +0100, Antonio Quartulli wrote:
> ARP messages are now parsed to make it possible to trigger special actions
> depending on their types (snooping).
> 
> Signed-off-by: Antonio Quartulli <ordex@autistici.org>
> ---
>  arp.c |   43 +++++++++++++++++++++++++++++++++++++++++++
>  arp.h |    7 +++++++
>  2 files changed, 50 insertions(+), 0 deletions(-)
> 
> diff --git a/arp.c b/arp.c
> index 39043b8..ea7cc1e 100644
> --- a/arp.c
> +++ b/arp.c
> @@ -183,3 +183,46 @@ out:
>  	kfree(cand);
>  	return ret;
>  }
> +
> +/* Returns arphdr->ar_op if the skb contains a valid ARP packet, otherwise
> + * returns 0 */
> +uint16_t arp_get_type(struct bat_priv *bat_priv, struct sk_buff *skb)
> +{
> +	struct arphdr *arphdr;
> +	struct ethhdr *ethhdr;
> +	uint16_t type = 0;
> +
> +	if (unlikely(!pskb_may_pull(skb, ETH_HLEN)))
> +		goto out;
> +
> +	ethhdr = (struct ethhdr *)skb_mac_header(skb);
> +
> +	if (ethhdr->h_proto != htons(ETH_P_ARP))
> +		goto out;
> +
> +	if (unlikely(!pskb_may_pull(skb, ETH_HLEN + arp_hdr_len(skb->dev) + 8 + 12)))
> +		goto out;

use ETH_ALEN * 2 + 4 * 2 instead to show where theses numbers come from.


> +
> +	arphdr = (struct arphdr *)(skb->data + sizeof(struct ethhdr));
> +
> +	/* Check whether the ARP packet carries a valid
> +	 * IP information */
> +	if (arphdr->ar_hrd != htons(ARPHRD_ETHER))
> +		goto out;
> +
> +	if (arphdr->ar_pro != htons(ETH_P_IP))
> +		goto out;
> +
> +	if (arphdr->ar_hln != ETH_ALEN)
> +		goto out;
> +
> +	if (arphdr->ar_pln != 4)
> +		goto out;
> +
> +	type = ntohs(arphdr->ar_op);
> +	bat_dbg(DBG_ARP, bat_priv, "ARP message of type %d recognised "
> +		"[%pM-%pI4 %pM-%pI4]\n", type, ARP_HW_SRC(skb),
> +		&ARP_IP_SRC(skb), ARP_HW_DST(skb), &ARP_IP_DST(skb));

Would you mind printing the type as string? something like REQUEST or REPLY instead of 1 and 2 ...


> +out:
> +	return type;
> +}
  

On Mon, Oct 31, 2011 at 01:10:04AM +0100, Simon Wunderlich wrote:
> This patch is not checkpatch.pl --strict clean
> 
> On Sun, Oct 30, 2011 at 09:56:00AM +0100, Antonio Quartulli wrote:
> > +	if (unlikely(!pskb_may_pull(skb, ETH_HLEN + arp_hdr_len(skb->dev) + 8 + 12)))
> > +		goto out;
> 
> use ETH_ALEN * 2 + 4 * 2 instead to show where theses numbers come from.

Actually this is a mistake, because I have recently seen that arp_hdr_len()
already includes those supplementary bytes.

> > +	bat_dbg(DBG_ARP, bat_priv, "ARP message of type %d recognised "
> > +		"[%pM-%pI4 %pM-%pI4]\n", type, ARP_HW_SRC(skb),
> > +		&ARP_IP_SRC(skb), ARP_HW_DST(skb), &ARP_IP_DST(skb));
> 
> Would you mind printing the type as string? something like REQUEST or REPLY instead of 1 and 2 ...

Oky


Thanks,