Subject: Re: [PATCH 2/4 2.6.28] cxgb3 - handle ARP replies for private iSCSI IP address

From: Andrew Morton <[email-masked]>
Date: Fri, 22 Aug 2008 12:12:50 -0700

On Fri, 22 Aug 2008 11:39:08 -0700
Karen Xie <[email-masked]> wrote:

> [PATCH 2/4 2.6.28] cxgb3 - handle ARP replies for private iSCSI IP address
> 
> From: Karen Xie <[email-masked]>
> 
> stg can be tricky ...
> [adding @adapter in cxgb3_arp_process doxygen header]
> The accelerated iSCSI traffic uses a private IP address unknown to the OS.
> The driver has to reply to ARP requests dedicated to the private IP address.
> 
> Signed-off-by: Divy Le Ray <[email-masked]>
> ---
> 
>  drivers/net/cxgb3/sge.c |   71 ++++++++++++++++++++++++++++++++++++++++++++---
>  1 files changed, 66 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/cxgb3/sge.c b/drivers/net/cxgb3/sge.c
> index 1b0861d..d2a9285 100644
> --- a/drivers/net/cxgb3/sge.c
> +++ b/drivers/net/cxgb3/sge.c
> @@ -36,6 +36,7 @@
>  #include <linux/ip.h>
>  #include <linux/tcp.h>
>  #include <linux/dma-mapping.h>
> +#include <net/arp.h>
>  #include "common.h"
>  #include "regs.h"
>  #include "sge_defs.h"
> @@ -1859,6 +1860,54 @@ static void restart_tx(struct sge_qset *qs)
>  }
>  
>  /**
> + *	cxgb3_arp_process - process an ARP request probing a private IP address
> + *	@adapter: the adapter
> + *	@skb: the skbuff containing the ARP request
> + *
> + *	Check if the ARP request is probing the private IP address
> + *	dedicated to iSCSI, generate an ARP reply if so.
> + */
> +static void cxgb3_arp_process(struct adapter *adapter, struct sk_buff *skb)
> +{
> +	struct net_device *dev = skb->dev;
> +	struct port_info *pi;
> +	struct arphdr *arp;
> +	unsigned char *arp_ptr;
> +	unsigned char *sha;
> +	u32 sip, tip;
> +
> +	if (!dev)
> +		return;

Can this happen?

> +	skb_reset_network_header(skb);
> +	arp = arp_hdr(skb);
> +
> +	if (arp->ar_op != htons(ARPOP_REQUEST))
> +		return;
> +
> +	arp_ptr = (unsigned char *)(arp + 1);
> +	sha = arp_ptr;
> +	arp_ptr += dev->addr_len;
> +	memcpy(&sip, arp_ptr, 4);
> +	arp_ptr += 4;
> +	arp_ptr += dev->addr_len;
> +	memcpy(&tip, arp_ptr, 4);

Should arp_hdr_len() be used here?

> +	pi = netdev_priv(dev);
> +	if (ntohl(tip) != pi->iscsi_ipaddr)
> +		return;
> +
> +	arp_send(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip, sha,
> +		 dev->dev_addr, sha);
> +
> +}
> +
> +static inline int is_arp(struct sk_buff *skb)
> +{
> +	return skb->protocol == htons(ETH_P_ARP);

Other net code uses __constant_htons() for this.

(Dunno why - if it makes a difference, htons() is broken?)