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

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Date:	Fri, 22 Aug 2008 14:32:43 -0500
From:	Steve Wise <swise@...ngridcomputing.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Karen Xie <kxie@...lsio.com>, netdev@...r.kernel.org,
	open-iscsi@...glegroups.com, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org, jgarzik@...ox.com,
	davem@...emloft.net, michaelc@...wisc.edu, rdreier@...co.com,
	daisyc@...ibm.com, wenxiong@...ibm.com, bhua@...ibm.com,
	divy@...lsio.com, dm@...lsio.com, leedom@...lsio.com
Subject: Re: [PATCH 2/4 2.6.28] cxgb3 - handle ARP replies for private iSCSI
 IP address

Andrew Morton wrote:
> On Fri, 22 Aug 2008 11:39:08 -0700
> Karen Xie <kxie@...lsio.com> wrote:
>
>   
>> [PATCH 2/4 2.6.28] cxgb3 - handle ARP replies for private iSCSI IP address
>>
>> From: Karen Xie <kxie@...lsio.com>
>>
>> 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 <divy@...lsio.com>
>> ---
>>
>>  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?)
>
>
>   
Doesn't this avoid complaints from sparse endian checking?


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