netdev - Re: [net-next PATCH] xen-netback: switch to use skb_partial_csum

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Date:	Thu, 11 Apr 2013 15:58:32 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	Ian Campbell <Ian.Campbell@...rix.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [net-next PATCH] xen-netback: switch to use skb_partial_csum_set()

On 04/11/2013 03:46 PM, Ian Campbell wrote:
> On Thu, 2013-04-11 at 07:35 +0100, Jason Wang wrote:
>> Switch to use skb_partial_csum_set() to simplify the codes.
> This is incremental on top of your previous patch, right?

It's an independent patch, since the previous patch has been applied.
>> Cc: Ian Campbell <ian.campbell@...rix.com>
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
>> ---
>> Note:
>> - Compile test only.
>> ---
>>  drivers/net/xen-netback/netback.c |   22 ++++++++--------------
>>  1 files changed, 8 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
>> index 83905a9..70631f0 100644
>> --- a/drivers/net/xen-netback/netback.c
>> +++ b/drivers/net/xen-netback/netback.c
>> @@ -1156,7 +1156,6 @@ static int netbk_set_skb_gso(struct xenvif *vif,
>>  static int checksum_setup(struct xenvif *vif, struct sk_buff *skb)
>>  {
>>  	struct iphdr *iph;
>> -	unsigned char *th;
>>  	int err = -EPROTO;
>>  	int recalculate_partial_csum = 0;
>>  
>> @@ -1180,28 +1179,26 @@ static int checksum_setup(struct xenvif *vif, struct sk_buff *skb)
>>  		goto out;
>>  
>>  	iph = (void *)skb->data;
>> -	th = skb->data + 4 * iph->ihl;
>> -	if (th >= skb_tail_pointer(skb))
>> -		goto out;
>> -
>> -	skb_set_transport_header(skb, 4 * iph->ihl);
> Is removing this line really correct?

After commit e5d5deca (net: core: let skb_partial_csum_set() set
transport header), this work was done by skb_partial_csum_set().
>
>> -	skb->csum_start = th - skb->head;
>>  	switch (iph->protocol) {
>>  	case IPPROTO_TCP:
>> -		skb->csum_offset = offsetof(struct tcphdr, check);
>> +		if (!skb_partial_csum_set(skb, 4 * iph->ihl,
>> +					  offsetof(struct tcphdr, check)))
>> +			goto out;
>>  
>>  		if (recalculate_partial_csum) {
>> -			struct tcphdr *tcph = (struct tcphdr *)th;
>> +			struct tcphdr *tcph = tcp_hdr(skb);
>>  			tcph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
>>  							 skb->len - iph->ihl*4,
>>  							 IPPROTO_TCP, 0);
>>  		}
>>  		break;
>>  	case IPPROTO_UDP:
>> -		skb->csum_offset = offsetof(struct udphdr, check);
>> +		if (!skb_partial_csum_set(skb, 4 * iph->ihl,
>> +					  offsetof(struct udphdr, check)))
>> +			goto out;
>>  
>>  		if (recalculate_partial_csum) {
>> -			struct udphdr *udph = (struct udphdr *)th;
>> +			struct udphdr *udph = udp_hdr(skb);
>>  			udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
>>  							 skb->len - iph->ihl*4,
>>  							 IPPROTO_UDP, 0);
>> @@ -1215,9 +1212,6 @@ static int checksum_setup(struct xenvif *vif, struct sk_buff *skb)
>>  		goto out;
>>  	}
>>  
>> -	if ((th + skb->csum_offset + 2) > skb_tail_pointer(skb))
>> -		goto out;
>> -
>>  	err = 0;
>>  
>>  out:
>

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