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

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Date:	Thu, 11 Apr 2013 09:03:40 +0100
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	Jason Wang <jasowang@...hat.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 Thu, 2013-04-11 at 08:58 +0100, Jason Wang wrote:
> 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().

Ah, my working tree must be out of date, thanks.

> >
> >> -	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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