Re: [PATCH next-next 4/6] net: Call skb_checksum_init in IPv4

[Joe Perches <joe@perches.com>]

On Mon, 2014-04-07 at 13:13 -0400, David Miller wrote:
> From: Tom Herbert <therbert@google.com>
> Date: Fri, 4 Apr 2014 17:27:36 -0700 (PDT)
> 
> > @@ -1454,6 +1454,13 @@ out_unlock:
> >  	return err;
> >  }
> >  
> > +__wsum inet_pseudo_compute(struct sk_buff *skb, int proto)
> > +{
> > +	return csum_tcpudp_nofold(ip_hdr(skb)->saddr, ip_hdr(skb)->daddr,
> > +				  skb->len, proto, 0);
> > +}
> > +EXPORT_SYMBOL(inet_pseudo_compute);
> 
> This is just adjusting arguments passed into to another inline
> function, please put this in a header and make it an inline too.

as ip_hdr involves a calculation via 

include/linux/ip.h:static inline struct iphdr *ip_hdr(const struct sk_buff *skb)
include/linux/ip.h-{
include/linux/ip.h-     return (struct iphdr *)skb_network_header(skb);
include/linux/ip.h-}

and

include/linux/skbuff.h:static inline unsigned char *skb_network_header(const struct sk_buff *skb)
include/linux/skbuff.h-{
include/linux/skbuff.h- return skb->head + skb->network_header;
include/linux/skbuff.h-}

I believe you could save an addition by using a temporary for ip_hdr

static inline __wsum inet_pseudo_compute(struct sk_buff *skb, int proto)
{
	const struct iphdr *iph = ip_hdr(skb);

	return csum_tcpudp_nofold(iph->saddr, iph->daddr, skb->len, proto, 0);
}