[PATCH net-next 01/11] ipv6: skb_put_zero() used to optimize code

[PATCH net-next 01/11] ipv6: skb_put_zero() used to optimize code

[yuan linyu]

From: yuan linyu <Linyu.Yuan@alcatel-sbell.com.cn>

Signed-off-by: yuan linyu <Linyu.Yuan@alcatel-sbell.com.cn>
---
 net/ipv6/mcast.c |  3 +--
 net/ipv6/ndisc.c | 13 ++-----------
 2 files changed, 3 insertions(+), 13 deletions(-)

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 07403fa..b186c67 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -2008,8 +2008,7 @@ static void igmp6_send(struct in6_addr *addr, struct net_device *dev, int type)
 
 	memcpy(skb_put(skb, sizeof(ra)), ra, sizeof(ra));
 
-	hdr = (struct mld_msg *) skb_put(skb, sizeof(struct mld_msg));
-	memset(hdr, 0, sizeof(struct mld_msg));
+	hdr = (struct mld_msg *) skb_put_zero(skb, sizeof(struct mld_msg));
 	hdr->mld_type = type;
 	hdr->mld_mca = *addr;
 
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index d310dc4..e6586ed 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -144,21 +144,12 @@ void __ndisc_fill_addr_option(struct sk_buff *skb, int type, void *data,
 			      int data_len, int pad)
 {
 	int space = __ndisc_opt_addr_space(data_len, pad);
-	u8 *opt = skb_put(skb, space);
+	u8 *opt = skb_put_zero(skb, space);
 
 	opt[0] = type;
 	opt[1] = space>>3;
 
-	memset(opt + 2, 0, pad);
-	opt   += pad;
-	space -= pad;
-
-	memcpy(opt+2, data, data_len);
-	data_len += 2;
-	opt += data_len;
-	space -= data_len;
-	if (space > 0)
-		memset(opt, 0, space);
+	memcpy(opt+2+pad, data, data_len);
 }
 EXPORT_SYMBOL_GPL(__ndisc_fill_addr_option);
 
-- 
2.7.4

Re: [PATCH net-next 01/11] ipv6: skb_put_zero() used to optimize code

[Stephen Hemminger]

On Wed, 14 Jun 2017 22:37:06 +0800
yuan linyu <cugyly@163.com> wrote:

> From: yuan linyu <Linyu.Yuan@alcatel-sbell.com.cn>
> 
> Signed-off-by: yuan linyu <Linyu.Yuan@alcatel-sbell.com.cn>
> ---
>  net/ipv6/mcast.c |  3 +--
>  net/ipv6/ndisc.c | 13 ++-----------
>  2 files changed, 3 insertions(+), 13 deletions(-)
> 
> diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
> index 07403fa..b186c67 100644
> --- a/net/ipv6/mcast.c
> +++ b/net/ipv6/mcast.c
> @@ -2008,8 +2008,7 @@ static void igmp6_send(struct in6_addr *addr, struct net_device *dev, int type)
>  
>  	memcpy(skb_put(skb, sizeof(ra)), ra, sizeof(ra));
>  
> -	hdr = (struct mld_msg *) skb_put(skb, sizeof(struct mld_msg));
> -	memset(hdr, 0, sizeof(struct mld_msg));
> +	hdr = (struct mld_msg *) skb_put_zero(skb, sizeof(struct mld_msg));

Why does skb_put_zero return char * instead of void *?
If returned void * it would save having to add lots of casts.

One could even go farther by making skb_put_zero a macro and
use typeof().

Re: [PATCH net-next 01/11] ipv6: skb_put_zero() used to optimize code

[Johannes Berg]

On Wed, 2017-06-14 at 08:44 -0700, Stephen Hemminger wrote:
> 
> >  	memcpy(skb_put(skb, sizeof(ra)), ra, sizeof(ra));
> >  
> > -	hdr = (struct mld_msg *) skb_put(skb, sizeof(struct
> > mld_msg));
> > -	memset(hdr, 0, sizeof(struct mld_msg));
> > +	hdr = (struct mld_msg *) skb_put_zero(skb, sizeof(struct
> > mld_msg));
> 
> Why does skb_put_zero return char * instead of void *?
> If returned void * it would save having to add lots of casts.
> 
> One could even go farther by making skb_put_zero a macro and
> use typeof().

I just copied it from skb_put() - you could ask the same there? :)

No objection to changing it though.

johannes

Re: [PATCH net-next 01/11] ipv6: skb_put_zero() used to optimize code

[Stephen Hemminger]

On Wed, 14 Jun 2017 21:01:32 +0200
Johannes Berg <johannes@sipsolutions.net> wrote:

> On Wed, 2017-06-14 at 08:44 -0700, Stephen Hemminger wrote:
> >   
> > >  	memcpy(skb_put(skb, sizeof(ra)), ra, sizeof(ra));
> > >  
> > > -	hdr = (struct mld_msg *) skb_put(skb, sizeof(struct
> > > mld_msg));
> > > -	memset(hdr, 0, sizeof(struct mld_msg));
> > > +	hdr = (struct mld_msg *) skb_put_zero(skb, sizeof(struct
> > > mld_msg));  
> > 
> > Why does skb_put_zero return char * instead of void *?
> > If returned void * it would save having to add lots of casts.
> > 
> > One could even go farther by making skb_put_zero a macro and
> > use typeof().  
> 
> I just copied it from skb_put() - you could ask the same there? :)

My taste is to  have less casts. Never understood why so many skb_
functions returned char *, probably a leftover from older Unix style.

Re: [PATCH net-next 01/11] ipv6: skb_put_zero() used to optimize code

[Johannes Berg]

On Wed, 2017-06-14 at 12:14 -0700, Stephen Hemminger wrote:
> 
> > I just copied it from skb_put() - you could ask the same there? :)
> 
> My taste is to  have less casts. Never understood why so many skb_
> functions returned char *, probably a leftover from older Unix style.

I agree, for many of them it's awkward and I often just put a (void *)
cast in there ...

I guess we can just make them void, and if anyone wants it I can easily
cook up an spatch to remove casts.

johannes