[bluetooth-next,10/10] ipv6: add ipv6_addr_prefix_copy

This patch adds a static inline function ipv6_addr_prefix_copy which
copies a ipv6 address prefix(argument pfx) into the ipv6 address prefix.
The prefix len is given by plen as bits. This function mainly based on
ipv6_addr_prefix which copies one address prefix from address into a new
ipv6 address destination and zero all other address bits.

The difference is that ipv6_addr_prefix_copy don't get a prefix from an
ipv6 address, it sets a prefix to an ipv6 address with keeping other
address bits. The use case is for context based address compression
inside 6LoWPAN IPHC header which keeping ipv6 prefixes inside a context
table to lookup address-bits without sending them.

Cc: David S. Miller <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Acked-by: Łukasz Duda <lukasz.duda@nordicsemi.no>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
---
 include/net/ipv6.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

Hi Dave,

> This patch adds a static inline function ipv6_addr_prefix_copy which
> copies a ipv6 address prefix(argument pfx) into the ipv6 address prefix.
> The prefix len is given by plen as bits. This function mainly based on
> ipv6_addr_prefix which copies one address prefix from address into a new
> ipv6 address destination and zero all other address bits.
> 
> The difference is that ipv6_addr_prefix_copy don't get a prefix from an
> ipv6 address, it sets a prefix to an ipv6 address with keeping other
> address bits. The use case is for context based address compression
> inside 6LoWPAN IPHC header which keeping ipv6 prefixes inside a context
> table to lookup address-bits without sending them.
> 
> Cc: David S. Miller <davem@davemloft.net>
> Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
> Cc: James Morris <jmorris@namei.org>
> Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
> Cc: Patrick McHardy <kaber@trash.net>
> Acked-by: Łukasz Duda <lukasz.duda@nordicsemi.no>
> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Acked-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
> Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
> Signed-off-by: Alexander Aring <alex.aring@gmail.com>
> ---
> include/net/ipv6.h | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
> 
> diff --git a/include/net/ipv6.h b/include/net/ipv6.h
> index 9a5c9f0..6570f37 100644
> --- a/include/net/ipv6.h
> +++ b/include/net/ipv6.h
> @@ -401,6 +401,21 @@ static inline void ipv6_addr_prefix(struct in6_addr *pfx,
> 		pfx->s6_addr[o] = addr->s6_addr[o] & (0xff00 >> b);
> }
> 
> +static inline void ipv6_addr_prefix_copy(struct in6_addr *addr,
> +					 const struct in6_addr *pfx,
> +					 int plen)
> +{
> +	/* caller must guarantee 0 <= plen <= 128 */
> +	int o = plen >> 3,
> +	    b = plen & 0x7;
> +
> +	memcpy(addr->s6_addr, pfx, o);
> +	if (b != 0) {
> +		addr->s6_addr[o] &= ~(0xff00 >> b);
> +		addr->s6_addr[o] |= (pfx->s6_addr[o] & (0xff00 >> b));
> +	}
> +}
> +
> static inline void __ipv6_addr_set_half(__be32 *addr,
> 					__be32 wh, __be32 wl)
> {

if there are no objections, I would like to take this change through the bluetooth-next tree.

Regards

Marcel

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From: Marcel Holtmann <marcel@holtmann.org>
Date: Wed, 9 Dec 2015 14:28:38 -1000

> if there are no objections, I would like to take this change through the bluetooth-next tree.

No problem:

Acked-by: David S. Miller <davem@davemloft.net>
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