netdev - RE: [PATCH net-next 7/8] net: Add calaulation of non folded IPV6 pseudo header checksum

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Date:	Thu, 30 Oct 2014 16:25:25 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Or Gerlitz' <ogerlitz@...lanox.com>,
	"David S. Miller" <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Matan Barak <matanb@...lanox.com>,
	Amir Vadai <amirv@...lanox.com>,
	Saeed Mahameed <saeedm@...lanox.com>,
	Shani Michaeli <shanim@...lanox.com>
Subject: RE: [PATCH net-next 7/8] net: Add calaulation of non folded IPV6
 pseudo header checksum

From: Or Gerlitz
> From: Shani Michaeli <shanim@...lanox.com>
> 
> Compute IPV6 pseudo header checksum without folding it to a 16 bit
> return value.
> 
> Signed-off-by: Shani Michaeli <shanim@...lanox.com>
> Signed-off-by: Matan Barak <matanb@...lanox.com>
> ---
>  include/net/ip6_checksum.h |   21 +++++++++++++++++++++
>  1 files changed, 21 insertions(+), 0 deletions(-)
> 
> diff --git a/include/net/ip6_checksum.h b/include/net/ip6_checksum.h
> index 1a49b73..c45d690 100644
> --- a/include/net/ip6_checksum.h
> +++ b/include/net/ip6_checksum.h
> @@ -41,6 +41,27 @@ __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
>  			__wsum csum);
>  #endif
> 
> +static inline __wsum csum_ipv6_magic_nofold(const struct in6_addr *saddr,
> +					    const struct in6_addr *daddr,
> +					    __u32 len, unsigned short proto,
> +					    __wsum sum)
> +{
> +	__wsum res = sum;
> +
> +	res = csum_add(res, (__force __wsum)saddr->in6_u.u6_addr32[0]);
> +	res = csum_add(res, (__force __wsum)saddr->in6_u.u6_addr32[1]);
> +	res = csum_add(res, (__force __wsum)saddr->in6_u.u6_addr32[2]);
> +	res = csum_add(res, (__force __wsum)saddr->in6_u.u6_addr32[3]);
> +	res = csum_add(res, (__force __wsum)daddr->in6_u.u6_addr32[0]);
> +	res = csum_add(res, (__force __wsum)daddr->in6_u.u6_addr32[1]);
> +	res = csum_add(res, (__force __wsum)daddr->in6_u.u6_addr32[2]);
> +	res = csum_add(res, (__force __wsum)daddr->in6_u.u6_addr32[3]);

That probably generates a very long dependency chain.

> +	res = csum_add(res, (__force __wsum)htonl(len));
> +	res = csum_add(res, (__force __wsum)htonl(proto));

htonl() doesn't look right for a 16bit value.
It might not matter (because the final checksum is 16bits).

	David

> +
> +	return res;
> +}
> +
>  static inline __wsum ip6_compute_pseudo(struct sk_buff *skb, int proto)
>  {
>  	return ~csum_unfold(csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> --
> 1.7.1
> 
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