Message-ID: <1461343880.7627.34.camel@edumazet-glaptop3.roam.corp.google.com>
Subject: Re: [PATCH net-next 2/9] libnl: nla_put_le64(): align on a 64-bit
 area
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Cc: netdev@vger.kernel.org, davem@davemloft.net, linux-kernel@vger.kernel.org,
        linux-wpan@vger.kernel.org, aar@pengutronix.de, pablo@netfilter.org,
        kaber@trash.net, kadlec@blackhole.kfki.hu, pshelar@nicira.com,
        kuznet@ms2.inr.ac.ru, jmorris@namei.org, yoshfuji@linux-ipv6.org,
        netfilter-devel@vger.kernel.org, dev@openvswitch.org,
        steffen.klassert@secunet.com, herbert@gondor.apana.org.au,
        bsingharora@gmail.com
Date: Fri, 22 Apr 2016 09:51:20 -0700
In-Reply-To: <1461339084-3849-3-git-send-email-nicolas.dichtel@6wind.com>
References: <1461339084-3849-1-git-send-email-nicolas.dichtel@6wind.com>
	 <1461339084-3849-3-git-send-email-nicolas.dichtel@6wind.com>
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On Fri, 2016-04-22 at 17:31 +0200, Nicolas Dichtel wrote:
> nla_data() is now aligned on a 64-bit area.
> 
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> ---
>  include/net/netlink.h     |  8 +++++---
>  include/net/nl802154.h    |  6 ++++++
>  net/ieee802154/nl802154.c | 13 ++++++++-----
>  3 files changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/include/net/netlink.h b/include/net/netlink.h
> index 6f51a8a06498..7f6b99483ab7 100644
> --- a/include/net/netlink.h
> +++ b/include/net/netlink.h
> @@ -878,14 +878,16 @@ static inline int nla_put_net64(struct sk_buff *skb, int attrtype, __be64 value)
>  }
>  
>  /**
> - * nla_put_le64 - Add a __le64 netlink attribute to a socket buffer
> + * nla_put_le64 - Add a __le64 netlink attribute to a socket buffer and align it
>   * @skb: socket buffer to add attribute to
>   * @attrtype: attribute type
>   * @value: numeric value
> + * @padattr: attribute type for the padding
>   */
> -static inline int nla_put_le64(struct sk_buff *skb, int attrtype, __le64 value)
> +static inline int nla_put_le64(struct sk_buff *skb, int attrtype, __le64 value,
> +			       int padattr)
>  {
> -	return nla_put(skb, attrtype, sizeof(__le64), &value);
> +	return nla_put_64bit(skb, attrtype, sizeof(__le64), &value, padattr);
>  }
>  

But _why_ is it needed ?

nla_put() has no alignment assumptions, it simply copies 8 bytes.

Seems this is going too far.