Re: [patch net-next v3 2/4] rtnetlink: add HW/SW stats distinction in rtnl_fill_stats

[Eric Dumazet <eric.dumazet@gmail.com>]

On Fri, 2016-05-13 at 16:54 +0200, Jiri Pirko wrote:
> From: Nogah Frankel <nogahf@mellanox.com>
> 
> Since hardware stats are now returned by default, add a way to
> query only software stats.
> They are saved in IFLA_SW_STATS64.
> (This option is valid only if the driver return HW stats in the
> default ndo stats)
> 
> Signed-off-by: Nogah Frankel <nogahf@mellanox.com>
> Signed-off-by: Jiri Pirko <jiri@mellanox.com>
> ---
> v2->v3:
> - avoided memcpy as requerted by DaveM
> v1->v2:
> - no change
> ---
>  include/uapi/linux/if_link.h |  1 +
>  net/core/rtnetlink.c         | 13 +++++++++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index bb36bd5..98175e7 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -156,6 +156,7 @@ enum {
>  	IFLA_GSO_MAX_SEGS,
>  	IFLA_GSO_MAX_SIZE,
>  	IFLA_PAD,
> +	IFLA_SW_STATS64,
>  	__IFLA_MAX
>  };
>  
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index d69c464..b0ebac6 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -1054,12 +1054,25 @@ static noinline_for_stack int rtnl_fill_stats(struct sk_buff *skb,
>  
>  	attr = nla_reserve_64bit(skb, IFLA_STATS64,
>  				 sizeof(struct rtnl_link_stats64), IFLA_PAD);
> +
>  	if (!attr)
>  		return -EMSGSIZE;
>  
>  	sp = nla_data(attr);
>  	dev_get_stats(dev, sp);
>  
> +	if (dev_have_sw_stats(dev)) {
> +		attr = nla_reserve_64bit(skb, IFLA_SW_STATS64,
> +					 sizeof(struct rtnl_link_stats64),
> +					 IFLA_PAD);
> +
> +		if (!attr)
> +			return -EMSGSIZE;
> +
> +		sp = nla_data(attr);
> +		dev_get_sw_stats(dev, sp);
> +	}
> +
>  	attr = nla_reserve(skb, IFLA_STATS,
>  			   sizeof(struct rtnl_link_stats));
>  	if (!attr)


You forgot to change if_nlmsg_size() ?

nla_total_size_64bit(sizeof(struct rtnl_link_stats64)) is quite big.