Subject: Re: [PATCH net-next 1/2] rtnetlink: add new RTM_GETSTATS message to dump link stats

From: Nicolas Dichtel <[email-masked]>
Date: Mon, 14 Mar 2016 16:00:52 +0100

Le 13/03/2016 02:56, Roopa Prabhu a écrit :
> From: Roopa Prabhu <[email-masked]>
>
> This patch adds a new RTM_GETSTATS message to query link stats via netlink
> from the kernel. RTM_NEWLINK also dumps stats today, but RTM_NEWLINK
> returns a lot more than just stats and is expensive in some cases when
> frequent polling for stats from userspace is a common operation.
>
> RTM_GETSTATS is an attempt to provide a light weight netlink message
> to explicity query only link stats from the kernel on an interface.
> The idea is to also keep it extensible so that new kinds of stats can be
> added to it in the future.
>
> This patch adds the following attribute for NETDEV stats:
> struct nla_policy ifla_stats_policy[IFLA_STATS_MAX + 1] = {
>          [IFLA_STATS_LINK64]  = { .len = sizeof(struct rtnl_link_stats64) },
> };
>
> This patch also allows for af family stats (an example af stats for IPV6
> is available with the second patch in the series).
>
> Like any other rtnetlink message, RTM_GETSTATS can be used to get stats of
> a single interface or all interfaces with NLM_F_DUMP.
>
> Future possible new types of stat attributes:
> - IFLA_MPLS_STATS  (nested. for mpls/mdev stats)
> - IFLA_EXTENDED_STATS (nested. extended software netdev stats like bridge,
>    vlan, vxlan etc)
> - IFLA_EXTENDED_HW_STATS (nested. extended hardware stats which are
>    available via ethtool today)
>
> This patch also declares a filter mask for all stat attributes.
> User has to provide a mask of stats attributes to query. This will be
> specified in a new hdr 'struct if_stats_msg' for stats messages.
>
> Without any attributes in the filter_mask, no stats will be returned.
>
> This patch has been tested with modified iproute2 ifstat.
>
> Suggested-by: Jamal Hadi Salim <[email-masked]>
> Signed-off-by: Roopa Prabhu <[email-masked]>
[snip]
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index 249eef9..0840f3e 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
[snip]
> +enum {
> +	IFLA_STATS_UNSPEC,
> +	IFLA_STATS_LINK64,
> +	IFLA_STATS_INET6,
IFLA_STATS_INET6 is part on patch #2, it's not used in this patch.

> +	__IFLA_STATS_MAX,
> +};
> +
> +#define IFLA_STATS_MAX (__IFLA_STATS_MAX - 1)
> +
> +#define IFLA_STATS_FILTER_BIT(ATTR)	(1 << (ATTR))
> +
>   #endif /* _UAPI_LINUX_IF_LINK_H */
> diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
> index ca764b5..2bbb300 100644
> --- a/include/uapi/linux/rtnetlink.h
> +++ b/include/uapi/linux/rtnetlink.h
> @@ -139,6 +139,13 @@ enum {
>   	RTM_GETNSID = 90,
>   #define RTM_GETNSID RTM_GETNSID
>
> +	RTM_NEWSTATS = 92,
> +#define RTM_NEWSTATS RTM_NEWSTATS
> +	RTM_DELSTATS = 93,
> +#define RTM_DELSTATS RTM_DELSTATS
RTM_DELSTATS is never used.

> +	RTM_GETSTATS = 94,
> +#define RTM_GETSTATS RTM_GETSTATS
> +
>   	__RTM_MAX,
>   #define RTM_MAX		(((__RTM_MAX + 3) & ~3) - 1)
>   };
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index d2d9e5e..d1e3d17 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
[snip]
> +static noinline size_t if_nlmsg_stats_size(const struct net_device *dev,
> +					   u32 filter_mask)
Why are you using the 'noinline' attribute?

> +{
> +	size_t size = 0;
> +
> +	if (filter_mask & IFLA_STATS_FILTER_BIT(IFLA_STATS_LINK64))
> +		size += nla_total_size(sizeof(struct rtnl_link_stats64));
> +
> +	size += rtnl_link_get_af_stats_size(dev, filter_mask);
> +
> +	return size;
> +}