[PATCH net-next v2] rtnetlink: honor RTEXT_FILTER_SKIP_STATS in IFLA_STATS

[Adrian Moreno]

Gathering interface statistics can be a relatively expensive operation
on certain systems as it requires iterating over all the cpus.

RTEXT_FILTER_SKIP_STATS was first introduced [1] to skip AF_INET6
statistics from interface dumps and it was then extended [2] to
also exclude IFLA_VF_INFO.

The semantics of the flag does not seem to be limited to AF_INET
or VF statistics and having a way to query the interface status
(e.g: carrier, address) without retrieving its statistics seems
reasonable. So this patch extends the use RTEXT_FILTER_SKIP_STATS
to also affect IFLA_STATS.

[1] https://lore.kernel.org/all/20150911204848.GC9687@xxxxxxxxxx/
[2] https://lore.kernel.org/all/20230611105108.122586-1-gal@xxxxxxxxxx/

Signed-off-by: Adrian Moreno <amorenoz@xxxxxxxxxx>
---
 net/core/rtnetlink.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 8040ff7c356e..aa09d026817b 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1275,8 +1275,9 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
 	       + nla_total_size(IFALIASZ) /* IFLA_IFALIAS */
 	       + nla_total_size(IFNAMSIZ) /* IFLA_QDISC */
 	       + nla_total_size_64bit(sizeof(struct rtnl_link_ifmap))
-	       + nla_total_size(sizeof(struct rtnl_link_stats))
-	       + nla_total_size_64bit(sizeof(struct rtnl_link_stats64))
+	       + ((ext_filter_mask & RTEXT_FILTER_SKIP_STATS) ? 0 :
+		  (nla_total_size(sizeof(struct rtnl_link_stats)) +
+		   nla_total_size_64bit(sizeof(struct rtnl_link_stats64))))
 	       + nla_total_size(MAX_ADDR_LEN) /* IFLA_ADDRESS */
 	       + nla_total_size(MAX_ADDR_LEN) /* IFLA_BROADCAST */
 	       + nla_total_size(4) /* IFLA_TXQLEN */
@@ -2123,7 +2124,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
 	if (rtnl_phys_switch_id_fill(skb, dev))
 		goto nla_put_failure;
 
-	if (rtnl_fill_stats(skb, dev))
+	if (!(ext_filter_mask & RTEXT_FILTER_SKIP_STATS) &&
+	    rtnl_fill_stats(skb, dev))
 		goto nla_put_failure;
 
 	if (rtnl_fill_vf(skb, dev, ext_filter_mask))
-- 
2.51.0