rtnetlink: honor RTEXT_FILTER_SKIP_STATS in IFLA_STATS

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@oracle.com/
[2] https://lore.kernel.org/all/20230611105108.122586-1-gal@nvidia.com/

Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Link: https://patch.msgid.link/20251103154006.1189707-1-amorenoz@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 576d5ec3bb364f411b55711293d5b49bf39e7f13..b1ed55141d8a7af5c8fa84723e55f8b22a2147d3 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1270,13 +1270,13 @@ static size_t rtnl_dpll_pin_size(const struct net_device *dev)
 static noinline size_t if_nlmsg_size(const struct net_device *dev,
                                     u32 ext_filter_mask)
 {
-       return NLMSG_ALIGN(sizeof(struct ifinfomsg))
+       size_t size;
+
+       size = NLMSG_ALIGN(sizeof(struct ifinfomsg))
               + nla_total_size(IFNAMSIZ) /* IFLA_IFNAME */
               + 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))
               + nla_total_size(MAX_ADDR_LEN) /* IFLA_ADDRESS */
               + nla_total_size(MAX_ADDR_LEN) /* IFLA_BROADCAST */
               + nla_total_size(4) /* IFLA_TXQLEN */
@@ -1329,6 +1329,12 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
               + nla_total_size(2)  /* IFLA_HEADROOM */
               + nla_total_size(2)  /* IFLA_TAILROOM */
               + 0;
+
+       if (!(ext_filter_mask & RTEXT_FILTER_SKIP_STATS))
+               size += nla_total_size(sizeof(struct rtnl_link_stats)) +
+                       nla_total_size_64bit(sizeof(struct rtnl_link_stats64));
+
+       return size;
 }
 
 static int rtnl_vf_ports_fill(struct sk_buff *skb, struct net_device *dev)
@@ -2123,7 +2129,8 @@ 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))