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rtnetlink: add RTEXT_FILTER_NAME_ONLY support to rtnl_dump_ifinfo()

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When user requests RTEXT_FILTER_NAME_ONLY flag, we limit the dump
parts to:

 - struct nlmsghdr
 - IFLA_IFNAME
 - IFLA_PROP_LIST (alternate names)

- This saves space in the dump, pushing more devices per system call.
- This can be done without acquiring RTNL.

I still have a medium term goal to avoid RTNL in rtnl_dump_ifinfo()
regardless of RTEXT_FILTER_NAME_ONLY being used.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260525083542.1565964-6-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-05-25 08:35:42 +00:00 committed by Jakub Kicinski
parent 6768c7c3d7
commit d628604f7e
1 changed files with 15 additions and 4 deletions
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19
net/core/rtnetlink.c
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@ -2499,6 +2499,7 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
int ops_srcu_index;
int master_idx = 0;
int netnsid = -1;
bool need_rtnl;
int err, i;
err = rtnl_valid_dump_ifinfo_req(nlh, cb->strict_check, tb, extack);
@ -2548,6 +2549,12 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
walk_entries:
err = 0;
need_rtnl = !(ext_filter_mask & RTEXT_FILTER_NAME_ONLY);
if (need_rtnl)
rtnl_lock();
else
rcu_read_lock();
for_each_netdev_dump(tgt_net, dev, ctx->ifindex) {
if (link_dump_filtered(dev, master_idx, kind_ops))
continue;
@ -2559,11 +2566,13 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
if (err < 0)
break;
}
cb->seq = tgt_net->dev_base_seq;
cb->seq = READ_ONCE(tgt_net->dev_base_seq);
nl_dump_check_consistent(cb, nlmsg_hdr(skb));
if (need_rtnl)
rtnl_unlock();
else
rcu_read_unlock();
out:
if (kind_ops)
@ -7159,7 +7168,9 @@ static const struct rtnl_msg_handler rtnetlink_rtnl_msg_handlers[] __initconst =
.flags = RTNL_FLAG_DOIT_PERNET_WIP},
{.msgtype = RTM_GETLINK, .doit = rtnl_getlink,
.dumpit = rtnl_dump_ifinfo,
.flags = RTNL_FLAG_DUMP_SPLIT_NLM_DONE | RTNL_FLAG_DOIT_UNLOCKED},
.flags = RTNL_FLAG_DUMP_SPLIT_NLM_DONE |
RTNL_FLAG_DOIT_UNLOCKED |
RTNL_FLAG_DUMP_UNLOCKED},
{.msgtype = RTM_SETLINK, .doit = rtnl_setlink,
.flags = RTNL_FLAG_DOIT_PERNET_WIP},
{.msgtype = RTM_GETADDR, .dumpit = rtnl_dump_all},