[PATCH net-next v4 2/8] net: ethtool: netlink: Allow per-netdevice DUMP operations

Maxime Chevallier
2025-03-24T10:40:26Z

We have a number of netlink commands in the ethnl family that may have
multiple objects to dump even for a single net_device, including :

- PLCA, PSE-PD, phy: one message per PHY device
- tsinfo: one message per timestamp source (netdev + phys)
- rss: One per RSS context

To get this behaviour, these netlink commands need to roll a custom
->dumpit().

To prepare making per-netdev DUMP more generic in ethnl, introduce a
member in the ethnl ops to indicate if a given command may allow
pernetdev DUMPs (also referred to as filtered DUMPs).

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
V4: - Don't hold RCU in the filtered path
- Move dump_all into a new separate helper

net/ethtool/netlink.c | 37 ++++++++++++++++++++++++++++++-------
net/ethtool/netlink.h | 2 ++
2 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 6b1725795435..31ab89ca0bcc 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -577,9 +577,7 @@ static int ethnl_default_dump_one(struct sk_buff *skb, struct net_device *dev,
return ret;
}

-/* Default ->dumpit() handler for GET requests. */
-static int ethnl_default_dumpit(struct sk_buff *skb,
- struct netlink_callback *cb)
+static int ethnl_dump_all(struct sk_buff *skb, struct netlink_callback *cb)
{
struct ethnl_dump_ctx *ctx = ethnl_dump_context(cb);
struct net *net = sock_net(skb->sk);
@@ -609,6 +607,31 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
return ret;
}

+/* Default ->dumpit() handler for GET requests. */
+static int ethnl_default_dumpit(struct sk_buff *skb,
+ struct netlink_callback *cb)
+{
+ struct ethnl_dump_ctx *ctx = ethnl_dump_context(cb);
+ int ret;
+
+ if (ctx->req_info->dev) {
+ /* Filtered DUMP request targeted to a single netdev. We already
+ * hold a ref to the netdev from ->start()
+ */
+ ret = ethnl_default_dump_one(skb, ctx->req_info->dev, ctx,
+ genl_info_dump(cb));
+ netdev_put(ctx->req_info->dev, &ctx->req_info->dev_tracker);
+
+ if (ret < 0 && ret != -EOPNOTSUPP && likely(skb->len))
+ ret = skb->len;
+
+ } else {
+ ret = ethnl_dump_all(skb, cb);
+ }
+
+ return ret;
+}
+
/* generic ->start() handler for GET requests */
static int ethnl_default_start(struct netlink_callback *cb)
{
@@ -636,10 +659,10 @@ static int ethnl_default_start(struct netlink_callback *cb)
}

ret = ethnl_default_parse(req_info, &info->info, ops, false);
- if (req_info->dev) {
- /* We ignore device specification in dump requests but as the
- * same parser as for non-dump (doit) requests is used, it
- * would take reference to the device if it finds one
+ if (req_info->dev && !ops->allow_pernetdev_dump) {
+ /* We ignore device specification in unfiltered dump requests
+ * but as the same parser as for non-dump (doit) requests is
+ * used, it would take reference to the device if it finds one
*/
netdev_put(req_info->dev, &req_info->dev_tracker);
req_info->dev = NULL;
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index ec6ab5443a6f..4aaa73282d6a 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -331,6 +331,7 @@ int ethnl_sock_priv_set(struct sk_buff *skb, struct net_device *dev, u32 portid,
* @req_info_size: size of request info
* @reply_data_size: size of reply data
* @allow_nodev_do: allow non-dump request with no device identification
+ * @allow_pernetdev_dump: allow filtering dump requests with ifname/ifindex
* @set_ntf_cmd: notification to generate on changes (SET)
* @parse_request:
* Parse request except common header (struct ethnl_req_info). Common
@@ -388,6 +389,7 @@ struct ethnl_request_ops {
unsigned int req_info_size;
unsigned int reply_data_size;
bool allow_nodev_do;
+ bool allow_pernetdev_dump;
u8 set_ntf_cmd;

int (*parse_request)(struct ethnl_req_info *req_info,
--
2.48.1