linux-kernel - [PATCH net-next v2 1/7] net: ethtool: netlink: Allow per-netdevice DUMP operations

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Message-ID: <20250308155440.267782-2-maxime.chevallier@bootlin.com>
Date: Sat,  8 Mar 2025 16:54:33 +0100
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: davem@...emloft.net,
	Andrew Lunn <andrew@...n.ch>,
	Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Heiner Kallweit <hkallweit1@...il.com>
Cc: Maxime Chevallier <maxime.chevallier@...tlin.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	thomas.petazzoni@...tlin.com,
	linux-arm-kernel@...ts.infradead.org,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Herve Codina <herve.codina@...tlin.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Köry Maincent <kory.maincent@...tlin.com>,
	Oleksij Rempel <o.rempel@...gutronix.de>,
	Simon Horman <horms@...nel.org>,
	Romain Gantois <romain.gantois@...tlin.com>,
	Piergiorgio Beruto <piergiorgio.beruto@...il.com>,
	Stanislav Fomichev <sdf@...ichev.me>
Subject: [PATCH net-next v2 1/7] net: ethtool: netlink: Allow per-netdevice DUMP operations

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@...tlin.com>
---
V2: - Rebase
    - Fix kdoc
    - Fix bissectabilitu by using the right function names

 net/ethtool/netlink.c | 45 ++++++++++++++++++++++++++++---------------
 net/ethtool/netlink.h |  2 ++
 2 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 70834947f474..11e4122b7707 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -586,21 +586,34 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
 	int ret = 0;
 
 	rcu_read_lock();
-	for_each_netdev_dump(net, dev, ctx->pos_ifindex) {
-		dev_hold(dev);
+	if (ctx->req_info->dev) {
+		dev = ctx->req_info->dev;
 		rcu_read_unlock();
-
-		ret = ethnl_default_dump_one(skb, dev, ctx, genl_info_dump(cb));
-
+		/* Filtered DUMP request targeted to a single netdev. We already
+		 * hold a ref to the netdev from ->start()
+		 */
+		ret = ethnl_default_dump_one(skb, dev, ctx,
+					     genl_info_dump(cb));
 		rcu_read_lock();
-		dev_put(dev);
-
-		if (ret < 0 && ret != -EOPNOTSUPP) {
-			if (likely(skb->len))
-				ret = skb->len;
-			break;
+		netdev_put(ctx->req_info->dev, &ctx->req_info->dev_tracker);
+	} else {
+		for_each_netdev_dump(net, dev, ctx->pos_ifindex) {
+			dev_hold(dev);
+			rcu_read_unlock();
+
+			ret = ethnl_default_dump_one(skb, dev, ctx,
+						     genl_info_dump(cb));
+
+			rcu_read_lock();
+			dev_put(dev);
+
+			if (ret < 0 && ret != -EOPNOTSUPP) {
+				if (likely(skb->len))
+					ret = skb->len;
+				break;
+			}
+			ret = 0;
 		}
-		ret = 0;
 	}
 	rcu_read_unlock();
 
@@ -634,10 +647,10 @@ 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