Merge branch 'netdev-support-dumping-a-single-netdev-in-qstats'

Jakub Kicinski says:

====================
netdev: support dumping a single netdev in qstats

I was writing a test for page pool which depended on qstats,
and got tired of having to filter dumps in user space.
Add support for dumping stats for a single netdev.

To get there we first need to add full support for extack
in dumps (and fix a dump error handling bug in YNL, sent
separately to the net tree).
====================

Link: https://lore.kernel.org/r/20240420023543.3300306-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 39 insertions, 13 deletions

diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 7004b3399c2b..dd6510f2c652 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -639,6 +639,24 @@ nla_put_failure:
 	return -EMSGSIZE;
 }
 
+static int
+netdev_nl_qstats_get_dump_one(struct net_device *netdev, unsigned int scope,
+			      struct sk_buff *skb, const struct genl_info *info,
+			      struct netdev_nl_dump_ctx *ctx)
+{
+	if (!netdev->stat_ops)
+		return 0;
+
+	switch (scope) {
+	case 0:
+		return netdev_nl_stats_by_netdev(netdev, skb, info);
+	case NETDEV_QSTATS_SCOPE_QUEUE:
+		return netdev_nl_stats_by_queue(netdev, skb, info, ctx);
+	}
+
+	return -EINVAL;	/* Should not happen, per netlink policy */
+}
+
 int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
 				struct netlink_callback *cb)
 {
@@ -646,6 +664,7 @@ int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
 	const struct genl_info *info = genl_info_dump(cb);
 	struct net *net = sock_net(skb->sk);
 	struct net_device *netdev;
+	unsigned int ifindex;
 	unsigned int scope;
 	int err = 0;
 
@@ -653,21 +672,28 @@ int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
 	if (info->attrs[NETDEV_A_QSTATS_SCOPE])
 		scope = nla_get_uint(info->attrs[NETDEV_A_QSTATS_SCOPE]);
 
-	rtnl_lock();
-	for_each_netdev_dump(net, netdev, ctx->ifindex) {
-		if (!netdev->stat_ops)
-			continue;
+	ifindex = 0;
+	if (info->attrs[NETDEV_A_QSTATS_IFINDEX])
+		ifindex = nla_get_u32(info->attrs[NETDEV_A_QSTATS_IFINDEX]);
 
-		switch (scope) {
-		case 0:
-			err = netdev_nl_stats_by_netdev(netdev, skb, info);
-			break;
-		case NETDEV_QSTATS_SCOPE_QUEUE:
-			err = netdev_nl_stats_by_queue(netdev, skb, info, ctx);
-			break;
+	rtnl_lock();
+	if (ifindex) {
+		netdev = __dev_get_by_index(net, ifindex);
+		if (netdev && netdev->stat_ops) {
+			err = netdev_nl_qstats_get_dump_one(netdev, scope, skb,
+							    info, ctx);
+		} else {
+			NL_SET_BAD_ATTR(info->extack,
+					info->attrs[NETDEV_A_QSTATS_IFINDEX]);
+			err = netdev ? -EOPNOTSUPP : -ENODEV;
+		}
+	} else {
+		for_each_netdev_dump(net, netdev, ctx->ifindex) {
+			err = netdev_nl_qstats_get_dump_one(netdev, scope, skb,
+							    info, ctx);
+			if (err < 0)
+				break;
 		}
-		if (err < 0)
-			break;
 	}
 	rtnl_unlock();