This patch adds handling for the ETHTOOL_GRXRINGS ioctl command in the
ethtool ioctl dispatcher. It introduces a new helper function
ethtool_get_rxrings() that calls the driver's get_rxnfc() callback with
appropriate parameters to retrieve the number of RX rings supported
by the device.

By explicitly handling ETHTOOL_GRXRINGS, userspace queries through
ethtool can now obtain RX ring information in a structured manner.

In this patch, ethtool_get_rxrings() is a simply copy of
ethtool_get_rxnfc().

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 net/ethtool/ioctl.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 15627afa4424f..4214ab33c3c81 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -1208,6 +1208,44 @@ static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
 	return 0;
 }
 
+static noinline_for_stack int ethtool_get_rxrings(struct net_device *dev,
+						  u32 cmd,
+						  void __user *useraddr)
+{
+	struct ethtool_rxnfc info;
+	size_t info_size = sizeof(info);
+	const struct ethtool_ops *ops = dev->ethtool_ops;
+	int ret;
+	void *rule_buf = NULL;
+
+	if (!ops->get_rxnfc)
+		return -EOPNOTSUPP;
+
+	ret = ethtool_rxnfc_copy_struct(cmd, &info, &info_size, useraddr);
+	if (ret)
+		return ret;
+
+	if (info.cmd == ETHTOOL_GRXCLSRLALL) {
+		if (info.rule_cnt > 0) {
+			if (info.rule_cnt <= KMALLOC_MAX_SIZE / sizeof(u32))
+				rule_buf = kcalloc(info.rule_cnt, sizeof(u32),
+						   GFP_USER);
+			if (!rule_buf)
+				return -ENOMEM;
+		}
+	}
+
+	ret = ops->get_rxnfc(dev, &info, rule_buf);
+	if (ret < 0)
+		goto err_out;
+
+	ret = ethtool_rxnfc_copy_to_user(useraddr, &info, info_size, rule_buf);
+err_out:
+	kfree(rule_buf);
+
+	return ret;
+}
+
 static noinline_for_stack int ethtool_get_rxnfc(struct net_device *dev,
 						u32 cmd, void __user *useraddr)
 {
@@ -3377,6 +3415,8 @@ __dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr,
 		rc = ethtool_set_rxfh_fields(dev, ethcmd, useraddr);
 		break;
 	case ETHTOOL_GRXRINGS:
+		rc = ethtool_get_rxrings(dev, ethcmd, useraddr);
+		break;
 	case ETHTOOL_GRXCLSRLCNT:
 	case ETHTOOL_GRXCLSRULE:
 	case ETHTOOL_GRXCLSRLALL:

-- 
2.47.3