net: ethtool: add support for ETHTOOL_GRXRINGS ioctl

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>
Link: https://patch.msgid.link/20250917-gxrings-v4-2-dae520e2e1cb@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 15627afa4424fce4a015225e4c378f6b731c5946..4214ab33c3c811836ae66a3a3a8b3295226b1be9 100644 (file)
--- 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: