ethtool: set device channel counts with CHANNELS_SET request

Implement CHANNELS_SET netlink request to set channel counts of a network
device. These are traditionally set with ETHTOOL_SCHANNELS ioctl request.

Like the ioctl implementation, the generic ethtool code checks if supplied
values do not exceed driver defined limits; if they do, first offending
attribute is reported using extack. Checks preventing removing channels
used for RX indirection table or zerocopy AF_XDP socket are also
implemented.

Move ethtool_get_max_rxfh_channel() helper into common.c so that it can be
used by both ioctl and netlink code.

v2:
  - fix netdev reference leak in error path (found by Jakub Kicinsky)

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 31 insertions, 0 deletions

diff --git a/net/ethtool/common.c b/net/ethtool/common.c
index 7b6969af5ae7..0b22741b2f8f 100644
--- a/net/ethtool/common.c
+++ b/net/ethtool/common.c
@@ -258,3 +258,34 @@ int __ethtool_get_link(struct net_device *dev)
 
 	return netif_running(dev) && dev->ethtool_ops->get_link(dev);
 }
+
+int ethtool_get_max_rxfh_channel(struct net_device *dev, u32 *max)
+{
+	u32 dev_size, current_max = 0;
+	u32 *indir;
+	int ret;
+
+	if (!dev->ethtool_ops->get_rxfh_indir_size ||
+	    !dev->ethtool_ops->get_rxfh)
+		return -EOPNOTSUPP;
+	dev_size = dev->ethtool_ops->get_rxfh_indir_size(dev);
+	if (dev_size == 0)
+		return -EOPNOTSUPP;
+
+	indir = kcalloc(dev_size, sizeof(indir[0]), GFP_USER);
+	if (!indir)
+		return -ENOMEM;
+
+	ret = dev->ethtool_ops->get_rxfh(dev, indir, NULL, NULL);
+	if (ret)
+		goto out;
+
+	while (dev_size--)
+		current_max = max(current_max, indir[dev_size]);
+
+	*max = current_max;
+
+out:
+	kfree(indir);
+	return ret;
+}