ethtool: Define and apply a default policy for RX flow hash indirection

All drivers that support modification of the RX flow hash indirection
table initialise it in the same way: RX rings are assigned to table
entries in rotation.  Make that default policy explicit by having them
call a ethtool_rxfh_indir_default() function.

In the ethtool core, add support for a zero size value for
ETHTOOL_SRXFHINDIR, which resets the table to this default.

Partly-suggested-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Acked-by: Shreyas N Bhatewara <sbhatewara@vmware.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 13 deletions

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index 69f71b8..597732c 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -581,31 +581,38 @@ static noinline_for_stack int ethtool_set_rxfh_indir(struct net_device *dev,
 			   sizeof(user_size)))
 		return -EFAULT;
 
-	if (user_size != dev_size)
+	if (user_size != 0 && user_size != dev_size)
 		return -EINVAL;
 
 	indir = kcalloc(dev_size, sizeof(indir[0]), GFP_USER);
 	if (!indir)
 		return -ENOMEM;
 
-	if (copy_from_user(indir,
-			   useraddr +
-			   offsetof(struct ethtool_rxfh_indir, ring_index[0]),
-			   dev_size * sizeof(indir[0]))) {
-		ret = -EFAULT;
-		goto out;
-	}
-
-	/* Validate ring indices */
 	rx_rings.cmd = ETHTOOL_GRXRINGS;
 	ret = dev->ethtool_ops->get_rxnfc(dev, &rx_rings, NULL);
 	if (ret)
 		goto out;
-	for (i = 0; i < dev_size; i++) {
-		if (indir[i] >= rx_rings.data) {
-			ret = -EINVAL;
+
+	if (user_size == 0) {
+		for (i = 0; i < dev_size; i++)
+			indir[i] = ethtool_rxfh_indir_default(i, rx_rings.data);
+	} else {
+		if (copy_from_user(indir,
+				  useraddr +
+				  offsetof(struct ethtool_rxfh_indir,
+					   ring_index[0]),
+				  dev_size * sizeof(indir[0]))) {
+			ret = -EFAULT;
 			goto out;
 		}
+
+		/* Validate ring indices */
+		for (i = 0; i < dev_size; i++) {
+			if (indir[i] >= rx_rings.data) {
+				ret = -EINVAL;
+				goto out;
+			}
+		}
 	}
 
 	ret = dev->ethtool_ops->set_rxfh_indir(dev, indir);