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 69f71b86b035..597732c989ca 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);