+#define BOND_INTERSECT_FEATURES \
+ (NETIF_F_SG|NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM)
+
+/*
+ * Compute the features available to the bonding device by
+ * intersection of all of the slave devices' BOND_INTERSECT_FEATURES.
+ * Call this after attaching or detaching a slave to update the
+ * bond's features.
+ */
+static int bond_compute_features(struct bonding *bond)
+{
+ int i;
+ struct slave *slave;
+ struct net_device *bond_dev = bond->dev;
+ int features = bond->bond_features;
+
+ bond_for_each_slave(bond, slave, i) {
+ struct net_device * slave_dev = slave->dev;
+ if (i == 0) {
+ features |= BOND_INTERSECT_FEATURES;
+ }
+ features &=
+ ~(~slave_dev->features & BOND_INTERSECT_FEATURES);
+ }
+
+ /* turn off NETIF_F_SG if we need a csum and h/w can't do it */
+ if ((features & NETIF_F_SG) &&
+ !(features & (NETIF_F_IP_CSUM |
+ NETIF_F_NO_CSUM |
+ NETIF_F_HW_CSUM))) {
+ features &= ~NETIF_F_SG;
+ }
+
+ bond_dev->features = features;
+
+ return 0;
+}
+