bonding: add packets_per_slave attribute netlink support

Add IFLA_BOND_PACKETS_PER_SLAVE to allow get/set of bonding parameter
packets_per_slave via netlink.

Signed-off-by: Scott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
index e313a8f..f8a2cd8 100644
--- a/drivers/net/bonding/bond_options.c
+++ b/drivers/net/bonding/bond_options.c
@@ -16,6 +16,7 @@
 #include <linux/netdevice.h>
 #include <linux/rwlock.h>
 #include <linux/rcupdate.h>
+#include <linux/reciprocal_div.h>
 #include "bonding.h"
 
 static bool bond_mode_is_valid(int mode)
@@ -633,3 +634,25 @@
 
 	return 0;
 }
+
+int bond_option_packets_per_slave_set(struct bonding *bond,
+				      int packets_per_slave)
+{
+	if (packets_per_slave < 0 || packets_per_slave > USHRT_MAX) {
+		pr_err("%s: packets_per_slave must be between 0 and %u\n",
+		       bond->dev->name, USHRT_MAX);
+		return -EINVAL;
+	}
+
+	if (bond->params.mode != BOND_MODE_ROUNDROBIN)
+		pr_warn("%s: Warning: packets_per_slave has effect only in balance-rr mode\n",
+			bond->dev->name);
+
+	if (packets_per_slave > 1)
+		bond->params.packets_per_slave =
+			reciprocal_value(packets_per_slave);
+	else
+		bond->params.packets_per_slave = packets_per_slave;
+
+	return 0;
+}