bonding: Send more than one gratuitous ARP when slave takes over

With IPoIB, reception of gratuitous ARP by neighboring hosts
is essential for a successful change of slaves in case of failure.
Otherwise, they won't learn about the HW address change and need
to wait a long time until the neighboring system gives up and sends
an ARP request to learn the new HW address.  This patch decreases
the chance for a lost of a gratuitous ARP packet by sending it more
than once. The number retries is configurable and can be set with a
module param.

Signed-off-by: Moni Shoua <monis@voltaire.com>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index 1f028579e53b..7a61e9a14386 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -951,6 +951,45 @@ out:
 static DEVICE_ATTR(lacp_rate, S_IRUGO | S_IWUSR, bonding_show_lacp, bonding_store_lacp);
 
 /*
+ * Show and set the number of grat ARP to send after a failover event.
+ */
+static ssize_t bonding_show_n_grat_arp(struct device *d,
+                                   struct device_attribute *attr,
+                                   char *buf)
+{
+        struct bonding *bond = to_bond(d);
+
+        return sprintf(buf, "%d\n", bond->params.num_grat_arp);
+}
+
+static ssize_t bonding_store_n_grat_arp(struct device *d,
+                                    struct device_attribute *attr,
+                                    const char *buf, size_t count)
+{
+        int new_value, ret = count;
+        struct bonding *bond = to_bond(d);
+
+        if (sscanf(buf, "%d", &new_value) != 1) {
+                printk(KERN_ERR DRV_NAME
+                       ": %s: no num_grat_arp value specified.\n",
+                       bond->dev->name);
+                ret = -EINVAL;
+                goto out;
+        }
+        if (new_value < 0 || new_value > 255) {
+                printk(KERN_ERR DRV_NAME
+                       ": %s: Invalid num_grat_arp value %d not in range 0-255; rejected.\n",
+                       bond->dev->name, new_value);
+                ret = -EINVAL;
+                goto out;
+        } else {
+                bond->params.num_grat_arp = new_value;
+        }
+out:
+        return ret;
+}
+static DEVICE_ATTR(num_grat_arp, S_IRUGO | S_IWUSR, bonding_show_n_grat_arp, bonding_store_n_grat_arp);
+/*
  * Show and set the MII monitor interval.  There are two tricky bits
  * here.  First, if MII monitoring is activated, then we must disable
  * ARP monitoring.  Second, if the timer isn't running, we must
@@ -1387,6 +1426,7 @@ static struct attribute *per_bond_attrs[] = {
         &dev_attr_updelay.attr,
         &dev_attr_lacp_rate.attr,
         &dev_attr_xmit_hash_policy.attr,
+        &dev_attr_num_grat_arp.attr,
         &dev_attr_miimon.attr,
         &dev_attr_primary.attr,
         &dev_attr_use_carrier.attr,