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>

3 files changed, 60 insertions, 4 deletions

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 2a0039f19377..fa3c2101fe75 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -88,6 +88,7 @@
 #define BOND_LINK_ARP_INTERV    0
 
 static int max_bonds    = BOND_DEFAULT_MAX_BONDS;
+static int num_grat_arp = 1;
 static int miimon       = BOND_LINK_MON_INTERV;
 static int updelay      = 0;
 static int downdelay    = 0;
@@ -104,6 +105,8 @@ struct bond_params bonding_defaults;
 
 module_param(max_bonds, int, 0);
 MODULE_PARM_DESC(max_bonds, "Max number of bonded devices");
+module_param(num_grat_arp, int, 0644);
+MODULE_PARM_DESC(num_grat_arp, "Number of gratuitous ARP packets to send on failover event");
 module_param(miimon, int, 0);
 MODULE_PARM_DESC(miimon, "Link check interval in milliseconds");
 module_param(updelay, int, 0);
@@ -1109,14 +1112,18 @@ void bond_change_active_slave(struct bonding *bond, struct slave *new_active)
                 if (new_active && bond->params.fail_over_mac)
                         memcpy(bond->dev->dev_addr,  new_active->dev->dev_addr,
                                 new_active->dev->addr_len);
+                bond->send_grat_arp = bond->params.num_grat_arp;
                 if (bond->curr_active_slave &&
                         test_bit(__LINK_STATE_LINKWATCH_PENDING,
                                         &bond->curr_active_slave->dev->state)) {
                         dprintk("delaying gratuitous arp on %s\n",
                                 bond->curr_active_slave->dev->name);
-                        bond->send_grat_arp = 1;
-                } else
-                        bond_send_gratuitous_arp(bond);
+                } else {
+                        if (bond->send_grat_arp > 0) {
+                                bond_send_gratuitous_arp(bond);
+                                bond->send_grat_arp--;
+                        }
+                }
         }
 }
 
@@ -2144,7 +2151,7 @@ static int __bond_mii_monitor(struct bonding *bond, int have_locks)
                         dprintk("sending delayed gratuitous arp on on %s\n",
                                 bond->curr_active_slave->dev->name);
                         bond_send_gratuitous_arp(bond);
-                        bond->send_grat_arp = 0;
+                        bond->send_grat_arp--;
                 }
         }
         read_lock(&bond->curr_slave_lock);
@@ -4626,6 +4633,13 @@ static int bond_check_params(struct bond_params *params)
                 use_carrier = 1;
         }
 
+        if (num_grat_arp < 0 || num_grat_arp > 255) {
+                printk(KERN_WARNING DRV_NAME
+                       ": Warning: num_grat_arp (%d) not in range 0-255 so it "
+                       "was reset to 1 \n", num_grat_arp);
+                num_grat_arp = 1;
+        }
+
         /* reset values for 802.3ad */
         if (bond_mode == BOND_MODE_8023AD) {
                 if (!miimon) {
@@ -4813,6 +4827,7 @@ static int bond_check_params(struct bond_params *params)
         params->mode = bond_mode;
         params->xmit_policy = xmit_hashtype;
         params->miimon = miimon;
+        params->num_grat_arp = num_grat_arp;
         params->arp_interval = arp_interval;
         params->arp_validate = arp_validate_value;
         params->updelay = updelay;
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,
diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
index 0ce7f4ae920f..46a2ed507b33 100644
--- a/drivers/net/bonding/bonding.h
+++ b/drivers/net/bonding/bonding.h
@@ -125,6 +125,7 @@ struct bond_params {
         int mode;
         int xmit_policy;
         int miimon;
+        int num_grat_arp;
         int arp_interval;
         int arp_validate;
         int use_carrier;