[PATCH] bonding: Validate probe replies in ARP monitor

	Add logic to check ARP request / reply packets used for ARP
monitor link integrity checking.

	The current method simply examines the slave device to see if it
has sent and received traffic; this can be fooled by extraneous traffic.
For example, if multiple hosts running bonding are behind a common
switch, the probe traffic from the multiple instances of bonding will
update the tx/rx times on each other's slave devices.

Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

6 files changed, 325 insertions, 10 deletions

diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt
index afac780445cd..dc942eaf490f 100644
--- a/Documentation/networking/bonding.txt
+++ b/Documentation/networking/bonding.txt
@@ -192,6 +192,17 @@ or, for backwards compatibility, the option value.  E.g.,
 arp_interval
 
         Specifies the ARP link monitoring frequency in milliseconds.
+
+        The ARP monitor works by periodically checking the slave
+        devices to determine whether they have sent or received
+        traffic recently (the precise criteria depends upon the
+        bonding mode, and the state of the slave).  Regular traffic is
+        generated via ARP probes issued for the addresses specified by
+        the arp_ip_target option.
+
+        This behavior can be modified by the arp_validate option,
+        below.
+
         If ARP monitoring is used in an etherchannel compatible mode
         (modes 0 and 2), the switch should be configured in a mode
         that evenly distributes packets across all links. If the
@@ -213,6 +224,54 @@ arp_ip_target
         maximum number of targets that can be specified is 16.  The
         default value is no IP addresses.
 
+arp_validate
+
+        Specifies whether or not ARP probes and replies should be
+        validated in the active-backup mode.  This causes the ARP
+        monitor to examine the incoming ARP requests and replies, and
+        only consider a slave to be up if it is receiving the
+        appropriate ARP traffic.
+
+        Possible values are:
+
+        none or 0
+
+                No validation is performed.  This is the default.
+
+        active or 1
+
+                Validation is performed only for the active slave.
+
+        backup or 2
+
+                Validation is performed only for backup slaves.
+
+        all or 3
+
+                Validation is performed for all slaves.
+
+        For the active slave, the validation checks ARP replies to
+        confirm that they were generated by an arp_ip_target.  Since
+        backup slaves do not typically receive these replies, the
+        validation performed for backup slaves is on the ARP request
+        sent out via the active slave.  It is possible that some
+        switch or network configurations may result in situations
+        wherein the backup slaves do not receive the ARP requests; in
+        such a situation, validation of backup slaves must be
+        disabled.
+
+        This option is useful in network configurations in which
+        multiple bonding hosts are concurrently issuing ARPs to one or
+        more targets beyond a common switch.  Should the link between
+        the switch and target fail (but not the switch itself), the
+        probe traffic generated by the multiple bonding instances will
+        fool the standard ARP monitor into considering the links as
+        still up.  Use of the arp_validate option can resolve this, as
+        the ARP monitor will only consider ARP requests and replies
+        associated with its own instance of bonding.
+
+        This option was added in bonding version 3.1.0.
+
 downdelay
 
         Specifies the time, in milliseconds, to wait before disabling
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index bafe62f7c9b7..fd521b05db83 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -96,6 +96,7 @@ static char *lacp_rate	= NULL;
 static char *xmit_hash_policy = NULL;
 static int arp_interval = BOND_LINK_ARP_INTERV;
 static char *arp_ip_target[BOND_MAX_ARP_TARGETS] = { NULL, };
+static char *arp_validate = NULL;
 struct bond_params bonding_defaults;
 
 module_param(max_bonds, int, 0);
@@ -127,6 +128,8 @@ module_param(arp_interval, int, 0);
 MODULE_PARM_DESC(arp_interval, "arp interval in milliseconds");
 module_param_array(arp_ip_target, charp, NULL, 0);
 MODULE_PARM_DESC(arp_ip_target, "arp targets in n.n.n.n form");
+module_param(arp_validate, charp, 0);
+MODULE_PARM_DESC(arp_validate, "validate src/dst of ARP probes: none (default), active, backup or all");
 
 /*----------------------------- Global variables ----------------------------*/
 
@@ -170,6 +173,14 @@ struct bond_parm_tbl xmit_hashtype_tbl[] = {
 {       NULL,                   -1},
 };
 
+struct bond_parm_tbl arp_validate_tbl[] = {
+{       "none",                 BOND_ARP_VALIDATE_NONE},
+{       "active",               BOND_ARP_VALIDATE_ACTIVE},
+{       "backup",               BOND_ARP_VALIDATE_BACKUP},
+{       "all",                  BOND_ARP_VALIDATE_ALL},
+{       NULL,                   -1},
+};
+
 /*-------------------------- Forward declarations ---------------------------*/
 
 static void bond_send_gratuitous_arp(struct bonding *bond);
@@ -1424,6 +1435,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 
         bond_compute_features(bond);
 
+        new_slave->last_arp_rx = jiffies;
+
         if (bond->params.miimon && !bond->params.use_carrier) {
                 link_reporting = bond_check_dev_link(bond, slave_dev, 1);
 
@@ -1785,7 +1798,8 @@ int bond_release(struct net_device *bond_dev, struct net_device *slave_dev)
         dev_set_mac_address(slave_dev, &addr);
 
         slave_dev->priv_flags &= ~(IFF_MASTER_8023AD | IFF_MASTER_ALB |
-                                   IFF_SLAVE_INACTIVE | IFF_BONDING);
+                                   IFF_SLAVE_INACTIVE | IFF_BONDING |
+                                   IFF_SLAVE_NEEDARP);
 
         kfree(slave);
 
@@ -2298,6 +2312,25 @@ static int bond_has_ip(struct bonding *bond)
         return 0;
 }
 
+static int bond_has_this_ip(struct bonding *bond, u32 ip)
+{
+        struct vlan_entry *vlan, *vlan_next;
+
+        if (ip == bond->master_ip)
+                return 1;
+
+        if (list_empty(&bond->vlan_list))
+                return 0;
+
+        list_for_each_entry_safe(vlan, vlan_next, &bond->vlan_list,
+                                 vlan_list) {
+                if (ip == vlan->vlan_ip)
+                        return 1;
+        }
+
+        return 0;
+}
+
 /*
  * We go to the (large) trouble of VLAN tagging ARP frames because
  * switches in VLAN mode (especially if ports are configured as
@@ -2436,6 +2469,93 @@ static void bond_send_gratuitous_arp(struct bonding *bond)
         }
 }
 
+static void bond_validate_arp(struct bonding *bond, struct slave *slave, u32 sip, u32 tip)
+{
+        int i;
+        u32 *targets = bond->params.arp_targets;
+
+        targets = bond->params.arp_targets;
+        for (i = 0; (i < BOND_MAX_ARP_TARGETS) && targets[i]; i++) {
+                dprintk("bva: sip %u.%u.%u.%u tip %u.%u.%u.%u t[%d] "
+                        "%u.%u.%u.%u bhti(tip) %d\n",
+                       NIPQUAD(sip), NIPQUAD(tip), i, NIPQUAD(targets[i]),
+                       bond_has_this_ip(bond, tip));
+                if (sip == targets[i]) {
+                        if (bond_has_this_ip(bond, tip))
+                                slave->last_arp_rx = jiffies;
+                        return;
+                }
+        }
+}
+
+static int bond_arp_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
+{
+        struct arphdr *arp;
+        struct slave *slave;
+        struct bonding *bond;
+        unsigned char *arp_ptr;
+        u32 sip, tip;
+
+        if (!(dev->priv_flags & IFF_BONDING) || !(dev->flags & IFF_MASTER))
+                goto out;
+
+        bond = dev->priv;
+        read_lock(&bond->lock);
+
+        dprintk("bond_arp_rcv: bond %s skb->dev %s orig_dev %s\n",
+                bond->dev->name, skb->dev ? skb->dev->name : "NULL",
+                orig_dev ? orig_dev->name : "NULL");
+
+        slave = bond_get_slave_by_dev(bond, orig_dev);
+        if (!slave || !slave_do_arp_validate(bond, slave))
+                goto out_unlock;
+
+        /* ARP header, plus 2 device addresses, plus 2 IP addresses.  */
+        if (!pskb_may_pull(skb, (sizeof(struct arphdr) +
+                                 (2 * dev->addr_len) +
+                                 (2 * sizeof(u32)))))
+                goto out_unlock;
+
+        arp = skb->nh.arph;
+        if (arp->ar_hln != dev->addr_len ||
+            skb->pkt_type == PACKET_OTHERHOST ||
+            skb->pkt_type == PACKET_LOOPBACK ||
+            arp->ar_hrd != htons(ARPHRD_ETHER) ||
+            arp->ar_pro != htons(ETH_P_IP) ||
+            arp->ar_pln != 4)
+                goto out_unlock;
+
+        arp_ptr = (unsigned char *)(arp + 1);
+        arp_ptr += dev->addr_len;
+        memcpy(&sip, arp_ptr, 4);
+        arp_ptr += 4 + dev->addr_len;
+        memcpy(&tip, arp_ptr, 4);
+
+        dprintk("bond_arp_rcv: %s %s/%d av %d sv %d sip %u.%u.%u.%u"
+                " tip %u.%u.%u.%u\n", bond->dev->name, slave->dev->name,
+                slave->state, bond->params.arp_validate,
+                slave_do_arp_validate(bond, slave), NIPQUAD(sip), NIPQUAD(tip));
+
+        /*
+         * Backup slaves won't see the ARP reply, but do come through
+         * here for each ARP probe (so we swap the sip/tip to validate
+         * the probe).  In a "redundant switch, common router" type of
+         * configuration, the ARP probe will (hopefully) travel from
+         * the active, through one switch, the router, then the other
+         * switch before reaching the backup.
+         */
+        if (slave->state == BOND_STATE_ACTIVE)
+                bond_validate_arp(bond, slave, sip, tip);
+        else
+                bond_validate_arp(bond, slave, tip, sip);
+
+out_unlock:
+        read_unlock(&bond->lock);
+out:
+        dev_kfree_skb(skb);
+        return NET_RX_SUCCESS;
+}
+
 /*
  * this function is called regularly to monitor each slave's link
  * ensuring that traffic is being sent and received when arp monitoring
@@ -2600,7 +2720,8 @@ void bond_activebackup_arp_mon(struct net_device *bond_dev)
          */
         bond_for_each_slave(bond, slave, i) {
                 if (slave->link != BOND_LINK_UP) {
-                        if ((jiffies - slave->dev->last_rx) <= delta_in_ticks) {
+                        if ((jiffies - slave_last_rx(bond, slave)) <=
+                             delta_in_ticks) {
 
                                 slave->link = BOND_LINK_UP;
 
@@ -2645,7 +2766,7 @@ void bond_activebackup_arp_mon(struct net_device *bond_dev)
 
                         if ((slave != bond->curr_active_slave) &&
                             (!bond->current_arp_slave) &&
-                            (((jiffies - slave->dev->last_rx) >= 3*delta_in_ticks) &&
+                            (((jiffies - slave_last_rx(bond, slave)) >= 3*delta_in_ticks) &&
                              bond_has_ip(bond))) {
                                 /* a backup slave has gone down; three times
                                  * the delta allows the current slave to be
@@ -2692,7 +2813,7 @@ void bond_activebackup_arp_mon(struct net_device *bond_dev)
                  * if it is up and needs to take over as the curr_active_slave
                  */
                 if ((((jiffies - slave->dev->trans_start) >= (2*delta_in_ticks)) ||
-            (((jiffies - slave->dev->last_rx) >= (2*delta_in_ticks)) &&
+            (((jiffies - slave_last_rx(bond, slave)) >= (2*delta_in_ticks)) &&
              bond_has_ip(bond))) &&
                     ((jiffies - slave->jiffies) >= 2*delta_in_ticks)) {
 
@@ -3315,6 +3436,21 @@ static void bond_unregister_lacpdu(struct bonding *bond)
         dev_remove_pack(&(BOND_AD_INFO(bond).ad_pkt_type));
 }
 
+void bond_register_arp(struct bonding *bond)
+{
+        struct packet_type *pt = &bond->arp_mon_pt;
+
+        pt->type = htons(ETH_P_ARP);
+        pt->dev = NULL; /*bond->dev;XXX*/
+        pt->func = bond_arp_rcv;
+        dev_add_pack(pt);
+}
+
+void bond_unregister_arp(struct bonding *bond)
+{
+        dev_remove_pack(&bond->arp_mon_pt);
+}
+
 /*---------------------------- Hashing Policies -----------------------------*/
 
 /*
@@ -3401,6 +3537,9 @@ static int bond_open(struct net_device *bond_dev)
                 } else {
                         arp_timer->function = (void *)&bond_loadbalance_arp_mon;
                 }
+                if (bond->params.arp_validate)
+                        bond_register_arp(bond);
+
                 add_timer(arp_timer);
         }
 
@@ -3428,6 +3567,9 @@ static int bond_close(struct net_device *bond_dev)
                 bond_unregister_lacpdu(bond);
         }
 
+        if (bond->params.arp_validate)
+                bond_unregister_arp(bond);
+
         write_lock_bh(&bond->lock);
 
 
@@ -4281,6 +4423,8 @@ int bond_parse_parm(char *mode_arg, struct bond_parm_tbl *tbl)
 
 static int bond_check_params(struct bond_params *params)
 {
+        int arp_validate_value;
+
         /*
          * Convert string parameters.
          */
@@ -4484,6 +4628,29 @@ static int bond_check_params(struct bond_params *params)
                 arp_interval = 0;
         }
 
+        if (arp_validate) {
+                if (bond_mode != BOND_MODE_ACTIVEBACKUP) {
+                        printk(KERN_ERR DRV_NAME
+               ": arp_validate only supported in active-backup mode\n");
+                        return -EINVAL;
+                }
+                if (!arp_interval) {
+                        printk(KERN_ERR DRV_NAME
+                               ": arp_validate requires arp_interval\n");
+                        return -EINVAL;
+                }
+
+                arp_validate_value = bond_parse_parm(arp_validate,
+                                                     arp_validate_tbl);
+                if (arp_validate_value == -1) {
+                        printk(KERN_ERR DRV_NAME
+                               ": Error: invalid arp_validate \"%s\"\n",
+                               arp_validate == NULL ? "NULL" : arp_validate);
+                        return -EINVAL;
+                }
+        } else
+                arp_validate_value = 0;
+
         if (miimon) {
                 printk(KERN_INFO DRV_NAME
                        ": MII link monitoring set to %d ms\n",
@@ -4492,8 +4659,10 @@ static int bond_check_params(struct bond_params *params)
                 int i;
 
                 printk(KERN_INFO DRV_NAME
-                       ": ARP monitoring set to %d ms with %d target(s):",
-                       arp_interval, arp_ip_count);
+                       ": ARP monitoring set to %d ms, validate %s, with %d target(s):",
+                       arp_interval,
+                       arp_validate_tbl[arp_validate_value].modename,
+                       arp_ip_count);
 
                 for (i = 0; i < arp_ip_count; i++)
                         printk (" %s", arp_ip_target[i]);
@@ -4527,6 +4696,7 @@ static int bond_check_params(struct bond_params *params)
         params->xmit_policy = xmit_hashtype;
         params->miimon = miimon;
         params->arp_interval = arp_interval;
+        params->arp_validate = arp_validate_value;
         params->updelay = updelay;
         params->downdelay = downdelay;
         params->use_carrier = use_carrier;
diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index 15b6a29bb4d4..ced9ed8f995a 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -51,6 +51,7 @@ extern struct bond_params bonding_defaults;
 extern struct bond_parm_tbl bond_mode_tbl[];
 extern struct bond_parm_tbl bond_lacp_tbl[];
 extern struct bond_parm_tbl xmit_hashtype_tbl[];
+extern struct bond_parm_tbl arp_validate_tbl[];
 
 static int expected_refcount = -1;
 static struct class *netdev_class;
@@ -503,6 +504,53 @@ out:
 static CLASS_DEVICE_ATTR(xmit_hash_policy, S_IRUGO | S_IWUSR, bonding_show_xmit_hash, bonding_store_xmit_hash);
 
 /*
+ * Show and set arp_validate.
+ */
+static ssize_t bonding_show_arp_validate(struct class_device *cd, char *buf)
+{
+        struct bonding *bond = to_bond(cd);
+
+        return sprintf(buf, "%s %d\n",
+                       arp_validate_tbl[bond->params.arp_validate].modename,
+                       bond->params.arp_validate) + 1;
+}
+
+static ssize_t bonding_store_arp_validate(struct class_device *cd, const char *buf, size_t count)
+{
+        int new_value;
+        struct bonding *bond = to_bond(cd);
+
+        new_value = bond_parse_parm((char *)buf, arp_validate_tbl);
+        if (new_value < 0) {
+                printk(KERN_ERR DRV_NAME
+                       ": %s: Ignoring invalid arp_validate value %s\n",
+                       bond->dev->name, buf);
+                return -EINVAL;
+        }
+        if (new_value && (bond->params.mode != BOND_MODE_ACTIVEBACKUP)) {
+                printk(KERN_ERR DRV_NAME
+                       ": %s: arp_validate only supported in active-backup mode.\n",
+                       bond->dev->name);
+                return -EINVAL;
+        }
+        printk(KERN_INFO DRV_NAME ": %s: setting arp_validate to %s (%d).\n",
+               bond->dev->name, arp_validate_tbl[new_value].modename,
+               new_value);
+
+        if (!bond->params.arp_validate && new_value) {
+                bond_register_arp(bond);
+        } else if (bond->params.arp_validate && !new_value) {
+                bond_unregister_arp(bond);
+        }
+
+        bond->params.arp_validate = new_value;
+
+        return count;
+}
+
+static CLASS_DEVICE_ATTR(arp_validate, S_IRUGO | S_IWUSR, bonding_show_arp_validate, bonding_store_arp_validate);
+
+/*
  * Show and set the arp timer interval.  There are two tricky bits
  * here.  First, if ARP monitoring is activated, then we must disable
  * MII monitoring.  Second, if the ARP timer isn't running, we must
@@ -914,6 +962,11 @@ static ssize_t bonding_store_miimon(struct class_device *cd, const char *buf, si
                                "ARP monitoring. Disabling ARP monitoring...\n",
                                bond->dev->name);
                         bond->params.arp_interval = 0;
+                        if (bond->params.arp_validate) {
+                                bond_unregister_arp(bond);
+                                bond->params.arp_validate =
+                                        BOND_ARP_VALIDATE_NONE;
+                        }
                         /* Kill ARP timer, else it brings bond's link down */
                         if (bond->mii_timer.function) {
                                 printk(KERN_INFO DRV_NAME
@@ -1273,6 +1326,7 @@ static CLASS_DEVICE_ATTR(ad_partner_mac, S_IRUGO, bonding_show_ad_partner_mac, N
 static struct attribute *per_bond_attrs[] = {
         &class_device_attr_slaves.attr,
         &class_device_attr_mode.attr,
+        &class_device_attr_arp_validate.attr,
         &class_device_attr_arp_interval.attr,
         &class_device_attr_arp_ip_target.attr,
         &class_device_attr_downdelay.attr,
diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
index 17caafe58247..db16fee40a5f 100644
--- a/drivers/net/bonding/bonding.h
+++ b/drivers/net/bonding/bonding.h
@@ -22,8 +22,8 @@
 #include "bond_3ad.h"
 #include "bond_alb.h"
 
-#define DRV_VERSION     "3.0.3"
-#define DRV_RELDATE     "March 23, 2006"
+#define DRV_VERSION     "3.1.0-test"
+#define DRV_RELDATE     "September 9, 2006"
 #define DRV_NAME        "bonding"
 #define DRV_DESCRIPTION "Ethernet Channel Bonding Driver"
 
@@ -126,6 +126,7 @@ struct bond_params {
         int xmit_policy;
         int miimon;
         int arp_interval;
+        int arp_validate;
         int use_carrier;
         int updelay;
         int downdelay;
@@ -151,6 +152,7 @@ struct slave {
         struct slave *prev;
         int    delay;
         u32    jiffies;
+        u32    last_arp_rx;
         s8     link;    /* one of BOND_LINK_XXXX */
         s8     state;   /* one of BOND_STATE_XXXX */
         u32    original_flags;
@@ -198,6 +200,7 @@ struct bonding {
         struct   bond_params params;
         struct   list_head vlan_list;
         struct   vlan_group *vlgrp;
+        struct   packet_type arp_mon_pt;
 };
 
 /**
@@ -228,6 +231,25 @@ static inline struct bonding *bond_get_bond_by_slave(struct slave *slave)
         return (struct bonding *)slave->dev->master->priv;
 }
 
+#define BOND_ARP_VALIDATE_NONE          0
+#define BOND_ARP_VALIDATE_ACTIVE        (1 << BOND_STATE_ACTIVE)
+#define BOND_ARP_VALIDATE_BACKUP        (1 << BOND_STATE_BACKUP)
+#define BOND_ARP_VALIDATE_ALL           (BOND_ARP_VALIDATE_ACTIVE | \
+                                         BOND_ARP_VALIDATE_BACKUP)
+
+extern inline int slave_do_arp_validate(struct bonding *bond, struct slave *slave)
+{
+        return bond->params.arp_validate & (1 << slave->state);
+}
+
+extern inline u32 slave_last_rx(struct bonding *bond, struct slave *slave)
+{
+        if (slave_do_arp_validate(bond, slave))
+                return slave->last_arp_rx;
+
+        return slave->dev->last_rx;
+}
+
 static inline void bond_set_slave_inactive_flags(struct slave *slave)
 {
         struct bonding *bond = slave->dev->master->priv;
@@ -235,12 +257,14 @@ static inline void bond_set_slave_inactive_flags(struct slave *slave)
             bond->params.mode != BOND_MODE_ALB)
                 slave->state = BOND_STATE_BACKUP;
         slave->dev->priv_flags |= IFF_SLAVE_INACTIVE;
+        if (slave_do_arp_validate(bond, slave))
+                slave->dev->priv_flags |= IFF_SLAVE_NEEDARP;
 }
 
 static inline void bond_set_slave_active_flags(struct slave *slave)
 {
         slave->state = BOND_STATE_ACTIVE;
-        slave->dev->priv_flags &= ~IFF_SLAVE_INACTIVE;
+        slave->dev->priv_flags &= ~(IFF_SLAVE_INACTIVE | IFF_SLAVE_NEEDARP);
 }
 
 static inline void bond_set_master_3ad_flags(struct bonding *bond)
@@ -284,6 +308,8 @@ int bond_parse_parm(char *mode_arg, struct bond_parm_tbl *tbl);
 const char *bond_mode_name(int mode);
 void bond_select_active_slave(struct bonding *bond);
 void bond_change_active_slave(struct bonding *bond, struct slave *new_active);
+void bond_register_arp(struct bonding *);
+void bond_unregister_arp(struct bonding *);
 
 #endif /* _LINUX_BONDING_H */
 
diff --git a/include/linux/if.h b/include/linux/if.h
index a023ec1274fe..8018c2e22c0c 100644
--- a/include/linux/if.h
+++ b/include/linux/if.h
@@ -60,6 +60,7 @@
 #define IFF_MASTER_8023AD       0x8     /* bonding master, 802.3ad.     */
 #define IFF_MASTER_ALB  0x10            /* bonding master, balance-alb. */
 #define IFF_BONDING     0x20            /* bonding master or slave      */
+#define IFF_SLAVE_NEEDARP 0x40          /* need ARPs for validation     */
 
 #define IF_GET_IFACE    0x0001          /* for querying only */
 #define IF_GET_PROTO    0x0002
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 43289127b458..afd80eff2725 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1016,7 +1016,8 @@ static inline int netif_needs_gso(struct net_device *dev, struct sk_buff *skb)
 }
 
 /* On bonding slaves other than the currently active slave, suppress
- * duplicates except for 802.3ad ETH_P_SLOW and alb non-mcast/bcast.
+ * duplicates except for 802.3ad ETH_P_SLOW, alb non-mcast/bcast, and
+ * ARP on active-backup slaves with arp_validate enabled.
  */
 static inline int skb_bond_should_drop(struct sk_buff *skb)
 {
@@ -1025,6 +1026,10 @@ static inline int skb_bond_should_drop(struct sk_buff *skb)
 
         if (master &&
             (dev->priv_flags & IFF_SLAVE_INACTIVE)) {
+                if ((dev->priv_flags & IFF_SLAVE_NEEDARP) &&
+                    skb->protocol == __constant_htons(ETH_P_ARP))
+                        return 0;
+
                 if (master->priv_flags & IFF_MASTER_ALB) {
                         if (skb->pkt_type != PACKET_BROADCAST &&
                             skb->pkt_type != PACKET_MULTICAST)