bonding: send arp requests even if there's no route to them

Currently we're only sending arp requests if we have a route to the target
(and, thus, can find out the source ip address).

There are some use cases, however, where we don't want/need to set an ip
address (or set up a specific route) for bonding to use arp monitoring *for
traffic generation*. We can easily send arp probes (arp requests with src
ip == 0) to generate arp broadcast responses from the target ip and use
them for determining if the target is up.

This, obviously, won't work with arp validation - because we don't have the
ip address set and, thus, will filter out the responses. So in that case -
print a warning.

CC: François CACHEREUL <f.cachereul@alphalink.fr>
CC: Zhenjie Chen <zhchen@redhat.com>
CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 12948b33451a37f2db51c53e12ff1effb31b4f80..12861e37d526a4af9b44411e86be6728d887ae26 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2155,8 +2155,13 @@ static void bond_arp_send_all(struct bonding *bond, struct slave *slave)
                rt = ip_route_output(dev_net(bond->dev), targets[i], 0,
                                     RTO_ONLINK, 0);
                if (IS_ERR(rt)) {
-                       pr_debug("%s: no route to arp_ip_target %pI4\n",
-                                bond->dev->name, &targets[i]);
+                       /* there's no route to target - try to send arp
+                        * probe to generate any traffic (arp_validate=0)
+                        */
+                       if (bond->params.arp_validate && net_ratelimit())
+                               pr_warn("%s: no route to arp_ip_target %pI4 and arp_validate is set\n",
+                                       bond->dev->name, &targets[i]);
+                       bond_arp_send(slave->dev, ARPOP_REQUEST, targets[i], 0, 0);
                        continue;
                }