bonding: send IPv6 neighbor advertisement on failover

This patch adds better IPv6 failover support for bonding devices,
especially when in active-backup mode and there are only IPv6 addresses
configured, as reported by Alex Sidorenko.

- Creates a new file, net/drivers/bonding/bond_ipv6.c, for the
   IPv6-specific routines.  Both regular bonds and VLANs over bonds
   are supported.

- Adds a new tunable, num_unsol_na, to limit the number of unsolicited
   IPv6 Neighbor Advertisements that are sent on a failover event.
   Default is 1.

- Creates two new IPv6 neighbor discovery functions:

   ndisc_build_skb()
   ndisc_send_skb()

   These were required to support VLANs since we have to be able to
   add the VLAN id to the skb since ndisc_send_na() and friends
   shouldn't be asked to do this.  These two routines are basically
   __ndisc_send() split into two pieces, in a slightly different order.

- Updates Documentation/networking/bonding.txt and bumps the rev of bond
   support to 3.4.0.

On failover, this new code will generate one packet:

- An unsolicited IPv6 Neighbor Advertisement, which helps the switch
   learn that the address has moved to the new slave.

Testing has shown that sending just the NA results in pretty good
behavior when in active-back mode, I saw no lost ping packets for example.

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt
index d733a428eff6..3f4d0fae7081 100644
--- a/Documentation/networking/bonding.txt
+++ b/Documentation/networking/bonding.txt
@@ -551,6 +551,16 @@ num_grat_arp
         affects only the active-backup mode.  This option was added for
         bonding version 3.3.0.
 
+num_unsol_na
+
+        Specifies the number of unsolicited IPv6 Neighbor Advertisements
+        to be issued after a failover event.  One unsolicited NA is issued
+        immediately after the failover.
+
+        The valid range is 0 - 255; the default value is 1.  This option
+        affects only the active-backup mode.  This option was added for
+        bonding version 3.4.0.
+
 primary
 
         A string (eth0, eth2, etc) specifying which slave is the