bonding: introduce primary_reselect option

In some cases there is not desirable to switch back to primary interface when
it's link recovers and rather stay with currently active one. We need to avoid
packetloss as much as we can in some cases. This is solved by introducing
primary_reselect option. Note that enslaved primary slave is set as current
active no matter what.

Patch modified by Jay Vosburgh as follows: fixed bug in action
after change of option setting via sysfs, revised the documentation
update, and bumped the bonding version number.

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 41 insertions, 1 deletions

diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt
index d5181ce9ff62..61f516b135b4 100644
--- a/Documentation/networking/bonding.txt
+++ b/Documentation/networking/bonding.txt
@@ -1,7 +1,7 @@
 
                 Linux Ethernet Bonding Driver HOWTO
 
-                Latest update: 12 November 2007
+                Latest update: 23 September 2009
 
 Initial release : Thomas Davis <tadavis at lbl.gov>
 Corrections, HA extensions : 2000/10/03-15 :
@@ -614,6 +614,46 @@ primary
 
         The primary option is only valid for active-backup mode.
 
+primary_reselect
+
+        Specifies the reselection policy for the primary slave.  This
+        affects how the primary slave is chosen to become the active slave
+        when failure of the active slave or recovery of the primary slave
+        occurs.  This option is designed to prevent flip-flopping between
+        the primary slave and other slaves.  Possible values are:
+
+        always or 0 (default)
+
+                The primary slave becomes the active slave whenever it
+                comes back up.
+
+        better or 1
+
+                The primary slave becomes the active slave when it comes
+                back up, if the speed and duplex of the primary slave is
+                better than the speed and duplex of the current active
+                slave.
+
+        failure or 2
+
+                The primary slave becomes the active slave only if the
+                current active slave fails and the primary slave is up.
+
+        The primary_reselect setting is ignored in two cases:
+
+                If no slaves are active, the first slave to recover is
+                made the active slave.
+
+                When initially enslaved, the primary slave is always made
+                the active slave.
+
+        Changing the primary_reselect policy via sysfs will cause an
+        immediate selection of the best active slave according to the new
+        policy.  This may or may not result in a change of the active
+        slave, depending upon the circumstances.
+
+        This option was added for bonding version 3.6.0.
+
 updelay
 
         Specifies the time, in milliseconds, to wait before enabling a