The patch main to fix the below circumstance:
Bonding  run in Active-Backup mode.
Out PC --> switcher
             port A --> eth0 --> bond0 --> xenbr0 --> netbackend --> DomU
             port B -- eth1 /
Or

Out PC (R)--> switcher A --> eth0 --> bond0 --> xenbr0 --> netbackend 
--> DomU
             \ switcher B -- eth1 /

When Switcher Port A (active port) don't reach, or switcher A don't reach,
the surroundings will changed to the below circumstance.
Out PC --> switcher
             port A -X- eth0 -- bond0 -- xenbr0 -- netbackend -- DomU
             port B -- eth1 /
Or

Out PC (R)--> switcher A -X- eth0 -- bond0 -- xenbr0 -- netbackend -- DomU
             \ switcher B -- eth1 /

So, the former traffic will be unreachable before find the correct path 
(by sending
ARP request).

So, the patch is main to found the bonding change event, and gratutious 
ARP initialtivly
to out PC find the correct path.

the correct path should be the below circumstance:
Out PC --> switcher
             port A -X- eth0 --> bond0 --> xenbr0 --> netbackend --> DomU
             port B --> eth1 /
Or

Out PC (R)--> switcher A -X- eth0 --> bond0 --> xenbr0 --> netbackend 
--> DomU
             \ switcher B --> eth1 /

Thanks,
Jason