Subject: xen-netback notify DomU to send ARP.

From: jianhai luan <[email-masked]>
Date: Tue, 08 Jan 2013 19:57:17 +0800

Hi,
   When Xen Dom0's network circumstance changed, DomU
should be notified in some special condition. For
example the below circumstance:
   ping from Guest A to DomU:
   Guest A --> eth0 - bond0 - xenbr0 --VIF(DOMU)
               eth1 /
   when eth0 inactive, and eth1 active.
   Guest A --> eth0   bond0 - xenbr0 --VIF(DOMU)
               eth1 /
   Guest A will don't reach to DomU. After Guest A
   send ARP request and DomU respond, Guest A will
   reach DomU. But some more second will be elapsed.
               eth0   bond0 - xenbr0 --VIF(DOMU)
   Guest A --> eth1/

If Xen netback watch the network change, will notify
DomU by change it own status. So netfront will watch
netback's change, and DomU send ARP initiative.

Thanks,
Jason