Subject: why are IPv6 addresses removed on link down

From: David Ahern <[email-masked]>
Date: Mon, 12 Jan 2015 22:06:44 -0700

We noticed that IPv6 addresses are removed on a link down. e.g.,
   ip link set dev eth1

Looking at the code it appears to be this code path in addrconf.c:

         case NETDEV_DOWN:
         case NETDEV_UNREGISTER:
                 /*
                  *      Remove all addresses from this interface.
                  */
                 addrconf_ifdown(dev, event != NETDEV_DOWN);
                 break;

IPv4 addresses are NOT removed on a link down. Is there a particular 
reason IPv6 addresses are?

Thanks,
David