icmp6_send() is too expensive

As mentioned here:
https://www.spinics.net/lists/netdev/msg505054.html

icmp6_send() can be expensive when there are a lot of devices and
anycast addresses. One solution I've prototyped is adding a global
hash table to store and allow more efficient searches for anycast
addresses.  This works and prevents the long delays I've seen when
many neighbors are invalidated in large numbers.

A colleague mentioned that another alternative may be to do something
like an rt6_lookup on the address and check for the RTF_ANYCAST flag.
This is much simpler, and I'm in the process of testing it now.

Is there any preference or recommendation as to which way to proceed
before I submit a patch?

Thanks,
Jeff