Inefficient call to ipv6_chk_acast_addr_src in icmp6_send

Hi,

The call to ipv6_chk_acast_addr_src in icmp6_send can be pretty costly on
systems with a lot of net_devices since it can end up looping through all
net_devices in a net namespace searching for an anycast address. A few
thousand icmp6 error packets can end up consuming a whole CPU.
I am thinking of fixing this by adding a hash table along the lines of
inet6_addr_lst,
providing a fast lookup for anycast addresses. Is that the right way to go?

Thanks,

Salam