Efficient way to get IPs attached to a specific interface by index / if_index

I am interested in getting the associated IPs with an interface, but by if_index, because all I actually have is an ipi6_ifindex from IPV6_PKTINFO / IPV6_RECVPKTINFO. I could use getifaddrs but, that would return struct ifaddrs which only has an ifa_name so I'd have to get the name and do a bunch of string comparisons, and it is particularly expensive to boot. I already have the ifindex, so it feels like there should be an efficient way to get the addresses associated with the device. But I can't find any solution.