in6_matchlen
blen = in6_matchlen(&besta->ia_addr.sin6_addr, dst);
tlen = in6_matchlen(IFA_IN6(ifa), dst);
new_matchlen = in6_matchlen(&ia->ia_addr.sin6_addr, &dst);
in6_matchlen(&ia_best->ia_addr.sin6_addr,
int in6_matchlen(struct in6_addr *, struct in6_addr *);