rem: if (l == -1) return addr_to_numeric(addrp);
add: if (l == -1) { strcpy(buf, "/"); strcat(buf, addr_to_numeric(addrp)); return buf; }
context: mask_to_numeric(const struct in6_addr *addrp){	static char buf[20];	int l = ipv6_prefix_length(addrp);	if (l == -1)		return addr_to_numeric(addrp);	sprintf(buf, "/%d", l);	return buf;}