Here are the data structures with brief descriptions:

Cstruct	A DNS query consists of a header, as described in 'struct xDNSMessage' It is followed by 1 or more queries, each one consisting of a name and a tail, with two fields: type and class
CuIntPtr	Uintptr_t is an unsigned integer type that is capable of storing a data pointer. Therefore it is safe to convert from a void pointer to a uintptr_t, using a union
CxIPv6_Couple	A util struct to list the IPv6 IP types, prefix and type bit mask
CxUnion32_t
CxUnionPtr_t