// DHCP message formatstruct DHCP_MESSAGE{   union   {      char buffer[1];      u_int8_t msg_type;		// Message type   } u_msg_type;	   union   {      char buffer[4];      u_int32_t trans_id;		// Transaction ID   } u_trans_id;	   struct OPTIONS *opt;			// Pointer to OPTIONS structure};// Options formatstruct OPTIONS{   union   {      char buffer[2];      u_int16_t opt_code;		// Type of option   } u_opt_code;   union   {      char buffer[2];      u_int16_t opt_len;		// Length of option data (in octets)   } u_opt_len;	   void *opt_data;			// Pointer to option data structure   };   // DUID structurestruct DUID{   union				// Duid type   {	char buffer[2];	u_int16_t duid_type;   } u_duid_type;   void *duid_type;			// Pointer to duid type structure   struct OPTIONS *opt;			// Pointer to next option};//DUID type 1struct DUID1{    union    {	char buffer[2];	u_int16_t haddr_type;		// Hardware type    } u_haddr_type;       union    {	char buffer[4];        u_int32_t time;			// Statically generated time value    } u_time;       u_int16_t haddr_len;			// Hardware address length      u_int8_t *link_layer_address;	// Hardware address};//DUID type 2struct DUID2{   union   {	char buffer[2];	u_int16_t identifier_length;	// Identifier length   } u_identifier_length;      int domain_name_len;   u_int8_t *identifier;		// Identifier   char *domain_name;			// Domain name};//DUID type 3struct DUID3{   union   {	char buffer[2];	u_int16_t haddr_type;		// Hardware type   } u_haddr_type;   u_int16_t haddr_len;			// Hardware address length      u_int8_t *link_layer_address;	// Hardware address};// IA option structurestruct IA{   union   {	char buffer[4];	u_int32_t iaid;			// IAID   } u_iaid;      union   {	char buffer[4];	u_int32_t t1;			// T1   } u_t1;   union   {	char buffer[4];	u_int32_t t2;			// T2   } u_t2;   u_int8_t status;			// IA status code   struct OPTIONS *opt;			// Pointer to IA Address option structur					// e};// IA Address option structurestruct IA_ADDRESS{   int t_bit;				// (Temporary address or not) 1 BIT   char addr_status;			// (Status of the address) 7 BITS   u_int8_t prefix_length;		// Prefix length of the address   u_int8_t addr[16];			// IPv6 address   union   {	char buffer[4];	u_int32_t pref_lifetime;	// Preferred lifetime   } u_pref_lifetime;   union   {	char buffer[4];	u_int32_t valid_lifetime;	// Valid lifetime   } u_valid_lifetime;   void *ia_addr_opt;			// IA Address options = NULL (for now)   struct OPTIONS *opt;			// Pointer to next option};// Preference optionstruct PREFERENCE{    u_int8_t preference_value;		// The server preference value    struct OPTIONS *opt;};// Status code optionstruct STATUS_CODE{   union   {	char buffer[2];	u_int16_t status_code;		// Status code   } u_status_code;      char *message;			// Status message   struct OPTIONS *opt;			// Pointer to next option};// Interface details structurestruct interface{    u_int16_t duid_type, identifier_length;    u_int32_t time;    u_int16_t haddr_type, haddr_len;    u_int8_t *haddr, *identifier;    int domain_name_len;        char *domain_name;    struct in6_addr *link_local_addr;        // Optional hints for values        struct in6_addr *pref_ipv6_addr;    u_int32_t pref_lifetime, valid_lifetime;};