/* these structures are word aligned */
#pragma pack(push)
#pragma pack(2) 
struct vlan_tag {
        u_int16_t v_tpid;
	u_int16_t v_tci;
};

struct dhcpv6_msg {	/* [RFC3315] ch 6 */
	u_int8_t msg_type;	/* Message type */
	u_int8_t xid[3];	/* transaction-id */
	char options[];		/* options */
};


struct dhcpv6_relay_msg {	/* [RFC3315] ch 7 */
	u_int8_t msg_type;	/* Message type */
	u_int8_t hop_count;	/* hop count */
	struct in6_addr link_addr;	/* link address */
	struct in6_addr peer_addr;	/* peer address */
	char options[];		/* options */
};

struct dhcpv6_option {	/* [RFC3315] generic option */
	u_int16_t code;	/* option-code */
	u_int16_t len;	/* option-len */
	char data[];	/* any */
};

#pragma pack(pop)

static struct dhcpv6_option *nextopt(const struct dhcpv6_option *opt) {
	return (struct dhcpv6_option *)((char *)opt + sizeof(struct dhcpv6_option) + ntohs(opt->len));
}


/* all the following are ref http://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xml */

/* message types */
/* 0	Reserved */	
#define DHCPV6_SOLICIT		1	/* [RFC3315] */
#define DHCPV6_ADVERTISE	2	/* [RFC3315] */
#define DHCPV6_REQUEST		3	/* [RFC3315] */
#define DHCPV6_CONFIRM		4	/* [RFC3315] */
#define DHCPV6_RENEW		5	/* [RFC3315] */
#define DHCPV6_REBIND		6	/* [RFC3315] */
#define DHCPV6_REPLY		7	/* [RFC3315] */
#define DHCPV6_RELEASE		8	/* [RFC3315] */
#define DHCPV6_DECLINE		9	/* [RFC3315] */
#define DHCPV6_RECONFIGURE	10	/* [RFC3315] */
#define DHCPV6_INFORMATION_REQ	11	/* [RFC3315] */
#define DHCPV6_RELAY_FORW	12	/* [RFC3315] */
#define DHCPV6_RELAY_REPL	13	/* [RFC3315] */
#define DHCPV6_LEASEQUERY	14	/* [RFC5007] */
#define DHCPV6_LEASEQUERY_REPLY	15	/* [RFC5007] */
#define DHCPV6_LEASEQUERY_DONE	16	/* [RFC5460] */
#define DHCPV6_LEASEQUERY_DATA	17	/* [RFC5460] */
/* 18-255	Unassigned */

/* option codes */
/* 0	Reserved	 */
#define OPTION_CLIENTID			1	/* [RFC3315] */
#define OPTION_SERVERID	       		2	/* [RFC3315] */
#define OPTION_IA_NA			3	/* [RFC3315] */
#define OPTION_IA_TA			4	/* [RFC3315] */
#define OPTION_IAADDR			5	/* [RFC3315] */
#define OPTION_ORO			6	/* [RFC3315] */
#define OPTION_PREFERENCE		7	/* [RFC3315] */
#define OPTION_ELAPSED_TIME		8	/* [RFC3315] */
#define OPTION_RELAY_MSG		9	/* [RFC3315] */
/* 10	Unassigned	 */
#define OPTION_AUTH			11	/* [RFC3315] */
#define OPTION_UNICAST			12	/* [RFC3315] */
#define OPTION_STATUS_CODE		13	/* [RFC3315] */
#define OPTION_RAPID_COMMIT		14	/* [RFC3315] */
#define OPTION_USER_CLASS		15	/* [RFC3315] */
#define OPTION_VENDOR_CLASS		16	/* [RFC3315] */
#define OPTION_VENDOR_OPTS		17	/* [RFC3315] */
#define OPTION_INTERFACE_ID		18	/* [RFC3315] */
#define OPTION_RECONF_MSG		19	/* [RFC3315] */
#define OPTION_RECONF_ACCEPT		20	/* [RFC3315] */
/* 21	SIP Servers Domain Name List	[RFC3319] */
/* 22	SIP Servers IPv6 Address List	[RFC3319] */
/* 23	DNS Recursive Name Server Option	[RFC3646] */
/* 24	Domain Search List option	[RFC3646] */
#define OPTION_IA_PD			25	/* [RFC3633] */
#define OPTION_IAPREFIX			26	/* [RFC3633] */
#define OPTION_NIS_SERVERS		27	/* [RFC3898] */
#define OPTION_NISP_SERVERS		28	/* [RFC3898] */
#define OPTION_NIS_DOMAIN_NAME		29	/* [RFC3898] */
#define OPTION_NISP_DOMAIN_NAME		30	/* [RFC3898] */
#define OPTION_SNTP_SERVERS		31	/* [RFC4075] */
#define OPTION_INFORMATION_REFRESH_TIME	32	/* [RFC4242] */
#define OPTION_BCMCS_SERVER_D		33	/* [RFC4280] */
#define OPTION_BCMCS_SERVER_A		34	/* [RFC4280] */
/* 35	Unassigned	 */
#define OPTION_GEOCONF_CIVIC		36	/* [RFC4776] */
#define OPTION_REMOTE_ID		37	/* [RFC4649] */
#define OPTION_SUBSCRIBER_ID		38	/* [RFC4580] */
#define OPTION_CLIENT_FQDN		39	/* [RFC4704] */
#define OPTION_PANA_AGENT		40	/* [RFC5192] */
#define OPTION_NEW_POSIX_TIMEZONE      	41	/* [RFC4833] */
#define OPTION_NEW_TZDB_TIMEZONE       	42	/* [RFC4833] */
#define OPTION_ERO			43	/* [RFC4994] */
#define OPTION_LQ_QUERY			44	/* [RFC5007] */
#define OPTION_CLIENT_DATA		45	/* [RFC5007] */
#define OPTION_CLT_TIME			46	/* [RFC5007] */
#define OPTION_LQ_RELAY_DATA		47	/* [RFC5007] */
#define OPTION_LQ_CLIENT_LINK		48	/* [RFC5007] */
#define OPTION_MIP6_HNINF		49	/* [RFC-ietf-mip6-hiopt-17] */
#define OPTION_MIP6_RELAY		50	/* [RFC-ietf-mip6-hiopt-17] */
#define OPTION_V6_LOST			51	/* [RFC5223] */
#define OPTION_CAPWAP_AC_V6		52	/* [RFC5417] */
#define OPTION_RELAY_ID			53	/* [RFC5460] */
#define OPTION_IPv6_Address_MoS		54	/* [RFC5678] */
#define OPTION_IPv6_FQDN_MoS		55	/* [RFC5678] */
#define OPTION_NTP_SERVER		56	/* [RFC5908] */
#define OPTION_V6_ACCESS_DOMAIN		57	/* [RFC5986] */
#define OPTION_SIP_UA_CS_LIST		58	/* [RFC6011] */
#define OPT_BOOTFILE_URL		59	/* [RFC5970] */
#define OPT_BOOTFILE_PARAM		60	/* [RFC5970] */
#define OPTION_CLIENT_ARCH_TYPE		61	/* [RFC5970] */
#define OPTION_NII			62	/* [RFC5970] */
#define OPTION_GEOLOCATION		63	/* [RFC6225] */
#define OPTION_AFTR_NAME		64	/* [RFC6334] */
#define OPTION_ERP_LOCAL_DOMAIN_NAME   	65	/* [RFC-ietf-hokey-ldn-discovery-10] */
#define OPTION_RSOO			66	/* [RFC-ietf-dhc-dhcpv6-relay-supplied-options-09] */
/* 67-255	Unassigned */

/* Status Codes */
#define Success			0	/* [RFC3315] */
#define UnspecFail		1	/* [RFC3315] */
#define NoAddrsAvail		2	/* [RFC3315] */
#define NoBinding		3	/* [RFC3315] */
#define NotOnLink		4	/* [RFC3315] */
#define UseMulticast		5	/* [RFC3315] */
#define NoPrefixAvail		6	/* [RFC3633] */
#define UnknownQueryType		7	/* [RFC5007] */
#define MalformedQuery		8	/* [RFC5007] */
#define NotConfigured		9	/* [RFC5007] */
#define NotAllowed		10	/* [RFC5007] */
#define QueryTerminated		11	/* [RFC5460] */
/* 12-255	Unassigned */


/* DUID types */
#define DUID_LLT       	1	/* [RFC3315] */
#define DUID_EN		2	/* [RFC3315] */
#define DUID_LL		3	/* [RFC3315] */
#define DUID_UUID      	4	/* [RFC6355] */