/*************************************************************************
 *
 * Copyright (C) 2018-2020 Ruilin Peng (Nick) <pymumu@gmail.com>.
 *
 * smartdns is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * smartdns is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef _DNS_HEAD_H
#define _DNS_HEAD_H

#define DNS_RR_A_LEN 4
#define DNS_RR_AAAA_LEN 16
#define DNS_MAX_CNAME_LEN 256
#define DNS_MAX_OPT_LEN 256
#define DNS_IN_PACKSIZE (512 * 4)
#define DNS_PACKSIZE (512 * 10)
#define DNS_DEFAULT_PACKET_SIZE 512

#define DNS_ADDR_FAMILY_IP 1
#define DNS_ADDR_FAMILY_IPV6 2

typedef enum dns_qr {
	DNS_QR_QUERY = 0,
	DNS_QR_ANSWER = 1,
} dns_qr;

typedef enum dns_rr_type {
	DNS_RRS_QD = 0,
	DNS_RRS_AN = 1,
	DNS_RRS_NS = 2,
	DNS_RRS_NR = 3,
	DNS_RRS_OPT = 4,
	DNS_RRS_END,
} dns_rr_type;

typedef enum dns_class { DNS_C_IN = 1, DNS_C_ANY = 255 } dns_class_t;

typedef enum dns_type {
	DNS_T_A = 1,
	DNS_T_NS = 2,
	DNS_T_CNAME = 5,
	DNS_T_SOA = 6,
	DNS_T_PTR = 12,
	DNS_T_MX = 15,
	DNS_T_TXT = 16,
	DNS_T_AAAA = 28,
	DNS_T_SRV = 33,
	DNS_T_OPT = 41,
	DNS_T_SSHFP = 44,
	DNS_T_SPF = 99,
	DNS_T_AXFR = 252,
	DNS_T_ALL = 255
} dns_type_t;

typedef enum dns_opt_code { 
	DNS_OPT_T_ECS = 8, 
	DNS_OPT_T_TCP_KEEPALIVE = 11,
	DNS_OPT_T_ALL = 255 
} dns_opt_code_t;

typedef enum dns_opcode {
	DNS_OP_QUERY = 0,
	DNS_OP_IQUERY = 1,
	DNS_OP_STATUS = 2,
	DNS_OP_NOTIFY = 4,
	DNS_OP_UPDATE = 5,
} dns_opcode_t; /* dns_opcode */

typedef enum dns_rtcode {
	DNS_RC_NOERROR = 0,
	DNS_RC_FORMERR = 1,
	DNS_RC_SERVFAIL = 2,
	DNS_RC_NXDOMAIN = 3,
	DNS_RC_NOTIMP = 4,
	DNS_RC_REFUSED = 5,
	DNS_RC_YXDOMAIN = 6,
	DNS_RC_YXRRSET = 7,
	DNS_RC_NXRRSET = 8,
	DNS_RC_NOTAUTH = 9,
	DNS_RC_NOTZONE = 10,
	/* EDNS(0) extended RCODEs */
	DNS_RC_BADVERS = 16,
} dns_rtcode_t; /* dns_rcode */

/* dns packet head */
struct dns_head {
	unsigned short id;      /* identification number */
	unsigned short qr;      /* Query/Response Flag */
	unsigned short opcode;  /* Operation Code */
	unsigned char aa;       /* Authoritative Answer Flag */
	unsigned char tc;       /* Truncation Flag */
	unsigned char rd;       /* Recursion Desired */
	unsigned char ra;       /* Recursion Available */
	unsigned short rcode;   /* Response Code */
	unsigned short qdcount; /* number of question entries */
	unsigned short ancount; /* number of answer entries */
	unsigned short nscount; /* number of authority entries */
	unsigned short nrcount; /* number of addititional resource entries */
} __attribute__((packed));

struct dns_rrs {
	unsigned short next;
	unsigned short len;
	dns_type_t type;
	unsigned char data[0];
};

/* packet haed */
struct dns_packet {
	struct dns_head head;
	unsigned short questions;
	unsigned short answers;
	unsigned short nameservers;
	unsigned short additional;
	unsigned short optcount;
	unsigned short optional;
	unsigned short payloadsize;
	int size;
	int len;
	unsigned char data[0];
};

/* RRS encode/decode context */
struct dns_data_context {
	unsigned char *data;
	unsigned char *ptr;
	unsigned int maxsize;
};

/* packet encode/decode context */
struct dns_context {
	struct dns_packet *packet;
	unsigned char *data;
	unsigned int maxsize;
	unsigned char *ptr;
};

/* SOA data */
struct dns_soa {
	char mname[DNS_MAX_CNAME_LEN];
	char rname[DNS_MAX_CNAME_LEN];
	unsigned int serial;
	unsigned int refresh;
	unsigned int retry;
	unsigned int expire;
	unsigned int minimum;
} __attribute__((packed));

#define DNS_OPT_ECS_FAMILY_IPV4 1
#define DNS_OPT_ECS_FAMILY_IPV6 2

/* OPT ECS */
struct dns_opt_ecs {
	unsigned short family;
	unsigned char source_prefix;
	unsigned char scope_prefix;
	unsigned char addr[DNS_RR_AAAA_LEN];
};

/* OPT */
struct dns_opt {
	unsigned short code;
	unsigned short length;
	unsigned char data[0];
} __attribute__((packed));

struct dns_rrs *dns_get_rrs_next(struct dns_packet *packet, struct dns_rrs *rrs);
struct dns_rrs *dns_get_rrs_start(struct dns_packet *packet, dns_rr_type type, int *count);

/*
 * Question
 */
int dns_add_domain(struct dns_packet *packet, char *domain, int qtype, int qclass);
int dns_get_domain(struct dns_rrs *rrs, char *domain, int maxsize, int *qtype, int *qclass);

/*
 * Answers
 */
int dns_add_CNAME(struct dns_packet *packet, dns_rr_type type, char *domain, int ttl, char *cname);
int dns_get_CNAME(struct dns_rrs *rrs, char *domain, int maxsize, int *ttl, char *cname, int cname_size);

int dns_add_A(struct dns_packet *packet, dns_rr_type type, char *domain, int ttl, unsigned char addr[DNS_RR_A_LEN]);
int dns_get_A(struct dns_rrs *rrs, char *domain, int maxsize, int *ttl, unsigned char addr[DNS_RR_A_LEN]);

int dns_add_PTR(struct dns_packet *packet, dns_rr_type type, char *domain, int ttl, char *cname);
int dns_get_PTR(struct dns_rrs *rrs, char *domain, int maxsize, int *ttl, char *cname, int cname_size);

int dns_add_AAAA(struct dns_packet *packet, dns_rr_type type, char *domain, int ttl, unsigned char addr[DNS_RR_AAAA_LEN]);
int dns_get_AAAA(struct dns_rrs *rrs, char *domain, int maxsize, int *ttl, unsigned char addr[DNS_RR_AAAA_LEN]);

int dns_add_SOA(struct dns_packet *packet, dns_rr_type type, char *domain, int ttl, struct dns_soa *soa);
int dns_get_SOA(struct dns_rrs *rrs, char *domain, int maxsize, int *ttl, struct dns_soa *soa);

int dns_add_NS(struct dns_packet *packet, dns_rr_type type, char *domain, int ttl, char *cname);
int dns_get_NS(struct dns_rrs *rrs, char *domain, int maxsize, int *ttl, char *cname, int cname_size);

int dns_set_OPT_payload_size(struct dns_packet *packet, int payload_size);
int dns_get_OPT_payload_size(struct dns_packet *packet);

int dns_add_OPT_ECS(struct dns_packet *packet, struct dns_opt_ecs *ecs);
int dns_get_OPT_ECS(struct dns_rrs *rrs, unsigned short *opt_code, unsigned short *opt_len, struct dns_opt_ecs *ecs);

int dns_add_OPT_TCP_KEEYALIVE(struct dns_packet *packet, unsigned short timeout);
int dns_get_OPT_TCP_KEEYALIVE(struct dns_rrs *rrs, unsigned short *opt_code, unsigned short *opt_len, unsigned short *timeout);
/*
 * Packet operation
 */
int dns_decode(struct dns_packet *packet, int maxsize, unsigned char *data, int size);
int dns_encode(unsigned char *data, int size, struct dns_packet *packet);

int dns_packet_init(struct dns_packet *packet, int size, struct dns_head *head);

#endif
