#ifndef __LTSM_H_
#define __LTSM_H_

#ifdef __cplusplus
extern "C"
{
#endif

/*
	LTSM 	: Light TCP State Machine.
	Version	: 2018-01-16
*/

/* RFC标准TCP协议栈状态机定义 */
enum full_tcp_state{
	FTSM_VOID,    /* 如果一个流的第一个包不是SYN包, 返回此值 */
	FTSM_SYN_SENT,
	FTSM_SYN_RCVD,
	FTSM_ESTABLISHED,
	FTSM_FIN_WAIT,
	FTSM_CLOSE_WAIT,
	FTSM_LAST_ACK,
	FTSM_TIME_WAIT,
	FTSM_CLOSED,
	FTSM_LISTEN,
	__FTSM_MAX,
};

/* 
	轻量TCP状态机定义, 
	实际只有三种状态:新建连接, 传输数据, 结束连接, 
	每个流必定包括1个START和1个CLOSE状态, 可能包括0或若干个DATA状态.
	
	VOID状态用于调用者快速判断是否需要创建新流.
*/
enum light_tcp_state{
	LTSM_VOID,   /* 如果一个流的第一个包不是SYN包, 返回此值 */
	LTSM_START,
	LTSM_DATA,
	LTSM_CLOSE,
};

struct ltsm_iphdr
  {
#if __BYTE_ORDER == __LITTLE_ENDIAN
    unsigned int ip_hl:4;		/* header length */
    unsigned int ip_v:4;		/* version */
#endif
#if __BYTE_ORDER == __BIG_ENDIAN
    unsigned int ip_v:4;		/* version */
    unsigned int ip_hl:4;		/* header length */
#endif
    u_int8_t ip_tos;			/* type of service */
    u_short ip_len;			/* total length */
    u_short ip_id;			/* identification */
    u_short ip_off;			/* fragment offset field */
#define	IP_RF 0x8000			/* reserved fragment flag */
#define	IP_DF 0x4000			/* dont fragment flag */
#define	IP_MF 0x2000			/* more fragments flag */
#define	IP_OFFMASK 0x1fff		/* mask for fragmenting bits */
    u_int8_t ip_ttl;			/* time to live */
    u_int8_t ip_p;			/* protocol */
    u_short ip_sum;			/* checksum */
    struct in_addr ip_src, ip_dst;	/* source and dest address */
  };
  
struct ltsm_tcphdr
  {
    u_int16_t th_sport;		/* source port */
    u_int16_t th_dport;		/* destination port */
    u_int32_t th_seq;		/* sequence number */
    u_int32_t th_ack;		/* acknowledgement number */
#  if __BYTE_ORDER == __LITTLE_ENDIAN
    u_int8_t th_x2:4;		/* (unused) */
    u_int8_t th_off:4;		/* data offset */
#  endif
#  if __BYTE_ORDER == __BIG_ENDIAN
    u_int8_t th_off:4;		/* data offset */
    u_int8_t th_x2:4;		/* (unused) */
#  endif
    u_int8_t th_flags;
#  define TH_FIN	0x01
#  define TH_SYN	0x02
#  define TH_RST	0x04
#  define TH_PUSH	0x08
#  define TH_ACK	0x10
#  define TH_URG	0x20
    u_int16_t th_win;		/* window */
    u_int16_t th_sum;		/* checksum */
    u_int16_t th_urp;		/* urgent pointer */
};

struct ltsm_result{
	enum full_tcp_state fstate;
	enum light_tcp_state lstate;
};

typedef void * ltsm_stream_handle;

ltsm_stream_handle ltsm_create_handle(void);

#define LTSM_DIR_C2S  0
#define LTSM_DIR_S2C  1

struct ltsm_result ltsm_get_current_state(ltsm_stream_handle pltsm, uint8_t tcp_flags, uint8_t dir);

const char *ltsm_fstate_ntop(enum full_tcp_state fstate);
const char *ltsm_lstate_ntop(enum light_tcp_state lstate);

void ltsm_destroy_handle(ltsm_stream_handle pltsm);

#ifdef __cplusplus
}
#endif

#endif