ax25_pad.h

/*-------------------------------------------------------------------
 *
 * Name:	ax25_pad.h
 *
 * Purpose:	Header file for using ax25_pad.c
 *
 *------------------------------------------------------------------*/

#ifndef AX25_PAD_H
#define AX25_PAD_H 1


#define AX25_MAX_REPEATERS 8
#define AX25_MIN_ADDRS 2	/* Destinatin & Source. */
#define AX25_MAX_ADDRS 10	/* Destination, Source, 8 digipeaters. */	

#define AX25_DESTINATION  0	/* Address positions in frame. */
#define AX25_SOURCE       1	
#define AX25_REPEATER_1   2
#define AX25_REPEATER_2   3
#define AX25_REPEATER_3   4
#define AX25_REPEATER_4   5
#define AX25_REPEATER_5   6
#define AX25_REPEATER_6   7
#define AX25_REPEATER_7   8
#define AX25_REPEATER_8   9

#define AX25_MAX_ADDR_LEN 12	/* In theory, you would expect the maximum length */
				/* to be 6 letters, dash, 2 digits, and nul for a */
				/* total of 10.  However, object labels can be 10 */
				/* characters so throw in a couple extra bytes */
				/* to be safe. */

#define AX25_MIN_INFO_LEN 0	/* Previously 1 when considering only APRS. */
				
#define AX25_MAX_INFO_LEN 2048	/* Maximum size for APRS. */
				/* AX.25 starts out with 256 as the default max */
				/* length but the end stations can negotiate */
				/* something different. */
				/* version 0.8:  Change from 256 to 2028 to */
				/* handle the larger paclen for Linux AX25. */

				/* These don't include the 2 bytes for the */
				/* HDLC frame FCS. */

/* 
 * Previously, for APRS only.
 * #define AX25_MIN_PACKET_LEN ( 2 * 7 + 2 + AX25_MIN_INFO_LEN)
 * #define AX25_MAX_PACKET_LEN ( AX25_MAX_ADDRS * 7 + 2 + AX25_MAX_INFO_LEN)
 */

/* The more general case. */
/* An AX.25 frame can have a control byte and no protocol. */

#define AX25_MIN_PACKET_LEN ( 2 * 7 + 1 )

#define AX25_MAX_PACKET_LEN ( AX25_MAX_ADDRS * 7 + 2 + 3 + AX25_MAX_INFO_LEN)


/*
 * packet_t is a pointer to a packet object.
 *
 * The actual implementation is not visible outside ax25_pad.c.
 */

#define AX25_UI_FRAME 3		/* Control field value. */

#define AX25_PID_NO_LAYER_3 0xf0		/* protocol ID used for APRS */
#define AX25_PID_SEGMENTATION_FRAGMENT 0x08
#define AX25_PID_ESCAPE_CHARACTER 0xff


#ifdef AX25_PAD_C	/* Keep this hidden - implementation could change. */

struct packet_s {

	int magic1;		/* for error checking. */

	int seq;		/* unique sequence number for debugging. */

	double release_time;	/* Time stamp in format returned by dtime_now(). */
				/* When to release from the SATgate mode delay queue. */

#define MAGIC 0x41583235

	struct packet_s *nextp;	/* Pointer to next in queue. */

	int num_addr;		/* Number of addresses in frame. */
				/* Range of AX25_MIN_ADDRS .. AX25_MAX_ADDRS for AX.25. */	
				/* It will be 0 if it doesn't look like AX.25. */
				/* -1 is used temporarily at allocation to mean */
				/* not determined yet. */



				/* 
 				 * The 7th octet of each address contains:
			         *
				 * Bits:   H  R  R  SSID  0
				 *
				 *   H 		for digipeaters set to 0 intially.
				 *		Changed to 1 when position has been used.
 				 *
				 *		for source & destination it is called
				 *		command/response.  Normally both 1 for APRS.
				 *		They should be opposites for connected mode.
				 *
				 *   R	R	Reserved.  Normally set to 1 1.
				 *
				 *   SSID	Substation ID.  Range of 0 - 15.
				 *
				 *   0		Usually 0 but 1 for last address.
				 */


#define SSID_H_MASK	0x80
#define SSID_H_SHIFT	7

#define SSID_RR_MASK	0x60
#define SSID_RR_SHIFT	5

#define SSID_SSID_MASK	0x1e
#define SSID_SSID_SHIFT	1

#define SSID_LAST_MASK	0x01


	int frame_len;		/* Frame length without CRC. */

	int modulo;		/* I & S frames have sequence numbers of either 3 bits (modulo 8) */
				/* or 7 bits (modulo 128).  This is conveyed by either 1 or 2 */
				/* control bytes.  Unfortunately, we can't determine this by looking */
				/* at an isolated frame.  We need to know about the context.  If we */
				/* are part of the conversation, we would know.  But if we are */
				/* just listening to others, this would be more difficult to determine. */

				/* For U frames:   	set to 0 - not applicable */
				/* For I & S frames:	8 or 128 if known.  0 if unknown. */

	unsigned char frame_data[AX25_MAX_PACKET_LEN+1];
				/* Raw frame contents, without the CRC. */
				

	int magic2;		/* Will get stomped on if above overflows. */
};




#else			/* Public view. */

struct packet_s {
	int secret;
};

#endif


typedef struct packet_s *packet_t;

typedef enum cmdres_e { cr_00 = 2, cr_cmd = 1, cr_res = 0, cr_11 = 3 } cmdres_t;


extern packet_t ax25_new (void);


#ifdef AX25_PAD_C	/* Keep this hidden - implementation could change. */


/*
 * APRS always has one control octet of 0x03 but the more
 * general AX.25 case is one or two control bytes depending on
 * whether "modulo 128 operation" is in effect.
 */

//#define DEBUGX 1

static inline int ax25_get_control_offset (packet_t this_p) 
{
	return (this_p->num_addr*7);
}

static inline int ax25_get_num_control (packet_t this_p)
{
	int c;

	c = this_p->frame_data[ax25_get_control_offset(this_p)];

	if ( (c & 0x01) == 0 ) {			/* I   xxxx xxx0 */
#if DEBUGX
	  dw_printf ("ax25_get_num_control, %02x is I frame, returns %d\n", c, (this_p->modulo == 128) ? 2 : 1);
#endif
	  return ((this_p->modulo == 128) ? 2 : 1);
	}

	if ( (c & 0x03) == 1 ) {			/* S   xxxx xx01 */
#if DEBUGX
	  dw_printf ("ax25_get_num_control, %02x is S frame, returns %d\n", c, (this_p->modulo == 128) ? 2 : 1);
#endif
	  return ((this_p->modulo == 128) ? 2 : 1);
	}

#if DEBUGX
	dw_printf ("ax25_get_num_control, %02x is U frame, always returns 1.\n", c);
#endif

	return (1);					/* U   xxxx xx11 */
}



/*
 * APRS always has one protocol octet of 0xF0 meaning no level 3
 * protocol but the more general case is 0, 1 or 2 protocol ID octets.
 */

static inline int ax25_get_pid_offset (packet_t this_p) 
{
	return (ax25_get_control_offset (this_p) + ax25_get_num_control(this_p));
}

static int ax25_get_num_pid (packet_t this_p)
{
	int c;
	int pid;

	c = this_p->frame_data[ax25_get_control_offset(this_p)];

	if ( (c & 0x01) == 0 ||				/* I   xxxx xxx0 */
	     c == 0x03 || c == 0x13) {			/* UI  000x 0011 */

	  pid = this_p->frame_data[ax25_get_pid_offset(this_p)];
#if DEBUGX
	  dw_printf ("ax25_get_num_pid, %02x is I or UI frame, pid = %02x, returns %d\n", c, pid, (pid==AX25_PID_ESCAPE_CHARACTER) ? 2 : 1);
#endif
	  if (pid == AX25_PID_ESCAPE_CHARACTER) {
	    return (2);			/* pid 1111 1111 means another follows. */
	  }
	  return (1);		
	}
#if DEBUGX
	dw_printf ("ax25_get_num_pid, %02x is neither I nor UI frame, returns 0\n", c);
#endif
	return (0);
}


/*
 * AX.25 has info field for 5 frame types depending on the control field.
 *
 *	xxxx xxx0	I
 *	000x 0011	UI		(which includes APRS)
 *	101x 1111	XID
 *	111x 0011	TEST
 *	100x 0111	FRMR
 *
 * APRS always has an Information field with at least one octet for the Data Type Indicator.  
 */

static inline int ax25_get_info_offset (packet_t this_p) 
{
	int offset = ax25_get_control_offset (this_p) + ax25_get_num_control(this_p) + ax25_get_num_pid(this_p);
#if DEBUGX
	dw_printf ("ax25_get_info_offset, returns %d\n", offset);
#endif
	return (offset);
}

static inline int ax25_get_num_info (packet_t this_p)
{
	int len;
	
	/* assuming AX.25 frame. */

	len = this_p->frame_len - this_p->num_addr * 7 - ax25_get_num_control(this_p) - ax25_get_num_pid(this_p);
	if (len < 0) {
	  len = 0;		/* print error? */
	}

	return (len);
}

#endif


typedef enum ax25_modulo_e { modulo_unknown = 0, modulo_8 = 8, modulo_128 = 128 } ax25_modulo_t;

typedef enum ax25_frame_type_e {

	frame_type_I = 0,	// Information

	frame_type_S_RR,	// Receive Ready - System Ready To Receive
	frame_type_S_RNR,	// Receive Not Ready - TNC Buffer Full
	frame_type_S_REJ,	// Reject Frame - Out of Sequence or Duplicate
	frame_type_S_SREJ,	// Selective Reject - Request single frame repeat

	frame_type_U_SABME,	// Set Async Balanced Mode, Extended
	frame_type_U_SABM,	// Set Async Balanced Mode
	frame_type_U_DISC,	// Disconnect
	frame_type_U_DM,	// Disconnect Mode
	frame_type_U_UA,	// Unnumbered Acknowledge
	frame_type_U_FRMR,	// Frame Reject
	frame_type_U_UI,	// Unnumbered Information
	frame_type_U_XID,	// Exchange Identification
	frame_type_U_TEST,	// Test
	frame_type_U,		// other Unnumbered, not used by AX.25.

	frame_not_AX25		// Could not get control byte from frame.
				// This must be last because value plus 1 is
				// for the size of an array.

} ax25_frame_type_t;
	

/* 
 * Originally this was a single number. 
 * Let's try something new in version 1.2.
 * Also collect AGC values from the mark and space filters.
 */

typedef struct alevel_s {

	int rec;
	int mark;
	int space;
	//float ms_ratio;	// TODO: take out after temporary investigation.
} alevel_t;


#ifndef AXTEST
// TODO: remove this?
#define AX25MEMDEBUG 1
#endif


#if AX25MEMDEBUG	// to investigate a memory leak problem


extern void ax25memdebug_set(void);
extern int ax25memdebug_get (void);
extern int ax25memdebug_seq (packet_t this_p);


extern packet_t ax25_from_text_debug (char *monitor, int strict, char *src_file, int src_line);
#define ax25_from_text(m,s) ax25_from_text_debug(m,s,__FILE__,__LINE__)

extern packet_t ax25_from_frame_debug (unsigned char *data, int len, alevel_t alevel, char *src_file, int src_line);
#define ax25_from_frame(d,l,a) ax25_from_frame_debug(d,l,a,__FILE__,__LINE__);

extern packet_t ax25_dup_debug (packet_t copy_from, char *src_file, int src_line);
#define ax25_dup(p) ax25_dup_debug(p,__FILE__,__LINE__);

extern void ax25_delete_debug (packet_t pp, char *src_file, int src_line);
#define ax25_delete(p) ax25_delete_debug(p,__FILE__,__LINE__);

#else

extern packet_t ax25_from_text (char *monitor, int strict);

extern packet_t ax25_from_frame (unsigned char *data, int len, alevel_t alevel);

extern packet_t ax25_dup (packet_t copy_from);

extern void ax25_delete (packet_t pp);

#endif




extern int ax25_parse_addr (int position, char *in_addr, int strict, char *out_addr, int *out_ssid, int *out_heard);
extern int ax25_check_addresses (packet_t pp);

extern packet_t ax25_unwrap_third_party (packet_t from_pp);

extern void ax25_set_addr (packet_t pp, int, char *);
extern void ax25_insert_addr (packet_t this_p, int n, char *ad);
extern void ax25_remove_addr (packet_t this_p, int n);

extern int ax25_get_num_addr (packet_t pp);
extern int ax25_get_num_repeaters (packet_t this_p);

extern void ax25_get_addr_with_ssid (packet_t pp, int n, char *station);
extern void ax25_get_addr_no_ssid (packet_t pp, int n, char *station);

extern int ax25_get_ssid (packet_t pp, int n);
extern void ax25_set_ssid (packet_t this_p, int n, int ssid);

extern int ax25_get_h (packet_t pp, int n);

extern void ax25_set_h (packet_t pp, int n);

extern int ax25_get_heard(packet_t this_p);

extern int ax25_get_first_not_repeated(packet_t pp);

extern int ax25_get_rr (packet_t this_p, int n);

extern int ax25_get_info (packet_t pp, unsigned char **paddr);
extern int ax25_cut_at_crlf (packet_t this_p);

extern void ax25_set_nextp (packet_t this_p, packet_t next_p);

extern int ax25_get_dti (packet_t this_p);

extern packet_t ax25_get_nextp (packet_t this_p);

extern void ax25_set_release_time (packet_t this_p, double release_time);
extern double ax25_get_release_time (packet_t this_p);

extern void ax25_set_modulo (packet_t this_p, int modulo);

extern void ax25_format_addrs (packet_t pp, char *);
extern void ax25_format_via_path (packet_t this_p, char *result, size_t result_size);

extern int ax25_pack (packet_t pp, unsigned char result[AX25_MAX_PACKET_LEN]);

extern ax25_frame_type_t ax25_frame_type (packet_t this_p, cmdres_t *cr, char *desc, int *pf, int *nr, int *ns); 

extern void ax25_hex_dump (packet_t this_p);

extern int ax25_is_aprs (packet_t pp);
extern int ax25_is_null_frame (packet_t this_p);

extern int ax25_get_control (packet_t this_p); 
extern int ax25_get_c2 (packet_t this_p); 

extern int ax25_get_pid (packet_t this_p);

extern int ax25_get_frame_len (packet_t this_p);

extern unsigned short ax25_dedupe_crc (packet_t pp);

extern unsigned short ax25_m_m_crc (packet_t pp);

extern void ax25_safe_print (char *, int, int ascii_only);

#define AX25_ALEVEL_TO_TEXT_SIZE 32	// overkill but safe.
extern int ax25_alevel_to_text (alevel_t alevel, char text[AX25_ALEVEL_TO_TEXT_SIZE]);


#endif /* AX25_PAD_H */

/* end ax25_pad.h */