/* AX.25 datagram (address) sub-layer definitions */

/* Maximum number of digipeaters */
#define	MAXDIGIS	7	/* 7 digipeaters plus src/dest */
#define	ALEN		6	/* Number of chars in callsign field */
#define	AXALEN		7	/* Total AX.25 address length, including SSID */

/* Internal representation of an AX.25 address */
struct ax25_addr {
	char call[ALEN];	
	char ssid;
#define	SSID		0x1e	/* Sub station ID */
#define	REPEATED	0x80	/* Has-been-repeated bit in repeater field */
#define	E		0x01	/* Address extension bit */
#define	C		0x80	/* Command/response designation */
};
#define	NULLAXADDR	(struct ax25_addr *)0
/* Our AX.25 address */
extern struct ax25_addr mycall;

/* AX.25 broadcast address: "QST   -0" in shifted ASCII */
extern struct ax25_addr ax25_bdcst;

/* Internal representation of an AX.25 header */
struct ax25 {
	struct ax25_addr dest;			/* Destination address */
	struct ax25_addr source;		/* Source address */
	struct ax25_addr digis[MAXDIGIS];	/* Digi string */
	int ndigis;				/* Number of digipeaters */
	int cmdrsp;				/* Command/response */
};

/* C-bit stuff */
#define	UNKNOWN		0
#define	COMMAND		1
#define	RESPONSE	2

/* Bit fields in AX.25 Level 3 Protocol IDs (PIDs)
 * The high order two bits control multi-frame messages.
 * The lower 6 bits is the actual PID. Single-frame messages are
 * sent with both the FIRST and LAST bits set, so that the resulting PIDs
 * are compatible with older code.
 */
#define	PID_FIRST	0x80	/* Frame is first in a message */
#define	PID_LAST	0x40	/* Frame is last in a message */
#define	PID_PID		0x3f	/* Protocol ID subfield */

#define	PID_IP		0x0c	/* ARPA Internet Protocol */
#define	PID_ARP		0x0d	/* ARPA Address Resolution Protocol */
#define	PID_NETROM	0x0f	/* NET/ROM */
#define	PID_NO_L3	0x30	/* No level 3 protocol */