Category : Network Files
Archive   : KA9Q.ZIP
Filename : AX25.H

/* 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 */