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/* SPDX-License-Identifier: GPL-2.0+ */
#include <errno.h>
#include <sys/socket.h>
#include <linux/ax25.h>
#include "utils.h"
const char *ax25_ntop1(const ax25_address *src, char *dst, socklen_t size);
/*
* AX.25 addresses are based on Amateur radio callsigns followed by an SSID
* like XXXXXX-SS where the callsign consists of up to 6 ASCII characters
* which are either letters or digits and the SSID is a decimal number in the
* range 0..15.
* Amateur radio callsigns are assigned by a country's relevant authorities
* and are 3..6 characters though a few countries have assigned callsigns
* longer than that. AX.25 is not able to handle such longer callsigns.
* There are further restrictions on the format of valid callsigns by
* applicable national and international law. Linux doesn't need to care and
* will happily accept anything that consists of 6 ASCII characters in the
* range of A-Z and 0-9 for a callsign such as the default AX.25 MAC address
* LINUX-1 and the default broadcast address QST-0.
* The SSID is just a number and not encoded in ASCII digits.
*
* Being based on HDLC AX.25 encodes addresses by shifting them one bit left
* thus zeroing bit 0, the HDLC extension bit for all but the last bit of
* a packet's address field but for our purposes here we're not considering
* the HDLC extension bit that is it will always be zero.
*
* Linux' internal representation of AX.25 addresses in Linux is very similar
* to this on the on-air or on-the-wire format. The callsign is padded to
* 6 octets by adding spaces, followed by the SSID octet then all 7 octets
* are left-shifted by one bit.
*
* For example, for the address "LINUX-1" the callsign is LINUX and SSID is 1
* the internal format is 98:92:9c:aa:b0:40:02.
*/
const char *ax25_ntop1(const ax25_address *src, char *dst, socklen_t size)
{
char c, *s;
int n;
for (n = 0, s = dst; n < 6; n++) {
c = (src->ax25_call[n] >> 1) & 0x7f;
if (c != ' ')
*s++ = c;
}
*s++ = '-';
n = ((src->ax25_call[6] >> 1) & 0x0f);
if (n > 9) {
*s++ = '1';
n -= 10;
}
*s++ = n + '0';
*s++ = '\0';
if (*dst == '\0' || *dst == '-') {
dst[0] = '*';
dst[1] = '\0';
}
return dst;
}
const char *ax25_ntop(int af, const void *addr, char *buf, socklen_t buflen)
{
switch (af) {
case AF_AX25:
errno = 0;
return ax25_ntop1((ax25_address *)addr, buf, buflen);
default:
errno = EAFNOSUPPORT;
}
return NULL;
}
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