| /* SPDX-License-Identifier: GPL-2.0+ */ |
| |
| #include <errno.h> |
| #include <sys/socket.h> |
| #include <netax25/ax25.h> |
| |
| #include "utils.h" |
| |
| /* |
| * AX.25 addresses are based on Amateur radio callsigns followed by an SSID |
| * like XXXXXX-SS where the callsign is up to 6 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. |
| * |
| * 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 byte. |
| * |
| * This for example turns "LINUX-1" where the callsign is LINUX and SSID is 1 |
| * into 98:92:9c:aa:b0:40:02. |
| */ |
| |
| static 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; |
| } |