From 9b8a97db9ec4b795e29e72289005fbc58484ebeb Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Tue, 9 Apr 2024 15:14:35 +0200 Subject: Adding upstream version 6.8.0. Signed-off-by: Daniel Baumann --- lib/ax25_ntop.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) create mode 100644 lib/ax25_ntop.c (limited to 'lib/ax25_ntop.c') diff --git a/lib/ax25_ntop.c b/lib/ax25_ntop.c new file mode 100644 index 0000000..3a72a43 --- /dev/null +++ b/lib/ax25_ntop.c @@ -0,0 +1,82 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ + +#include +#include +#include + +#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; +} -- cgit v1.2.3