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8bced38a94
ax25.h isn't guaranteed to be avilable in netax25/*; it's dependent on our choice of libc (it's not available on musl at least) [0]. Let's use the version from linux-headers. [0] https://sourceware.org/glibc/wiki/Synchronizing_Headers Bug: https://bugs.gentoo.org/831102 Signed-off-by: Sam James <sam@gentoo.org> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
83 lines
2.4 KiB
C
83 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ */
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#include <errno.h>
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#include <sys/socket.h>
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#include <linux/ax25.h>
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#include "utils.h"
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const char *ax25_ntop1(const ax25_address *src, char *dst, socklen_t size);
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/*
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* AX.25 addresses are based on Amateur radio callsigns followed by an SSID
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* like XXXXXX-SS where the callsign consists of up to 6 ASCII characters
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* which are either letters or digits and the SSID is a decimal number in the
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* range 0..15.
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* Amateur radio callsigns are assigned by a country's relevant authorities
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* and are 3..6 characters though a few countries have assigned callsigns
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* longer than that. AX.25 is not able to handle such longer callsigns.
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* There are further restrictions on the format of valid callsigns by
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* applicable national and international law. Linux doesn't need to care and
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* will happily accept anything that consists of 6 ASCII characters in the
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* range of A-Z and 0-9 for a callsign such as the default AX.25 MAC address
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* LINUX-1 and the default broadcast address QST-0.
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* The SSID is just a number and not encoded in ASCII digits.
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*
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* Being based on HDLC AX.25 encodes addresses by shifting them one bit left
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* thus zeroing bit 0, the HDLC extension bit for all but the last bit of
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* a packet's address field but for our purposes here we're not considering
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* the HDLC extension bit that is it will always be zero.
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*
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* Linux' internal representation of AX.25 addresses in Linux is very similar
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* to this on the on-air or on-the-wire format. The callsign is padded to
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* 6 octets by adding spaces, followed by the SSID octet then all 7 octets
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* are left-shifted by one bit.
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*
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* For example, for the address "LINUX-1" the callsign is LINUX and SSID is 1
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* the internal format is 98:92:9c:aa:b0:40:02.
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*/
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const char *ax25_ntop1(const ax25_address *src, char *dst, socklen_t size)
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{
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char c, *s;
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int n;
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for (n = 0, s = dst; n < 6; n++) {
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c = (src->ax25_call[n] >> 1) & 0x7f;
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if (c != ' ')
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*s++ = c;
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}
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*s++ = '-';
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n = ((src->ax25_call[6] >> 1) & 0x0f);
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if (n > 9) {
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*s++ = '1';
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n -= 10;
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}
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*s++ = n + '0';
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*s++ = '\0';
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if (*dst == '\0' || *dst == '-') {
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dst[0] = '*';
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dst[1] = '\0';
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}
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return dst;
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}
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const char *ax25_ntop(int af, const void *addr, char *buf, socklen_t buflen)
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{
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switch (af) {
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case AF_AX25:
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errno = 0;
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return ax25_ntop1((ax25_address *)addr, buf, buflen);
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default:
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errno = EAFNOSUPPORT;
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}
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return NULL;
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}
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