xref: /linux/net/ax25/ax25_addr.c (revision 2da68a77) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *
4  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
5  */
6 #include <linux/errno.h>
7 #include <linux/types.h>
8 #include <linux/socket.h>
9 #include <linux/in.h>
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/timer.h>
13 #include <linux/string.h>
14 #include <linux/sockios.h>
15 #include <linux/net.h>
16 #include <net/ax25.h>
17 #include <linux/inet.h>
18 #include <linux/netdevice.h>
19 #include <linux/skbuff.h>
20 #include <net/sock.h>
21 #include <linux/uaccess.h>
22 #include <linux/fcntl.h>
23 #include <linux/mm.h>
24 #include <linux/interrupt.h>
25 
26 /*
27  * The default broadcast address of an interface is QST-0; the default address
28  * is LINUX-1.  The null address is defined as a callsign of all spaces with
29  * an SSID of zero.
30  */
31 
32 const ax25_address ax25_bcast =
33 	{{'Q' << 1, 'S' << 1, 'T' << 1, ' ' << 1, ' ' << 1, ' ' << 1, 0 << 1}};
34 const ax25_address ax25_defaddr =
35 	{{'L' << 1, 'I' << 1, 'N' << 1, 'U' << 1, 'X' << 1, ' ' << 1, 1 << 1}};
36 const ax25_address null_ax25_address =
37 	{{' ' << 1, ' ' << 1, ' ' << 1, ' ' << 1, ' ' << 1, ' ' << 1, 0 << 1}};
38 
39 EXPORT_SYMBOL_GPL(ax25_bcast);
40 EXPORT_SYMBOL_GPL(ax25_defaddr);
41 EXPORT_SYMBOL(null_ax25_address);
42 
43 /*
44  *	ax25 -> ascii conversion
45  */
46 char *ax2asc(char *buf, const ax25_address *a)
47 {
48 	char c, *s;
49 	int n;
50 
51 	for (n = 0, s = buf; n < 6; n++) {
52 		c = (a->ax25_call[n] >> 1) & 0x7F;
53 
54 		if (c != ' ') *s++ = c;
55 	}
56 
57 	*s++ = '-';
58 
59 	if ((n = ((a->ax25_call[6] >> 1) & 0x0F)) > 9) {
60 		*s++ = '1';
61 		n -= 10;
62 	}
63 
64 	*s++ = n + '0';
65 	*s++ = '\0';
66 
67 	if (*buf == '\0' || *buf == '-')
68 	   return "*";
69 
70 	return buf;
71 
72 }
73 
74 EXPORT_SYMBOL(ax2asc);
75 
76 /*
77  *	ascii -> ax25 conversion
78  */
79 void asc2ax(ax25_address *addr, const char *callsign)
80 {
81 	const char *s;
82 	int n;
83 
84 	for (s = callsign, n = 0; n < 6; n++) {
85 		if (*s != '\0' && *s != '-')
86 			addr->ax25_call[n] = *s++;
87 		else
88 			addr->ax25_call[n] = ' ';
89 		addr->ax25_call[n] <<= 1;
90 		addr->ax25_call[n] &= 0xFE;
91 	}
92 
93 	if (*s++ == '\0') {
94 		addr->ax25_call[6] = 0x00;
95 		return;
96 	}
97 
98 	addr->ax25_call[6] = *s++ - '0';
99 
100 	if (*s != '\0') {
101 		addr->ax25_call[6] *= 10;
102 		addr->ax25_call[6] += *s++ - '0';
103 	}
104 
105 	addr->ax25_call[6] <<= 1;
106 	addr->ax25_call[6] &= 0x1E;
107 }
108 
109 EXPORT_SYMBOL(asc2ax);
110 
111 /*
112  *	Compare two ax.25 addresses
113  */
114 int ax25cmp(const ax25_address *a, const ax25_address *b)
115 {
116 	int ct = 0;
117 
118 	while (ct < 6) {
119 		if ((a->ax25_call[ct] & 0xFE) != (b->ax25_call[ct] & 0xFE))	/* Clean off repeater bits */
120 			return 1;
121 		ct++;
122 	}
123 
124 	if ((a->ax25_call[ct] & 0x1E) == (b->ax25_call[ct] & 0x1E))	/* SSID without control bit */
125 		return 0;
126 
127 	return 2;			/* Partial match */
128 }
129 
130 EXPORT_SYMBOL(ax25cmp);
131 
132 /*
133  *	Compare two AX.25 digipeater paths.
134  */
135 int ax25digicmp(const ax25_digi *digi1, const ax25_digi *digi2)
136 {
137 	int i;
138 
139 	if (digi1->ndigi != digi2->ndigi)
140 		return 1;
141 
142 	if (digi1->lastrepeat != digi2->lastrepeat)
143 		return 1;
144 
145 	for (i = 0; i < digi1->ndigi; i++)
146 		if (ax25cmp(&digi1->calls[i], &digi2->calls[i]) != 0)
147 			return 1;
148 
149 	return 0;
150 }
151 
152 /*
153  *	Given an AX.25 address pull of to, from, digi list, command/response and the start of data
154  *
155  */
156 const unsigned char *ax25_addr_parse(const unsigned char *buf, int len,
157 	ax25_address *src, ax25_address *dest, ax25_digi *digi, int *flags,
158 	int *dama)
159 {
160 	int d = 0;
161 
162 	if (len < 14) return NULL;
163 
164 	if (flags != NULL) {
165 		*flags = 0;
166 
167 		if (buf[6] & AX25_CBIT)
168 			*flags = AX25_COMMAND;
169 		if (buf[13] & AX25_CBIT)
170 			*flags = AX25_RESPONSE;
171 	}
172 
173 	if (dama != NULL)
174 		*dama = ~buf[13] & AX25_DAMA_FLAG;
175 
176 	/* Copy to, from */
177 	if (dest != NULL)
178 		memcpy(dest, buf + 0, AX25_ADDR_LEN);
179 	if (src != NULL)
180 		memcpy(src,  buf + 7, AX25_ADDR_LEN);
181 
182 	buf += 2 * AX25_ADDR_LEN;
183 	len -= 2 * AX25_ADDR_LEN;
184 
185 	digi->lastrepeat = -1;
186 	digi->ndigi      = 0;
187 
188 	while (!(buf[-1] & AX25_EBIT)) {
189 		if (d >= AX25_MAX_DIGIS)
190 			return NULL;
191 		if (len < AX25_ADDR_LEN)
192 			return NULL;
193 
194 		memcpy(&digi->calls[d], buf, AX25_ADDR_LEN);
195 		digi->ndigi = d + 1;
196 
197 		if (buf[6] & AX25_HBIT) {
198 			digi->repeated[d] = 1;
199 			digi->lastrepeat  = d;
200 		} else {
201 			digi->repeated[d] = 0;
202 		}
203 
204 		buf += AX25_ADDR_LEN;
205 		len -= AX25_ADDR_LEN;
206 		d++;
207 	}
208 
209 	return buf;
210 }
211 
212 /*
213  *	Assemble an AX.25 header from the bits
214  */
215 int ax25_addr_build(unsigned char *buf, const ax25_address *src,
216 	const ax25_address *dest, const ax25_digi *d, int flag, int modulus)
217 {
218 	int len = 0;
219 	int ct  = 0;
220 
221 	memcpy(buf, dest, AX25_ADDR_LEN);
222 	buf[6] &= ~(AX25_EBIT | AX25_CBIT);
223 	buf[6] |= AX25_SSSID_SPARE;
224 
225 	if (flag == AX25_COMMAND) buf[6] |= AX25_CBIT;
226 
227 	buf += AX25_ADDR_LEN;
228 	len += AX25_ADDR_LEN;
229 
230 	memcpy(buf, src, AX25_ADDR_LEN);
231 	buf[6] &= ~(AX25_EBIT | AX25_CBIT);
232 	buf[6] &= ~AX25_SSSID_SPARE;
233 
234 	if (modulus == AX25_MODULUS)
235 		buf[6] |= AX25_SSSID_SPARE;
236 	else
237 		buf[6] |= AX25_ESSID_SPARE;
238 
239 	if (flag == AX25_RESPONSE) buf[6] |= AX25_CBIT;
240 
241 	/*
242 	 *	Fast path the normal digiless path
243 	 */
244 	if (d == NULL || d->ndigi == 0) {
245 		buf[6] |= AX25_EBIT;
246 		return 2 * AX25_ADDR_LEN;
247 	}
248 
249 	buf += AX25_ADDR_LEN;
250 	len += AX25_ADDR_LEN;
251 
252 	while (ct < d->ndigi) {
253 		memcpy(buf, &d->calls[ct], AX25_ADDR_LEN);
254 
255 		if (d->repeated[ct])
256 			buf[6] |= AX25_HBIT;
257 		else
258 			buf[6] &= ~AX25_HBIT;
259 
260 		buf[6] &= ~AX25_EBIT;
261 		buf[6] |= AX25_SSSID_SPARE;
262 
263 		buf += AX25_ADDR_LEN;
264 		len += AX25_ADDR_LEN;
265 		ct++;
266 	}
267 
268 	buf[-1] |= AX25_EBIT;
269 
270 	return len;
271 }
272 
273 int ax25_addr_size(const ax25_digi *dp)
274 {
275 	if (dp == NULL)
276 		return 2 * AX25_ADDR_LEN;
277 
278 	return AX25_ADDR_LEN * (2 + dp->ndigi);
279 }
280 
281 /*
282  *	Reverse Digipeat List. May not pass both parameters as same struct
283  */
284 void ax25_digi_invert(const ax25_digi *in, ax25_digi *out)
285 {
286 	int ct;
287 
288 	out->ndigi      = in->ndigi;
289 	out->lastrepeat = in->ndigi - in->lastrepeat - 2;
290 
291 	/* Invert the digipeaters */
292 	for (ct = 0; ct < in->ndigi; ct++) {
293 		out->calls[ct] = in->calls[in->ndigi - ct - 1];
294 
295 		if (ct <= out->lastrepeat) {
296 			out->calls[ct].ax25_call[6] |= AX25_HBIT;
297 			out->repeated[ct]            = 1;
298 		} else {
299 			out->calls[ct].ax25_call[6] &= ~AX25_HBIT;
300 			out->repeated[ct]            = 0;
301 		}
302 	}
303 }
304