xref: /linux/net/ax25/ax25_addr.c (revision 70868eac) 
1 /*
2  * This program is free software; you can redistribute it and/or modify
3  * it under the terms of the GNU General Public License as published by
4  * the Free Software Foundation; either version 2 of the License, or
5  * (at your option) any later version.
6  *
7  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
8  */
9 #include <linux/errno.h>
10 #include <linux/types.h>
11 #include <linux/socket.h>
12 #include <linux/in.h>
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/timer.h>
17 #include <linux/string.h>
18 #include <linux/sockios.h>
19 #include <linux/net.h>
20 #include <net/ax25.h>
21 #include <linux/inet.h>
22 #include <linux/netdevice.h>
23 #include <linux/skbuff.h>
24 #include <net/sock.h>
25 #include <asm/uaccess.h>
26 #include <asm/system.h>
27 #include <linux/fcntl.h>
28 #include <linux/mm.h>
29 #include <linux/interrupt.h>
30 
31 /*
32  *	The null address is defined as a callsign of all spaces with an
33  *	SSID of zero.
34  */
35 ax25_address null_ax25_address = {{0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x00}};
36 
37 EXPORT_SYMBOL(null_ax25_address);
38 
39 /*
40  *	ax25 -> ascii conversion
41  */
42 char *ax2asc(char *buf, ax25_address *a)
43 {
44 	char c, *s;
45 	int n;
46 
47 	for (n = 0, s = buf; n < 6; n++) {
48 		c = (a->ax25_call[n] >> 1) & 0x7F;
49 
50 		if (c != ' ') *s++ = c;
51 	}
52 
53 	*s++ = '-';
54 
55 	if ((n = ((a->ax25_call[6] >> 1) & 0x0F)) > 9) {
56 		*s++ = '1';
57 		n -= 10;
58 	}
59 
60 	*s++ = n + '0';
61 	*s++ = '\0';
62 
63 	if (*buf == '\0' || *buf == '-')
64 	   return "*";
65 
66 	return buf;
67 
68 }
69 
70 EXPORT_SYMBOL(ax2asc);
71 
72 /*
73  *	ascii -> ax25 conversion
74  */
75 void asc2ax(ax25_address *addr, char *callsign)
76 {
77 	char *s;
78 	int n;
79 
80 	for (s = callsign, n = 0; n < 6; n++) {
81 		if (*s != '\0' && *s != '-')
82 			addr->ax25_call[n] = *s++;
83 		else
84 			addr->ax25_call[n] = ' ';
85 		addr->ax25_call[n] <<= 1;
86 		addr->ax25_call[n] &= 0xFE;
87 	}
88 
89 	if (*s++ == '\0') {
90 		addr->ax25_call[6] = 0x00;
91 		return;
92 	}
93 
94 	addr->ax25_call[6] = *s++ - '0';
95 
96 	if (*s != '\0') {
97 		addr->ax25_call[6] *= 10;
98 		addr->ax25_call[6] += *s++ - '0';
99 	}
100 
101 	addr->ax25_call[6] <<= 1;
102 	addr->ax25_call[6] &= 0x1E;
103 }
104 
105 EXPORT_SYMBOL(asc2ax);
106 
107 /*
108  *	Compare two ax.25 addresses
109  */
110 int ax25cmp(ax25_address *a, ax25_address *b)
111 {
112 	int ct = 0;
113 
114 	while (ct < 6) {
115 		if ((a->ax25_call[ct] & 0xFE) != (b->ax25_call[ct] & 0xFE))	/* Clean off repeater bits */
116 			return 1;
117 		ct++;
118 	}
119 
120  	if ((a->ax25_call[ct] & 0x1E) == (b->ax25_call[ct] & 0x1E))	/* SSID without control bit */
121  		return 0;
122 
123  	return 2;			/* Partial match */
124 }
125 
126 EXPORT_SYMBOL(ax25cmp);
127 
128 /*
129  *	Compare two AX.25 digipeater paths.
130  */
131 int ax25digicmp(ax25_digi *digi1, ax25_digi *digi2)
132 {
133 	int i;
134 
135 	if (digi1->ndigi != digi2->ndigi)
136 		return 1;
137 
138 	if (digi1->lastrepeat != digi2->lastrepeat)
139 		return 1;
140 
141 	for (i = 0; i < digi1->ndigi; i++)
142 		if (ax25cmp(&digi1->calls[i], &digi2->calls[i]) != 0)
143 			return 1;
144 
145 	return 0;
146 }
147 
148 /*
149  *	Given an AX.25 address pull of to, from, digi list, command/response and the start of data
150  *
151  */
152 unsigned char *ax25_addr_parse(unsigned char *buf, int len, ax25_address *src, ax25_address *dest, ax25_digi *digi, int *flags, int *dama)
153 {
154 	int d = 0;
155 
156 	if (len < 14) return NULL;
157 
158 	if (flags != NULL) {
159 		*flags = 0;
160 
161 		if (buf[6] & AX25_CBIT)
162 			*flags = AX25_COMMAND;
163 		if (buf[13] & AX25_CBIT)
164 			*flags = AX25_RESPONSE;
165 	}
166 
167 	if (dama != NULL)
168 		*dama = ~buf[13] & AX25_DAMA_FLAG;
169 
170 	/* Copy to, from */
171 	if (dest != NULL)
172 		memcpy(dest, buf + 0, AX25_ADDR_LEN);
173 	if (src != NULL)
174 		memcpy(src,  buf + 7, AX25_ADDR_LEN);
175 
176 	buf += 2 * AX25_ADDR_LEN;
177 	len -= 2 * AX25_ADDR_LEN;
178 
179 	digi->lastrepeat = -1;
180 	digi->ndigi      = 0;
181 
182 	while (!(buf[-1] & AX25_EBIT)) {
183 		if (d >= AX25_MAX_DIGIS)  return NULL;	/* Max of 6 digis */
184 		if (len < 7) return NULL;	/* Short packet */
185 
186 		memcpy(&digi->calls[d], buf, AX25_ADDR_LEN);
187 		digi->ndigi = d + 1;
188 
189 		if (buf[6] & AX25_HBIT) {
190 			digi->repeated[d] = 1;
191 			digi->lastrepeat  = d;
192 		} else {
193 			digi->repeated[d] = 0;
194 		}
195 
196 		buf += AX25_ADDR_LEN;
197 		len -= AX25_ADDR_LEN;
198 		d++;
199 	}
200 
201 	return buf;
202 }
203 
204 /*
205  *	Assemble an AX.25 header from the bits
206  */
207 int ax25_addr_build(unsigned char *buf, ax25_address *src, ax25_address *dest, ax25_digi *d, int flag, int modulus)
208 {
209 	int len = 0;
210 	int ct  = 0;
211 
212 	memcpy(buf, dest, AX25_ADDR_LEN);
213 	buf[6] &= ~(AX25_EBIT | AX25_CBIT);
214 	buf[6] |= AX25_SSSID_SPARE;
215 
216 	if (flag == AX25_COMMAND) buf[6] |= AX25_CBIT;
217 
218 	buf += AX25_ADDR_LEN;
219 	len += AX25_ADDR_LEN;
220 
221 	memcpy(buf, src, AX25_ADDR_LEN);
222 	buf[6] &= ~(AX25_EBIT | AX25_CBIT);
223 	buf[6] &= ~AX25_SSSID_SPARE;
224 
225 	if (modulus == AX25_MODULUS)
226 		buf[6] |= AX25_SSSID_SPARE;
227 	else
228 		buf[6] |= AX25_ESSID_SPARE;
229 
230 	if (flag == AX25_RESPONSE) buf[6] |= AX25_CBIT;
231 
232 	/*
233 	 *	Fast path the normal digiless path
234 	 */
235 	if (d == NULL || d->ndigi == 0) {
236 		buf[6] |= AX25_EBIT;
237 		return 2 * AX25_ADDR_LEN;
238 	}
239 
240 	buf += AX25_ADDR_LEN;
241 	len += AX25_ADDR_LEN;
242 
243 	while (ct < d->ndigi) {
244 		memcpy(buf, &d->calls[ct], AX25_ADDR_LEN);
245 
246 		if (d->repeated[ct])
247 			buf[6] |= AX25_HBIT;
248 		else
249 			buf[6] &= ~AX25_HBIT;
250 
251 		buf[6] &= ~AX25_EBIT;
252 		buf[6] |= AX25_SSSID_SPARE;
253 
254 		buf += AX25_ADDR_LEN;
255 		len += AX25_ADDR_LEN;
256 		ct++;
257 	}
258 
259 	buf[-1] |= AX25_EBIT;
260 
261 	return len;
262 }
263 
264 int ax25_addr_size(ax25_digi *dp)
265 {
266 	if (dp == NULL)
267 		return 2 * AX25_ADDR_LEN;
268 
269 	return AX25_ADDR_LEN * (2 + dp->ndigi);
270 }
271 
272 /*
273  *	Reverse Digipeat List. May not pass both parameters as same struct
274  */
275 void ax25_digi_invert(ax25_digi *in, ax25_digi *out)
276 {
277 	int ct;
278 
279 	out->ndigi      = in->ndigi;
280 	out->lastrepeat = in->ndigi - in->lastrepeat - 2;
281 
282 	/* Invert the digipeaters */
283 	for (ct = 0; ct < in->ndigi; ct++) {
284 		out->calls[ct] = in->calls[in->ndigi - ct - 1];
285 
286 		if (ct <= out->lastrepeat) {
287 			out->calls[ct].ax25_call[6] |= AX25_HBIT;
288 			out->repeated[ct]            = 1;
289 		} else {
290 			out->calls[ct].ax25_call[6] &= ~AX25_HBIT;
291 			out->repeated[ct]            = 0;
292 		}
293 	}
294 }
295 
296