xref: /linux/net/ax25/ax25_addr.c (revision 2624f124b3b5d550ab2fbef7ee3bc0e1fed09722) 
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/sched.h>
15 #include <linux/timer.h>
16 #include <linux/string.h>
17 #include <linux/sockios.h>
18 #include <linux/net.h>
19 #include <net/ax25.h>
20 #include <linux/inet.h>
21 #include <linux/netdevice.h>
22 #include <linux/skbuff.h>
23 #include <net/sock.h>
24 #include <asm/uaccess.h>
25 #include <asm/system.h>
26 #include <linux/fcntl.h>
27 #include <linux/mm.h>
28 #include <linux/interrupt.h>
29 
30 /*
31  *	The null address is defined as a callsign of all spaces with an
32  *	SSID of zero.
33  */
34 ax25_address null_ax25_address = {{0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x00}};
35 
36 /*
37  *	ax25 -> ascii conversion
38  */
39 char *ax2asc(char *buf, ax25_address *a)
40 {
41 	char c, *s;
42 	int n;
43 
44 	for (n = 0, s = buf; n < 6; n++) {
45 		c = (a->ax25_call[n] >> 1) & 0x7F;
46 
47 		if (c != ' ') *s++ = c;
48 	}
49 
50 	*s++ = '-';
51 
52 	if ((n = ((a->ax25_call[6] >> 1) & 0x0F)) > 9) {
53 		*s++ = '1';
54 		n -= 10;
55 	}
56 
57 	*s++ = n + '0';
58 	*s++ = '\0';
59 
60 	if (*buf == '\0' || *buf == '-')
61 	   return "*";
62 
63 	return buf;
64 
65 }
66 
67 /*
68  *	ascii -> ax25 conversion
69  */
70 void asc2ax(ax25_address *addr, char *callsign)
71 {
72 	char *s;
73 	int n;
74 
75 	for (s = callsign, n = 0; n < 6; n++) {
76 		if (*s != '\0' && *s != '-')
77 			addr->ax25_call[n] = *s++;
78 		else
79 			addr->ax25_call[n] = ' ';
80 		addr->ax25_call[n] <<= 1;
81 		addr->ax25_call[n] &= 0xFE;
82 	}
83 
84 	if (*s++ == '\0') {
85 		addr->ax25_call[6] = 0x00;
86 		return;
87 	}
88 
89 	addr->ax25_call[6] = *s++ - '0';
90 
91 	if (*s != '\0') {
92 		addr->ax25_call[6] *= 10;
93 		addr->ax25_call[6] += *s++ - '0';
94 	}
95 
96 	addr->ax25_call[6] <<= 1;
97 	addr->ax25_call[6] &= 0x1E;
98 }
99 
100 /*
101  *	Compare two ax.25 addresses
102  */
103 int ax25cmp(ax25_address *a, ax25_address *b)
104 {
105 	int ct = 0;
106 
107 	while (ct < 6) {
108 		if ((a->ax25_call[ct] & 0xFE) != (b->ax25_call[ct] & 0xFE))	/* Clean off repeater bits */
109 			return 1;
110 		ct++;
111 	}
112 
113  	if ((a->ax25_call[ct] & 0x1E) == (b->ax25_call[ct] & 0x1E))	/* SSID without control bit */
114  		return 0;
115 
116  	return 2;			/* Partial match */
117 }
118 
119 /*
120  *	Compare two AX.25 digipeater paths.
121  */
122 int ax25digicmp(ax25_digi *digi1, ax25_digi *digi2)
123 {
124 	int i;
125 
126 	if (digi1->ndigi != digi2->ndigi)
127 		return 1;
128 
129 	if (digi1->lastrepeat != digi2->lastrepeat)
130 		return 1;
131 
132 	for (i = 0; i < digi1->ndigi; i++)
133 		if (ax25cmp(&digi1->calls[i], &digi2->calls[i]) != 0)
134 			return 1;
135 
136 	return 0;
137 }
138 
139 /*
140  *	Given an AX.25 address pull of to, from, digi list, command/response and the start of data
141  *
142  */
143 unsigned char *ax25_addr_parse(unsigned char *buf, int len, ax25_address *src, ax25_address *dest, ax25_digi *digi, int *flags, int *dama)
144 {
145 	int d = 0;
146 
147 	if (len < 14) return NULL;
148 
149 	if (flags != NULL) {
150 		*flags = 0;
151 
152 		if (buf[6] & AX25_CBIT)
153 			*flags = AX25_COMMAND;
154 		if (buf[13] & AX25_CBIT)
155 			*flags = AX25_RESPONSE;
156 	}
157 
158 	if (dama != NULL)
159 		*dama = ~buf[13] & AX25_DAMA_FLAG;
160 
161 	/* Copy to, from */
162 	if (dest != NULL)
163 		memcpy(dest, buf + 0, AX25_ADDR_LEN);
164 	if (src != NULL)
165 		memcpy(src,  buf + 7, AX25_ADDR_LEN);
166 
167 	buf += 2 * AX25_ADDR_LEN;
168 	len -= 2 * AX25_ADDR_LEN;
169 
170 	digi->lastrepeat = -1;
171 	digi->ndigi      = 0;
172 
173 	while (!(buf[-1] & AX25_EBIT)) {
174 		if (d >= AX25_MAX_DIGIS)  return NULL;	/* Max of 6 digis */
175 		if (len < 7) return NULL;	/* Short packet */
176 
177 		memcpy(&digi->calls[d], buf, AX25_ADDR_LEN);
178 		digi->ndigi = d + 1;
179 
180 		if (buf[6] & AX25_HBIT) {
181 			digi->repeated[d] = 1;
182 			digi->lastrepeat  = d;
183 		} else {
184 			digi->repeated[d] = 0;
185 		}
186 
187 		buf += AX25_ADDR_LEN;
188 		len -= AX25_ADDR_LEN;
189 		d++;
190 	}
191 
192 	return buf;
193 }
194 
195 /*
196  *	Assemble an AX.25 header from the bits
197  */
198 int ax25_addr_build(unsigned char *buf, ax25_address *src, ax25_address *dest, ax25_digi *d, int flag, int modulus)
199 {
200 	int len = 0;
201 	int ct  = 0;
202 
203 	memcpy(buf, dest, AX25_ADDR_LEN);
204 	buf[6] &= ~(AX25_EBIT | AX25_CBIT);
205 	buf[6] |= AX25_SSSID_SPARE;
206 
207 	if (flag == AX25_COMMAND) buf[6] |= AX25_CBIT;
208 
209 	buf += AX25_ADDR_LEN;
210 	len += AX25_ADDR_LEN;
211 
212 	memcpy(buf, src, AX25_ADDR_LEN);
213 	buf[6] &= ~(AX25_EBIT | AX25_CBIT);
214 	buf[6] &= ~AX25_SSSID_SPARE;
215 
216 	if (modulus == AX25_MODULUS)
217 		buf[6] |= AX25_SSSID_SPARE;
218 	else
219 		buf[6] |= AX25_ESSID_SPARE;
220 
221 	if (flag == AX25_RESPONSE) buf[6] |= AX25_CBIT;
222 
223 	/*
224 	 *	Fast path the normal digiless path
225 	 */
226 	if (d == NULL || d->ndigi == 0) {
227 		buf[6] |= AX25_EBIT;
228 		return 2 * AX25_ADDR_LEN;
229 	}
230 
231 	buf += AX25_ADDR_LEN;
232 	len += AX25_ADDR_LEN;
233 
234 	while (ct < d->ndigi) {
235 		memcpy(buf, &d->calls[ct], AX25_ADDR_LEN);
236 
237 		if (d->repeated[ct])
238 			buf[6] |= AX25_HBIT;
239 		else
240 			buf[6] &= ~AX25_HBIT;
241 
242 		buf[6] &= ~AX25_EBIT;
243 		buf[6] |= AX25_SSSID_SPARE;
244 
245 		buf += AX25_ADDR_LEN;
246 		len += AX25_ADDR_LEN;
247 		ct++;
248 	}
249 
250 	buf[-1] |= AX25_EBIT;
251 
252 	return len;
253 }
254 
255 int ax25_addr_size(ax25_digi *dp)
256 {
257 	if (dp == NULL)
258 		return 2 * AX25_ADDR_LEN;
259 
260 	return AX25_ADDR_LEN * (2 + dp->ndigi);
261 }
262 
263 /*
264  *	Reverse Digipeat List. May not pass both parameters as same struct
265  */
266 void ax25_digi_invert(ax25_digi *in, ax25_digi *out)
267 {
268 	int ct;
269 
270 	out->ndigi      = in->ndigi;
271 	out->lastrepeat = in->ndigi - in->lastrepeat - 2;
272 
273 	/* Invert the digipeaters */
274 	for (ct = 0; ct < in->ndigi; ct++) {
275 		out->calls[ct] = in->calls[in->ndigi - ct - 1];
276 
277 		if (ct <= out->lastrepeat) {
278 			out->calls[ct].ax25_call[6] |= AX25_HBIT;
279 			out->repeated[ct]            = 1;
280 		} else {
281 			out->calls[ct].ax25_call[6] &= ~AX25_HBIT;
282 			out->repeated[ct]            = 0;
283 		}
284 	}
285 }
286 
287