1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * X.25 Packet Layer release 002 |
4 | * |
5 | * This is ALPHA test software. This code may break your machine, |
6 | * randomly fail to work with new releases, misbehave and/or generally |
7 | * screw up. It might even work. |
8 | * |
9 | * This code REQUIRES 2.1.15 or higher |
10 | * |
11 | * History |
12 | * X.25 001 Split from x25_subr.c |
13 | * mar/20/00 Daniela Squassoni Disabling/enabling of facilities |
14 | * negotiation. |
15 | * apr/14/05 Shaun Pereira - Allow fast select with no restriction |
16 | * on response. |
17 | */ |
18 | |
19 | #define pr_fmt(fmt) "X25: " fmt |
20 | |
21 | #include <linux/kernel.h> |
22 | #include <linux/string.h> |
23 | #include <linux/skbuff.h> |
24 | #include <net/sock.h> |
25 | #include <net/x25.h> |
26 | |
27 | /** |
28 | * x25_parse_facilities - Parse facilities from skb into the facilities structs |
29 | * |
30 | * @skb: sk_buff to parse |
31 | * @facilities: Regular facilities, updated as facilities are found |
32 | * @dte_facs: ITU DTE facilities, updated as DTE facilities are found |
33 | * @vc_fac_mask: mask is updated with all facilities found |
34 | * |
35 | * Return codes: |
36 | * -1 - Parsing error, caller should drop call and clean up |
37 | * 0 - Parse OK, this skb has no facilities |
38 | * >0 - Parse OK, returns the length of the facilities header |
39 | * |
40 | */ |
41 | int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities, |
42 | struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask) |
43 | { |
44 | unsigned char *p; |
45 | unsigned int len; |
46 | |
47 | *vc_fac_mask = 0; |
48 | |
49 | /* |
50 | * The kernel knows which facilities were set on an incoming call but |
51 | * currently this information is not available to userspace. Here we |
52 | * give userspace who read incoming call facilities 0 length to indicate |
53 | * it wasn't set. |
54 | */ |
55 | dte_facs->calling_len = 0; |
56 | dte_facs->called_len = 0; |
57 | memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae)); |
58 | memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae)); |
59 | |
60 | if (!pskb_may_pull(skb, len: 1)) |
61 | return 0; |
62 | |
63 | len = skb->data[0]; |
64 | |
65 | if (!pskb_may_pull(skb, len: 1 + len)) |
66 | return -1; |
67 | |
68 | p = skb->data + 1; |
69 | |
70 | while (len > 0) { |
71 | switch (*p & X25_FAC_CLASS_MASK) { |
72 | case X25_FAC_CLASS_A: |
73 | if (len < 2) |
74 | return -1; |
75 | switch (*p) { |
76 | case X25_FAC_REVERSE: |
77 | if((p[1] & 0x81) == 0x81) { |
78 | facilities->reverse = p[1] & 0x81; |
79 | *vc_fac_mask |= X25_MASK_REVERSE; |
80 | break; |
81 | } |
82 | |
83 | if((p[1] & 0x01) == 0x01) { |
84 | facilities->reverse = p[1] & 0x01; |
85 | *vc_fac_mask |= X25_MASK_REVERSE; |
86 | break; |
87 | } |
88 | |
89 | if((p[1] & 0x80) == 0x80) { |
90 | facilities->reverse = p[1] & 0x80; |
91 | *vc_fac_mask |= X25_MASK_REVERSE; |
92 | break; |
93 | } |
94 | |
95 | if(p[1] == 0x00) { |
96 | facilities->reverse |
97 | = X25_DEFAULT_REVERSE; |
98 | *vc_fac_mask |= X25_MASK_REVERSE; |
99 | break; |
100 | } |
101 | fallthrough; |
102 | case X25_FAC_THROUGHPUT: |
103 | facilities->throughput = p[1]; |
104 | *vc_fac_mask |= X25_MASK_THROUGHPUT; |
105 | break; |
106 | case X25_MARKER: |
107 | break; |
108 | default: |
109 | pr_debug("unknown facility " |
110 | "%02X, value %02X\n" , |
111 | p[0], p[1]); |
112 | break; |
113 | } |
114 | p += 2; |
115 | len -= 2; |
116 | break; |
117 | case X25_FAC_CLASS_B: |
118 | if (len < 3) |
119 | return -1; |
120 | switch (*p) { |
121 | case X25_FAC_PACKET_SIZE: |
122 | facilities->pacsize_in = p[1]; |
123 | facilities->pacsize_out = p[2]; |
124 | *vc_fac_mask |= X25_MASK_PACKET_SIZE; |
125 | break; |
126 | case X25_FAC_WINDOW_SIZE: |
127 | facilities->winsize_in = p[1]; |
128 | facilities->winsize_out = p[2]; |
129 | *vc_fac_mask |= X25_MASK_WINDOW_SIZE; |
130 | break; |
131 | default: |
132 | pr_debug("unknown facility " |
133 | "%02X, values %02X, %02X\n" , |
134 | p[0], p[1], p[2]); |
135 | break; |
136 | } |
137 | p += 3; |
138 | len -= 3; |
139 | break; |
140 | case X25_FAC_CLASS_C: |
141 | if (len < 4) |
142 | return -1; |
143 | pr_debug("unknown facility %02X, " |
144 | "values %02X, %02X, %02X\n" , |
145 | p[0], p[1], p[2], p[3]); |
146 | p += 4; |
147 | len -= 4; |
148 | break; |
149 | case X25_FAC_CLASS_D: |
150 | if (len < p[1] + 2) |
151 | return -1; |
152 | switch (*p) { |
153 | case X25_FAC_CALLING_AE: |
154 | if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1) |
155 | return -1; |
156 | if (p[2] > X25_MAX_AE_LEN) |
157 | return -1; |
158 | dte_facs->calling_len = p[2]; |
159 | memcpy(dte_facs->calling_ae, &p[3], p[1] - 1); |
160 | *vc_fac_mask |= X25_MASK_CALLING_AE; |
161 | break; |
162 | case X25_FAC_CALLED_AE: |
163 | if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1) |
164 | return -1; |
165 | if (p[2] > X25_MAX_AE_LEN) |
166 | return -1; |
167 | dte_facs->called_len = p[2]; |
168 | memcpy(dte_facs->called_ae, &p[3], p[1] - 1); |
169 | *vc_fac_mask |= X25_MASK_CALLED_AE; |
170 | break; |
171 | default: |
172 | pr_debug("unknown facility %02X," |
173 | "length %d\n" , p[0], p[1]); |
174 | break; |
175 | } |
176 | len -= p[1] + 2; |
177 | p += p[1] + 2; |
178 | break; |
179 | } |
180 | } |
181 | |
182 | return p - skb->data; |
183 | } |
184 | |
185 | /* |
186 | * Create a set of facilities. |
187 | */ |
188 | int x25_create_facilities(unsigned char *buffer, |
189 | struct x25_facilities *facilities, |
190 | struct x25_dte_facilities *dte_facs, unsigned long facil_mask) |
191 | { |
192 | unsigned char *p = buffer + 1; |
193 | int len; |
194 | |
195 | if (!facil_mask) { |
196 | /* |
197 | * Length of the facilities field in call_req or |
198 | * call_accept packets |
199 | */ |
200 | buffer[0] = 0; |
201 | len = 1; /* 1 byte for the length field */ |
202 | return len; |
203 | } |
204 | |
205 | if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) { |
206 | *p++ = X25_FAC_REVERSE; |
207 | *p++ = facilities->reverse; |
208 | } |
209 | |
210 | if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) { |
211 | *p++ = X25_FAC_THROUGHPUT; |
212 | *p++ = facilities->throughput; |
213 | } |
214 | |
215 | if ((facilities->pacsize_in || facilities->pacsize_out) && |
216 | (facil_mask & X25_MASK_PACKET_SIZE)) { |
217 | *p++ = X25_FAC_PACKET_SIZE; |
218 | *p++ = facilities->pacsize_in ? : facilities->pacsize_out; |
219 | *p++ = facilities->pacsize_out ? : facilities->pacsize_in; |
220 | } |
221 | |
222 | if ((facilities->winsize_in || facilities->winsize_out) && |
223 | (facil_mask & X25_MASK_WINDOW_SIZE)) { |
224 | *p++ = X25_FAC_WINDOW_SIZE; |
225 | *p++ = facilities->winsize_in ? : facilities->winsize_out; |
226 | *p++ = facilities->winsize_out ? : facilities->winsize_in; |
227 | } |
228 | |
229 | if (facil_mask & (X25_MASK_CALLING_AE|X25_MASK_CALLED_AE)) { |
230 | *p++ = X25_MARKER; |
231 | *p++ = X25_DTE_SERVICES; |
232 | } |
233 | |
234 | if (dte_facs->calling_len && (facil_mask & X25_MASK_CALLING_AE)) { |
235 | unsigned int bytecount = (dte_facs->calling_len + 1) >> 1; |
236 | *p++ = X25_FAC_CALLING_AE; |
237 | *p++ = 1 + bytecount; |
238 | *p++ = dte_facs->calling_len; |
239 | memcpy(p, dte_facs->calling_ae, bytecount); |
240 | p += bytecount; |
241 | } |
242 | |
243 | if (dte_facs->called_len && (facil_mask & X25_MASK_CALLED_AE)) { |
244 | unsigned int bytecount = (dte_facs->called_len % 2) ? |
245 | dte_facs->called_len / 2 + 1 : |
246 | dte_facs->called_len / 2; |
247 | *p++ = X25_FAC_CALLED_AE; |
248 | *p++ = 1 + bytecount; |
249 | *p++ = dte_facs->called_len; |
250 | memcpy(p, dte_facs->called_ae, bytecount); |
251 | p+=bytecount; |
252 | } |
253 | |
254 | len = p - buffer; |
255 | buffer[0] = len - 1; |
256 | |
257 | return len; |
258 | } |
259 | |
260 | /* |
261 | * Try to reach a compromise on a set of facilities. |
262 | * |
263 | * The only real problem is with reverse charging. |
264 | */ |
265 | int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk, |
266 | struct x25_facilities *new, struct x25_dte_facilities *dte) |
267 | { |
268 | struct x25_sock *x25 = x25_sk(sk); |
269 | struct x25_facilities *ours = &x25->facilities; |
270 | struct x25_facilities theirs; |
271 | int len; |
272 | |
273 | memset(&theirs, 0, sizeof(theirs)); |
274 | memcpy(new, ours, sizeof(*new)); |
275 | memset(dte, 0, sizeof(*dte)); |
276 | |
277 | len = x25_parse_facilities(skb, facilities: &theirs, dte_facs: dte, vc_fac_mask: &x25->vc_facil_mask); |
278 | if (len < 0) |
279 | return len; |
280 | |
281 | /* |
282 | * They want reverse charging, we won't accept it. |
283 | */ |
284 | if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) { |
285 | SOCK_DEBUG(sk, "X.25: rejecting reverse charging request\n" ); |
286 | return -1; |
287 | } |
288 | |
289 | new->reverse = theirs.reverse; |
290 | |
291 | if (theirs.throughput) { |
292 | int theirs_in = theirs.throughput & 0x0f; |
293 | int theirs_out = theirs.throughput & 0xf0; |
294 | int ours_in = ours->throughput & 0x0f; |
295 | int ours_out = ours->throughput & 0xf0; |
296 | if (!ours_in || theirs_in < ours_in) { |
297 | SOCK_DEBUG(sk, "X.25: inbound throughput negotiated\n" ); |
298 | new->throughput = (new->throughput & 0xf0) | theirs_in; |
299 | } |
300 | if (!ours_out || theirs_out < ours_out) { |
301 | SOCK_DEBUG(sk, |
302 | "X.25: outbound throughput negotiated\n" ); |
303 | new->throughput = (new->throughput & 0x0f) | theirs_out; |
304 | } |
305 | } |
306 | |
307 | if (theirs.pacsize_in && theirs.pacsize_out) { |
308 | if (theirs.pacsize_in < ours->pacsize_in) { |
309 | SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down\n" ); |
310 | new->pacsize_in = theirs.pacsize_in; |
311 | } |
312 | if (theirs.pacsize_out < ours->pacsize_out) { |
313 | SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down\n" ); |
314 | new->pacsize_out = theirs.pacsize_out; |
315 | } |
316 | } |
317 | |
318 | if (theirs.winsize_in && theirs.winsize_out) { |
319 | if (theirs.winsize_in < ours->winsize_in) { |
320 | SOCK_DEBUG(sk, "X.25: window size inwards negotiated down\n" ); |
321 | new->winsize_in = theirs.winsize_in; |
322 | } |
323 | if (theirs.winsize_out < ours->winsize_out) { |
324 | SOCK_DEBUG(sk, "X.25: window size outwards negotiated down\n" ); |
325 | new->winsize_out = theirs.winsize_out; |
326 | } |
327 | } |
328 | |
329 | return len; |
330 | } |
331 | |
332 | /* |
333 | * Limit values of certain facilities according to the capability of the |
334 | * currently attached x25 link. |
335 | */ |
336 | void x25_limit_facilities(struct x25_facilities *facilities, |
337 | struct x25_neigh *nb) |
338 | { |
339 | |
340 | if (!nb->extended) { |
341 | if (facilities->winsize_in > 7) { |
342 | pr_debug("incoming winsize limited to 7\n" ); |
343 | facilities->winsize_in = 7; |
344 | } |
345 | if (facilities->winsize_out > 7) { |
346 | facilities->winsize_out = 7; |
347 | pr_debug("outgoing winsize limited to 7\n" ); |
348 | } |
349 | } |
350 | } |
351 | |