1/*
2 *	X.25 Packet Layer release 002
3 *
4 *	This is ALPHA test software. This code may break your machine,
5 *	randomly fail to work with new releases, misbehave and/or generally
6 *	screw up. It might even work.
7 *
8 *	This code REQUIRES 2.1.15 or higher
9 *
10 *	This module:
11 *		This module is free software; you can redistribute it and/or
12 *		modify it under the terms of the GNU General Public License
13 *		as published by the Free Software Foundation; either version
14 *		2 of the License, or (at your option) any later version.
15 *
16 *	History
17 *	X.25 001	Split from x25_subr.c
18 *	mar/20/00	Daniela Squassoni Disabling/enabling of facilities
19 *					  negotiation.
20 *	apr/14/05	Shaun Pereira - Allow fast select with no restriction
21 *					on response.
22 */
23
24#define pr_fmt(fmt) "X25: " fmt
25
26#include <linux/kernel.h>
27#include <linux/string.h>
28#include <linux/skbuff.h>
29#include <net/sock.h>
30#include <net/x25.h>
31
32/**
33 * x25_parse_facilities - Parse facilities from skb into the facilities structs
34 *
35 * @skb: sk_buff to parse
36 * @facilities: Regular facilities, updated as facilities are found
37 * @dte_facs: ITU DTE facilities, updated as DTE facilities are found
38 * @vc_fac_mask: mask is updated with all facilities found
39 *
40 * Return codes:
41 *  -1 - Parsing error, caller should drop call and clean up
42 *   0 - Parse OK, this skb has no facilities
43 *  >0 - Parse OK, returns the length of the facilities header
44 *
45 */
46int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
47		struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
48{
49	unsigned char *p;
50	unsigned int len;
51
52	*vc_fac_mask = 0;
53
54	/*
55	 * The kernel knows which facilities were set on an incoming call but
56	 * currently this information is not available to userspace.  Here we
57	 * give userspace who read incoming call facilities 0 length to indicate
58	 * it wasn't set.
59	 */
60	dte_facs->calling_len = 0;
61	dte_facs->called_len = 0;
62	memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae));
63	memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae));
64
65	if (!pskb_may_pull(skb, 1))
66		return 0;
67
68	len = skb->data[0];
69
70	if (!pskb_may_pull(skb, 1 + len))
71		return -1;
72
73	p = skb->data + 1;
74
75	while (len > 0) {
76		switch (*p & X25_FAC_CLASS_MASK) {
77		case X25_FAC_CLASS_A:
78			if (len < 2)
79				return -1;
80			switch (*p) {
81			case X25_FAC_REVERSE:
82				if((p[1] & 0x81) == 0x81) {
83					facilities->reverse = p[1] & 0x81;
84					*vc_fac_mask |= X25_MASK_REVERSE;
85					break;
86				}
87
88				if((p[1] & 0x01) == 0x01) {
89					facilities->reverse = p[1] & 0x01;
90					*vc_fac_mask |= X25_MASK_REVERSE;
91					break;
92				}
93
94				if((p[1] & 0x80) == 0x80) {
95					facilities->reverse = p[1] & 0x80;
96					*vc_fac_mask |= X25_MASK_REVERSE;
97					break;
98				}
99
100				if(p[1] == 0x00) {
101					facilities->reverse
102						= X25_DEFAULT_REVERSE;
103					*vc_fac_mask |= X25_MASK_REVERSE;
104					break;
105				}
106
107			case X25_FAC_THROUGHPUT:
108				facilities->throughput = p[1];
109				*vc_fac_mask |= X25_MASK_THROUGHPUT;
110				break;
111			case X25_MARKER:
112				break;
113			default:
114				pr_debug("unknown facility "
115				       "%02X, value %02X\n",
116				       p[0], p[1]);
117				break;
118			}
119			p   += 2;
120			len -= 2;
121			break;
122		case X25_FAC_CLASS_B:
123			if (len < 3)
124				return -1;
125			switch (*p) {
126			case X25_FAC_PACKET_SIZE:
127				facilities->pacsize_in  = p[1];
128				facilities->pacsize_out = p[2];
129				*vc_fac_mask |= X25_MASK_PACKET_SIZE;
130				break;
131			case X25_FAC_WINDOW_SIZE:
132				facilities->winsize_in  = p[1];
133				facilities->winsize_out = p[2];
134				*vc_fac_mask |= X25_MASK_WINDOW_SIZE;
135				break;
136			default:
137				pr_debug("unknown facility "
138				       "%02X, values %02X, %02X\n",
139				       p[0], p[1], p[2]);
140				break;
141			}
142			p   += 3;
143			len -= 3;
144			break;
145		case X25_FAC_CLASS_C:
146			if (len < 4)
147				return -1;
148			pr_debug("unknown facility %02X, "
149			       "values %02X, %02X, %02X\n",
150			       p[0], p[1], p[2], p[3]);
151			p   += 4;
152			len -= 4;
153			break;
154		case X25_FAC_CLASS_D:
155			if (len < p[1] + 2)
156				return -1;
157			switch (*p) {
158			case X25_FAC_CALLING_AE:
159				if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
160					return -1;
161				if (p[2] > X25_MAX_AE_LEN)
162					return -1;
163				dte_facs->calling_len = p[2];
164				memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
165				*vc_fac_mask |= X25_MASK_CALLING_AE;
166				break;
167			case X25_FAC_CALLED_AE:
168				if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
169					return -1;
170				if (p[2] > X25_MAX_AE_LEN)
171					return -1;
172				dte_facs->called_len = p[2];
173				memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
174				*vc_fac_mask |= X25_MASK_CALLED_AE;
175				break;
176			default:
177				pr_debug("unknown facility %02X,"
178					"length %d\n", p[0], p[1]);
179				break;
180			}
181			len -= p[1] + 2;
182			p += p[1] + 2;
183			break;
184		}
185	}
186
187	return p - skb->data;
188}
189
190/*
191 *	Create a set of facilities.
192 */
193int x25_create_facilities(unsigned char *buffer,
194		struct x25_facilities *facilities,
195		struct x25_dte_facilities *dte_facs, unsigned long facil_mask)
196{
197	unsigned char *p = buffer + 1;
198	int len;
199
200	if (!facil_mask) {
201		/*
202		 * Length of the facilities field in call_req or
203		 * call_accept packets
204		 */
205		buffer[0] = 0;
206		len = 1; /* 1 byte for the length field */
207		return len;
208	}
209
210	if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
211		*p++ = X25_FAC_REVERSE;
212		*p++ = facilities->reverse;
213	}
214
215	if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
216		*p++ = X25_FAC_THROUGHPUT;
217		*p++ = facilities->throughput;
218	}
219
220	if ((facilities->pacsize_in || facilities->pacsize_out) &&
221	    (facil_mask & X25_MASK_PACKET_SIZE)) {
222		*p++ = X25_FAC_PACKET_SIZE;
223		*p++ = facilities->pacsize_in ? : facilities->pacsize_out;
224		*p++ = facilities->pacsize_out ? : facilities->pacsize_in;
225	}
226
227	if ((facilities->winsize_in || facilities->winsize_out) &&
228	    (facil_mask & X25_MASK_WINDOW_SIZE)) {
229		*p++ = X25_FAC_WINDOW_SIZE;
230		*p++ = facilities->winsize_in ? : facilities->winsize_out;
231		*p++ = facilities->winsize_out ? : facilities->winsize_in;
232	}
233
234	if (facil_mask & (X25_MASK_CALLING_AE|X25_MASK_CALLED_AE)) {
235		*p++ = X25_MARKER;
236		*p++ = X25_DTE_SERVICES;
237	}
238
239	if (dte_facs->calling_len && (facil_mask & X25_MASK_CALLING_AE)) {
240		unsigned int bytecount = (dte_facs->calling_len + 1) >> 1;
241		*p++ = X25_FAC_CALLING_AE;
242		*p++ = 1 + bytecount;
243		*p++ = dte_facs->calling_len;
244		memcpy(p, dte_facs->calling_ae, bytecount);
245		p += bytecount;
246	}
247
248	if (dte_facs->called_len && (facil_mask & X25_MASK_CALLED_AE)) {
249		unsigned int bytecount = (dte_facs->called_len % 2) ?
250		dte_facs->called_len / 2 + 1 :
251		dte_facs->called_len / 2;
252		*p++ = X25_FAC_CALLED_AE;
253		*p++ = 1 + bytecount;
254		*p++ = dte_facs->called_len;
255		memcpy(p, dte_facs->called_ae, bytecount);
256		p+=bytecount;
257	}
258
259	len       = p - buffer;
260	buffer[0] = len - 1;
261
262	return len;
263}
264
265/*
266 *	Try to reach a compromise on a set of facilities.
267 *
268 *	The only real problem is with reverse charging.
269 */
270int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
271		struct x25_facilities *new, struct x25_dte_facilities *dte)
272{
273	struct x25_sock *x25 = x25_sk(sk);
274	struct x25_facilities *ours = &x25->facilities;
275	struct x25_facilities theirs;
276	int len;
277
278	memset(&theirs, 0, sizeof(theirs));
279	memcpy(new, ours, sizeof(*new));
280
281	len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
282	if (len < 0)
283		return len;
284
285	/*
286	 *	They want reverse charging, we won't accept it.
287	 */
288	if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
289		SOCK_DEBUG(sk, "X.25: rejecting reverse charging request\n");
290		return -1;
291	}
292
293	new->reverse = theirs.reverse;
294
295	if (theirs.throughput) {
296		int theirs_in =  theirs.throughput & 0x0f;
297		int theirs_out = theirs.throughput & 0xf0;
298		int ours_in  = ours->throughput & 0x0f;
299		int ours_out = ours->throughput & 0xf0;
300		if (!ours_in || theirs_in < ours_in) {
301			SOCK_DEBUG(sk, "X.25: inbound throughput negotiated\n");
302			new->throughput = (new->throughput & 0xf0) | theirs_in;
303		}
304		if (!ours_out || theirs_out < ours_out) {
305			SOCK_DEBUG(sk,
306				"X.25: outbound throughput negotiated\n");
307			new->throughput = (new->throughput & 0x0f) | theirs_out;
308		}
309	}
310
311	if (theirs.pacsize_in && theirs.pacsize_out) {
312		if (theirs.pacsize_in < ours->pacsize_in) {
313			SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down\n");
314			new->pacsize_in = theirs.pacsize_in;
315		}
316		if (theirs.pacsize_out < ours->pacsize_out) {
317			SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down\n");
318			new->pacsize_out = theirs.pacsize_out;
319		}
320	}
321
322	if (theirs.winsize_in && theirs.winsize_out) {
323		if (theirs.winsize_in < ours->winsize_in) {
324			SOCK_DEBUG(sk, "X.25: window size inwards negotiated down\n");
325			new->winsize_in = theirs.winsize_in;
326		}
327		if (theirs.winsize_out < ours->winsize_out) {
328			SOCK_DEBUG(sk, "X.25: window size outwards negotiated down\n");
329			new->winsize_out = theirs.winsize_out;
330		}
331	}
332
333	return len;
334}
335
336/*
337 *	Limit values of certain facilities according to the capability of the
338 *      currently attached x25 link.
339 */
340void x25_limit_facilities(struct x25_facilities *facilities,
341			  struct x25_neigh *nb)
342{
343
344	if (!nb->extended) {
345		if (facilities->winsize_in  > 7) {
346			pr_debug("incoming winsize limited to 7\n");
347			facilities->winsize_in = 7;
348		}
349		if (facilities->winsize_out > 7) {
350			facilities->winsize_out = 7;
351			pr_debug("outgoing winsize limited to 7\n");
352		}
353	}
354}
355