summaryrefslogtreecommitdiffstats
path: root/debian/grub-extras/disabled/gpxe/src/net/dhcpopts.c
blob: c1940f1f5420bce20da756b12bd7d888c7687ad8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
/*
 * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <gpxe/dhcp.h>
#include <gpxe/dhcpopts.h>

/** @file
 *
 * DHCP options
 *
 */

/**
 * Obtain printable version of a DHCP option tag
 *
 * @v tag		DHCP option tag
 * @ret name		String representation of the tag
 *
 */
static inline char * dhcp_tag_name ( unsigned int tag ) {
	static char name[8];

	if ( DHCP_IS_ENCAP_OPT ( tag ) ) {
		snprintf ( name, sizeof ( name ), "%d.%d",
			   DHCP_ENCAPSULATOR ( tag ),
			   DHCP_ENCAPSULATED ( tag ) );
	} else {
		snprintf ( name, sizeof ( name ), "%d", tag );
	}
	return name;
}

/**
 * Get pointer to DHCP option
 *
 * @v options		DHCP options block
 * @v offset		Offset within options block
 * @ret option		DHCP option
 */
static inline __attribute__ (( always_inline )) struct dhcp_option *
dhcp_option ( struct dhcp_options *options, unsigned int offset ) {
	return ( ( struct dhcp_option * ) ( options->data + offset ) );
}

/**
 * Get offset of a DHCP option
 *
 * @v options		DHCP options block
 * @v option		DHCP option
 * @ret offset		Offset within options block
 */
static inline __attribute__ (( always_inline )) int
dhcp_option_offset ( struct dhcp_options *options,
		     struct dhcp_option *option ) {
	return ( ( ( void * ) option ) - options->data );
}

/**
 * Calculate length of any DHCP option
 *
 * @v option		DHCP option
 * @ret len		Length (including tag and length field)
 */
static unsigned int dhcp_option_len ( struct dhcp_option *option ) {
	if ( ( option->tag == DHCP_END ) || ( option->tag == DHCP_PAD ) ) {
		return 1;
	} else {
		return ( option->len + DHCP_OPTION_HEADER_LEN );
	}
}

/**
 * Find DHCP option within DHCP options block, and its encapsulator (if any)
 *
 * @v options		DHCP options block
 * @v tag		DHCP option tag to search for
 * @ret encap_offset	Offset of encapsulating DHCP option
 * @ret offset		Offset of DHCP option, or negative error
 *
 * Searches for the DHCP option matching the specified tag within the
 * DHCP option block.  Encapsulated options may be searched for by
 * using DHCP_ENCAP_OPT() to construct the tag value.
 *
 * If the option is encapsulated, and @c encapsulator is non-NULL, it
 * will be filled in with the offset of the encapsulating option.
 *
 * This routine is designed to be paranoid.  It does not assume that
 * the option data is well-formatted, and so must guard against flaws
 * such as options missing a @c DHCP_END terminator, or options whose
 * length would take them beyond the end of the data block.
 */
static int find_dhcp_option_with_encap ( struct dhcp_options *options,
					 unsigned int tag,
					 int *encap_offset ) {
	unsigned int original_tag __attribute__ (( unused )) = tag;
	struct dhcp_option *option;
	int offset = 0;
	ssize_t remaining = options->len;
	unsigned int option_len;

	/* Sanity check */
	if ( tag == DHCP_PAD )
		return -ENOENT;

	/* Search for option */
	while ( remaining ) {
		/* Calculate length of this option.  Abort processing
		 * if the length is malformed (i.e. takes us beyond
		 * the end of the data block).
		 */
		option = dhcp_option ( options, offset );
		option_len = dhcp_option_len ( option );
		remaining -= option_len;
		if ( remaining < 0 )
			break;
		/* Check for explicit end marker */
		if ( option->tag == DHCP_END )
			break;
		/* Check for matching tag */
		if ( option->tag == tag ) {
			DBGC ( options, "DHCPOPT %p found %s (length %d)\n",
			       options, dhcp_tag_name ( original_tag ),
			       option_len );
			return offset;
		}
		/* Check for start of matching encapsulation block */
		if ( DHCP_IS_ENCAP_OPT ( tag ) &&
		     ( option->tag == DHCP_ENCAPSULATOR ( tag ) ) ) {
			if ( encap_offset )
				*encap_offset = offset;
			/* Continue search within encapsulated option block */
			tag = DHCP_ENCAPSULATED ( tag );
			remaining = option_len;
			offset += DHCP_OPTION_HEADER_LEN;
			continue;
		}
		offset += option_len;
	}

	return -ENOENT;
}

/**
 * Resize a DHCP option
 *
 * @v options		DHCP option block
 * @v offset		Offset of option to resize
 * @v encap_offset	Offset of encapsulating offset (or -ve for none)
 * @v old_len		Old length (including header)
 * @v new_len		New length (including header)
 * @v can_realloc	Can reallocate options data if necessary
 * @ret rc		Return status code
 */
static int resize_dhcp_option ( struct dhcp_options *options,
				int offset, int encap_offset,
				size_t old_len, size_t new_len,
				int can_realloc ) {
	struct dhcp_option *encapsulator;
	struct dhcp_option *option;
	ssize_t delta = ( new_len - old_len );
	size_t new_options_len;
	size_t new_encapsulator_len;
	void *new_data;
	void *source;
	void *dest;
	void *end;

	/* Check for sufficient space, and update length fields */
	if ( new_len > DHCP_MAX_LEN ) {
		DBGC ( options, "DHCPOPT %p overlength option\n", options );
		return -ENOSPC;
	}
	new_options_len = ( options->len + delta );
	if ( new_options_len > options->max_len ) {
		/* Reallocate options block if allowed to do so. */
		if ( can_realloc ) {
			new_data = realloc ( options->data, new_options_len );
			if ( ! new_data ) {
				DBGC ( options, "DHCPOPT %p could not "
				       "reallocate to %zd bytes\n", options,
				       new_options_len );
				return -ENOMEM;
			}
			options->data = new_data;
			options->max_len = new_options_len;
		} else {
			DBGC ( options, "DHCPOPT %p out of space\n", options );
			return -ENOMEM;
		}
	}
	if ( encap_offset >= 0 ) {
		encapsulator = dhcp_option ( options, encap_offset );
		new_encapsulator_len = ( encapsulator->len + delta );
		if ( new_encapsulator_len > DHCP_MAX_LEN ) {
			DBGC ( options, "DHCPOPT %p overlength encapsulator\n",
			       options );
			return -ENOSPC;
		}
		encapsulator->len = new_encapsulator_len;
	}
	options->len = new_options_len;

	/* Move remainder of option data */
	option = dhcp_option ( options, offset );
	source = ( ( ( void * ) option ) + old_len );
	dest = ( ( ( void * ) option ) + new_len );
	end = ( options->data + options->max_len );
	memmove ( dest, source, ( end - dest ) );

	return 0;
}

/**
 * Set value of DHCP option
 *
 * @v options		DHCP option block
 * @v tag		DHCP option tag
 * @v data		New value for DHCP option
 * @v len		Length of value, in bytes
 * @v can_realloc	Can reallocate options data if necessary
 * @ret offset		Offset of DHCP option, or negative error
 *
 * Sets the value of a DHCP option within the options block.  The
 * option may or may not already exist.  Encapsulators will be created
 * (and deleted) as necessary.
 *
 * This call may fail due to insufficient space in the options block.
 * If it does fail, and the option existed previously, the option will
 * be left with its original value.
 */
static int set_dhcp_option ( struct dhcp_options *options, unsigned int tag,
			     const void *data, size_t len,
			     int can_realloc ) {
	static const uint8_t empty_encapsulator[] = { DHCP_END };
	int offset;
	int encap_offset = -1;
	int creation_offset = 0;
	struct dhcp_option *option;
	unsigned int encap_tag = DHCP_ENCAPSULATOR ( tag );
	size_t old_len = 0;
	size_t new_len = ( len ? ( len + DHCP_OPTION_HEADER_LEN ) : 0 );
	int rc;

	/* Sanity check */
	if ( tag == DHCP_PAD )
		return -ENOTTY;

	/* Find old instance of this option, if any */
	offset = find_dhcp_option_with_encap ( options, tag, &encap_offset );
	if ( offset >= 0 ) {
		old_len = dhcp_option_len ( dhcp_option ( options, offset ) );
		DBGC ( options, "DHCPOPT %p resizing %s from %zd to %zd\n",
		       options, dhcp_tag_name ( tag ), old_len, new_len );
	} else {
		DBGC ( options, "DHCPOPT %p creating %s (length %zd)\n",
		       options, dhcp_tag_name ( tag ), new_len );
	}

	/* Ensure that encapsulator exists, if required */
	if ( encap_tag ) {
		if ( encap_offset < 0 )
			encap_offset = set_dhcp_option ( options, encap_tag,
							 empty_encapsulator, 1,
							 can_realloc );
		if ( encap_offset < 0 )
			return encap_offset;
		creation_offset = ( encap_offset + DHCP_OPTION_HEADER_LEN );
	}

	/* Create new option if necessary */
	if ( offset < 0 )
		offset = creation_offset;

	/* Resize option to fit new data */
	if ( ( rc = resize_dhcp_option ( options, offset, encap_offset,
					 old_len, new_len,
					 can_realloc ) ) != 0 )
		return rc;

	/* Copy new data into option, if applicable */
	if ( len ) {
		option = dhcp_option ( options, offset );
		option->tag = tag;
		option->len = len;
		memcpy ( &option->data, data, len );
	}

	/* Delete encapsulator if there's nothing else left in it */
	if ( encap_offset >= 0 ) {
		option = dhcp_option ( options, encap_offset );
		if ( option->len <= 1 )
			set_dhcp_option ( options, encap_tag, NULL, 0, 0 );
	}

	return offset;
}

/**
 * Store value of DHCP option setting
 *
 * @v options		DHCP option block
 * @v tag		Setting tag number
 * @v data		Setting data, or NULL to clear setting
 * @v len		Length of setting data
 * @ret rc		Return status code
 */
int dhcpopt_store ( struct dhcp_options *options, unsigned int tag,
		    const void *data, size_t len ) {
	int offset;

	offset = set_dhcp_option ( options, tag, data, len, 0 );
	if ( offset < 0 )
		return offset;
	return 0;
}

/**
 * Store value of DHCP option setting, extending options block if necessary
 *
 * @v options		DHCP option block
 * @v tag		Setting tag number
 * @v data		Setting data, or NULL to clear setting
 * @v len		Length of setting data
 * @ret rc		Return status code
 */
int dhcpopt_extensible_store ( struct dhcp_options *options, unsigned int tag,
			       const void *data, size_t len ) {
	int offset;

	offset = set_dhcp_option ( options, tag, data, len, 1 );
	if ( offset < 0 )
		return offset;
	return 0;
}

/**
 * Fetch value of DHCP option setting
 *
 * @v options		DHCP option block
 * @v tag		Setting tag number
 * @v data		Buffer to fill with setting data
 * @v len		Length of buffer
 * @ret len		Length of setting data, or negative error
 */
int dhcpopt_fetch ( struct dhcp_options *options, unsigned int tag,
		    void *data, size_t len ) {
	int offset;
	struct dhcp_option *option;
	size_t option_len;

	offset = find_dhcp_option_with_encap ( options, tag, NULL );
	if ( offset < 0 )
		return offset;

	option = dhcp_option ( options, offset );
	option_len = option->len;
	if ( len > option_len )
		len = option_len;
	memcpy ( data, option->data, len );

	return option_len;
}

/**
 * Recalculate length of DHCP options block
 *
 * @v options		Uninitialised DHCP option block
 *
 * The "used length" field will be updated based on scanning through
 * the block to find the end of the options.
 */
static void dhcpopt_update_len ( struct dhcp_options *options ) {
	struct dhcp_option *option;
	int offset = 0;
	ssize_t remaining = options->max_len;
	unsigned int option_len;

	/* Find last non-pad option */
	options->len = 0;
	while ( remaining ) {
		option = dhcp_option ( options, offset );
		option_len = dhcp_option_len ( option );
		remaining -= option_len;
		if ( remaining < 0 )
			break;
		offset += option_len;
		if ( option->tag != DHCP_PAD )
			options->len = offset;
	}
}

/**
 * Initialise prepopulated block of DHCP options
 *
 * @v options		Uninitialised DHCP option block
 * @v data		Memory for DHCP option data
 * @v max_len		Length of memory for DHCP option data
 *
 * The memory content must already be filled with valid DHCP options.
 * A zeroed block counts as a block of valid DHCP options.
 */
void dhcpopt_init ( struct dhcp_options *options, void *data,
		    size_t max_len ) {

	/* Fill in fields */
	options->data = data;
	options->max_len = max_len;

	/* Update length */
	dhcpopt_update_len ( options );

	DBGC ( options, "DHCPOPT %p created (data %p len %#zx max_len %#zx)\n",
	       options, options->data, options->len, options->max_len );
}