1/*
2 *  net/dccp/options.c
3 *
4 *  An implementation of the DCCP protocol
5 *  Copyright (c) 2005 Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
6 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
7 *  Copyright (c) 2005 Ian McDonald <ian.mcdonald@jandi.co.nz>
8 *
9 *      This program is free software; you can redistribute it and/or
10 *      modify it under the terms of the GNU General Public License
11 *      as published by the Free Software Foundation; either version
12 *      2 of the License, or (at your option) any later version.
13 */
14#include <linux/dccp.h>
15#include <linux/module.h>
16#include <linux/types.h>
17#include <asm/unaligned.h>
18#include <linux/kernel.h>
19#include <linux/skbuff.h>
20
21#include "ackvec.h"
22#include "ccid.h"
23#include "dccp.h"
24#include "feat.h"
25
26u64 dccp_decode_value_var(const u8 *bf, const u8 len)
27{
28	u64 value = 0;
29
30	if (len >= DCCP_OPTVAL_MAXLEN)
31		value += ((u64)*bf++) << 40;
32	if (len > 4)
33		value += ((u64)*bf++) << 32;
34	if (len > 3)
35		value += ((u64)*bf++) << 24;
36	if (len > 2)
37		value += ((u64)*bf++) << 16;
38	if (len > 1)
39		value += ((u64)*bf++) << 8;
40	if (len > 0)
41		value += *bf;
42
43	return value;
44}
45
46/**
47 * dccp_parse_options  -  Parse DCCP options present in @skb
48 * @sk: client|server|listening dccp socket (when @dreq != NULL)
49 * @dreq: request socket to use during connection setup, or NULL
50 */
51int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
52		       struct sk_buff *skb)
53{
54	struct dccp_sock *dp = dccp_sk(sk);
55	const struct dccp_hdr *dh = dccp_hdr(skb);
56	const u8 pkt_type = DCCP_SKB_CB(skb)->dccpd_type;
57	u64 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
58	unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
59	unsigned char *opt_ptr = options;
60	const unsigned char *opt_end = (unsigned char *)dh +
61					(dh->dccph_doff * 4);
62	struct dccp_options_received *opt_recv = &dp->dccps_options_received;
63	unsigned char opt, len;
64	unsigned char *uninitialized_var(value);
65	u32 elapsed_time;
66	__be32 opt_val;
67	int rc;
68	int mandatory = 0;
69
70	memset(opt_recv, 0, sizeof(*opt_recv));
71
72	opt = len = 0;
73	while (opt_ptr != opt_end) {
74		opt   = *opt_ptr++;
75		len   = 0;
76		value = NULL;
77
78		/* Check if this isn't a single byte option */
79		if (opt > DCCPO_MAX_RESERVED) {
80			if (opt_ptr == opt_end)
81				goto out_nonsensical_length;
82
83			len = *opt_ptr++;
84			if (len < 2)
85				goto out_nonsensical_length;
86			/*
87			 * Remove the type and len fields, leaving
88			 * just the value size
89			 */
90			len	-= 2;
91			value	= opt_ptr;
92			opt_ptr += len;
93
94			if (opt_ptr > opt_end)
95				goto out_nonsensical_length;
96		}
97
98		/*
99		 * CCID-Specific Options (from RFC 4340, sec. 10.3):
100		 *
101		 * Option numbers 128 through 191 are for options sent from the
102		 * HC-Sender to the HC-Receiver; option numbers 192 through 255
103		 * are for options sent from the HC-Receiver to	the HC-Sender.
104		 *
105		 * CCID-specific options are ignored during connection setup, as
106		 * negotiation may still be in progress (see RFC 4340, 10.3).
107		 * The same applies to Ack Vectors, as these depend on the CCID.
108		 *
109		 */
110		if (dreq != NULL && (opt >= 128 ||
111		    opt == DCCPO_ACK_VECTOR_0 || opt == DCCPO_ACK_VECTOR_1))
112			goto ignore_option;
113
114		switch (opt) {
115		case DCCPO_PADDING:
116			break;
117		case DCCPO_MANDATORY:
118			if (mandatory)
119				goto out_invalid_option;
120			if (pkt_type != DCCP_PKT_DATA)
121				mandatory = 1;
122			break;
123		case DCCPO_NDP_COUNT:
124			if (len > 6)
125				goto out_invalid_option;
126
127			opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
128			dccp_pr_debug("%s opt: NDP count=%llu\n", dccp_role(sk),
129				      (unsigned long long)opt_recv->dccpor_ndp);
130			break;
131		case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R:
132			if (pkt_type == DCCP_PKT_DATA)      /* RFC 4340, 6 */
133				break;
134			rc = dccp_feat_parse_options(sk, dreq, mandatory, opt,
135						    *value, value + 1, len - 1);
136			if (rc)
137				goto out_featneg_failed;
138			break;
139		case DCCPO_ACK_VECTOR_0:
140		case DCCPO_ACK_VECTOR_1:
141			if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
142				break;
143			if (dp->dccps_hc_rx_ackvec != NULL &&
144			    dccp_ackvec_parse(sk, skb, &ackno, opt, value, len))
145				goto out_invalid_option;
146			break;
147		case DCCPO_TIMESTAMP:
148			if (len != 4)
149				goto out_invalid_option;
150			/*
151			 * RFC 4340 13.1: "The precise time corresponding to
152			 * Timestamp Value zero is not specified". We use
153			 * zero to indicate absence of a meaningful timestamp.
154			 */
155			opt_val = get_unaligned((__be32 *)value);
156			if (unlikely(opt_val == 0)) {
157				DCCP_WARN("Timestamp with zero value\n");
158				break;
159			}
160
161			if (dreq != NULL) {
162				dreq->dreq_timestamp_echo = ntohl(opt_val);
163				dreq->dreq_timestamp_time = dccp_timestamp();
164			} else {
165				opt_recv->dccpor_timestamp =
166					dp->dccps_timestamp_echo = ntohl(opt_val);
167				dp->dccps_timestamp_time = dccp_timestamp();
168			}
169			dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n",
170				      dccp_role(sk), ntohl(opt_val),
171				      (unsigned long long)
172				      DCCP_SKB_CB(skb)->dccpd_ack_seq);
173			break;
174		case DCCPO_TIMESTAMP_ECHO:
175			if (len != 4 && len != 6 && len != 8)
176				goto out_invalid_option;
177
178			opt_val = get_unaligned((__be32 *)value);
179			opt_recv->dccpor_timestamp_echo = ntohl(opt_val);
180
181			dccp_pr_debug("%s rx opt: TIMESTAMP_ECHO=%u, len=%d, "
182				      "ackno=%llu", dccp_role(sk),
183				      opt_recv->dccpor_timestamp_echo,
184				      len + 2,
185				      (unsigned long long)
186				      DCCP_SKB_CB(skb)->dccpd_ack_seq);
187
188			value += 4;
189
190			if (len == 4) {		/* no elapsed time included */
191				dccp_pr_debug_cat("\n");
192				break;
193			}
194
195			if (len == 6) {		/* 2-byte elapsed time */
196				__be16 opt_val2 = get_unaligned((__be16 *)value);
197				elapsed_time = ntohs(opt_val2);
198			} else {		/* 4-byte elapsed time */
199				opt_val = get_unaligned((__be32 *)value);
200				elapsed_time = ntohl(opt_val);
201			}
202
203			dccp_pr_debug_cat(", ELAPSED_TIME=%u\n", elapsed_time);
204
205			/* Give precedence to the biggest ELAPSED_TIME */
206			if (elapsed_time > opt_recv->dccpor_elapsed_time)
207				opt_recv->dccpor_elapsed_time = elapsed_time;
208			break;
209		case DCCPO_ELAPSED_TIME:
210			if (dccp_packet_without_ack(skb))   /* RFC 4340, 13.2 */
211				break;
212
213			if (len == 2) {
214				__be16 opt_val2 = get_unaligned((__be16 *)value);
215				elapsed_time = ntohs(opt_val2);
216			} else if (len == 4) {
217				opt_val = get_unaligned((__be32 *)value);
218				elapsed_time = ntohl(opt_val);
219			} else {
220				goto out_invalid_option;
221			}
222
223			if (elapsed_time > opt_recv->dccpor_elapsed_time)
224				opt_recv->dccpor_elapsed_time = elapsed_time;
225
226			dccp_pr_debug("%s rx opt: ELAPSED_TIME=%d\n",
227				      dccp_role(sk), elapsed_time);
228			break;
229		case 128 ... 191: {
230			const u16 idx = value - options;
231
232			if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
233						     opt, len, idx,
234						     value) != 0)
235				goto out_invalid_option;
236		}
237			break;
238		case 192 ... 255: {
239			const u16 idx = value - options;
240
241			if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
242						     opt, len, idx,
243						     value) != 0)
244				goto out_invalid_option;
245		}
246			break;
247		default:
248			DCCP_CRIT("DCCP(%p): option %d(len=%d) not "
249				  "implemented, ignoring", sk, opt, len);
250			break;
251		}
252ignore_option:
253		if (opt != DCCPO_MANDATORY)
254			mandatory = 0;
255	}
256
257	/* mandatory was the last byte in option list -> reset connection */
258	if (mandatory)
259		goto out_invalid_option;
260
261out_nonsensical_length:
262	/* RFC 4340, 5.8: ignore option and all remaining option space */
263	return 0;
264
265out_invalid_option:
266	DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
267	rc = DCCP_RESET_CODE_OPTION_ERROR;
268out_featneg_failed:
269	DCCP_WARN("DCCP(%p): Option %d (len=%d) error=%u\n", sk, opt, len, rc);
270	DCCP_SKB_CB(skb)->dccpd_reset_code = rc;
271	DCCP_SKB_CB(skb)->dccpd_reset_data[0] = opt;
272	DCCP_SKB_CB(skb)->dccpd_reset_data[1] = len > 0 ? value[0] : 0;
273	DCCP_SKB_CB(skb)->dccpd_reset_data[2] = len > 1 ? value[1] : 0;
274	return -1;
275}
276
277EXPORT_SYMBOL_GPL(dccp_parse_options);
278
279void dccp_encode_value_var(const u64 value, u8 *to, const u8 len)
280{
281	if (len >= DCCP_OPTVAL_MAXLEN)
282		*to++ = (value & 0xFF0000000000ull) >> 40;
283	if (len > 4)
284		*to++ = (value & 0xFF00000000ull) >> 32;
285	if (len > 3)
286		*to++ = (value & 0xFF000000) >> 24;
287	if (len > 2)
288		*to++ = (value & 0xFF0000) >> 16;
289	if (len > 1)
290		*to++ = (value & 0xFF00) >> 8;
291	if (len > 0)
292		*to++ = (value & 0xFF);
293}
294
295static inline u8 dccp_ndp_len(const u64 ndp)
296{
297	if (likely(ndp <= 0xFF))
298		return 1;
299	return likely(ndp <= USHRT_MAX) ? 2 : (ndp <= UINT_MAX ? 4 : 6);
300}
301
302int dccp_insert_option(struct sk_buff *skb, const unsigned char option,
303		       const void *value, const unsigned char len)
304{
305	unsigned char *to;
306
307	if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 2 > DCCP_MAX_OPT_LEN)
308		return -1;
309
310	DCCP_SKB_CB(skb)->dccpd_opt_len += len + 2;
311
312	to    = skb_push(skb, len + 2);
313	*to++ = option;
314	*to++ = len + 2;
315
316	memcpy(to, value, len);
317	return 0;
318}
319
320EXPORT_SYMBOL_GPL(dccp_insert_option);
321
322static int dccp_insert_option_ndp(struct sock *sk, struct sk_buff *skb)
323{
324	struct dccp_sock *dp = dccp_sk(sk);
325	u64 ndp = dp->dccps_ndp_count;
326
327	if (dccp_non_data_packet(skb))
328		++dp->dccps_ndp_count;
329	else
330		dp->dccps_ndp_count = 0;
331
332	if (ndp > 0) {
333		unsigned char *ptr;
334		const int ndp_len = dccp_ndp_len(ndp);
335		const int len = ndp_len + 2;
336
337		if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
338			return -1;
339
340		DCCP_SKB_CB(skb)->dccpd_opt_len += len;
341
342		ptr = skb_push(skb, len);
343		*ptr++ = DCCPO_NDP_COUNT;
344		*ptr++ = len;
345		dccp_encode_value_var(ndp, ptr, ndp_len);
346	}
347
348	return 0;
349}
350
351static inline int dccp_elapsed_time_len(const u32 elapsed_time)
352{
353	return elapsed_time == 0 ? 0 : elapsed_time <= 0xFFFF ? 2 : 4;
354}
355
356int dccp_insert_option_elapsed_time(struct sk_buff *skb, u32 elapsed_time)
357{
358	const int elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
359	const int len = 2 + elapsed_time_len;
360	unsigned char *to;
361
362	if (elapsed_time_len == 0)
363		return 0;
364
365	if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
366		return -1;
367
368	DCCP_SKB_CB(skb)->dccpd_opt_len += len;
369
370	to    = skb_push(skb, len);
371	*to++ = DCCPO_ELAPSED_TIME;
372	*to++ = len;
373
374	if (elapsed_time_len == 2) {
375		const __be16 var16 = htons((u16)elapsed_time);
376		memcpy(to, &var16, 2);
377	} else {
378		const __be32 var32 = htonl(elapsed_time);
379		memcpy(to, &var32, 4);
380	}
381
382	return 0;
383}
384
385EXPORT_SYMBOL_GPL(dccp_insert_option_elapsed_time);
386
387int dccp_insert_option_timestamp(struct sk_buff *skb)
388{
389	__be32 now = htonl(dccp_timestamp());
390	/* yes this will overflow but that is the point as we want a
391	 * 10 usec 32 bit timer which mean it wraps every 11.9 hours */
392
393	return dccp_insert_option(skb, DCCPO_TIMESTAMP, &now, sizeof(now));
394}
395
396EXPORT_SYMBOL_GPL(dccp_insert_option_timestamp);
397
398static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
399					     struct dccp_request_sock *dreq,
400					     struct sk_buff *skb)
401{
402	__be32 tstamp_echo;
403	unsigned char *to;
404	u32 elapsed_time, elapsed_time_len, len;
405
406	if (dreq != NULL) {
407		elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time;
408		tstamp_echo  = htonl(dreq->dreq_timestamp_echo);
409		dreq->dreq_timestamp_echo = 0;
410	} else {
411		elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time;
412		tstamp_echo  = htonl(dp->dccps_timestamp_echo);
413		dp->dccps_timestamp_echo = 0;
414	}
415
416	elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
417	len = 6 + elapsed_time_len;
418
419	if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
420		return -1;
421
422	DCCP_SKB_CB(skb)->dccpd_opt_len += len;
423
424	to    = skb_push(skb, len);
425	*to++ = DCCPO_TIMESTAMP_ECHO;
426	*to++ = len;
427
428	memcpy(to, &tstamp_echo, 4);
429	to += 4;
430
431	if (elapsed_time_len == 2) {
432		const __be16 var16 = htons((u16)elapsed_time);
433		memcpy(to, &var16, 2);
434	} else if (elapsed_time_len == 4) {
435		const __be32 var32 = htonl(elapsed_time);
436		memcpy(to, &var32, 4);
437	}
438
439	return 0;
440}
441
442/**
443 * dccp_insert_option_mandatory  -  Mandatory option (5.8.2)
444 * Note that since we are using skb_push, this function needs to be called
445 * _after_ inserting the option it is supposed to influence (stack order).
446 */
447int dccp_insert_option_mandatory(struct sk_buff *skb)
448{
449	if (DCCP_SKB_CB(skb)->dccpd_opt_len >= DCCP_MAX_OPT_LEN)
450		return -1;
451
452	DCCP_SKB_CB(skb)->dccpd_opt_len++;
453	*skb_push(skb, 1) = DCCPO_MANDATORY;
454	return 0;
455}
456
457/**
458 * dccp_insert_fn_opt  -  Insert single Feature-Negotiation option into @skb
459 * @type: %DCCPO_CHANGE_L, %DCCPO_CHANGE_R, %DCCPO_CONFIRM_L, %DCCPO_CONFIRM_R
460 * @feat: one out of %dccp_feature_numbers
461 * @val: NN value or SP array (preferred element first) to copy
462 * @len: true length of @val in bytes (excluding first element repetition)
463 * @repeat_first: whether to copy the first element of @val twice
464 * The last argument is used to construct Confirm options, where the preferred
465 * value and the preference list appear separately (RFC 4340, 6.3.1). Preference
466 * lists are kept such that the preferred entry is always first, so we only need
467 * to copy twice, and avoid the overhead of cloning into a bigger array.
468 */
469int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
470		       u8 *val, u8 len, bool repeat_first)
471{
472	u8 tot_len, *to;
473
474	/* take the `Feature' field and possible repetition into account */
475	if (len > (DCCP_SINGLE_OPT_MAXLEN - 2)) {
476		DCCP_WARN("length %u for feature %u too large\n", len, feat);
477		return -1;
478	}
479
480	if (unlikely(val == NULL || len == 0))
481		len = repeat_first = 0;
482	tot_len = 3 + repeat_first + len;
483
484	if (DCCP_SKB_CB(skb)->dccpd_opt_len + tot_len > DCCP_MAX_OPT_LEN) {
485		DCCP_WARN("packet too small for feature %d option!\n", feat);
486		return -1;
487	}
488	DCCP_SKB_CB(skb)->dccpd_opt_len += tot_len;
489
490	to    = skb_push(skb, tot_len);
491	*to++ = type;
492	*to++ = tot_len;
493	*to++ = feat;
494
495	if (repeat_first)
496		*to++ = *val;
497	if (len)
498		memcpy(to, val, len);
499	return 0;
500}
501
502/* The length of all options needs to be a multiple of 4 (5.8) */
503static void dccp_insert_option_padding(struct sk_buff *skb)
504{
505	int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
506
507	if (padding != 0) {
508		padding = 4 - padding;
509		memset(skb_push(skb, padding), 0, padding);
510		DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
511	}
512}
513
514int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
515{
516	struct dccp_sock *dp = dccp_sk(sk);
517
518	DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
519
520	if (dp->dccps_send_ndp_count && dccp_insert_option_ndp(sk, skb))
521		return -1;
522
523	if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA) {
524
525		/* Feature Negotiation */
526		if (dccp_feat_insert_opts(dp, NULL, skb))
527			return -1;
528
529		if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST) {
530			/*
531			 * Obtain RTT sample from Request/Response exchange.
532			 * This is currently used for TFRC initialisation.
533			 */
534			if (dccp_insert_option_timestamp(skb))
535				return -1;
536
537		} else if (dp->dccps_hc_rx_ackvec != NULL &&
538			   dccp_ackvec_pending(dp->dccps_hc_rx_ackvec) &&
539			   dccp_insert_option_ackvec(sk, skb)) {
540				return -1;
541		}
542	}
543
544	if (dp->dccps_hc_rx_insert_options) {
545		if (ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb))
546			return -1;
547		dp->dccps_hc_rx_insert_options = 0;
548	}
549
550	if (dp->dccps_timestamp_echo != 0 &&
551	    dccp_insert_option_timestamp_echo(dp, NULL, skb))
552		return -1;
553
554	dccp_insert_option_padding(skb);
555	return 0;
556}
557
558int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb)
559{
560	DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
561
562	if (dccp_feat_insert_opts(NULL, dreq, skb))
563		return -1;
564
565	/* Obtain RTT sample from Response/Ack exchange (used by TFRC). */
566	if (dccp_insert_option_timestamp(skb))
567		return -1;
568
569	if (dreq->dreq_timestamp_echo != 0 &&
570	    dccp_insert_option_timestamp_echo(NULL, dreq, skb))
571		return -1;
572
573	dccp_insert_option_padding(skb);
574	return 0;
575}
576