xref: /linux/net/dccp/feat.c (revision d0034a7a4ac7fae708146ac0059b9c47a1543f0d)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  net/dccp/feat.c
4  *
5  *  Feature negotiation for the DCCP protocol (RFC 4340, section 6)
6  *
7  *  Copyright (c) 2008 Gerrit Renker <gerrit@erg.abdn.ac.uk>
8  *  Rewrote from scratch, some bits from earlier code by
9  *  Copyright (c) 2005 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
10  *
11  *  ASSUMPTIONS
12  *  -----------
13  *  o Feature negotiation is coordinated with connection setup (as in TCP), wild
14  *    changes of parameters of an established connection are not supported.
15  *  o Changing non-negotiable (NN) values is supported in state OPEN/PARTOPEN.
16  *  o All currently known SP features have 1-byte quantities. If in the future
17  *    extensions of RFCs 4340..42 define features with item lengths larger than
18  *    one byte, a feature-specific extension of the code will be required.
19  */
20 #include <linux/module.h>
21 #include <linux/slab.h>
22 #include "ccid.h"
23 #include "feat.h"
24 
25 /* feature-specific sysctls - initialised to the defaults from RFC 4340, 6.4 */
26 unsigned long	sysctl_dccp_sequence_window __read_mostly = 100;
27 int		sysctl_dccp_rx_ccid	    __read_mostly = 2,
28 		sysctl_dccp_tx_ccid	    __read_mostly = 2;
29 
30 /*
31  * Feature activation handlers.
32  *
33  * These all use an u64 argument, to provide enough room for NN/SP features. At
34  * this stage the negotiated values have been checked to be within their range.
35  */
dccp_hdlr_ccid(struct sock * sk,u64 ccid,bool rx)36 static int dccp_hdlr_ccid(struct sock *sk, u64 ccid, bool rx)
37 {
38 	struct dccp_sock *dp = dccp_sk(sk);
39 	struct ccid *new_ccid = ccid_new(ccid, sk, rx);
40 
41 	if (new_ccid == NULL)
42 		return -ENOMEM;
43 
44 	if (rx) {
45 		ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
46 		dp->dccps_hc_rx_ccid = new_ccid;
47 	} else {
48 		ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
49 		dp->dccps_hc_tx_ccid = new_ccid;
50 	}
51 	return 0;
52 }
53 
dccp_hdlr_seq_win(struct sock * sk,u64 seq_win,bool rx)54 static int dccp_hdlr_seq_win(struct sock *sk, u64 seq_win, bool rx)
55 {
56 	struct dccp_sock *dp = dccp_sk(sk);
57 
58 	if (rx) {
59 		dp->dccps_r_seq_win = seq_win;
60 		/* propagate changes to update SWL/SWH */
61 		dccp_update_gsr(sk, dp->dccps_gsr);
62 	} else {
63 		dp->dccps_l_seq_win = seq_win;
64 		/* propagate changes to update AWL */
65 		dccp_update_gss(sk, dp->dccps_gss);
66 	}
67 	return 0;
68 }
69 
dccp_hdlr_ack_ratio(struct sock * sk,u64 ratio,bool rx)70 static int dccp_hdlr_ack_ratio(struct sock *sk, u64 ratio, bool rx)
71 {
72 	if (rx)
73 		dccp_sk(sk)->dccps_r_ack_ratio = ratio;
74 	else
75 		dccp_sk(sk)->dccps_l_ack_ratio = ratio;
76 	return 0;
77 }
78 
dccp_hdlr_ackvec(struct sock * sk,u64 enable,bool rx)79 static int dccp_hdlr_ackvec(struct sock *sk, u64 enable, bool rx)
80 {
81 	struct dccp_sock *dp = dccp_sk(sk);
82 
83 	if (rx) {
84 		if (enable && dp->dccps_hc_rx_ackvec == NULL) {
85 			dp->dccps_hc_rx_ackvec = dccp_ackvec_alloc(gfp_any());
86 			if (dp->dccps_hc_rx_ackvec == NULL)
87 				return -ENOMEM;
88 		} else if (!enable) {
89 			dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
90 			dp->dccps_hc_rx_ackvec = NULL;
91 		}
92 	}
93 	return 0;
94 }
95 
dccp_hdlr_ndp(struct sock * sk,u64 enable,bool rx)96 static int dccp_hdlr_ndp(struct sock *sk, u64 enable, bool rx)
97 {
98 	if (!rx)
99 		dccp_sk(sk)->dccps_send_ndp_count = (enable > 0);
100 	return 0;
101 }
102 
103 /*
104  * Minimum Checksum Coverage is located at the RX side (9.2.1). This means that
105  * `rx' holds when the sending peer informs about his partial coverage via a
106  * ChangeR() option. In the other case, we are the sender and the receiver
107  * announces its coverage via ChangeL() options. The policy here is to honour
108  * such communication by enabling the corresponding partial coverage - but only
109  * if it has not been set manually before; the warning here means that all
110  * packets will be dropped.
111  */
dccp_hdlr_min_cscov(struct sock * sk,u64 cscov,bool rx)112 static int dccp_hdlr_min_cscov(struct sock *sk, u64 cscov, bool rx)
113 {
114 	struct dccp_sock *dp = dccp_sk(sk);
115 
116 	if (rx)
117 		dp->dccps_pcrlen = cscov;
118 	else {
119 		if (dp->dccps_pcslen == 0)
120 			dp->dccps_pcslen = cscov;
121 		else if (cscov > dp->dccps_pcslen)
122 			DCCP_WARN("CsCov %u too small, peer requires >= %u\n",
123 				  dp->dccps_pcslen, (u8)cscov);
124 	}
125 	return 0;
126 }
127 
128 static const struct {
129 	u8			feat_num;		/* DCCPF_xxx */
130 	enum dccp_feat_type	rxtx;			/* RX or TX  */
131 	enum dccp_feat_type	reconciliation;		/* SP or NN  */
132 	u8			default_value;		/* as in 6.4 */
133 	int (*activation_hdlr)(struct sock *sk, u64 val, bool rx);
134 /*
135  *    Lookup table for location and type of features (from RFC 4340/4342)
136  *  +--------------------------+----+-----+----+----+---------+-----------+
137  *  | Feature                  | Location | Reconc. | Initial |  Section  |
138  *  |                          | RX | TX  | SP | NN |  Value  | Reference |
139  *  +--------------------------+----+-----+----+----+---------+-----------+
140  *  | DCCPF_CCID               |    |  X  | X  |    |   2     | 10        |
141  *  | DCCPF_SHORT_SEQNOS       |    |  X  | X  |    |   0     |  7.6.1    |
142  *  | DCCPF_SEQUENCE_WINDOW    |    |  X  |    | X  | 100     |  7.5.2    |
143  *  | DCCPF_ECN_INCAPABLE      | X  |     | X  |    |   0     | 12.1      |
144  *  | DCCPF_ACK_RATIO          |    |  X  |    | X  |   2     | 11.3      |
145  *  | DCCPF_SEND_ACK_VECTOR    | X  |     | X  |    |   0     | 11.5      |
146  *  | DCCPF_SEND_NDP_COUNT     |    |  X  | X  |    |   0     |  7.7.2    |
147  *  | DCCPF_MIN_CSUM_COVER     | X  |     | X  |    |   0     |  9.2.1    |
148  *  | DCCPF_DATA_CHECKSUM      | X  |     | X  |    |   0     |  9.3.1    |
149  *  | DCCPF_SEND_LEV_RATE      | X  |     | X  |    |   0     | 4342/8.4  |
150  *  +--------------------------+----+-----+----+----+---------+-----------+
151  */
152 } dccp_feat_table[] = {
153 	{ DCCPF_CCID,		 FEAT_AT_TX, FEAT_SP, 2,   dccp_hdlr_ccid     },
154 	{ DCCPF_SHORT_SEQNOS,	 FEAT_AT_TX, FEAT_SP, 0,   NULL },
155 	{ DCCPF_SEQUENCE_WINDOW, FEAT_AT_TX, FEAT_NN, 100, dccp_hdlr_seq_win  },
156 	{ DCCPF_ECN_INCAPABLE,	 FEAT_AT_RX, FEAT_SP, 0,   NULL },
157 	{ DCCPF_ACK_RATIO,	 FEAT_AT_TX, FEAT_NN, 2,   dccp_hdlr_ack_ratio},
158 	{ DCCPF_SEND_ACK_VECTOR, FEAT_AT_RX, FEAT_SP, 0,   dccp_hdlr_ackvec   },
159 	{ DCCPF_SEND_NDP_COUNT,  FEAT_AT_TX, FEAT_SP, 0,   dccp_hdlr_ndp      },
160 	{ DCCPF_MIN_CSUM_COVER,  FEAT_AT_RX, FEAT_SP, 0,   dccp_hdlr_min_cscov},
161 	{ DCCPF_DATA_CHECKSUM,	 FEAT_AT_RX, FEAT_SP, 0,   NULL },
162 	{ DCCPF_SEND_LEV_RATE,	 FEAT_AT_RX, FEAT_SP, 0,   NULL },
163 };
164 #define DCCP_FEAT_SUPPORTED_MAX		ARRAY_SIZE(dccp_feat_table)
165 
166 /**
167  * dccp_feat_index  -  Hash function to map feature number into array position
168  * @feat_num: feature to hash, one of %dccp_feature_numbers
169  *
170  * Returns consecutive array index or -1 if the feature is not understood.
171  */
dccp_feat_index(u8 feat_num)172 static int dccp_feat_index(u8 feat_num)
173 {
174 	/* The first 9 entries are occupied by the types from RFC 4340, 6.4 */
175 	if (feat_num > DCCPF_RESERVED && feat_num <= DCCPF_DATA_CHECKSUM)
176 		return feat_num - 1;
177 
178 	/*
179 	 * Other features: add cases for new feature types here after adding
180 	 * them to the above table.
181 	 */
182 	switch (feat_num) {
183 	case DCCPF_SEND_LEV_RATE:
184 			return DCCP_FEAT_SUPPORTED_MAX - 1;
185 	}
186 	return -1;
187 }
188 
dccp_feat_type(u8 feat_num)189 static u8 dccp_feat_type(u8 feat_num)
190 {
191 	int idx = dccp_feat_index(feat_num);
192 
193 	if (idx < 0)
194 		return FEAT_UNKNOWN;
195 	return dccp_feat_table[idx].reconciliation;
196 }
197 
dccp_feat_default_value(u8 feat_num)198 static int dccp_feat_default_value(u8 feat_num)
199 {
200 	int idx = dccp_feat_index(feat_num);
201 	/*
202 	 * There are no default values for unknown features, so encountering a
203 	 * negative index here indicates a serious problem somewhere else.
204 	 */
205 	DCCP_BUG_ON(idx < 0);
206 
207 	return idx < 0 ? 0 : dccp_feat_table[idx].default_value;
208 }
209 
210 /*
211  *	Debugging and verbose-printing section
212  */
dccp_feat_fname(const u8 feat)213 static const char *dccp_feat_fname(const u8 feat)
214 {
215 	static const char *const feature_names[] = {
216 		[DCCPF_RESERVED]	= "Reserved",
217 		[DCCPF_CCID]		= "CCID",
218 		[DCCPF_SHORT_SEQNOS]	= "Allow Short Seqnos",
219 		[DCCPF_SEQUENCE_WINDOW]	= "Sequence Window",
220 		[DCCPF_ECN_INCAPABLE]	= "ECN Incapable",
221 		[DCCPF_ACK_RATIO]	= "Ack Ratio",
222 		[DCCPF_SEND_ACK_VECTOR]	= "Send ACK Vector",
223 		[DCCPF_SEND_NDP_COUNT]	= "Send NDP Count",
224 		[DCCPF_MIN_CSUM_COVER]	= "Min. Csum Coverage",
225 		[DCCPF_DATA_CHECKSUM]	= "Send Data Checksum",
226 	};
227 	if (feat > DCCPF_DATA_CHECKSUM && feat < DCCPF_MIN_CCID_SPECIFIC)
228 		return feature_names[DCCPF_RESERVED];
229 
230 	if (feat ==  DCCPF_SEND_LEV_RATE)
231 		return "Send Loss Event Rate";
232 	if (feat >= DCCPF_MIN_CCID_SPECIFIC)
233 		return "CCID-specific";
234 
235 	return feature_names[feat];
236 }
237 
238 static const char *const dccp_feat_sname[] = {
239 	"DEFAULT", "INITIALISING", "CHANGING", "UNSTABLE", "STABLE",
240 };
241 
242 #ifdef CONFIG_IP_DCCP_DEBUG
dccp_feat_oname(const u8 opt)243 static const char *dccp_feat_oname(const u8 opt)
244 {
245 	switch (opt) {
246 	case DCCPO_CHANGE_L:  return "Change_L";
247 	case DCCPO_CONFIRM_L: return "Confirm_L";
248 	case DCCPO_CHANGE_R:  return "Change_R";
249 	case DCCPO_CONFIRM_R: return "Confirm_R";
250 	}
251 	return NULL;
252 }
253 
dccp_feat_printval(u8 feat_num,dccp_feat_val const * val)254 static void dccp_feat_printval(u8 feat_num, dccp_feat_val const *val)
255 {
256 	u8 i, type = dccp_feat_type(feat_num);
257 
258 	if (val == NULL || (type == FEAT_SP && val->sp.vec == NULL))
259 		dccp_pr_debug_cat("(NULL)");
260 	else if (type == FEAT_SP)
261 		for (i = 0; i < val->sp.len; i++)
262 			dccp_pr_debug_cat("%s%u", i ? " " : "", val->sp.vec[i]);
263 	else if (type == FEAT_NN)
264 		dccp_pr_debug_cat("%llu", (unsigned long long)val->nn);
265 	else
266 		dccp_pr_debug_cat("unknown type %u", type);
267 }
268 
dccp_feat_printvals(u8 feat_num,u8 * list,u8 len)269 static void dccp_feat_printvals(u8 feat_num, u8 *list, u8 len)
270 {
271 	u8 type = dccp_feat_type(feat_num);
272 	dccp_feat_val fval = { .sp.vec = list, .sp.len = len };
273 
274 	if (type == FEAT_NN)
275 		fval.nn = dccp_decode_value_var(list, len);
276 	dccp_feat_printval(feat_num, &fval);
277 }
278 
dccp_feat_print_entry(struct dccp_feat_entry const * entry)279 static void dccp_feat_print_entry(struct dccp_feat_entry const *entry)
280 {
281 	dccp_debug("   * %s %s = ", entry->is_local ? "local" : "remote",
282 				    dccp_feat_fname(entry->feat_num));
283 	dccp_feat_printval(entry->feat_num, &entry->val);
284 	dccp_pr_debug_cat(", state=%s %s\n", dccp_feat_sname[entry->state],
285 			  entry->needs_confirm ? "(Confirm pending)" : "");
286 }
287 
288 #define dccp_feat_print_opt(opt, feat, val, len, mandatory)	do {	      \
289 	dccp_pr_debug("%s(%s, ", dccp_feat_oname(opt), dccp_feat_fname(feat));\
290 	dccp_feat_printvals(feat, val, len);				      \
291 	dccp_pr_debug_cat(") %s\n", mandatory ? "!" : "");	} while (0)
292 
293 #define dccp_feat_print_fnlist(fn_list)  {		\
294 	const struct dccp_feat_entry *___entry;		\
295 							\
296 	dccp_pr_debug("List Dump:\n");			\
297 	list_for_each_entry(___entry, fn_list, node)	\
298 		dccp_feat_print_entry(___entry);	\
299 }
300 #else	/* ! CONFIG_IP_DCCP_DEBUG */
301 #define dccp_feat_print_opt(opt, feat, val, len, mandatory)
302 #define dccp_feat_print_fnlist(fn_list)
303 #endif
304 
__dccp_feat_activate(struct sock * sk,const int idx,const bool is_local,dccp_feat_val const * fval)305 static int __dccp_feat_activate(struct sock *sk, const int idx,
306 				const bool is_local, dccp_feat_val const *fval)
307 {
308 	bool rx;
309 	u64 val;
310 
311 	if (idx < 0 || idx >= DCCP_FEAT_SUPPORTED_MAX)
312 		return -1;
313 	if (dccp_feat_table[idx].activation_hdlr == NULL)
314 		return 0;
315 
316 	if (fval == NULL) {
317 		val = dccp_feat_table[idx].default_value;
318 	} else if (dccp_feat_table[idx].reconciliation == FEAT_SP) {
319 		if (fval->sp.vec == NULL) {
320 			/*
321 			 * This can happen when an empty Confirm is sent
322 			 * for an SP (i.e. known) feature. In this case
323 			 * we would be using the default anyway.
324 			 */
325 			DCCP_CRIT("Feature #%d undefined: using default", idx);
326 			val = dccp_feat_table[idx].default_value;
327 		} else {
328 			val = fval->sp.vec[0];
329 		}
330 	} else {
331 		val = fval->nn;
332 	}
333 
334 	/* Location is RX if this is a local-RX or remote-TX feature */
335 	rx = (is_local == (dccp_feat_table[idx].rxtx == FEAT_AT_RX));
336 
337 	dccp_debug("   -> activating %s %s, %sval=%llu\n", rx ? "RX" : "TX",
338 		   dccp_feat_fname(dccp_feat_table[idx].feat_num),
339 		   fval ? "" : "default ",  (unsigned long long)val);
340 
341 	return dccp_feat_table[idx].activation_hdlr(sk, val, rx);
342 }
343 
344 /**
345  * dccp_feat_activate  -  Activate feature value on socket
346  * @sk: fully connected DCCP socket (after handshake is complete)
347  * @feat_num: feature to activate, one of %dccp_feature_numbers
348  * @local: whether local (1) or remote (0) @feat_num is meant
349  * @fval: the value (SP or NN) to activate, or NULL to use the default value
350  *
351  * For general use this function is preferable over __dccp_feat_activate().
352  */
dccp_feat_activate(struct sock * sk,u8 feat_num,bool local,dccp_feat_val const * fval)353 static int dccp_feat_activate(struct sock *sk, u8 feat_num, bool local,
354 			      dccp_feat_val const *fval)
355 {
356 	return __dccp_feat_activate(sk, dccp_feat_index(feat_num), local, fval);
357 }
358 
359 /* Test for "Req'd" feature (RFC 4340, 6.4) */
dccp_feat_must_be_understood(u8 feat_num)360 static inline int dccp_feat_must_be_understood(u8 feat_num)
361 {
362 	return	feat_num == DCCPF_CCID || feat_num == DCCPF_SHORT_SEQNOS ||
363 		feat_num == DCCPF_SEQUENCE_WINDOW;
364 }
365 
366 /* copy constructor, fval must not already contain allocated memory */
dccp_feat_clone_sp_val(dccp_feat_val * fval,u8 const * val,u8 len)367 static int dccp_feat_clone_sp_val(dccp_feat_val *fval, u8 const *val, u8 len)
368 {
369 	fval->sp.len = len;
370 	if (fval->sp.len > 0) {
371 		fval->sp.vec = kmemdup(val, len, gfp_any());
372 		if (fval->sp.vec == NULL) {
373 			fval->sp.len = 0;
374 			return -ENOMEM;
375 		}
376 	}
377 	return 0;
378 }
379 
dccp_feat_val_destructor(u8 feat_num,dccp_feat_val * val)380 static void dccp_feat_val_destructor(u8 feat_num, dccp_feat_val *val)
381 {
382 	if (unlikely(val == NULL))
383 		return;
384 	if (dccp_feat_type(feat_num) == FEAT_SP)
385 		kfree(val->sp.vec);
386 	memset(val, 0, sizeof(*val));
387 }
388 
389 static struct dccp_feat_entry *
dccp_feat_clone_entry(struct dccp_feat_entry const * original)390 	      dccp_feat_clone_entry(struct dccp_feat_entry const *original)
391 {
392 	struct dccp_feat_entry *new;
393 	u8 type = dccp_feat_type(original->feat_num);
394 
395 	if (type == FEAT_UNKNOWN)
396 		return NULL;
397 
398 	new = kmemdup(original, sizeof(struct dccp_feat_entry), gfp_any());
399 	if (new == NULL)
400 		return NULL;
401 
402 	if (type == FEAT_SP && dccp_feat_clone_sp_val(&new->val,
403 						      original->val.sp.vec,
404 						      original->val.sp.len)) {
405 		kfree(new);
406 		return NULL;
407 	}
408 	return new;
409 }
410 
dccp_feat_entry_destructor(struct dccp_feat_entry * entry)411 static void dccp_feat_entry_destructor(struct dccp_feat_entry *entry)
412 {
413 	if (entry != NULL) {
414 		dccp_feat_val_destructor(entry->feat_num, &entry->val);
415 		kfree(entry);
416 	}
417 }
418 
419 /*
420  * List management functions
421  *
422  * Feature negotiation lists rely on and maintain the following invariants:
423  * - each feat_num in the list is known, i.e. we know its type and default value
424  * - each feat_num/is_local combination is unique (old entries are overwritten)
425  * - SP values are always freshly allocated
426  * - list is sorted in increasing order of feature number (faster lookup)
427  */
dccp_feat_list_lookup(struct list_head * fn_list,u8 feat_num,bool is_local)428 static struct dccp_feat_entry *dccp_feat_list_lookup(struct list_head *fn_list,
429 						     u8 feat_num, bool is_local)
430 {
431 	struct dccp_feat_entry *entry;
432 
433 	list_for_each_entry(entry, fn_list, node) {
434 		if (entry->feat_num == feat_num && entry->is_local == is_local)
435 			return entry;
436 		else if (entry->feat_num > feat_num)
437 			break;
438 	}
439 	return NULL;
440 }
441 
442 /**
443  * dccp_feat_entry_new  -  Central list update routine (called by all others)
444  * @head:  list to add to
445  * @feat:  feature number
446  * @local: whether the local (1) or remote feature with number @feat is meant
447  *
448  * This is the only constructor and serves to ensure the above invariants.
449  */
450 static struct dccp_feat_entry *
dccp_feat_entry_new(struct list_head * head,u8 feat,bool local)451 	      dccp_feat_entry_new(struct list_head *head, u8 feat, bool local)
452 {
453 	struct dccp_feat_entry *entry;
454 
455 	list_for_each_entry(entry, head, node)
456 		if (entry->feat_num == feat && entry->is_local == local) {
457 			dccp_feat_val_destructor(entry->feat_num, &entry->val);
458 			return entry;
459 		} else if (entry->feat_num > feat) {
460 			head = &entry->node;
461 			break;
462 		}
463 
464 	entry = kmalloc(sizeof(*entry), gfp_any());
465 	if (entry != NULL) {
466 		entry->feat_num = feat;
467 		entry->is_local = local;
468 		list_add_tail(&entry->node, head);
469 	}
470 	return entry;
471 }
472 
473 /**
474  * dccp_feat_push_change  -  Add/overwrite a Change option in the list
475  * @fn_list: feature-negotiation list to update
476  * @feat: one of %dccp_feature_numbers
477  * @local: whether local (1) or remote (0) @feat_num is meant
478  * @mandatory: whether to use Mandatory feature negotiation options
479  * @fval: pointer to NN/SP value to be inserted (will be copied)
480  */
dccp_feat_push_change(struct list_head * fn_list,u8 feat,u8 local,u8 mandatory,dccp_feat_val * fval)481 static int dccp_feat_push_change(struct list_head *fn_list, u8 feat, u8 local,
482 				 u8 mandatory, dccp_feat_val *fval)
483 {
484 	struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
485 
486 	if (new == NULL)
487 		return -ENOMEM;
488 
489 	new->feat_num	     = feat;
490 	new->is_local	     = local;
491 	new->state	     = FEAT_INITIALISING;
492 	new->needs_confirm   = false;
493 	new->empty_confirm   = false;
494 	new->val	     = *fval;
495 	new->needs_mandatory = mandatory;
496 
497 	return 0;
498 }
499 
500 /**
501  * dccp_feat_push_confirm  -  Add a Confirm entry to the FN list
502  * @fn_list: feature-negotiation list to add to
503  * @feat: one of %dccp_feature_numbers
504  * @local: whether local (1) or remote (0) @feat_num is being confirmed
505  * @fval: pointer to NN/SP value to be inserted or NULL
506  *
507  * Returns 0 on success, a Reset code for further processing otherwise.
508  */
dccp_feat_push_confirm(struct list_head * fn_list,u8 feat,u8 local,dccp_feat_val * fval)509 static int dccp_feat_push_confirm(struct list_head *fn_list, u8 feat, u8 local,
510 				  dccp_feat_val *fval)
511 {
512 	struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
513 
514 	if (new == NULL)
515 		return DCCP_RESET_CODE_TOO_BUSY;
516 
517 	new->feat_num	     = feat;
518 	new->is_local	     = local;
519 	new->state	     = FEAT_STABLE;	/* transition in 6.6.2 */
520 	new->needs_confirm   = true;
521 	new->empty_confirm   = (fval == NULL);
522 	new->val.nn	     = 0;		/* zeroes the whole structure */
523 	if (!new->empty_confirm)
524 		new->val     = *fval;
525 	new->needs_mandatory = false;
526 
527 	return 0;
528 }
529 
dccp_push_empty_confirm(struct list_head * fn_list,u8 feat,u8 local)530 static int dccp_push_empty_confirm(struct list_head *fn_list, u8 feat, u8 local)
531 {
532 	return dccp_feat_push_confirm(fn_list, feat, local, NULL);
533 }
534 
dccp_feat_list_pop(struct dccp_feat_entry * entry)535 static inline void dccp_feat_list_pop(struct dccp_feat_entry *entry)
536 {
537 	list_del(&entry->node);
538 	dccp_feat_entry_destructor(entry);
539 }
540 
dccp_feat_list_purge(struct list_head * fn_list)541 void dccp_feat_list_purge(struct list_head *fn_list)
542 {
543 	struct dccp_feat_entry *entry, *next;
544 
545 	list_for_each_entry_safe(entry, next, fn_list, node)
546 		dccp_feat_entry_destructor(entry);
547 	INIT_LIST_HEAD(fn_list);
548 }
549 EXPORT_SYMBOL_GPL(dccp_feat_list_purge);
550 
551 /* generate @to as full clone of @from - @to must not contain any nodes */
dccp_feat_clone_list(struct list_head const * from,struct list_head * to)552 int dccp_feat_clone_list(struct list_head const *from, struct list_head *to)
553 {
554 	struct dccp_feat_entry *entry, *new;
555 
556 	INIT_LIST_HEAD(to);
557 	list_for_each_entry(entry, from, node) {
558 		new = dccp_feat_clone_entry(entry);
559 		if (new == NULL)
560 			goto cloning_failed;
561 		list_add_tail(&new->node, to);
562 	}
563 	return 0;
564 
565 cloning_failed:
566 	dccp_feat_list_purge(to);
567 	return -ENOMEM;
568 }
569 
570 /**
571  * dccp_feat_valid_nn_length  -  Enforce length constraints on NN options
572  * @feat_num: feature to return length of, one of %dccp_feature_numbers
573  *
574  * Length is between 0 and %DCCP_OPTVAL_MAXLEN. Used for outgoing packets only,
575  * incoming options are accepted as long as their values are valid.
576  */
dccp_feat_valid_nn_length(u8 feat_num)577 static u8 dccp_feat_valid_nn_length(u8 feat_num)
578 {
579 	if (feat_num == DCCPF_ACK_RATIO)	/* RFC 4340, 11.3 and 6.6.8 */
580 		return 2;
581 	if (feat_num == DCCPF_SEQUENCE_WINDOW)	/* RFC 4340, 7.5.2 and 6.5  */
582 		return 6;
583 	return 0;
584 }
585 
dccp_feat_is_valid_nn_val(u8 feat_num,u64 val)586 static u8 dccp_feat_is_valid_nn_val(u8 feat_num, u64 val)
587 {
588 	switch (feat_num) {
589 	case DCCPF_ACK_RATIO:
590 		return val <= DCCPF_ACK_RATIO_MAX;
591 	case DCCPF_SEQUENCE_WINDOW:
592 		return val >= DCCPF_SEQ_WMIN && val <= DCCPF_SEQ_WMAX;
593 	}
594 	return 0;	/* feature unknown - so we can't tell */
595 }
596 
597 /* check that SP values are within the ranges defined in RFC 4340 */
dccp_feat_is_valid_sp_val(u8 feat_num,u8 val)598 static u8 dccp_feat_is_valid_sp_val(u8 feat_num, u8 val)
599 {
600 	switch (feat_num) {
601 	case DCCPF_CCID:
602 		return val == DCCPC_CCID2 || val == DCCPC_CCID3;
603 	/* Type-check Boolean feature values: */
604 	case DCCPF_SHORT_SEQNOS:
605 	case DCCPF_ECN_INCAPABLE:
606 	case DCCPF_SEND_ACK_VECTOR:
607 	case DCCPF_SEND_NDP_COUNT:
608 	case DCCPF_DATA_CHECKSUM:
609 	case DCCPF_SEND_LEV_RATE:
610 		return val < 2;
611 	case DCCPF_MIN_CSUM_COVER:
612 		return val < 16;
613 	}
614 	return 0;			/* feature unknown */
615 }
616 
dccp_feat_sp_list_ok(u8 feat_num,u8 const * sp_list,u8 sp_len)617 static u8 dccp_feat_sp_list_ok(u8 feat_num, u8 const *sp_list, u8 sp_len)
618 {
619 	if (sp_list == NULL || sp_len < 1)
620 		return 0;
621 	while (sp_len--)
622 		if (!dccp_feat_is_valid_sp_val(feat_num, *sp_list++))
623 			return 0;
624 	return 1;
625 }
626 
627 /**
628  * dccp_feat_insert_opts  -  Generate FN options from current list state
629  * @skb: next sk_buff to be sent to the peer
630  * @dp: for client during handshake and general negotiation
631  * @dreq: used by the server only (all Changes/Confirms in LISTEN/RESPOND)
632  */
dccp_feat_insert_opts(struct dccp_sock * dp,struct dccp_request_sock * dreq,struct sk_buff * skb)633 int dccp_feat_insert_opts(struct dccp_sock *dp, struct dccp_request_sock *dreq,
634 			  struct sk_buff *skb)
635 {
636 	struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
637 	struct dccp_feat_entry *pos, *next;
638 	u8 opt, type, len, *ptr, nn_in_nbo[DCCP_OPTVAL_MAXLEN];
639 	bool rpt;
640 
641 	/* put entries into @skb in the order they appear in the list */
642 	list_for_each_entry_safe_reverse(pos, next, fn, node) {
643 		opt  = dccp_feat_genopt(pos);
644 		type = dccp_feat_type(pos->feat_num);
645 		rpt  = false;
646 
647 		if (pos->empty_confirm) {
648 			len = 0;
649 			ptr = NULL;
650 		} else {
651 			if (type == FEAT_SP) {
652 				len = pos->val.sp.len;
653 				ptr = pos->val.sp.vec;
654 				rpt = pos->needs_confirm;
655 			} else if (type == FEAT_NN) {
656 				len = dccp_feat_valid_nn_length(pos->feat_num);
657 				ptr = nn_in_nbo;
658 				dccp_encode_value_var(pos->val.nn, ptr, len);
659 			} else {
660 				DCCP_BUG("unknown feature %u", pos->feat_num);
661 				return -1;
662 			}
663 		}
664 		dccp_feat_print_opt(opt, pos->feat_num, ptr, len, 0);
665 
666 		if (dccp_insert_fn_opt(skb, opt, pos->feat_num, ptr, len, rpt))
667 			return -1;
668 		if (pos->needs_mandatory && dccp_insert_option_mandatory(skb))
669 			return -1;
670 
671 		if (skb->sk->sk_state == DCCP_OPEN &&
672 		    (opt == DCCPO_CONFIRM_R || opt == DCCPO_CONFIRM_L)) {
673 			/*
674 			 * Confirms don't get retransmitted (6.6.3) once the
675 			 * connection is in state OPEN
676 			 */
677 			dccp_feat_list_pop(pos);
678 		} else {
679 			/*
680 			 * Enter CHANGING after transmitting the Change
681 			 * option (6.6.2).
682 			 */
683 			if (pos->state == FEAT_INITIALISING)
684 				pos->state = FEAT_CHANGING;
685 		}
686 	}
687 	return 0;
688 }
689 
690 /**
691  * __feat_register_nn  -  Register new NN value on socket
692  * @fn: feature-negotiation list to register with
693  * @feat: an NN feature from %dccp_feature_numbers
694  * @mandatory: use Mandatory option if 1
695  * @nn_val: value to register (restricted to 4 bytes)
696  *
697  * Note that NN features are local by definition (RFC 4340, 6.3.2).
698  */
__feat_register_nn(struct list_head * fn,u8 feat,u8 mandatory,u64 nn_val)699 static int __feat_register_nn(struct list_head *fn, u8 feat,
700 			      u8 mandatory, u64 nn_val)
701 {
702 	dccp_feat_val fval = { .nn = nn_val };
703 
704 	if (dccp_feat_type(feat) != FEAT_NN ||
705 	    !dccp_feat_is_valid_nn_val(feat, nn_val))
706 		return -EINVAL;
707 
708 	/* Don't bother with default values, they will be activated anyway. */
709 	if (nn_val - (u64)dccp_feat_default_value(feat) == 0)
710 		return 0;
711 
712 	return dccp_feat_push_change(fn, feat, 1, mandatory, &fval);
713 }
714 
715 /**
716  * __feat_register_sp  -  Register new SP value/list on socket
717  * @fn: feature-negotiation list to register with
718  * @feat: an SP feature from %dccp_feature_numbers
719  * @is_local: whether the local (1) or the remote (0) @feat is meant
720  * @mandatory: use Mandatory option if 1
721  * @sp_val: SP value followed by optional preference list
722  * @sp_len: length of @sp_val in bytes
723  */
__feat_register_sp(struct list_head * fn,u8 feat,u8 is_local,u8 mandatory,u8 const * sp_val,u8 sp_len)724 static int __feat_register_sp(struct list_head *fn, u8 feat, u8 is_local,
725 			      u8 mandatory, u8 const *sp_val, u8 sp_len)
726 {
727 	dccp_feat_val fval;
728 
729 	if (dccp_feat_type(feat) != FEAT_SP ||
730 	    !dccp_feat_sp_list_ok(feat, sp_val, sp_len))
731 		return -EINVAL;
732 
733 	/* Avoid negotiating alien CCIDs by only advertising supported ones */
734 	if (feat == DCCPF_CCID && !ccid_support_check(sp_val, sp_len))
735 		return -EOPNOTSUPP;
736 
737 	if (dccp_feat_clone_sp_val(&fval, sp_val, sp_len))
738 		return -ENOMEM;
739 
740 	if (dccp_feat_push_change(fn, feat, is_local, mandatory, &fval)) {
741 		kfree(fval.sp.vec);
742 		return -ENOMEM;
743 	}
744 
745 	return 0;
746 }
747 
748 /**
749  * dccp_feat_register_sp  -  Register requests to change SP feature values
750  * @sk: client or listening socket
751  * @feat: one of %dccp_feature_numbers
752  * @is_local: whether the local (1) or remote (0) @feat is meant
753  * @list: array of preferred values, in descending order of preference
754  * @len: length of @list in bytes
755  */
dccp_feat_register_sp(struct sock * sk,u8 feat,u8 is_local,u8 const * list,u8 len)756 int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
757 			  u8 const *list, u8 len)
758 {	 /* any changes must be registered before establishing the connection */
759 	if (sk->sk_state != DCCP_CLOSED)
760 		return -EISCONN;
761 	if (dccp_feat_type(feat) != FEAT_SP)
762 		return -EINVAL;
763 	return __feat_register_sp(&dccp_sk(sk)->dccps_featneg, feat, is_local,
764 				  0, list, len);
765 }
766 
767 /**
768  * dccp_feat_nn_get  -  Query current/pending value of NN feature
769  * @sk: DCCP socket of an established connection
770  * @feat: NN feature number from %dccp_feature_numbers
771  *
772  * For a known NN feature, returns value currently being negotiated, or
773  * current (confirmed) value if no negotiation is going on.
774  */
dccp_feat_nn_get(struct sock * sk,u8 feat)775 u64 dccp_feat_nn_get(struct sock *sk, u8 feat)
776 {
777 	if (dccp_feat_type(feat) == FEAT_NN) {
778 		struct dccp_sock *dp = dccp_sk(sk);
779 		struct dccp_feat_entry *entry;
780 
781 		entry = dccp_feat_list_lookup(&dp->dccps_featneg, feat, 1);
782 		if (entry != NULL)
783 			return entry->val.nn;
784 
785 		switch (feat) {
786 		case DCCPF_ACK_RATIO:
787 			return dp->dccps_l_ack_ratio;
788 		case DCCPF_SEQUENCE_WINDOW:
789 			return dp->dccps_l_seq_win;
790 		}
791 	}
792 	DCCP_BUG("attempt to look up unsupported feature %u", feat);
793 	return 0;
794 }
795 EXPORT_SYMBOL_GPL(dccp_feat_nn_get);
796 
797 /**
798  * dccp_feat_signal_nn_change  -  Update NN values for an established connection
799  * @sk: DCCP socket of an established connection
800  * @feat: NN feature number from %dccp_feature_numbers
801  * @nn_val: the new value to use
802  *
803  * This function is used to communicate NN updates out-of-band.
804  */
dccp_feat_signal_nn_change(struct sock * sk,u8 feat,u64 nn_val)805 int dccp_feat_signal_nn_change(struct sock *sk, u8 feat, u64 nn_val)
806 {
807 	struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
808 	dccp_feat_val fval = { .nn = nn_val };
809 	struct dccp_feat_entry *entry;
810 
811 	if (sk->sk_state != DCCP_OPEN && sk->sk_state != DCCP_PARTOPEN)
812 		return 0;
813 
814 	if (dccp_feat_type(feat) != FEAT_NN ||
815 	    !dccp_feat_is_valid_nn_val(feat, nn_val))
816 		return -EINVAL;
817 
818 	if (nn_val == dccp_feat_nn_get(sk, feat))
819 		return 0;	/* already set or negotiation under way */
820 
821 	entry = dccp_feat_list_lookup(fn, feat, 1);
822 	if (entry != NULL) {
823 		dccp_pr_debug("Clobbering existing NN entry %llu -> %llu\n",
824 			      (unsigned long long)entry->val.nn,
825 			      (unsigned long long)nn_val);
826 		dccp_feat_list_pop(entry);
827 	}
828 
829 	inet_csk_schedule_ack(sk);
830 	return dccp_feat_push_change(fn, feat, 1, 0, &fval);
831 }
832 EXPORT_SYMBOL_GPL(dccp_feat_signal_nn_change);
833 
834 /*
835  *	Tracking features whose value depend on the choice of CCID
836  *
837  * This is designed with an extension in mind so that a list walk could be done
838  * before activating any features. However, the existing framework was found to
839  * work satisfactorily up until now, the automatic verification is left open.
840  * When adding new CCIDs, add a corresponding dependency table here.
841  */
dccp_feat_ccid_deps(u8 ccid,bool is_local)842 static const struct ccid_dependency *dccp_feat_ccid_deps(u8 ccid, bool is_local)
843 {
844 	static const struct ccid_dependency ccid2_dependencies[2][2] = {
845 		/*
846 		 * CCID2 mandates Ack Vectors (RFC 4341, 4.): as CCID is a TX
847 		 * feature and Send Ack Vector is an RX feature, `is_local'
848 		 * needs to be reversed.
849 		 */
850 		{	/* Dependencies of the receiver-side (remote) CCID2 */
851 			{
852 				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
853 				.is_local	= true,
854 				.is_mandatory	= true,
855 				.val		= 1
856 			},
857 			{ 0, 0, 0, 0 }
858 		},
859 		{	/* Dependencies of the sender-side (local) CCID2 */
860 			{
861 				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
862 				.is_local	= false,
863 				.is_mandatory	= true,
864 				.val		= 1
865 			},
866 			{ 0, 0, 0, 0 }
867 		}
868 	};
869 	static const struct ccid_dependency ccid3_dependencies[2][5] = {
870 		{	/*
871 			 * Dependencies of the receiver-side CCID3
872 			 */
873 			{	/* locally disable Ack Vectors */
874 				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
875 				.is_local	= true,
876 				.is_mandatory	= false,
877 				.val		= 0
878 			},
879 			{	/* see below why Send Loss Event Rate is on */
880 				.dependent_feat	= DCCPF_SEND_LEV_RATE,
881 				.is_local	= true,
882 				.is_mandatory	= true,
883 				.val		= 1
884 			},
885 			{	/* NDP Count is needed as per RFC 4342, 6.1.1 */
886 				.dependent_feat	= DCCPF_SEND_NDP_COUNT,
887 				.is_local	= false,
888 				.is_mandatory	= true,
889 				.val		= 1
890 			},
891 			{ 0, 0, 0, 0 },
892 		},
893 		{	/*
894 			 * CCID3 at the TX side: we request that the HC-receiver
895 			 * will not send Ack Vectors (they will be ignored, so
896 			 * Mandatory is not set); we enable Send Loss Event Rate
897 			 * (Mandatory since the implementation does not support
898 			 * the Loss Intervals option of RFC 4342, 8.6).
899 			 * The last two options are for peer's information only.
900 			*/
901 			{
902 				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
903 				.is_local	= false,
904 				.is_mandatory	= false,
905 				.val		= 0
906 			},
907 			{
908 				.dependent_feat	= DCCPF_SEND_LEV_RATE,
909 				.is_local	= false,
910 				.is_mandatory	= true,
911 				.val		= 1
912 			},
913 			{	/* this CCID does not support Ack Ratio */
914 				.dependent_feat	= DCCPF_ACK_RATIO,
915 				.is_local	= true,
916 				.is_mandatory	= false,
917 				.val		= 0
918 			},
919 			{	/* tell receiver we are sending NDP counts */
920 				.dependent_feat	= DCCPF_SEND_NDP_COUNT,
921 				.is_local	= true,
922 				.is_mandatory	= false,
923 				.val		= 1
924 			},
925 			{ 0, 0, 0, 0 }
926 		}
927 	};
928 	switch (ccid) {
929 	case DCCPC_CCID2:
930 		return ccid2_dependencies[is_local];
931 	case DCCPC_CCID3:
932 		return ccid3_dependencies[is_local];
933 	default:
934 		return NULL;
935 	}
936 }
937 
938 /**
939  * dccp_feat_propagate_ccid - Resolve dependencies of features on choice of CCID
940  * @fn: feature-negotiation list to update
941  * @id: CCID number to track
942  * @is_local: whether TX CCID (1) or RX CCID (0) is meant
943  *
944  * This function needs to be called after registering all other features.
945  */
dccp_feat_propagate_ccid(struct list_head * fn,u8 id,bool is_local)946 static int dccp_feat_propagate_ccid(struct list_head *fn, u8 id, bool is_local)
947 {
948 	const struct ccid_dependency *table = dccp_feat_ccid_deps(id, is_local);
949 	int i, rc = (table == NULL);
950 
951 	for (i = 0; rc == 0 && table[i].dependent_feat != DCCPF_RESERVED; i++)
952 		if (dccp_feat_type(table[i].dependent_feat) == FEAT_SP)
953 			rc = __feat_register_sp(fn, table[i].dependent_feat,
954 						    table[i].is_local,
955 						    table[i].is_mandatory,
956 						    &table[i].val, 1);
957 		else
958 			rc = __feat_register_nn(fn, table[i].dependent_feat,
959 						    table[i].is_mandatory,
960 						    table[i].val);
961 	return rc;
962 }
963 
964 /**
965  * dccp_feat_finalise_settings  -  Finalise settings before starting negotiation
966  * @dp: client or listening socket (settings will be inherited)
967  *
968  * This is called after all registrations (socket initialisation, sysctls, and
969  * sockopt calls), and before sending the first packet containing Change options
970  * (ie. client-Request or server-Response), to ensure internal consistency.
971  */
dccp_feat_finalise_settings(struct dccp_sock * dp)972 int dccp_feat_finalise_settings(struct dccp_sock *dp)
973 {
974 	struct list_head *fn = &dp->dccps_featneg;
975 	struct dccp_feat_entry *entry;
976 	int i = 2, ccids[2] = { -1, -1 };
977 
978 	/*
979 	 * Propagating CCIDs:
980 	 * 1) not useful to propagate CCID settings if this host advertises more
981 	 *    than one CCID: the choice of CCID  may still change - if this is
982 	 *    the client, or if this is the server and the client sends
983 	 *    singleton CCID values.
984 	 * 2) since is that propagate_ccid changes the list, we defer changing
985 	 *    the sorted list until after the traversal.
986 	 */
987 	list_for_each_entry(entry, fn, node)
988 		if (entry->feat_num == DCCPF_CCID && entry->val.sp.len == 1)
989 			ccids[entry->is_local] = entry->val.sp.vec[0];
990 	while (i--)
991 		if (ccids[i] > 0 && dccp_feat_propagate_ccid(fn, ccids[i], i))
992 			return -1;
993 	dccp_feat_print_fnlist(fn);
994 	return 0;
995 }
996 
997 /**
998  * dccp_feat_server_ccid_dependencies  -  Resolve CCID-dependent features
999  * @dreq: server socket to resolve
1000  *
1001  * It is the server which resolves the dependencies once the CCID has been
1002  * fully negotiated. If no CCID has been negotiated, it uses the default CCID.
1003  */
dccp_feat_server_ccid_dependencies(struct dccp_request_sock * dreq)1004 int dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq)
1005 {
1006 	struct list_head *fn = &dreq->dreq_featneg;
1007 	struct dccp_feat_entry *entry;
1008 	u8 is_local, ccid;
1009 
1010 	for (is_local = 0; is_local <= 1; is_local++) {
1011 		entry = dccp_feat_list_lookup(fn, DCCPF_CCID, is_local);
1012 
1013 		if (entry != NULL && !entry->empty_confirm)
1014 			ccid = entry->val.sp.vec[0];
1015 		else
1016 			ccid = dccp_feat_default_value(DCCPF_CCID);
1017 
1018 		if (dccp_feat_propagate_ccid(fn, ccid, is_local))
1019 			return -1;
1020 	}
1021 	return 0;
1022 }
1023 
1024 /* Select the first entry in @servlist that also occurs in @clilist (6.3.1) */
dccp_feat_preflist_match(u8 * servlist,u8 slen,u8 * clilist,u8 clen)1025 static int dccp_feat_preflist_match(u8 *servlist, u8 slen, u8 *clilist, u8 clen)
1026 {
1027 	u8 c, s;
1028 
1029 	for (s = 0; s < slen; s++)
1030 		for (c = 0; c < clen; c++)
1031 			if (servlist[s] == clilist[c])
1032 				return servlist[s];
1033 	return -1;
1034 }
1035 
1036 /**
1037  * dccp_feat_prefer  -  Move preferred entry to the start of array
1038  * @preferred_value: entry to move to start of array
1039  * @array: array of preferred entries
1040  * @array_len: size of the array
1041  *
1042  * Reorder the @array_len elements in @array so that @preferred_value comes
1043  * first. Returns >0 to indicate that @preferred_value does occur in @array.
1044  */
dccp_feat_prefer(u8 preferred_value,u8 * array,u8 array_len)1045 static u8 dccp_feat_prefer(u8 preferred_value, u8 *array, u8 array_len)
1046 {
1047 	u8 i, does_occur = 0;
1048 
1049 	if (array != NULL) {
1050 		for (i = 0; i < array_len; i++)
1051 			if (array[i] == preferred_value) {
1052 				array[i] = array[0];
1053 				does_occur++;
1054 			}
1055 		if (does_occur)
1056 			array[0] = preferred_value;
1057 	}
1058 	return does_occur;
1059 }
1060 
1061 /**
1062  * dccp_feat_reconcile  -  Reconcile SP preference lists
1063  *  @fv: SP list to reconcile into
1064  *  @arr: received SP preference list
1065  *  @len: length of @arr in bytes
1066  *  @is_server: whether this side is the server (and @fv is the server's list)
1067  *  @reorder: whether to reorder the list in @fv after reconciling with @arr
1068  * When successful, > 0 is returned and the reconciled list is in @fval.
1069  * A value of 0 means that negotiation failed (no shared entry).
1070  */
dccp_feat_reconcile(dccp_feat_val * fv,u8 * arr,u8 len,bool is_server,bool reorder)1071 static int dccp_feat_reconcile(dccp_feat_val *fv, u8 *arr, u8 len,
1072 			       bool is_server, bool reorder)
1073 {
1074 	int rc;
1075 
1076 	if (!fv->sp.vec || !arr) {
1077 		DCCP_CRIT("NULL feature value or array");
1078 		return 0;
1079 	}
1080 
1081 	if (is_server)
1082 		rc = dccp_feat_preflist_match(fv->sp.vec, fv->sp.len, arr, len);
1083 	else
1084 		rc = dccp_feat_preflist_match(arr, len, fv->sp.vec, fv->sp.len);
1085 
1086 	if (!reorder)
1087 		return rc;
1088 	if (rc < 0)
1089 		return 0;
1090 
1091 	/*
1092 	 * Reorder list: used for activating features and in dccp_insert_fn_opt.
1093 	 */
1094 	return dccp_feat_prefer(rc, fv->sp.vec, fv->sp.len);
1095 }
1096 
1097 /**
1098  * dccp_feat_change_recv  -  Process incoming ChangeL/R options
1099  * @fn: feature-negotiation list to update
1100  * @is_mandatory: whether the Change was preceded by a Mandatory option
1101  * @opt: %DCCPO_CHANGE_L or %DCCPO_CHANGE_R
1102  * @feat: one of %dccp_feature_numbers
1103  * @val: NN value or SP value/preference list
1104  * @len: length of @val in bytes
1105  * @server: whether this node is the server (1) or the client (0)
1106  */
dccp_feat_change_recv(struct list_head * fn,u8 is_mandatory,u8 opt,u8 feat,u8 * val,u8 len,const bool server)1107 static u8 dccp_feat_change_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
1108 				u8 feat, u8 *val, u8 len, const bool server)
1109 {
1110 	u8 defval, type = dccp_feat_type(feat);
1111 	const bool local = (opt == DCCPO_CHANGE_R);
1112 	struct dccp_feat_entry *entry;
1113 	dccp_feat_val fval;
1114 
1115 	if (len == 0 || type == FEAT_UNKNOWN)		/* 6.1 and 6.6.8 */
1116 		goto unknown_feature_or_value;
1117 
1118 	dccp_feat_print_opt(opt, feat, val, len, is_mandatory);
1119 
1120 	/*
1121 	 *	Negotiation of NN features: Change R is invalid, so there is no
1122 	 *	simultaneous negotiation; hence we do not look up in the list.
1123 	 */
1124 	if (type == FEAT_NN) {
1125 		if (local || len > sizeof(fval.nn))
1126 			goto unknown_feature_or_value;
1127 
1128 		/* 6.3.2: "The feature remote MUST accept any valid value..." */
1129 		fval.nn = dccp_decode_value_var(val, len);
1130 		if (!dccp_feat_is_valid_nn_val(feat, fval.nn))
1131 			goto unknown_feature_or_value;
1132 
1133 		return dccp_feat_push_confirm(fn, feat, local, &fval);
1134 	}
1135 
1136 	/*
1137 	 *	Unidirectional/simultaneous negotiation of SP features (6.3.1)
1138 	 */
1139 	entry = dccp_feat_list_lookup(fn, feat, local);
1140 	if (entry == NULL) {
1141 		/*
1142 		 * No particular preferences have been registered. We deal with
1143 		 * this situation by assuming that all valid values are equally
1144 		 * acceptable, and apply the following checks:
1145 		 * - if the peer's list is a singleton, we accept a valid value;
1146 		 * - if we are the server, we first try to see if the peer (the
1147 		 *   client) advertises the default value. If yes, we use it,
1148 		 *   otherwise we accept the preferred value;
1149 		 * - else if we are the client, we use the first list element.
1150 		 */
1151 		if (dccp_feat_clone_sp_val(&fval, val, 1))
1152 			return DCCP_RESET_CODE_TOO_BUSY;
1153 
1154 		if (len > 1 && server) {
1155 			defval = dccp_feat_default_value(feat);
1156 			if (dccp_feat_preflist_match(&defval, 1, val, len) > -1)
1157 				fval.sp.vec[0] = defval;
1158 		} else if (!dccp_feat_is_valid_sp_val(feat, fval.sp.vec[0])) {
1159 			kfree(fval.sp.vec);
1160 			goto unknown_feature_or_value;
1161 		}
1162 
1163 		/* Treat unsupported CCIDs like invalid values */
1164 		if (feat == DCCPF_CCID && !ccid_support_check(fval.sp.vec, 1)) {
1165 			kfree(fval.sp.vec);
1166 			goto not_valid_or_not_known;
1167 		}
1168 
1169 		return dccp_feat_push_confirm(fn, feat, local, &fval);
1170 
1171 	} else if (entry->state == FEAT_UNSTABLE) {	/* 6.6.2 */
1172 		return 0;
1173 	}
1174 
1175 	if (dccp_feat_reconcile(&entry->val, val, len, server, true)) {
1176 		entry->empty_confirm = false;
1177 	} else if (is_mandatory) {
1178 		return DCCP_RESET_CODE_MANDATORY_ERROR;
1179 	} else if (entry->state == FEAT_INITIALISING) {
1180 		/*
1181 		 * Failed simultaneous negotiation (server only): try to `save'
1182 		 * the connection by checking whether entry contains the default
1183 		 * value for @feat. If yes, send an empty Confirm to signal that
1184 		 * the received Change was not understood - which implies using
1185 		 * the default value.
1186 		 * If this also fails, we use Reset as the last resort.
1187 		 */
1188 		WARN_ON(!server);
1189 		defval = dccp_feat_default_value(feat);
1190 		if (!dccp_feat_reconcile(&entry->val, &defval, 1, server, true))
1191 			return DCCP_RESET_CODE_OPTION_ERROR;
1192 		entry->empty_confirm = true;
1193 	}
1194 	entry->needs_confirm   = true;
1195 	entry->needs_mandatory = false;
1196 	entry->state	       = FEAT_STABLE;
1197 	return 0;
1198 
1199 unknown_feature_or_value:
1200 	if (!is_mandatory)
1201 		return dccp_push_empty_confirm(fn, feat, local);
1202 
1203 not_valid_or_not_known:
1204 	return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1205 			    : DCCP_RESET_CODE_OPTION_ERROR;
1206 }
1207 
1208 /**
1209  * dccp_feat_confirm_recv  -  Process received Confirm options
1210  * @fn: feature-negotiation list to update
1211  * @is_mandatory: whether @opt was preceded by a Mandatory option
1212  * @opt: %DCCPO_CONFIRM_L or %DCCPO_CONFIRM_R
1213  * @feat: one of %dccp_feature_numbers
1214  * @val: NN value or SP value/preference list
1215  * @len: length of @val in bytes
1216  * @server: whether this node is server (1) or client (0)
1217  */
dccp_feat_confirm_recv(struct list_head * fn,u8 is_mandatory,u8 opt,u8 feat,u8 * val,u8 len,const bool server)1218 static u8 dccp_feat_confirm_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
1219 				 u8 feat, u8 *val, u8 len, const bool server)
1220 {
1221 	u8 *plist, plen, type = dccp_feat_type(feat);
1222 	const bool local = (opt == DCCPO_CONFIRM_R);
1223 	struct dccp_feat_entry *entry = dccp_feat_list_lookup(fn, feat, local);
1224 
1225 	dccp_feat_print_opt(opt, feat, val, len, is_mandatory);
1226 
1227 	if (entry == NULL) {	/* nothing queued: ignore or handle error */
1228 		if (is_mandatory && type == FEAT_UNKNOWN)
1229 			return DCCP_RESET_CODE_MANDATORY_ERROR;
1230 
1231 		if (!local && type == FEAT_NN)		/* 6.3.2 */
1232 			goto confirmation_failed;
1233 		return 0;
1234 	}
1235 
1236 	if (entry->state != FEAT_CHANGING)		/* 6.6.2 */
1237 		return 0;
1238 
1239 	if (len == 0) {
1240 		if (dccp_feat_must_be_understood(feat))	/* 6.6.7 */
1241 			goto confirmation_failed;
1242 		/*
1243 		 * Empty Confirm during connection setup: this means reverting
1244 		 * to the `old' value, which in this case is the default. Since
1245 		 * we handle default values automatically when no other values
1246 		 * have been set, we revert to the old value by removing this
1247 		 * entry from the list.
1248 		 */
1249 		dccp_feat_list_pop(entry);
1250 		return 0;
1251 	}
1252 
1253 	if (type == FEAT_NN) {
1254 		if (len > sizeof(entry->val.nn))
1255 			goto confirmation_failed;
1256 
1257 		if (entry->val.nn == dccp_decode_value_var(val, len))
1258 			goto confirmation_succeeded;
1259 
1260 		DCCP_WARN("Bogus Confirm for non-existing value\n");
1261 		goto confirmation_failed;
1262 	}
1263 
1264 	/*
1265 	 * Parsing SP Confirms: the first element of @val is the preferred
1266 	 * SP value which the peer confirms, the remainder depends on @len.
1267 	 * Note that only the confirmed value need to be a valid SP value.
1268 	 */
1269 	if (!dccp_feat_is_valid_sp_val(feat, *val))
1270 		goto confirmation_failed;
1271 
1272 	if (len == 1) {		/* peer didn't supply a preference list */
1273 		plist = val;
1274 		plen  = len;
1275 	} else {		/* preferred value + preference list */
1276 		plist = val + 1;
1277 		plen  = len - 1;
1278 	}
1279 
1280 	/* Check whether the peer got the reconciliation right (6.6.8) */
1281 	if (dccp_feat_reconcile(&entry->val, plist, plen, server, 0) != *val) {
1282 		DCCP_WARN("Confirm selected the wrong value %u\n", *val);
1283 		return DCCP_RESET_CODE_OPTION_ERROR;
1284 	}
1285 	entry->val.sp.vec[0] = *val;
1286 
1287 confirmation_succeeded:
1288 	entry->state = FEAT_STABLE;
1289 	return 0;
1290 
1291 confirmation_failed:
1292 	DCCP_WARN("Confirmation failed\n");
1293 	return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1294 			    : DCCP_RESET_CODE_OPTION_ERROR;
1295 }
1296 
1297 /**
1298  * dccp_feat_handle_nn_established  -  Fast-path reception of NN options
1299  * @sk:		socket of an established DCCP connection
1300  * @mandatory:	whether @opt was preceded by a Mandatory option
1301  * @opt:	%DCCPO_CHANGE_L | %DCCPO_CONFIRM_R (NN only)
1302  * @feat:	NN number, one of %dccp_feature_numbers
1303  * @val:	NN value
1304  * @len:	length of @val in bytes
1305  *
1306  * This function combines the functionality of change_recv/confirm_recv, with
1307  * the following differences (reset codes are the same):
1308  *    - cleanup after receiving the Confirm;
1309  *    - values are directly activated after successful parsing;
1310  *    - deliberately restricted to NN features.
1311  * The restriction to NN features is essential since SP features can have non-
1312  * predictable outcomes (depending on the remote configuration), and are inter-
1313  * dependent (CCIDs for instance cause further dependencies).
1314  */
dccp_feat_handle_nn_established(struct sock * sk,u8 mandatory,u8 opt,u8 feat,u8 * val,u8 len)1315 static u8 dccp_feat_handle_nn_established(struct sock *sk, u8 mandatory, u8 opt,
1316 					  u8 feat, u8 *val, u8 len)
1317 {
1318 	struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
1319 	const bool local = (opt == DCCPO_CONFIRM_R);
1320 	struct dccp_feat_entry *entry;
1321 	u8 type = dccp_feat_type(feat);
1322 	dccp_feat_val fval;
1323 
1324 	dccp_feat_print_opt(opt, feat, val, len, mandatory);
1325 
1326 	/* Ignore non-mandatory unknown and non-NN features */
1327 	if (type == FEAT_UNKNOWN) {
1328 		if (local && !mandatory)
1329 			return 0;
1330 		goto fast_path_unknown;
1331 	} else if (type != FEAT_NN) {
1332 		return 0;
1333 	}
1334 
1335 	/*
1336 	 * We don't accept empty Confirms, since in fast-path feature
1337 	 * negotiation the values are enabled immediately after sending
1338 	 * the Change option.
1339 	 * Empty Changes on the other hand are invalid (RFC 4340, 6.1).
1340 	 */
1341 	if (len == 0 || len > sizeof(fval.nn))
1342 		goto fast_path_unknown;
1343 
1344 	if (opt == DCCPO_CHANGE_L) {
1345 		fval.nn = dccp_decode_value_var(val, len);
1346 		if (!dccp_feat_is_valid_nn_val(feat, fval.nn))
1347 			goto fast_path_unknown;
1348 
1349 		if (dccp_feat_push_confirm(fn, feat, local, &fval) ||
1350 		    dccp_feat_activate(sk, feat, local, &fval))
1351 			return DCCP_RESET_CODE_TOO_BUSY;
1352 
1353 		/* set the `Ack Pending' flag to piggyback a Confirm */
1354 		inet_csk_schedule_ack(sk);
1355 
1356 	} else if (opt == DCCPO_CONFIRM_R) {
1357 		entry = dccp_feat_list_lookup(fn, feat, local);
1358 		if (entry == NULL || entry->state != FEAT_CHANGING)
1359 			return 0;
1360 
1361 		fval.nn = dccp_decode_value_var(val, len);
1362 		/*
1363 		 * Just ignore a value that doesn't match our current value.
1364 		 * If the option changes twice within two RTTs, then at least
1365 		 * one CONFIRM will be received for the old value after a
1366 		 * new CHANGE was sent.
1367 		 */
1368 		if (fval.nn != entry->val.nn)
1369 			return 0;
1370 
1371 		/* Only activate after receiving the Confirm option (6.6.1). */
1372 		dccp_feat_activate(sk, feat, local, &fval);
1373 
1374 		/* It has been confirmed - so remove the entry */
1375 		dccp_feat_list_pop(entry);
1376 
1377 	} else {
1378 		DCCP_WARN("Received illegal option %u\n", opt);
1379 		goto fast_path_failed;
1380 	}
1381 	return 0;
1382 
1383 fast_path_unknown:
1384 	if (!mandatory)
1385 		return dccp_push_empty_confirm(fn, feat, local);
1386 
1387 fast_path_failed:
1388 	return mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1389 			 : DCCP_RESET_CODE_OPTION_ERROR;
1390 }
1391 
1392 /**
1393  * dccp_feat_parse_options  -  Process Feature-Negotiation Options
1394  * @sk: for general use and used by the client during connection setup
1395  * @dreq: used by the server during connection setup
1396  * @mandatory: whether @opt was preceded by a Mandatory option
1397  * @opt: %DCCPO_CHANGE_L | %DCCPO_CHANGE_R | %DCCPO_CONFIRM_L | %DCCPO_CONFIRM_R
1398  * @feat: one of %dccp_feature_numbers
1399  * @val: value contents of @opt
1400  * @len: length of @val in bytes
1401  *
1402  * Returns 0 on success, a Reset code for ending the connection otherwise.
1403  */
dccp_feat_parse_options(struct sock * sk,struct dccp_request_sock * dreq,u8 mandatory,u8 opt,u8 feat,u8 * val,u8 len)1404 int dccp_feat_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
1405 			    u8 mandatory, u8 opt, u8 feat, u8 *val, u8 len)
1406 {
1407 	struct dccp_sock *dp = dccp_sk(sk);
1408 	struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
1409 	bool server = false;
1410 
1411 	switch (sk->sk_state) {
1412 	/*
1413 	 *	Negotiation during connection setup
1414 	 */
1415 	case DCCP_LISTEN:
1416 		server = true;
1417 		fallthrough;
1418 	case DCCP_REQUESTING:
1419 		switch (opt) {
1420 		case DCCPO_CHANGE_L:
1421 		case DCCPO_CHANGE_R:
1422 			return dccp_feat_change_recv(fn, mandatory, opt, feat,
1423 						     val, len, server);
1424 		case DCCPO_CONFIRM_R:
1425 		case DCCPO_CONFIRM_L:
1426 			return dccp_feat_confirm_recv(fn, mandatory, opt, feat,
1427 						      val, len, server);
1428 		}
1429 		break;
1430 	/*
1431 	 *	Support for exchanging NN options on an established connection.
1432 	 */
1433 	case DCCP_OPEN:
1434 	case DCCP_PARTOPEN:
1435 		return dccp_feat_handle_nn_established(sk, mandatory, opt, feat,
1436 						       val, len);
1437 	}
1438 	return 0;	/* ignore FN options in all other states */
1439 }
1440 
1441 /**
1442  * dccp_feat_init  -  Seed feature negotiation with host-specific defaults
1443  * @sk: Socket to initialize.
1444  *
1445  * This initialises global defaults, depending on the value of the sysctls.
1446  * These can later be overridden by registering changes via setsockopt calls.
1447  * The last link in the chain is finalise_settings, to make sure that between
1448  * here and the start of actual feature negotiation no inconsistencies enter.
1449  *
1450  * All features not appearing below use either defaults or are otherwise
1451  * later adjusted through dccp_feat_finalise_settings().
1452  */
dccp_feat_init(struct sock * sk)1453 int dccp_feat_init(struct sock *sk)
1454 {
1455 	struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
1456 	u8 on = 1, off = 0;
1457 	int rc;
1458 	struct {
1459 		u8 *val;
1460 		u8 len;
1461 	} tx, rx;
1462 
1463 	/* Non-negotiable (NN) features */
1464 	rc = __feat_register_nn(fn, DCCPF_SEQUENCE_WINDOW, 0,
1465 				    sysctl_dccp_sequence_window);
1466 	if (rc)
1467 		return rc;
1468 
1469 	/* Server-priority (SP) features */
1470 
1471 	/* Advertise that short seqnos are not supported (7.6.1) */
1472 	rc = __feat_register_sp(fn, DCCPF_SHORT_SEQNOS, true, true, &off, 1);
1473 	if (rc)
1474 		return rc;
1475 
1476 	/* RFC 4340 12.1: "If a DCCP is not ECN capable, ..." */
1477 	rc = __feat_register_sp(fn, DCCPF_ECN_INCAPABLE, true, true, &on, 1);
1478 	if (rc)
1479 		return rc;
1480 
1481 	/*
1482 	 * We advertise the available list of CCIDs and reorder according to
1483 	 * preferences, to avoid failure resulting from negotiating different
1484 	 * singleton values (which always leads to failure).
1485 	 * These settings can still (later) be overridden via sockopts.
1486 	 */
1487 	if (ccid_get_builtin_ccids(&tx.val, &tx.len))
1488 		return -ENOBUFS;
1489 	if (ccid_get_builtin_ccids(&rx.val, &rx.len)) {
1490 		kfree(tx.val);
1491 		return -ENOBUFS;
1492 	}
1493 
1494 	if (!dccp_feat_prefer(sysctl_dccp_tx_ccid, tx.val, tx.len) ||
1495 	    !dccp_feat_prefer(sysctl_dccp_rx_ccid, rx.val, rx.len))
1496 		goto free_ccid_lists;
1497 
1498 	rc = __feat_register_sp(fn, DCCPF_CCID, true, false, tx.val, tx.len);
1499 	if (rc)
1500 		goto free_ccid_lists;
1501 
1502 	rc = __feat_register_sp(fn, DCCPF_CCID, false, false, rx.val, rx.len);
1503 
1504 free_ccid_lists:
1505 	kfree(tx.val);
1506 	kfree(rx.val);
1507 	return rc;
1508 }
1509 
dccp_feat_activate_values(struct sock * sk,struct list_head * fn_list)1510 int dccp_feat_activate_values(struct sock *sk, struct list_head *fn_list)
1511 {
1512 	struct dccp_sock *dp = dccp_sk(sk);
1513 	struct dccp_feat_entry *cur, *next;
1514 	int idx;
1515 	dccp_feat_val *fvals[DCCP_FEAT_SUPPORTED_MAX][2] = {
1516 		 [0 ... DCCP_FEAT_SUPPORTED_MAX-1] = { NULL, NULL }
1517 	};
1518 
1519 	list_for_each_entry(cur, fn_list, node) {
1520 		/*
1521 		 * An empty Confirm means that either an unknown feature type
1522 		 * or an invalid value was present. In the first case there is
1523 		 * nothing to activate, in the other the default value is used.
1524 		 */
1525 		if (cur->empty_confirm)
1526 			continue;
1527 
1528 		idx = dccp_feat_index(cur->feat_num);
1529 		if (idx < 0) {
1530 			DCCP_BUG("Unknown feature %u", cur->feat_num);
1531 			goto activation_failed;
1532 		}
1533 		if (cur->state != FEAT_STABLE) {
1534 			DCCP_CRIT("Negotiation of %s %s failed in state %s",
1535 				  cur->is_local ? "local" : "remote",
1536 				  dccp_feat_fname(cur->feat_num),
1537 				  dccp_feat_sname[cur->state]);
1538 			goto activation_failed;
1539 		}
1540 		fvals[idx][cur->is_local] = &cur->val;
1541 	}
1542 
1543 	/*
1544 	 * Activate in decreasing order of index, so that the CCIDs are always
1545 	 * activated as the last feature. This avoids the case where a CCID
1546 	 * relies on the initialisation of one or more features that it depends
1547 	 * on (e.g. Send NDP Count, Send Ack Vector, and Ack Ratio features).
1548 	 */
1549 	for (idx = DCCP_FEAT_SUPPORTED_MAX; --idx >= 0;)
1550 		if (__dccp_feat_activate(sk, idx, 0, fvals[idx][0]) ||
1551 		    __dccp_feat_activate(sk, idx, 1, fvals[idx][1])) {
1552 			DCCP_CRIT("Could not activate %d", idx);
1553 			goto activation_failed;
1554 		}
1555 
1556 	/* Clean up Change options which have been confirmed already */
1557 	list_for_each_entry_safe(cur, next, fn_list, node)
1558 		if (!cur->needs_confirm)
1559 			dccp_feat_list_pop(cur);
1560 
1561 	dccp_pr_debug("Activation OK\n");
1562 	return 0;
1563 
1564 activation_failed:
1565 	/*
1566 	 * We clean up everything that may have been allocated, since
1567 	 * it is difficult to track at which stage negotiation failed.
1568 	 * This is ok, since all allocation functions below are robust
1569 	 * against NULL arguments.
1570 	 */
1571 	ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
1572 	ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
1573 	dp->dccps_hc_rx_ccid = dp->dccps_hc_tx_ccid = NULL;
1574 	dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
1575 	dp->dccps_hc_rx_ackvec = NULL;
1576 	return -1;
1577 }
1578