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 */
  26unsigned long	sysctl_dccp_sequence_window __read_mostly = 100;
  27int		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 */
  36static 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
  54static 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
  70static 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
  79static 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
  96static 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 */
 112static 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
 128static 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 */
 172static 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
 189static 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
 198static 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 */
 213static 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
 238static const char *const dccp_feat_sname[] = {
 239	"DEFAULT", "INITIALISING", "CHANGING", "UNSTABLE", "STABLE",
 240};
 241
 242#ifdef CONFIG_IP_DCCP_DEBUG
 243static 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
 254static 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
 269static 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
 279static 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
 305static 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 */
 353static 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) */
 360static 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 */
 367static 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
 380static 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
 389static struct dccp_feat_entry *
 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
 411static 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 */
 428static 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 */
 450static struct dccp_feat_entry *
 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 */
 481static 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 */
 509static 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
 530static 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
 535static 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
 541void 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}
 549EXPORT_SYMBOL_GPL(dccp_feat_list_purge);
 550
 551/* generate @to as full clone of @from - @to must not contain any nodes */
 552int 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
 565cloning_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 */
 577static 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
 586static 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 */
 598static 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
 617static 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 */
 633int 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 */
 699static 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 */
 724static 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 */
 756int 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 */
 775u64 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}
 795EXPORT_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 */
 805int 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}
 832EXPORT_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 */
 842static 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 */
 946static 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 */
 972int 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 */
1004int 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) */
1025static 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 */
1045static 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 */
1071static 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 */
1107static 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		if (dccp_feat_push_confirm(fn, feat, local, &fval)) {
1170			kfree(fval.sp.vec);
1171			return DCCP_RESET_CODE_TOO_BUSY;
1172		}
1173
1174		return 0;
1175	} else if (entry->state == FEAT_UNSTABLE) {	/* 6.6.2 */
1176		return 0;
1177	}
1178
1179	if (dccp_feat_reconcile(&entry->val, val, len, server, true)) {
1180		entry->empty_confirm = false;
1181	} else if (is_mandatory) {
1182		return DCCP_RESET_CODE_MANDATORY_ERROR;
1183	} else if (entry->state == FEAT_INITIALISING) {
1184		/*
1185		 * Failed simultaneous negotiation (server only): try to `save'
1186		 * the connection by checking whether entry contains the default
1187		 * value for @feat. If yes, send an empty Confirm to signal that
1188		 * the received Change was not understood - which implies using
1189		 * the default value.
1190		 * If this also fails, we use Reset as the last resort.
1191		 */
1192		WARN_ON(!server);
1193		defval = dccp_feat_default_value(feat);
1194		if (!dccp_feat_reconcile(&entry->val, &defval, 1, server, true))
1195			return DCCP_RESET_CODE_OPTION_ERROR;
1196		entry->empty_confirm = true;
1197	}
1198	entry->needs_confirm   = true;
1199	entry->needs_mandatory = false;
1200	entry->state	       = FEAT_STABLE;
1201	return 0;
1202
1203unknown_feature_or_value:
1204	if (!is_mandatory)
1205		return dccp_push_empty_confirm(fn, feat, local);
1206
1207not_valid_or_not_known:
1208	return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1209			    : DCCP_RESET_CODE_OPTION_ERROR;
1210}
1211
1212/**
1213 * dccp_feat_confirm_recv  -  Process received Confirm options
1214 * @fn: feature-negotiation list to update
1215 * @is_mandatory: whether @opt was preceded by a Mandatory option
1216 * @opt: %DCCPO_CONFIRM_L or %DCCPO_CONFIRM_R
1217 * @feat: one of %dccp_feature_numbers
1218 * @val: NN value or SP value/preference list
1219 * @len: length of @val in bytes
1220 * @server: whether this node is server (1) or client (0)
1221 */
1222static u8 dccp_feat_confirm_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
1223				 u8 feat, u8 *val, u8 len, const bool server)
1224{
1225	u8 *plist, plen, type = dccp_feat_type(feat);
1226	const bool local = (opt == DCCPO_CONFIRM_R);
1227	struct dccp_feat_entry *entry = dccp_feat_list_lookup(fn, feat, local);
1228
1229	dccp_feat_print_opt(opt, feat, val, len, is_mandatory);
1230
1231	if (entry == NULL) {	/* nothing queued: ignore or handle error */
1232		if (is_mandatory && type == FEAT_UNKNOWN)
1233			return DCCP_RESET_CODE_MANDATORY_ERROR;
1234
1235		if (!local && type == FEAT_NN)		/* 6.3.2 */
1236			goto confirmation_failed;
1237		return 0;
1238	}
1239
1240	if (entry->state != FEAT_CHANGING)		/* 6.6.2 */
1241		return 0;
1242
1243	if (len == 0) {
1244		if (dccp_feat_must_be_understood(feat))	/* 6.6.7 */
1245			goto confirmation_failed;
1246		/*
1247		 * Empty Confirm during connection setup: this means reverting
1248		 * to the `old' value, which in this case is the default. Since
1249		 * we handle default values automatically when no other values
1250		 * have been set, we revert to the old value by removing this
1251		 * entry from the list.
1252		 */
1253		dccp_feat_list_pop(entry);
1254		return 0;
1255	}
1256
1257	if (type == FEAT_NN) {
1258		if (len > sizeof(entry->val.nn))
1259			goto confirmation_failed;
1260
1261		if (entry->val.nn == dccp_decode_value_var(val, len))
1262			goto confirmation_succeeded;
1263
1264		DCCP_WARN("Bogus Confirm for non-existing value\n");
1265		goto confirmation_failed;
1266	}
1267
1268	/*
1269	 * Parsing SP Confirms: the first element of @val is the preferred
1270	 * SP value which the peer confirms, the remainder depends on @len.
1271	 * Note that only the confirmed value need to be a valid SP value.
1272	 */
1273	if (!dccp_feat_is_valid_sp_val(feat, *val))
1274		goto confirmation_failed;
1275
1276	if (len == 1) {		/* peer didn't supply a preference list */
1277		plist = val;
1278		plen  = len;
1279	} else {		/* preferred value + preference list */
1280		plist = val + 1;
1281		plen  = len - 1;
1282	}
1283
1284	/* Check whether the peer got the reconciliation right (6.6.8) */
1285	if (dccp_feat_reconcile(&entry->val, plist, plen, server, 0) != *val) {
1286		DCCP_WARN("Confirm selected the wrong value %u\n", *val);
1287		return DCCP_RESET_CODE_OPTION_ERROR;
1288	}
1289	entry->val.sp.vec[0] = *val;
1290
1291confirmation_succeeded:
1292	entry->state = FEAT_STABLE;
1293	return 0;
1294
1295confirmation_failed:
1296	DCCP_WARN("Confirmation failed\n");
1297	return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1298			    : DCCP_RESET_CODE_OPTION_ERROR;
1299}
1300
1301/**
1302 * dccp_feat_handle_nn_established  -  Fast-path reception of NN options
1303 * @sk:		socket of an established DCCP connection
1304 * @mandatory:	whether @opt was preceded by a Mandatory option
1305 * @opt:	%DCCPO_CHANGE_L | %DCCPO_CONFIRM_R (NN only)
1306 * @feat:	NN number, one of %dccp_feature_numbers
1307 * @val:	NN value
1308 * @len:	length of @val in bytes
1309 *
1310 * This function combines the functionality of change_recv/confirm_recv, with
1311 * the following differences (reset codes are the same):
1312 *    - cleanup after receiving the Confirm;
1313 *    - values are directly activated after successful parsing;
1314 *    - deliberately restricted to NN features.
1315 * The restriction to NN features is essential since SP features can have non-
1316 * predictable outcomes (depending on the remote configuration), and are inter-
1317 * dependent (CCIDs for instance cause further dependencies).
1318 */
1319static u8 dccp_feat_handle_nn_established(struct sock *sk, u8 mandatory, u8 opt,
1320					  u8 feat, u8 *val, u8 len)
1321{
1322	struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
1323	const bool local = (opt == DCCPO_CONFIRM_R);
1324	struct dccp_feat_entry *entry;
1325	u8 type = dccp_feat_type(feat);
1326	dccp_feat_val fval;
1327
1328	dccp_feat_print_opt(opt, feat, val, len, mandatory);
1329
1330	/* Ignore non-mandatory unknown and non-NN features */
1331	if (type == FEAT_UNKNOWN) {
1332		if (local && !mandatory)
1333			return 0;
1334		goto fast_path_unknown;
1335	} else if (type != FEAT_NN) {
1336		return 0;
1337	}
1338
1339	/*
1340	 * We don't accept empty Confirms, since in fast-path feature
1341	 * negotiation the values are enabled immediately after sending
1342	 * the Change option.
1343	 * Empty Changes on the other hand are invalid (RFC 4340, 6.1).
1344	 */
1345	if (len == 0 || len > sizeof(fval.nn))
1346		goto fast_path_unknown;
1347
1348	if (opt == DCCPO_CHANGE_L) {
1349		fval.nn = dccp_decode_value_var(val, len);
1350		if (!dccp_feat_is_valid_nn_val(feat, fval.nn))
1351			goto fast_path_unknown;
1352
1353		if (dccp_feat_push_confirm(fn, feat, local, &fval) ||
1354		    dccp_feat_activate(sk, feat, local, &fval))
1355			return DCCP_RESET_CODE_TOO_BUSY;
1356
1357		/* set the `Ack Pending' flag to piggyback a Confirm */
1358		inet_csk_schedule_ack(sk);
1359
1360	} else if (opt == DCCPO_CONFIRM_R) {
1361		entry = dccp_feat_list_lookup(fn, feat, local);
1362		if (entry == NULL || entry->state != FEAT_CHANGING)
1363			return 0;
1364
1365		fval.nn = dccp_decode_value_var(val, len);
1366		/*
1367		 * Just ignore a value that doesn't match our current value.
1368		 * If the option changes twice within two RTTs, then at least
1369		 * one CONFIRM will be received for the old value after a
1370		 * new CHANGE was sent.
1371		 */
1372		if (fval.nn != entry->val.nn)
1373			return 0;
1374
1375		/* Only activate after receiving the Confirm option (6.6.1). */
1376		dccp_feat_activate(sk, feat, local, &fval);
1377
1378		/* It has been confirmed - so remove the entry */
1379		dccp_feat_list_pop(entry);
1380
1381	} else {
1382		DCCP_WARN("Received illegal option %u\n", opt);
1383		goto fast_path_failed;
1384	}
1385	return 0;
1386
1387fast_path_unknown:
1388	if (!mandatory)
1389		return dccp_push_empty_confirm(fn, feat, local);
1390
1391fast_path_failed:
1392	return mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1393			 : DCCP_RESET_CODE_OPTION_ERROR;
1394}
1395
1396/**
1397 * dccp_feat_parse_options  -  Process Feature-Negotiation Options
1398 * @sk: for general use and used by the client during connection setup
1399 * @dreq: used by the server during connection setup
1400 * @mandatory: whether @opt was preceded by a Mandatory option
1401 * @opt: %DCCPO_CHANGE_L | %DCCPO_CHANGE_R | %DCCPO_CONFIRM_L | %DCCPO_CONFIRM_R
1402 * @feat: one of %dccp_feature_numbers
1403 * @val: value contents of @opt
1404 * @len: length of @val in bytes
1405 *
1406 * Returns 0 on success, a Reset code for ending the connection otherwise.
1407 */
1408int dccp_feat_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
1409			    u8 mandatory, u8 opt, u8 feat, u8 *val, u8 len)
1410{
1411	struct dccp_sock *dp = dccp_sk(sk);
1412	struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
1413	bool server = false;
1414
1415	switch (sk->sk_state) {
1416	/*
1417	 *	Negotiation during connection setup
1418	 */
1419	case DCCP_LISTEN:
1420		server = true;
1421		fallthrough;
1422	case DCCP_REQUESTING:
1423		switch (opt) {
1424		case DCCPO_CHANGE_L:
1425		case DCCPO_CHANGE_R:
1426			return dccp_feat_change_recv(fn, mandatory, opt, feat,
1427						     val, len, server);
1428		case DCCPO_CONFIRM_R:
1429		case DCCPO_CONFIRM_L:
1430			return dccp_feat_confirm_recv(fn, mandatory, opt, feat,
1431						      val, len, server);
1432		}
1433		break;
1434	/*
1435	 *	Support for exchanging NN options on an established connection.
1436	 */
1437	case DCCP_OPEN:
1438	case DCCP_PARTOPEN:
1439		return dccp_feat_handle_nn_established(sk, mandatory, opt, feat,
1440						       val, len);
1441	}
1442	return 0;	/* ignore FN options in all other states */
1443}
1444
1445/**
1446 * dccp_feat_init  -  Seed feature negotiation with host-specific defaults
1447 * @sk: Socket to initialize.
1448 *
1449 * This initialises global defaults, depending on the value of the sysctls.
1450 * These can later be overridden by registering changes via setsockopt calls.
1451 * The last link in the chain is finalise_settings, to make sure that between
1452 * here and the start of actual feature negotiation no inconsistencies enter.
1453 *
1454 * All features not appearing below use either defaults or are otherwise
1455 * later adjusted through dccp_feat_finalise_settings().
1456 */
1457int dccp_feat_init(struct sock *sk)
1458{
1459	struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
1460	u8 on = 1, off = 0;
1461	int rc;
1462	struct {
1463		u8 *val;
1464		u8 len;
1465	} tx, rx;
1466
1467	/* Non-negotiable (NN) features */
1468	rc = __feat_register_nn(fn, DCCPF_SEQUENCE_WINDOW, 0,
1469				    sysctl_dccp_sequence_window);
1470	if (rc)
1471		return rc;
1472
1473	/* Server-priority (SP) features */
1474
1475	/* Advertise that short seqnos are not supported (7.6.1) */
1476	rc = __feat_register_sp(fn, DCCPF_SHORT_SEQNOS, true, true, &off, 1);
1477	if (rc)
1478		return rc;
1479
1480	/* RFC 4340 12.1: "If a DCCP is not ECN capable, ..." */
1481	rc = __feat_register_sp(fn, DCCPF_ECN_INCAPABLE, true, true, &on, 1);
1482	if (rc)
1483		return rc;
1484
1485	/*
1486	 * We advertise the available list of CCIDs and reorder according to
1487	 * preferences, to avoid failure resulting from negotiating different
1488	 * singleton values (which always leads to failure).
1489	 * These settings can still (later) be overridden via sockopts.
1490	 */
1491	if (ccid_get_builtin_ccids(&tx.val, &tx.len))
1492		return -ENOBUFS;
1493	if (ccid_get_builtin_ccids(&rx.val, &rx.len)) {
1494		kfree(tx.val);
1495		return -ENOBUFS;
1496	}
1497
1498	if (!dccp_feat_prefer(sysctl_dccp_tx_ccid, tx.val, tx.len) ||
1499	    !dccp_feat_prefer(sysctl_dccp_rx_ccid, rx.val, rx.len))
1500		goto free_ccid_lists;
1501
1502	rc = __feat_register_sp(fn, DCCPF_CCID, true, false, tx.val, tx.len);
1503	if (rc)
1504		goto free_ccid_lists;
1505
1506	rc = __feat_register_sp(fn, DCCPF_CCID, false, false, rx.val, rx.len);
1507
1508free_ccid_lists:
1509	kfree(tx.val);
1510	kfree(rx.val);
1511	return rc;
1512}
1513
1514int dccp_feat_activate_values(struct sock *sk, struct list_head *fn_list)
1515{
1516	struct dccp_sock *dp = dccp_sk(sk);
1517	struct dccp_feat_entry *cur, *next;
1518	int idx;
1519	dccp_feat_val *fvals[DCCP_FEAT_SUPPORTED_MAX][2] = {
1520		 [0 ... DCCP_FEAT_SUPPORTED_MAX-1] = { NULL, NULL }
1521	};
1522
1523	list_for_each_entry(cur, fn_list, node) {
1524		/*
1525		 * An empty Confirm means that either an unknown feature type
1526		 * or an invalid value was present. In the first case there is
1527		 * nothing to activate, in the other the default value is used.
1528		 */
1529		if (cur->empty_confirm)
1530			continue;
1531
1532		idx = dccp_feat_index(cur->feat_num);
1533		if (idx < 0) {
1534			DCCP_BUG("Unknown feature %u", cur->feat_num);
1535			goto activation_failed;
1536		}
1537		if (cur->state != FEAT_STABLE) {
1538			DCCP_CRIT("Negotiation of %s %s failed in state %s",
1539				  cur->is_local ? "local" : "remote",
1540				  dccp_feat_fname(cur->feat_num),
1541				  dccp_feat_sname[cur->state]);
1542			goto activation_failed;
1543		}
1544		fvals[idx][cur->is_local] = &cur->val;
1545	}
1546
1547	/*
1548	 * Activate in decreasing order of index, so that the CCIDs are always
1549	 * activated as the last feature. This avoids the case where a CCID
1550	 * relies on the initialisation of one or more features that it depends
1551	 * on (e.g. Send NDP Count, Send Ack Vector, and Ack Ratio features).
1552	 */
1553	for (idx = DCCP_FEAT_SUPPORTED_MAX; --idx >= 0;)
1554		if (__dccp_feat_activate(sk, idx, 0, fvals[idx][0]) ||
1555		    __dccp_feat_activate(sk, idx, 1, fvals[idx][1])) {
1556			DCCP_CRIT("Could not activate %d", idx);
1557			goto activation_failed;
1558		}
1559
1560	/* Clean up Change options which have been confirmed already */
1561	list_for_each_entry_safe(cur, next, fn_list, node)
1562		if (!cur->needs_confirm)
1563			dccp_feat_list_pop(cur);
1564
1565	dccp_pr_debug("Activation OK\n");
1566	return 0;
1567
1568activation_failed:
1569	/*
1570	 * We clean up everything that may have been allocated, since
1571	 * it is difficult to track at which stage negotiation failed.
1572	 * This is ok, since all allocation functions below are robust
1573	 * against NULL arguments.
1574	 */
1575	ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
1576	ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
1577	dp->dccps_hc_rx_ccid = dp->dccps_hc_tx_ccid = NULL;
1578	dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
1579	dp->dccps_hc_rx_ackvec = NULL;
1580	return -1;
1581}