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