net/dccp/feat.c

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