net/dccp/feat.c

   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 */
  31 unsigned long   sysctl_dccp_sequence_window __read_mostly = 100;
  32 int             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  */
  41 static 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
  59 static 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
  75 static 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
  84 static 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
 101 static 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  */
 117 static 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
 133 static 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  */
 175 static 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
 192 static 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
 201 static 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  */
 216 static 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
 241 static const char *const dccp_feat_sname[] = {
 242         "DEFAULT", "INITIALISING", "CHANGING", "UNSTABLE", "STABLE",
 243 };
 244
 245 #ifdef CONFIG_IP_DCCP_DEBUG
 246 static 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
 257 static 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
 272 static 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
 282 static 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
 308 static 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  */
 356 static 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) */
 363 static 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 */
 370 static 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
 383 static 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
 392 static 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
 414 static 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  */
 431 static 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  */
 453 static 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  * @mandatory: whether to use Mandatory feature negotiation options
 482  * @fval: pointer to NN/SP value to be inserted (will be copied)
 483  */
 484 static 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  */
 512 static 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
 533 static 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
 538 static 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
 544 void 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 }
 552 EXPORT_SYMBOL_GPL(dccp_feat_list_purge);
 553
 554 /* generate @to as full clone of @from - @to must not contain any nodes */
 555 int 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
 568 cloning_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  */
 578 static 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
 587 static 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 */
 599 static 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
 618 static 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  */
 634 int 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  */
 700 static 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  */
 725 static 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  */
 752 int 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  */
 771 u64 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 }
 791 EXPORT_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  */
 801 int 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 }
 828 EXPORT_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  */
 838 static 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  */
 942 static 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  */
 968 int 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  */
 998 int 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) */
1019 static 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  */
1035 static 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  *  @fv: 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  */
1061 static 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  */
1097 static 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
1189 unknown_feature_or_value:
1190         if (!is_mandatory)
1191                 return dccp_push_empty_confirm(fn, feat, local);
1192
1193 not_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  */
1208 static 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
1277 confirmation_succeeded:
1278         entry->state = FEAT_STABLE;
1279         return 0;
1280
1281 confirmation_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  */
1305 static 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
1373 fast_path_unknown:
1374         if (!mandatory)
1375                 return dccp_push_empty_confirm(fn, feat, local);
1376
1377 fast_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  */
1394 int 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  */
1440 int 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                 return -ENOBUFS;
1476         if (ccid_get_builtin_ccids(&rx.val, &rx.len)) {
1477                 kfree(tx.val);
1478                 return -ENOBUFS;
1479         }
1480
1481         if (!dccp_feat_prefer(sysctl_dccp_tx_ccid, tx.val, tx.len) ||
1482             !dccp_feat_prefer(sysctl_dccp_rx_ccid, rx.val, rx.len))
1483                 goto free_ccid_lists;
1484
1485         rc = __feat_register_sp(fn, DCCPF_CCID, true, false, tx.val, tx.len);
1486         if (rc)
1487                 goto free_ccid_lists;
1488
1489         rc = __feat_register_sp(fn, DCCPF_CCID, false, false, rx.val, rx.len);
1490
1491 free_ccid_lists:
1492         kfree(tx.val);
1493         kfree(rx.val);
1494         return rc;
1495 }
1496
1497 int dccp_feat_activate_values(struct sock *sk, struct list_head *fn_list)
1498 {
1499         struct dccp_sock *dp = dccp_sk(sk);
1500         struct dccp_feat_entry *cur, *next;
1501         int idx;
1502         dccp_feat_val *fvals[DCCP_FEAT_SUPPORTED_MAX][2] = {
1503                  [0 ... DCCP_FEAT_SUPPORTED_MAX-1] = { NULL, NULL }
1504         };
1505
1506         list_for_each_entry(cur, fn_list, node) {
1507                 /*
1508                  * An empty Confirm means that either an unknown feature type
1509                  * or an invalid value was present. In the first case there is
1510                  * nothing to activate, in the other the default value is used.
1511                  */
1512                 if (cur->empty_confirm)
1513                         continue;
1514
1515                 idx = dccp_feat_index(cur->feat_num);
1516                 if (idx < 0) {
1517                         DCCP_BUG("Unknown feature %u", cur->feat_num);
1518                         goto activation_failed;
1519                 }
1520                 if (cur->state != FEAT_STABLE) {
1521                         DCCP_CRIT("Negotiation of %s %s failed in state %s",
1522                                   cur->is_local ? "local" : "remote",
1523                                   dccp_feat_fname(cur->feat_num),
1524                                   dccp_feat_sname[cur->state]);
1525                         goto activation_failed;
1526                 }
1527                 fvals[idx][cur->is_local] = &cur->val;
1528         }
1529
1530         /*
1531          * Activate in decreasing order of index, so that the CCIDs are always
1532          * activated as the last feature. This avoids the case where a CCID
1533          * relies on the initialisation of one or more features that it depends
1534          * on (e.g. Send NDP Count, Send Ack Vector, and Ack Ratio features).
1535          */
1536         for (idx = DCCP_FEAT_SUPPORTED_MAX; --idx >= 0;)
1537                 if (__dccp_feat_activate(sk, idx, 0, fvals[idx][0]) ||
1538                     __dccp_feat_activate(sk, idx, 1, fvals[idx][1])) {
1539                         DCCP_CRIT("Could not activate %d", idx);
1540                         goto activation_failed;
1541                 }
1542
1543         /* Clean up Change options which have been confirmed already */
1544         list_for_each_entry_safe(cur, next, fn_list, node)
1545                 if (!cur->needs_confirm)
1546                         dccp_feat_list_pop(cur);
1547
1548         dccp_pr_debug("Activation OK\n");
1549         return 0;
1550
1551 activation_failed:
1552         /*
1553          * We clean up everything that may have been allocated, since
1554          * it is difficult to track at which stage negotiation failed.
1555          * This is ok, since all allocation functions below are robust
1556          * against NULL arguments.
1557          */
1558         ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
1559         ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
1560         dp->dccps_hc_rx_ccid = dp->dccps_hc_tx_ccid = NULL;
1561         dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
1562         dp->dccps_hc_rx_ackvec = NULL;
1563         return -1;
1564 }