net/dccp/feat.c

   1 /*
   2  *  net/dccp/feat.c
   3  *
   4  *  An implementation of the DCCP protocol
   5  *  Andrea Bittau <a.bittau@cs.ucl.ac.uk>
   6  *
   7  *  ASSUMPTIONS
   8  *  -----------
   9  *  o Feature negotiation is coordinated with connection setup (as in TCP), wild
  10  *    changes of parameters of an established connection are not supported.
  11  *  o All currently known SP features have 1-byte quantities. If in the future
  12  *    extensions of RFCs 4340..42 define features with item lengths larger than
  13  *    one byte, a feature-specific extension of the code will be required.
  14  *
  15  *  This program is free software; you can redistribute it and/or
  16  *  modify it under the terms of the GNU General Public License
  17  *  as published by the Free Software Foundation; either version
  18  *  2 of the License, or (at your option) any later version.
  19  */
  20
  21 #include <linux/module.h>
  22
  23 #include "ccid.h"
  24 #include "feat.h"
  25
  26 #define DCCP_FEAT_SP_NOAGREE (-123)
  27
  28 static const struct {
  29         u8                      feat_num;               /* DCCPF_xxx */
  30         enum dccp_feat_type     rxtx;                   /* RX or TX  */
  31         enum dccp_feat_type     reconciliation;         /* SP or NN  */
  32         u8                      default_value;          /* as in 6.4 */
  33 /*
  34  *    Lookup table for location and type of features (from RFC 4340/4342)
  35  *  +--------------------------+----+-----+----+----+---------+-----------+
  36  *  | Feature                  | Location | Reconc. | Initial |  Section  |
  37  *  |                          | RX | TX  | SP | NN |  Value  | Reference |
  38  *  +--------------------------+----+-----+----+----+---------+-----------+
  39  *  | DCCPF_CCID               |    |  X  | X  |    |   2     | 10        |
  40  *  | DCCPF_SHORT_SEQNOS       |    |  X  | X  |    |   0     |  7.6.1    |
  41  *  | DCCPF_SEQUENCE_WINDOW    |    |  X  |    | X  | 100     |  7.5.2    |
  42  *  | DCCPF_ECN_INCAPABLE      | X  |     | X  |    |   0     | 12.1      |
  43  *  | DCCPF_ACK_RATIO          |    |  X  |    | X  |   2     | 11.3      |
  44  *  | DCCPF_SEND_ACK_VECTOR    | X  |     | X  |    |   0     | 11.5      |
  45  *  | DCCPF_SEND_NDP_COUNT     |    |  X  | X  |    |   0     |  7.7.2    |
  46  *  | DCCPF_MIN_CSUM_COVER     | X  |     | X  |    |   0     |  9.2.1    |
  47  *  | DCCPF_DATA_CHECKSUM      | X  |     | X  |    |   0     |  9.3.1    |
  48  *  | DCCPF_SEND_LEV_RATE      | X  |     | X  |    |   0     | 4342/8.4  |
  49  *  +--------------------------+----+-----+----+----+---------+-----------+
  50  */
  51 } dccp_feat_table[] = {
  52         { DCCPF_CCID,            FEAT_AT_TX, FEAT_SP, 2 },
  53         { DCCPF_SHORT_SEQNOS,    FEAT_AT_TX, FEAT_SP, 0 },
  54         { DCCPF_SEQUENCE_WINDOW, FEAT_AT_TX, FEAT_NN, 100 },
  55         { DCCPF_ECN_INCAPABLE,   FEAT_AT_RX, FEAT_SP, 0 },
  56         { DCCPF_ACK_RATIO,       FEAT_AT_TX, FEAT_NN, 2 },
  57         { DCCPF_SEND_ACK_VECTOR, FEAT_AT_RX, FEAT_SP, 0 },
  58         { DCCPF_SEND_NDP_COUNT,  FEAT_AT_TX, FEAT_SP, 0 },
  59         { DCCPF_MIN_CSUM_COVER,  FEAT_AT_RX, FEAT_SP, 0 },
  60         { DCCPF_DATA_CHECKSUM,   FEAT_AT_RX, FEAT_SP, 0 },
  61         { DCCPF_SEND_LEV_RATE,   FEAT_AT_RX, FEAT_SP, 0 },
  62 };
  63 #define DCCP_FEAT_SUPPORTED_MAX         ARRAY_SIZE(dccp_feat_table)
  64
  65 /**
  66  * dccp_feat_index  -  Hash function to map feature number into array position
  67  * Returns consecutive array index or -1 if the feature is not understood.
  68  */
  69 static int dccp_feat_index(u8 feat_num)
  70 {
  71         /* The first 9 entries are occupied by the types from RFC 4340, 6.4 */
  72         if (feat_num > DCCPF_RESERVED && feat_num <= DCCPF_DATA_CHECKSUM)
  73                 return feat_num - 1;
  74
  75         /*
  76          * Other features: add cases for new feature types here after adding
  77          * them to the above table.
  78          */
  79         switch (feat_num) {
  80         case DCCPF_SEND_LEV_RATE:
  81                         return DCCP_FEAT_SUPPORTED_MAX - 1;
  82         }
  83         return -1;
  84 }
  85
  86 static u8 dccp_feat_type(u8 feat_num)
  87 {
  88         int idx = dccp_feat_index(feat_num);
  89
  90         if (idx < 0)
  91                 return FEAT_UNKNOWN;
  92         return dccp_feat_table[idx].reconciliation;
  93 }
  94
  95 static int dccp_feat_default_value(u8 feat_num)
  96 {
  97         int idx = dccp_feat_index(feat_num);
  98         /*
  99          * There are no default values for unknown features, so encountering a
 100          * negative index here indicates a serious problem somewhere else.
 101          */
 102         DCCP_BUG_ON(idx < 0);
 103
 104         return idx < 0 ? 0 : dccp_feat_table[idx].default_value;
 105 }
 106
 107 /* copy constructor, fval must not already contain allocated memory */
 108 static int dccp_feat_clone_sp_val(dccp_feat_val *fval, u8 const *val, u8 len)
 109 {
 110         fval->sp.len = len;
 111         if (fval->sp.len > 0) {
 112                 fval->sp.vec = kmemdup(val, len, gfp_any());
 113                 if (fval->sp.vec == NULL) {
 114                         fval->sp.len = 0;
 115                         return -ENOBUFS;
 116                 }
 117         }
 118         return 0;
 119 }
 120
 121 static void dccp_feat_val_destructor(u8 feat_num, dccp_feat_val *val)
 122 {
 123         if (unlikely(val == NULL))
 124                 return;
 125         if (dccp_feat_type(feat_num) == FEAT_SP)
 126                 kfree(val->sp.vec);
 127         memset(val, 0, sizeof(*val));
 128 }
 129
 130 static struct dccp_feat_entry *
 131               dccp_feat_clone_entry(struct dccp_feat_entry const *original)
 132 {
 133         struct dccp_feat_entry *new;
 134         u8 type = dccp_feat_type(original->feat_num);
 135
 136         if (type == FEAT_UNKNOWN)
 137                 return NULL;
 138
 139         new = kmemdup(original, sizeof(struct dccp_feat_entry), gfp_any());
 140         if (new == NULL)
 141                 return NULL;
 142
 143         if (type == FEAT_SP && dccp_feat_clone_sp_val(&new->val,
 144                                                       original->val.sp.vec,
 145                                                       original->val.sp.len)) {
 146                 kfree(new);
 147                 return NULL;
 148         }
 149         return new;
 150 }
 151
 152 static void dccp_feat_entry_destructor(struct dccp_feat_entry *entry)
 153 {
 154         if (entry != NULL) {
 155                 dccp_feat_val_destructor(entry->feat_num, &entry->val);
 156                 kfree(entry);
 157         }
 158 }
 159
 160 /*
 161  * List management functions
 162  *
 163  * Feature negotiation lists rely on and maintain the following invariants:
 164  * - each feat_num in the list is known, i.e. we know its type and default value
 165  * - each feat_num/is_local combination is unique (old entries are overwritten)
 166  * - SP values are always freshly allocated
 167  * - list is sorted in increasing order of feature number (faster lookup)
 168  */
 169 static struct dccp_feat_entry *dccp_feat_list_lookup(struct list_head *fn_list,
 170                                                      u8 feat_num, bool is_local)
 171 {
 172         struct dccp_feat_entry *entry;
 173
 174         list_for_each_entry(entry, fn_list, node) {
 175                 if (entry->feat_num == feat_num && entry->is_local == is_local)
 176                         return entry;
 177                 else if (entry->feat_num > feat_num)
 178                         break;
 179         }
 180         return NULL;
 181 }
 182
 183 /**
 184  * dccp_feat_entry_new  -  Central list update routine (called by all others)
 185  * @head:  list to add to
 186  * @feat:  feature number
 187  * @local: whether the local (1) or remote feature with number @feat is meant
 188  * This is the only constructor and serves to ensure the above invariants.
 189  */
 190 static struct dccp_feat_entry *
 191               dccp_feat_entry_new(struct list_head *head, u8 feat, bool local)
 192 {
 193         struct dccp_feat_entry *entry;
 194
 195         list_for_each_entry(entry, head, node)
 196                 if (entry->feat_num == feat && entry->is_local == local) {
 197                         dccp_feat_val_destructor(entry->feat_num, &entry->val);
 198                         return entry;
 199                 } else if (entry->feat_num > feat) {
 200                         head = &entry->node;
 201                         break;
 202                 }
 203
 204         entry = kmalloc(sizeof(*entry), gfp_any());
 205         if (entry != NULL) {
 206                 entry->feat_num = feat;
 207                 entry->is_local = local;
 208                 list_add_tail(&entry->node, head);
 209         }
 210         return entry;
 211 }
 212
 213 /**
 214  * dccp_feat_push_change  -  Add/overwrite a Change option in the list
 215  * @fn_list: feature-negotiation list to update
 216  * @feat: one of %dccp_feature_numbers
 217  * @local: whether local (1) or remote (0) @feat_num is meant
 218  * @needs_mandatory: whether to use Mandatory feature negotiation options
 219  * @fval: pointer to NN/SP value to be inserted (will be copied)
 220  */
 221 static int dccp_feat_push_change(struct list_head *fn_list, u8 feat, u8 local,
 222                                  u8 mandatory, dccp_feat_val *fval)
 223 {
 224         struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
 225
 226         if (new == NULL)
 227                 return -ENOMEM;
 228
 229         new->feat_num        = feat;
 230         new->is_local        = local;
 231         new->state           = FEAT_INITIALISING;
 232         new->needs_confirm   = 0;
 233         new->empty_confirm   = 0;
 234         new->val             = *fval;
 235         new->needs_mandatory = mandatory;
 236
 237         return 0;
 238 }
 239
 240 static inline void dccp_feat_list_pop(struct dccp_feat_entry *entry)
 241 {
 242         list_del(&entry->node);
 243         dccp_feat_entry_destructor(entry);
 244 }
 245
 246 void dccp_feat_list_purge(struct list_head *fn_list)
 247 {
 248         struct dccp_feat_entry *entry, *next;
 249
 250         list_for_each_entry_safe(entry, next, fn_list, node)
 251                 dccp_feat_entry_destructor(entry);
 252         INIT_LIST_HEAD(fn_list);
 253 }
 254 EXPORT_SYMBOL_GPL(dccp_feat_list_purge);
 255
 256 /* generate @to as full clone of @from - @to must not contain any nodes */
 257 int dccp_feat_clone_list(struct list_head const *from, struct list_head *to)
 258 {
 259         struct dccp_feat_entry *entry, *new;
 260
 261         INIT_LIST_HEAD(to);
 262         list_for_each_entry(entry, from, node) {
 263                 new = dccp_feat_clone_entry(entry);
 264                 if (new == NULL)
 265                         goto cloning_failed;
 266                 list_add_tail(&new->node, to);
 267         }
 268         return 0;
 269
 270 cloning_failed:
 271         dccp_feat_list_purge(to);
 272         return -ENOMEM;
 273 }
 274
 275 /**
 276  * dccp_feat_valid_nn_length  -  Enforce length constraints on NN options
 277  * Length is between 0 and %DCCP_OPTVAL_MAXLEN. Used for outgoing packets only,
 278  * incoming options are accepted as long as their values are valid.
 279  */
 280 static u8 dccp_feat_valid_nn_length(u8 feat_num)
 281 {
 282         if (feat_num == DCCPF_ACK_RATIO)        /* RFC 4340, 11.3 and 6.6.8 */
 283                 return 2;
 284         if (feat_num == DCCPF_SEQUENCE_WINDOW)  /* RFC 4340, 7.5.2 and 6.5  */
 285                 return 6;
 286         return 0;
 287 }
 288
 289 static u8 dccp_feat_is_valid_nn_val(u8 feat_num, u64 val)
 290 {
 291         switch (feat_num) {
 292         case DCCPF_ACK_RATIO:
 293                 return val <= DCCPF_ACK_RATIO_MAX;
 294         case DCCPF_SEQUENCE_WINDOW:
 295                 return val >= DCCPF_SEQ_WMIN && val <= DCCPF_SEQ_WMAX;
 296         }
 297         return 0;       /* feature unknown - so we can't tell */
 298 }
 299
 300 /* check that SP values are within the ranges defined in RFC 4340 */
 301 static u8 dccp_feat_is_valid_sp_val(u8 feat_num, u8 val)
 302 {
 303         switch (feat_num) {
 304         case DCCPF_CCID:
 305                 return val == DCCPC_CCID2 || val == DCCPC_CCID3;
 306         /* Type-check Boolean feature values: */
 307         case DCCPF_SHORT_SEQNOS:
 308         case DCCPF_ECN_INCAPABLE:
 309         case DCCPF_SEND_ACK_VECTOR:
 310         case DCCPF_SEND_NDP_COUNT:
 311         case DCCPF_DATA_CHECKSUM:
 312         case DCCPF_SEND_LEV_RATE:
 313                 return val < 2;
 314         case DCCPF_MIN_CSUM_COVER:
 315                 return val < 16;
 316         }
 317         return 0;                       /* feature unknown */
 318 }
 319
 320 static u8 dccp_feat_sp_list_ok(u8 feat_num, u8 const *sp_list, u8 sp_len)
 321 {
 322         if (sp_list == NULL || sp_len < 1)
 323                 return 0;
 324         while (sp_len--)
 325                 if (!dccp_feat_is_valid_sp_val(feat_num, *sp_list++))
 326                         return 0;
 327         return 1;
 328 }
 329
 330 /**
 331  * dccp_feat_insert_opts  -  Generate FN options from current list state
 332  * @skb: next sk_buff to be sent to the peer
 333  * @dp: for client during handshake and general negotiation
 334  * @dreq: used by the server only (all Changes/Confirms in LISTEN/RESPOND)
 335  */
 336 int dccp_feat_insert_opts(struct dccp_sock *dp, struct dccp_request_sock *dreq,
 337                           struct sk_buff *skb)
 338 {
 339         struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
 340         struct dccp_feat_entry *pos, *next;
 341         u8 opt, type, len, *ptr, nn_in_nbo[DCCP_OPTVAL_MAXLEN];
 342         bool rpt;
 343
 344         /* put entries into @skb in the order they appear in the list */
 345         list_for_each_entry_safe_reverse(pos, next, fn, node) {
 346                 opt  = dccp_feat_genopt(pos);
 347                 type = dccp_feat_type(pos->feat_num);
 348                 rpt  = false;
 349
 350                 if (pos->empty_confirm) {
 351                         len = 0;
 352                         ptr = NULL;
 353                 } else {
 354                         if (type == FEAT_SP) {
 355                                 len = pos->val.sp.len;
 356                                 ptr = pos->val.sp.vec;
 357                                 rpt = pos->needs_confirm;
 358                         } else if (type == FEAT_NN) {
 359                                 len = dccp_feat_valid_nn_length(pos->feat_num);
 360                                 ptr = nn_in_nbo;
 361                                 dccp_encode_value_var(pos->val.nn, ptr, len);
 362                         } else {
 363                                 DCCP_BUG("unknown feature %u", pos->feat_num);
 364                                 return -1;
 365                         }
 366                 }
 367
 368                 if (dccp_insert_fn_opt(skb, opt, pos->feat_num, ptr, len, rpt))
 369                         return -1;
 370                 if (pos->needs_mandatory && dccp_insert_option_mandatory(skb))
 371                         return -1;
 372                 /*
 373                  * Enter CHANGING after transmitting the Change option (6.6.2).
 374                  */
 375                 if (pos->state == FEAT_INITIALISING)
 376                         pos->state = FEAT_CHANGING;
 377         }
 378         return 0;
 379 }
 380
 381 /**
 382  * __feat_register_nn  -  Register new NN value on socket
 383  * @fn: feature-negotiation list to register with
 384  * @feat: an NN feature from %dccp_feature_numbers
 385  * @mandatory: use Mandatory option if 1
 386  * @nn_val: value to register (restricted to 4 bytes)
 387  * Note that NN features are local by definition (RFC 4340, 6.3.2).
 388  */
 389 static int __feat_register_nn(struct list_head *fn, u8 feat,
 390                               u8 mandatory, u64 nn_val)
 391 {
 392         dccp_feat_val fval = { .nn = nn_val };
 393
 394         if (dccp_feat_type(feat) != FEAT_NN ||
 395             !dccp_feat_is_valid_nn_val(feat, nn_val))
 396                 return -EINVAL;
 397
 398         /* Don't bother with default values, they will be activated anyway. */
 399         if (nn_val - (u64)dccp_feat_default_value(feat) == 0)
 400                 return 0;
 401
 402         return dccp_feat_push_change(fn, feat, 1, mandatory, &fval);
 403 }
 404
 405 /**
 406  * __feat_register_sp  -  Register new SP value/list on socket
 407  * @fn: feature-negotiation list to register with
 408  * @feat: an SP feature from %dccp_feature_numbers
 409  * @is_local: whether the local (1) or the remote (0) @feat is meant
 410  * @mandatory: use Mandatory option if 1
 411  * @sp_val: SP value followed by optional preference list
 412  * @sp_len: length of @sp_val in bytes
 413  */
 414 static int __feat_register_sp(struct list_head *fn, u8 feat, u8 is_local,
 415                               u8 mandatory, u8 const *sp_val, u8 sp_len)
 416 {
 417         dccp_feat_val fval;
 418
 419         if (dccp_feat_type(feat) != FEAT_SP ||
 420             !dccp_feat_sp_list_ok(feat, sp_val, sp_len))
 421                 return -EINVAL;
 422
 423         /* Avoid negotiating alien CCIDs by only advertising supported ones */
 424         if (feat == DCCPF_CCID && !ccid_support_check(sp_val, sp_len))
 425                 return -EOPNOTSUPP;
 426
 427         if (dccp_feat_clone_sp_val(&fval, sp_val, sp_len))
 428                 return -ENOMEM;
 429
 430         return dccp_feat_push_change(fn, feat, is_local, mandatory, &fval);
 431 }
 432
 433 /**
 434  * dccp_feat_register_sp  -  Register requests to change SP feature values
 435  * @sk: client or listening socket
 436  * @feat: one of %dccp_feature_numbers
 437  * @is_local: whether the local (1) or remote (0) @feat is meant
 438  * @list: array of preferred values, in descending order of preference
 439  * @len: length of @list in bytes
 440  */
 441 int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
 442                           u8 const *list, u8 len)
 443 {        /* any changes must be registered before establishing the connection */
 444         if (sk->sk_state != DCCP_CLOSED)
 445                 return -EISCONN;
 446         if (dccp_feat_type(feat) != FEAT_SP)
 447                 return -EINVAL;
 448         return __feat_register_sp(&dccp_sk(sk)->dccps_featneg, feat, is_local,
 449                                   0, list, len);
 450 }
 451
 452 /* Analogous to dccp_feat_register_sp(), but for non-negotiable values */
 453 int dccp_feat_register_nn(struct sock *sk, u8 feat, u64 val)
 454 {
 455         /* any changes must be registered before establishing the connection */
 456         if (sk->sk_state != DCCP_CLOSED)
 457                 return -EISCONN;
 458         if (dccp_feat_type(feat) != FEAT_NN)
 459                 return -EINVAL;
 460         return __feat_register_nn(&dccp_sk(sk)->dccps_featneg, feat, 0, val);
 461 }
 462
 463 /*
 464  *      Tracking features whose value depend on the choice of CCID
 465  *
 466  * This is designed with an extension in mind so that a list walk could be done
 467  * before activating any features. However, the existing framework was found to
 468  * work satisfactorily up until now, the automatic verification is left open.
 469  * When adding new CCIDs, add a corresponding dependency table here.
 470  */
 471 static const struct ccid_dependency *dccp_feat_ccid_deps(u8 ccid, bool is_local)
 472 {
 473         static const struct ccid_dependency ccid2_dependencies[2][2] = {
 474                 /*
 475                  * CCID2 mandates Ack Vectors (RFC 4341, 4.): as CCID is a TX
 476                  * feature and Send Ack Vector is an RX feature, `is_local'
 477                  * needs to be reversed.
 478                  */
 479                 {       /* Dependencies of the receiver-side (remote) CCID2 */
 480                         {
 481                                 .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 482                                 .is_local       = true,
 483                                 .is_mandatory   = true,
 484                                 .val            = 1
 485                         },
 486                         { 0, 0, 0, 0 }
 487                 },
 488                 {       /* Dependencies of the sender-side (local) CCID2 */
 489                         {
 490                                 .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 491                                 .is_local       = false,
 492                                 .is_mandatory   = true,
 493                                 .val            = 1
 494                         },
 495                         { 0, 0, 0, 0 }
 496                 }
 497         };
 498         static const struct ccid_dependency ccid3_dependencies[2][5] = {
 499                 {       /*
 500                          * Dependencies of the receiver-side CCID3
 501                          */
 502                         {       /* locally disable Ack Vectors */
 503                                 .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 504                                 .is_local       = true,
 505                                 .is_mandatory   = false,
 506                                 .val            = 0
 507                         },
 508                         {       /* see below why Send Loss Event Rate is on */
 509                                 .dependent_feat = DCCPF_SEND_LEV_RATE,
 510                                 .is_local       = true,
 511                                 .is_mandatory   = true,
 512                                 .val            = 1
 513                         },
 514                         {       /* NDP Count is needed as per RFC 4342, 6.1.1 */
 515                                 .dependent_feat = DCCPF_SEND_NDP_COUNT,
 516                                 .is_local       = false,
 517                                 .is_mandatory   = true,
 518                                 .val            = 1
 519                         },
 520                         { 0, 0, 0, 0 },
 521                 },
 522                 {       /*
 523                          * CCID3 at the TX side: we request that the HC-receiver
 524                          * will not send Ack Vectors (they will be ignored, so
 525                          * Mandatory is not set); we enable Send Loss Event Rate
 526                          * (Mandatory since the implementation does not support
 527                          * the Loss Intervals option of RFC 4342, 8.6).
 528                          * The last two options are for peer's information only.
 529                         */
 530                         {
 531                                 .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 532                                 .is_local       = false,
 533                                 .is_mandatory   = false,
 534                                 .val            = 0
 535                         },
 536                         {
 537                                 .dependent_feat = DCCPF_SEND_LEV_RATE,
 538                                 .is_local       = false,
 539                                 .is_mandatory   = true,
 540                                 .val            = 1
 541                         },
 542                         {       /* this CCID does not support Ack Ratio */
 543                                 .dependent_feat = DCCPF_ACK_RATIO,
 544                                 .is_local       = true,
 545                                 .is_mandatory   = false,
 546                                 .val            = 0
 547                         },
 548                         {       /* tell receiver we are sending NDP counts */
 549                                 .dependent_feat = DCCPF_SEND_NDP_COUNT,
 550                                 .is_local       = true,
 551                                 .is_mandatory   = false,
 552                                 .val            = 1
 553                         },
 554                         { 0, 0, 0, 0 }
 555                 }
 556         };
 557         switch (ccid) {
 558         case DCCPC_CCID2:
 559                 return ccid2_dependencies[is_local];
 560         case DCCPC_CCID3:
 561                 return ccid3_dependencies[is_local];
 562         default:
 563                 return NULL;
 564         }
 565 }
 566
 567 /**
 568  * dccp_feat_propagate_ccid - Resolve dependencies of features on choice of CCID
 569  * @fn: feature-negotiation list to update
 570  * @id: CCID number to track
 571  * @is_local: whether TX CCID (1) or RX CCID (0) is meant
 572  * This function needs to be called after registering all other features.
 573  */
 574 static int dccp_feat_propagate_ccid(struct list_head *fn, u8 id, bool is_local)
 575 {
 576         const struct ccid_dependency *table = dccp_feat_ccid_deps(id, is_local);
 577         int i, rc = (table == NULL);
 578
 579         for (i = 0; rc == 0 && table[i].dependent_feat != DCCPF_RESERVED; i++)
 580                 if (dccp_feat_type(table[i].dependent_feat) == FEAT_SP)
 581                         rc = __feat_register_sp(fn, table[i].dependent_feat,
 582                                                     table[i].is_local,
 583                                                     table[i].is_mandatory,
 584                                                     &table[i].val, 1);
 585                 else
 586                         rc = __feat_register_nn(fn, table[i].dependent_feat,
 587                                                     table[i].is_mandatory,
 588                                                     table[i].val);
 589         return rc;
 590 }
 591
 592 /**
 593  * dccp_feat_finalise_settings  -  Finalise settings before starting negotiation
 594  * @dp: client or listening socket (settings will be inherited)
 595  * This is called after all registrations (socket initialisation, sysctls, and
 596  * sockopt calls), and before sending the first packet containing Change options
 597  * (ie. client-Request or server-Response), to ensure internal consistency.
 598  */
 599 int dccp_feat_finalise_settings(struct dccp_sock *dp)
 600 {
 601         struct list_head *fn = &dp->dccps_featneg;
 602         struct dccp_feat_entry *entry;
 603         int i = 2, ccids[2] = { -1, -1 };
 604
 605         /*
 606          * Propagating CCIDs:
 607          * 1) not useful to propagate CCID settings if this host advertises more
 608          *    than one CCID: the choice of CCID  may still change - if this is
 609          *    the client, or if this is the server and the client sends
 610          *    singleton CCID values.
 611          * 2) since is that propagate_ccid changes the list, we defer changing
 612          *    the sorted list until after the traversal.
 613          */
 614         list_for_each_entry(entry, fn, node)
 615                 if (entry->feat_num == DCCPF_CCID && entry->val.sp.len == 1)
 616                         ccids[entry->is_local] = entry->val.sp.vec[0];
 617         while (i--)
 618                 if (ccids[i] > 0 && dccp_feat_propagate_ccid(fn, ccids[i], i))
 619                         return -1;
 620         return 0;
 621 }
 622
 623 /**
 624  * dccp_feat_server_ccid_dependencies  -  Resolve CCID-dependent features
 625  * It is the server which resolves the dependencies once the CCID has been
 626  * fully negotiated. If no CCID has been negotiated, it uses the default CCID.
 627  */
 628 int dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq)
 629 {
 630         struct list_head *fn = &dreq->dreq_featneg;
 631         struct dccp_feat_entry *entry;
 632         u8 is_local, ccid;
 633
 634         for (is_local = 0; is_local <= 1; is_local++) {
 635                 entry = dccp_feat_list_lookup(fn, DCCPF_CCID, is_local);
 636
 637                 if (entry != NULL && !entry->empty_confirm)
 638                         ccid = entry->val.sp.vec[0];
 639                 else
 640                         ccid = dccp_feat_default_value(DCCPF_CCID);
 641
 642                 if (dccp_feat_propagate_ccid(fn, ccid, is_local))
 643                         return -1;
 644         }
 645         return 0;
 646 }
 647
 648 static int dccp_feat_update_ccid(struct sock *sk, u8 type, u8 new_ccid_nr)
 649 {
 650         struct dccp_sock *dp = dccp_sk(sk);
 651         struct dccp_minisock *dmsk = dccp_msk(sk);
 652         /* figure out if we are changing our CCID or the peer's */
 653         const int rx = type == DCCPO_CHANGE_R;
 654         const u8 ccid_nr = rx ? dmsk->dccpms_rx_ccid : dmsk->dccpms_tx_ccid;
 655         struct ccid *new_ccid;
 656
 657         /* Check if nothing is being changed. */
 658         if (ccid_nr == new_ccid_nr)
 659                 return 0;
 660
 661         new_ccid = ccid_new(new_ccid_nr, sk, rx, GFP_ATOMIC);
 662         if (new_ccid == NULL)
 663                 return -ENOMEM;
 664
 665         if (rx) {
 666                 ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
 667                 dp->dccps_hc_rx_ccid = new_ccid;
 668                 dmsk->dccpms_rx_ccid = new_ccid_nr;
 669         } else {
 670                 ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
 671                 dp->dccps_hc_tx_ccid = new_ccid;
 672                 dmsk->dccpms_tx_ccid = new_ccid_nr;
 673         }
 674
 675         return 0;
 676 }
 677
 678 static int dccp_feat_update(struct sock *sk, u8 type, u8 feat, u8 val)
 679 {
 680         dccp_feat_debug(type, feat, val);
 681
 682         switch (feat) {
 683         case DCCPF_CCID:
 684                 return dccp_feat_update_ccid(sk, type, val);
 685         default:
 686                 dccp_pr_debug("UNIMPLEMENTED: %s(%d, ...)\n",
 687                               dccp_feat_typename(type), feat);
 688                 break;
 689         }
 690         return 0;
 691 }
 692
 693 static int dccp_feat_reconcile(struct sock *sk, struct dccp_opt_pend *opt,
 694                                u8 *rpref, u8 rlen)
 695 {
 696         struct dccp_sock *dp = dccp_sk(sk);
 697         u8 *spref, slen, *res = NULL;
 698         int i, j, rc, agree = 1;
 699
 700         BUG_ON(rpref == NULL);
 701
 702         /* check if we are the black sheep */
 703         if (dp->dccps_role == DCCP_ROLE_CLIENT) {
 704                 spref = rpref;
 705                 slen  = rlen;
 706                 rpref = opt->dccpop_val;
 707                 rlen  = opt->dccpop_len;
 708         } else {
 709                 spref = opt->dccpop_val;
 710                 slen  = opt->dccpop_len;
 711         }
 712         /*
 713          * Now we have server preference list in spref and client preference in
 714          * rpref
 715          */
 716         BUG_ON(spref == NULL);
 717         BUG_ON(rpref == NULL);
 718
 719         /* FIXME sanity check vals */
 720
 721         /* Are values in any order?  XXX Lame "algorithm" here */
 722         for (i = 0; i < slen; i++) {
 723                 for (j = 0; j < rlen; j++) {
 724                         if (spref[i] == rpref[j]) {
 725                                 res = &spref[i];
 726                                 break;
 727                         }
 728                 }
 729                 if (res)
 730                         break;
 731         }
 732
 733         /* we didn't agree on anything */
 734         if (res == NULL) {
 735                 /* confirm previous value */
 736                 switch (opt->dccpop_feat) {
 737                 case DCCPF_CCID:
 738                         /* XXX did i get this right? =P */
 739                         if (opt->dccpop_type == DCCPO_CHANGE_L)
 740                                 res = &dccp_msk(sk)->dccpms_tx_ccid;
 741                         else
 742                                 res = &dccp_msk(sk)->dccpms_rx_ccid;
 743                         break;
 744
 745                 default:
 746                         DCCP_BUG("Fell through, feat=%d", opt->dccpop_feat);
 747                         /* XXX implement res */
 748                         return -EFAULT;
 749                 }
 750
 751                 dccp_pr_debug("Don't agree... reconfirming %d\n", *res);
 752                 agree = 0; /* this is used for mandatory options... */
 753         }
 754
 755         /* need to put result and our preference list */
 756         rlen = 1 + opt->dccpop_len;
 757         rpref = kmalloc(rlen, GFP_ATOMIC);
 758         if (rpref == NULL)
 759                 return -ENOMEM;
 760
 761         *rpref = *res;
 762         memcpy(&rpref[1], opt->dccpop_val, opt->dccpop_len);
 763
 764         /* put it in the "confirm queue" */
 765         if (opt->dccpop_sc == NULL) {
 766                 opt->dccpop_sc = kmalloc(sizeof(*opt->dccpop_sc), GFP_ATOMIC);
 767                 if (opt->dccpop_sc == NULL) {
 768                         kfree(rpref);
 769                         return -ENOMEM;
 770                 }
 771         } else {
 772                 /* recycle the confirm slot */
 773                 BUG_ON(opt->dccpop_sc->dccpoc_val == NULL);
 774                 kfree(opt->dccpop_sc->dccpoc_val);
 775                 dccp_pr_debug("recycling confirm slot\n");
 776         }
 777         memset(opt->dccpop_sc, 0, sizeof(*opt->dccpop_sc));
 778
 779         opt->dccpop_sc->dccpoc_val = rpref;
 780         opt->dccpop_sc->dccpoc_len = rlen;
 781
 782         /* update the option on our side [we are about to send the confirm] */
 783         rc = dccp_feat_update(sk, opt->dccpop_type, opt->dccpop_feat, *res);
 784         if (rc) {
 785                 kfree(opt->dccpop_sc->dccpoc_val);
 786                 kfree(opt->dccpop_sc);
 787                 opt->dccpop_sc = NULL;
 788                 return rc;
 789         }
 790
 791         dccp_pr_debug("Will confirm %d\n", *rpref);
 792
 793         /* say we want to change to X but we just got a confirm X, suppress our
 794          * change
 795          */
 796         if (!opt->dccpop_conf) {
 797                 if (*opt->dccpop_val == *res)
 798                         opt->dccpop_conf = 1;
 799                 dccp_pr_debug("won't ask for change of same feature\n");
 800         }
 801
 802         return agree ? 0 : DCCP_FEAT_SP_NOAGREE; /* used for mandatory opts */
 803 }
 804
 805 static int dccp_feat_sp(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
 806 {
 807         struct dccp_minisock *dmsk = dccp_msk(sk);
 808         struct dccp_opt_pend *opt;
 809         int rc = 1;
 810         u8 t;
 811
 812         /*
 813          * We received a CHANGE.  We gotta match it against our own preference
 814          * list.  If we got a CHANGE_R it means it's a change for us, so we need
 815          * to compare our CHANGE_L list.
 816          */
 817         if (type == DCCPO_CHANGE_L)
 818                 t = DCCPO_CHANGE_R;
 819         else
 820                 t = DCCPO_CHANGE_L;
 821
 822         /* find our preference list for this feature */
 823         list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
 824                 if (opt->dccpop_type != t || opt->dccpop_feat != feature)
 825                         continue;
 826
 827                 /* find the winner from the two preference lists */
 828                 rc = dccp_feat_reconcile(sk, opt, val, len);
 829                 break;
 830         }
 831
 832         /* We didn't deal with the change.  This can happen if we have no
 833          * preference list for the feature.  In fact, it just shouldn't
 834          * happen---if we understand a feature, we should have a preference list
 835          * with at least the default value.
 836          */
 837         BUG_ON(rc == 1);
 838
 839         return rc;
 840 }
 841
 842 static int dccp_feat_nn(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
 843 {
 844         struct dccp_opt_pend *opt;
 845         struct dccp_minisock *dmsk = dccp_msk(sk);
 846         u8 *copy;
 847         int rc;
 848
 849         /* NN features must be Change L (sec. 6.3.2) */
 850         if (type != DCCPO_CHANGE_L) {
 851                 dccp_pr_debug("received %s for NN feature %d\n",
 852                                 dccp_feat_typename(type), feature);
 853                 return -EFAULT;
 854         }
 855
 856         /* XXX sanity check opt val */
 857
 858         /* copy option so we can confirm it */
 859         opt = kzalloc(sizeof(*opt), GFP_ATOMIC);
 860         if (opt == NULL)
 861                 return -ENOMEM;
 862
 863         copy = kmemdup(val, len, GFP_ATOMIC);
 864         if (copy == NULL) {
 865                 kfree(opt);
 866                 return -ENOMEM;
 867         }
 868
 869         opt->dccpop_type = DCCPO_CONFIRM_R; /* NN can only confirm R */
 870         opt->dccpop_feat = feature;
 871         opt->dccpop_val  = copy;
 872         opt->dccpop_len  = len;
 873
 874         /* change feature */
 875         rc = dccp_feat_update(sk, type, feature, *val);
 876         if (rc) {
 877                 kfree(opt->dccpop_val);
 878                 kfree(opt);
 879                 return rc;
 880         }
 881
 882         dccp_feat_debug(type, feature, *copy);
 883
 884         list_add_tail(&opt->dccpop_node, &dmsk->dccpms_conf);
 885
 886         return 0;
 887 }
 888
 889 static void dccp_feat_empty_confirm(struct dccp_minisock *dmsk,
 890                                     u8 type, u8 feature)
 891 {
 892         /* XXX check if other confirms for that are queued and recycle slot */
 893         struct dccp_opt_pend *opt = kzalloc(sizeof(*opt), GFP_ATOMIC);
 894
 895         if (opt == NULL) {
 896                 /* XXX what do we do?  Ignoring should be fine.  It's a change
 897                  * after all =P
 898                  */
 899                 return;
 900         }
 901
 902         switch (type) {
 903         case DCCPO_CHANGE_L:
 904                 opt->dccpop_type = DCCPO_CONFIRM_R;
 905                 break;
 906         case DCCPO_CHANGE_R:
 907                 opt->dccpop_type = DCCPO_CONFIRM_L;
 908                 break;
 909         default:
 910                 DCCP_WARN("invalid type %d\n", type);
 911                 kfree(opt);
 912                 return;
 913         }
 914         opt->dccpop_feat = feature;
 915         opt->dccpop_val  = NULL;
 916         opt->dccpop_len  = 0;
 917
 918         /* change feature */
 919         dccp_pr_debug("Empty %s(%d)\n", dccp_feat_typename(type), feature);
 920
 921         list_add_tail(&opt->dccpop_node, &dmsk->dccpms_conf);
 922 }
 923
 924 static void dccp_feat_flush_confirm(struct sock *sk)
 925 {
 926         struct dccp_minisock *dmsk = dccp_msk(sk);
 927         /* Check if there is anything to confirm in the first place */
 928         int yes = !list_empty(&dmsk->dccpms_conf);
 929
 930         if (!yes) {
 931                 struct dccp_opt_pend *opt;
 932
 933                 list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
 934                         if (opt->dccpop_conf) {
 935                                 yes = 1;
 936                                 break;
 937                         }
 938                 }
 939         }
 940
 941         if (!yes)
 942                 return;
 943
 944         /* OK there is something to confirm... */
 945         /* XXX check if packet is in flight?  Send delayed ack?? */
 946         if (sk->sk_state == DCCP_OPEN)
 947                 dccp_send_ack(sk);
 948 }
 949
 950 int dccp_feat_change_recv(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
 951 {
 952         int rc;
 953
 954         /* Ignore Change requests other than during connection setup */
 955         if (sk->sk_state != DCCP_LISTEN && sk->sk_state != DCCP_REQUESTING)
 956                 return 0;
 957         dccp_feat_debug(type, feature, *val);
 958
 959         /* figure out if it's SP or NN feature */
 960         switch (feature) {
 961         /* deal with SP features */
 962         case DCCPF_CCID:
 963                 rc = dccp_feat_sp(sk, type, feature, val, len);
 964                 break;
 965
 966         /* deal with NN features */
 967         case DCCPF_ACK_RATIO:
 968                 rc = dccp_feat_nn(sk, type, feature, val, len);
 969                 break;
 970
 971         /* XXX implement other features */
 972         default:
 973                 dccp_pr_debug("UNIMPLEMENTED: not handling %s(%d, ...)\n",
 974                               dccp_feat_typename(type), feature);
 975                 rc = -EFAULT;
 976                 break;
 977         }
 978
 979         /* check if there were problems changing features */
 980         if (rc) {
 981                 /* If we don't agree on SP, we sent a confirm for old value.
 982                  * However we propagate rc to caller in case option was
 983                  * mandatory
 984                  */
 985                 if (rc != DCCP_FEAT_SP_NOAGREE)
 986                         dccp_feat_empty_confirm(dccp_msk(sk), type, feature);
 987         }
 988
 989         /* generate the confirm [if required] */
 990         dccp_feat_flush_confirm(sk);
 991
 992         return rc;
 993 }
 994
 995 EXPORT_SYMBOL_GPL(dccp_feat_change_recv);
 996
 997 int dccp_feat_confirm_recv(struct sock *sk, u8 type, u8 feature,
 998                            u8 *val, u8 len)
 999 {
1000         u8 t;
1001         struct dccp_opt_pend *opt;
1002         struct dccp_minisock *dmsk = dccp_msk(sk);
1003         int found = 0;
1004         int all_confirmed = 1;
1005
1006         /* Ignore Confirm options other than during connection setup */
1007         if (sk->sk_state != DCCP_LISTEN && sk->sk_state != DCCP_REQUESTING)
1008                 return 0;
1009         dccp_feat_debug(type, feature, *val);
1010
1011         /* locate our change request */
1012         switch (type) {
1013         case DCCPO_CONFIRM_L: t = DCCPO_CHANGE_R; break;
1014         case DCCPO_CONFIRM_R: t = DCCPO_CHANGE_L; break;
1015         default:              DCCP_WARN("invalid type %d\n", type);
1016                               return 1;
1017
1018         }
1019         /* XXX sanity check feature value */
1020
1021         list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
1022                 if (!opt->dccpop_conf && opt->dccpop_type == t &&
1023                     opt->dccpop_feat == feature) {
1024                         found = 1;
1025                         dccp_pr_debug("feature %d found\n", opt->dccpop_feat);
1026
1027                         /* XXX do sanity check */
1028
1029                         opt->dccpop_conf = 1;
1030
1031                         /* We got a confirmation---change the option */
1032                         dccp_feat_update(sk, opt->dccpop_type,
1033                                          opt->dccpop_feat, *val);
1034
1035                         /* XXX check the return value of dccp_feat_update */
1036                         break;
1037                 }
1038
1039                 if (!opt->dccpop_conf)
1040                         all_confirmed = 0;
1041         }
1042
1043         if (!found)
1044                 dccp_pr_debug("%s(%d, ...) never requested\n",
1045                               dccp_feat_typename(type), feature);
1046         return 0;
1047 }
1048
1049 EXPORT_SYMBOL_GPL(dccp_feat_confirm_recv);
1050
1051 void dccp_feat_clean(struct dccp_minisock *dmsk)
1052 {
1053         struct dccp_opt_pend *opt, *next;
1054
1055         list_for_each_entry_safe(opt, next, &dmsk->dccpms_pending,
1056                                  dccpop_node) {
1057                 BUG_ON(opt->dccpop_val == NULL);
1058                 kfree(opt->dccpop_val);
1059
1060                 if (opt->dccpop_sc != NULL) {
1061                         BUG_ON(opt->dccpop_sc->dccpoc_val == NULL);
1062                         kfree(opt->dccpop_sc->dccpoc_val);
1063                         kfree(opt->dccpop_sc);
1064                 }
1065
1066                 kfree(opt);
1067         }
1068         INIT_LIST_HEAD(&dmsk->dccpms_pending);
1069
1070         list_for_each_entry_safe(opt, next, &dmsk->dccpms_conf, dccpop_node) {
1071                 BUG_ON(opt == NULL);
1072                 if (opt->dccpop_val != NULL)
1073                         kfree(opt->dccpop_val);
1074                 kfree(opt);
1075         }
1076         INIT_LIST_HEAD(&dmsk->dccpms_conf);
1077 }
1078
1079 EXPORT_SYMBOL_GPL(dccp_feat_clean);
1080
1081 /* this is to be called only when a listening sock creates its child.  It is
1082  * assumed by the function---the confirm is not duplicated, but rather it is
1083  * "passed on".
1084  */
1085 int dccp_feat_clone(struct sock *oldsk, struct sock *newsk)
1086 {
1087         struct dccp_minisock *olddmsk = dccp_msk(oldsk);
1088         struct dccp_minisock *newdmsk = dccp_msk(newsk);
1089         struct dccp_opt_pend *opt;
1090         int rc = 0;
1091
1092         INIT_LIST_HEAD(&newdmsk->dccpms_pending);
1093         INIT_LIST_HEAD(&newdmsk->dccpms_conf);
1094
1095         list_for_each_entry(opt, &olddmsk->dccpms_pending, dccpop_node) {
1096                 struct dccp_opt_pend *newopt;
1097                 /* copy the value of the option */
1098                 u8 *val = kmemdup(opt->dccpop_val, opt->dccpop_len, GFP_ATOMIC);
1099
1100                 if (val == NULL)
1101                         goto out_clean;
1102
1103                 newopt = kmemdup(opt, sizeof(*newopt), GFP_ATOMIC);
1104                 if (newopt == NULL) {
1105                         kfree(val);
1106                         goto out_clean;
1107                 }
1108
1109                 /* insert the option */
1110                 newopt->dccpop_val = val;
1111                 list_add_tail(&newopt->dccpop_node, &newdmsk->dccpms_pending);
1112
1113                 /* XXX what happens with backlogs and multiple connections at
1114                  * once...
1115                  */
1116                 /* the master socket no longer needs to worry about confirms */
1117                 opt->dccpop_sc = NULL; /* it's not a memleak---new socket has it */
1118
1119                 /* reset state for a new socket */
1120                 opt->dccpop_conf = 0;
1121         }
1122
1123         /* XXX not doing anything about the conf queue */
1124
1125 out:
1126         return rc;
1127
1128 out_clean:
1129         dccp_feat_clean(newdmsk);
1130         rc = -ENOMEM;
1131         goto out;
1132 }
1133
1134 EXPORT_SYMBOL_GPL(dccp_feat_clone);
1135
1136 int dccp_feat_init(struct sock *sk)
1137 {
1138         struct dccp_sock *dp = dccp_sk(sk);
1139         struct dccp_minisock *dmsk = dccp_msk(sk);
1140         int rc;
1141
1142         INIT_LIST_HEAD(&dmsk->dccpms_pending);  /* XXX no longer used */
1143         INIT_LIST_HEAD(&dmsk->dccpms_conf);     /* XXX no longer used */
1144
1145         /* CCID L */
1146         rc = __feat_register_sp(&dp->dccps_featneg, DCCPF_CCID, 1, 0,
1147                                 &dmsk->dccpms_tx_ccid, 1);
1148         if (rc)
1149                 goto out;
1150
1151         /* CCID R */
1152         rc = __feat_register_sp(&dp->dccps_featneg, DCCPF_CCID, 0, 0,
1153                                 &dmsk->dccpms_rx_ccid, 1);
1154         if (rc)
1155                 goto out;
1156
1157         /* Ack ratio */
1158         rc = __feat_register_nn(&dp->dccps_featneg, DCCPF_ACK_RATIO, 0,
1159                                 dp->dccps_l_ack_ratio);
1160 out:
1161         return rc;
1162 }
1163
1164 EXPORT_SYMBOL_GPL(dccp_feat_init);
1165
1166 #ifdef CONFIG_IP_DCCP_DEBUG
1167 const char *dccp_feat_typename(const u8 type)
1168 {
1169         switch(type) {
1170         case DCCPO_CHANGE_L:  return("ChangeL");
1171         case DCCPO_CONFIRM_L: return("ConfirmL");
1172         case DCCPO_CHANGE_R:  return("ChangeR");
1173         case DCCPO_CONFIRM_R: return("ConfirmR");
1174         /* the following case must not appear in feature negotation  */
1175         default:              dccp_pr_debug("unknown type %d [BUG!]\n", type);
1176         }
1177         return NULL;
1178 }
1179
1180 EXPORT_SYMBOL_GPL(dccp_feat_typename);
1181
1182 const char *dccp_feat_name(const u8 feat)
1183 {
1184         static const char *feature_names[] = {
1185                 [DCCPF_RESERVED]        = "Reserved",
1186                 [DCCPF_CCID]            = "CCID",
1187                 [DCCPF_SHORT_SEQNOS]    = "Allow Short Seqnos",
1188                 [DCCPF_SEQUENCE_WINDOW] = "Sequence Window",
1189                 [DCCPF_ECN_INCAPABLE]   = "ECN Incapable",
1190                 [DCCPF_ACK_RATIO]       = "Ack Ratio",
1191                 [DCCPF_SEND_ACK_VECTOR] = "Send ACK Vector",
1192                 [DCCPF_SEND_NDP_COUNT]  = "Send NDP Count",
1193                 [DCCPF_MIN_CSUM_COVER]  = "Min. Csum Coverage",
1194                 [DCCPF_DATA_CHECKSUM]   = "Send Data Checksum",
1195         };
1196         if (feat > DCCPF_DATA_CHECKSUM && feat < DCCPF_MIN_CCID_SPECIFIC)
1197                 return feature_names[DCCPF_RESERVED];
1198
1199         if (feat ==  DCCPF_SEND_LEV_RATE)
1200                 return "Send Loss Event Rate";
1201         if (feat >= DCCPF_MIN_CCID_SPECIFIC)
1202                 return "CCID-specific";
1203
1204         return feature_names[feat];
1205 }
1206
1207 EXPORT_SYMBOL_GPL(dccp_feat_name);
1208 #endif /* CONFIG_IP_DCCP_DEBUG */