linux/net/dccp/feat.c
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   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 All currently known SP features have 1-byte quantities. If in the future
  16 *    extensions of RFCs 4340..42 define features with item lengths larger than
  17 *    one byte, a feature-specific extension of the code will be required.
  18 *
  19 *  This program is free software; you can redistribute it and/or
  20 *  modify it under the terms of the GNU General Public License
  21 *  as published by the Free Software Foundation; either version
  22 *  2 of the License, or (at your option) any later version.
  23 */
  24#include <linux/module.h>
  25#include "ccid.h"
  26#include "feat.h"
  27
  28/* feature-specific sysctls - initialised to the defaults from RFC 4340, 6.4 */
  29unsigned long   sysctl_dccp_sequence_window __read_mostly = 100;
  30int             sysctl_dccp_rx_ccid         __read_mostly = 2,
  31                sysctl_dccp_tx_ccid         __read_mostly = 2;
  32
  33/*
  34 * Feature activation handlers.
  35 *
  36 * These all use an u64 argument, to provide enough room for NN/SP features. At
  37 * this stage the negotiated values have been checked to be within their range.
  38 */
  39static int dccp_hdlr_ccid(struct sock *sk, u64 ccid, bool rx)
  40{
  41        struct dccp_sock *dp = dccp_sk(sk);
  42        struct ccid *new_ccid = ccid_new(ccid, sk, rx);
  43
  44        if (new_ccid == NULL)
  45                return -ENOMEM;
  46
  47        if (rx) {
  48                ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
  49                dp->dccps_hc_rx_ccid = new_ccid;
  50        } else {
  51                ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
  52                dp->dccps_hc_tx_ccid = new_ccid;
  53        }
  54        return 0;
  55}
  56
  57static int dccp_hdlr_seq_win(struct sock *sk, u64 seq_win, bool rx)
  58{
  59        struct dccp_sock *dp = dccp_sk(sk);
  60
  61        if (rx) {
  62                dp->dccps_r_seq_win = seq_win;
  63                /* propagate changes to update SWL/SWH */
  64                dccp_update_gsr(sk, dp->dccps_gsr);
  65        } else {
  66                dp->dccps_l_seq_win = seq_win;
  67                /* propagate changes to update AWL */
  68                dccp_update_gss(sk, dp->dccps_gss);
  69        }
  70        return 0;
  71}
  72
  73static int dccp_hdlr_ack_ratio(struct sock *sk, u64 ratio, bool rx)
  74{
  75        if (rx)
  76                dccp_sk(sk)->dccps_r_ack_ratio = ratio;
  77        else
  78                dccp_sk(sk)->dccps_l_ack_ratio = ratio;
  79        return 0;
  80}
  81
  82static int dccp_hdlr_ackvec(struct sock *sk, u64 enable, bool rx)
  83{
  84        struct dccp_sock *dp = dccp_sk(sk);
  85
  86        if (rx) {
  87                if (enable && dp->dccps_hc_rx_ackvec == NULL) {
  88                        dp->dccps_hc_rx_ackvec = dccp_ackvec_alloc(gfp_any());
  89                        if (dp->dccps_hc_rx_ackvec == NULL)
  90                                return -ENOMEM;
  91                } else if (!enable) {
  92                        dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
  93                        dp->dccps_hc_rx_ackvec = NULL;
  94                }
  95        }
  96        return 0;
  97}
  98
  99static int dccp_hdlr_ndp(struct sock *sk, u64 enable, bool rx)
 100{
 101        if (!rx)
 102                dccp_sk(sk)->dccps_send_ndp_count = (enable > 0);
 103        return 0;
 104}
 105
 106/*
 107 * Minimum Checksum Coverage is located at the RX side (9.2.1). This means that
 108 * `rx' holds when the sending peer informs about his partial coverage via a
 109 * ChangeR() option. In the other case, we are the sender and the receiver
 110 * announces its coverage via ChangeL() options. The policy here is to honour
 111 * such communication by enabling the corresponding partial coverage - but only
 112 * if it has not been set manually before; the warning here means that all
 113 * packets will be dropped.
 114 */
 115static int dccp_hdlr_min_cscov(struct sock *sk, u64 cscov, bool rx)
 116{
 117        struct dccp_sock *dp = dccp_sk(sk);
 118
 119        if (rx)
 120                dp->dccps_pcrlen = cscov;
 121        else {
 122                if (dp->dccps_pcslen == 0)
 123                        dp->dccps_pcslen = cscov;
 124                else if (cscov > dp->dccps_pcslen)
 125                        DCCP_WARN("CsCov %u too small, peer requires >= %u\n",
 126                                  dp->dccps_pcslen, (u8)cscov);
 127        }
 128        return 0;
 129}
 130
 131static const struct {
 132        u8                      feat_num;               /* DCCPF_xxx */
 133        enum dccp_feat_type     rxtx;                   /* RX or TX  */
 134        enum dccp_feat_type     reconciliation;         /* SP or NN  */
 135        u8                      default_value;          /* as in 6.4 */
 136        int (*activation_hdlr)(struct sock *sk, u64 val, bool rx);
 137/*
 138 *    Lookup table for location and type of features (from RFC 4340/4342)
 139 *  +--------------------------+----+-----+----+----+---------+-----------+
 140 *  | Feature                  | Location | Reconc. | Initial |  Section  |
 141 *  |                          | RX | TX  | SP | NN |  Value  | Reference |
 142 *  +--------------------------+----+-----+----+----+---------+-----------+
 143 *  | DCCPF_CCID               |    |  X  | X  |    |   2     | 10        |
 144 *  | DCCPF_SHORT_SEQNOS       |    |  X  | X  |    |   0     |  7.6.1    |
 145 *  | DCCPF_SEQUENCE_WINDOW    |    |  X  |    | X  | 100     |  7.5.2    |
 146 *  | DCCPF_ECN_INCAPABLE      | X  |     | X  |    |   0     | 12.1      |
 147 *  | DCCPF_ACK_RATIO          |    |  X  |    | X  |   2     | 11.3      |
 148 *  | DCCPF_SEND_ACK_VECTOR    | X  |     | X  |    |   0     | 11.5      |
 149 *  | DCCPF_SEND_NDP_COUNT     |    |  X  | X  |    |   0     |  7.7.2    |
 150 *  | DCCPF_MIN_CSUM_COVER     | X  |     | X  |    |   0     |  9.2.1    |
 151 *  | DCCPF_DATA_CHECKSUM      | X  |     | X  |    |   0     |  9.3.1    |
 152 *  | DCCPF_SEND_LEV_RATE      | X  |     | X  |    |   0     | 4342/8.4  |
 153 *  +--------------------------+----+-----+----+----+---------+-----------+
 154 */
 155} dccp_feat_table[] = {
 156        { DCCPF_CCID,            FEAT_AT_TX, FEAT_SP, 2,   dccp_hdlr_ccid     },
 157        { DCCPF_SHORT_SEQNOS,    FEAT_AT_TX, FEAT_SP, 0,   NULL },
 158        { DCCPF_SEQUENCE_WINDOW, FEAT_AT_TX, FEAT_NN, 100, dccp_hdlr_seq_win  },
 159        { DCCPF_ECN_INCAPABLE,   FEAT_AT_RX, FEAT_SP, 0,   NULL },
 160        { DCCPF_ACK_RATIO,       FEAT_AT_TX, FEAT_NN, 2,   dccp_hdlr_ack_ratio},
 161        { DCCPF_SEND_ACK_VECTOR, FEAT_AT_RX, FEAT_SP, 0,   dccp_hdlr_ackvec   },
 162        { DCCPF_SEND_NDP_COUNT,  FEAT_AT_TX, FEAT_SP, 0,   dccp_hdlr_ndp      },
 163        { DCCPF_MIN_CSUM_COVER,  FEAT_AT_RX, FEAT_SP, 0,   dccp_hdlr_min_cscov},
 164        { DCCPF_DATA_CHECKSUM,   FEAT_AT_RX, FEAT_SP, 0,   NULL },
 165        { DCCPF_SEND_LEV_RATE,   FEAT_AT_RX, FEAT_SP, 0,   NULL },
 166};
 167#define DCCP_FEAT_SUPPORTED_MAX         ARRAY_SIZE(dccp_feat_table)
 168
 169/**
 170 * dccp_feat_index  -  Hash function to map feature number into array position
 171 * Returns consecutive array index or -1 if the feature is not understood.
 172 */
 173static int dccp_feat_index(u8 feat_num)
 174{
 175        /* The first 9 entries are occupied by the types from RFC 4340, 6.4 */
 176        if (feat_num > DCCPF_RESERVED && feat_num <= DCCPF_DATA_CHECKSUM)
 177                return feat_num - 1;
 178
 179        /*
 180         * Other features: add cases for new feature types here after adding
 181         * them to the above table.
 182         */
 183        switch (feat_num) {
 184        case DCCPF_SEND_LEV_RATE:
 185                        return DCCP_FEAT_SUPPORTED_MAX - 1;
 186        }
 187        return -1;
 188}
 189
 190static u8 dccp_feat_type(u8 feat_num)
 191{
 192        int idx = dccp_feat_index(feat_num);
 193
 194        if (idx < 0)
 195                return FEAT_UNKNOWN;
 196        return dccp_feat_table[idx].reconciliation;
 197}
 198
 199static int dccp_feat_default_value(u8 feat_num)
 200{
 201        int idx = dccp_feat_index(feat_num);
 202        /*
 203         * There are no default values for unknown features, so encountering a
 204         * negative index here indicates a serious problem somewhere else.
 205         */
 206        DCCP_BUG_ON(idx < 0);
 207
 208        return idx < 0 ? 0 : dccp_feat_table[idx].default_value;
 209}
 210
 211/*
 212 *      Debugging and verbose-printing section
 213 */
 214static const char *dccp_feat_fname(const u8 feat)
 215{
 216        static const char *feature_names[] = {
 217                [DCCPF_RESERVED]        = "Reserved",
 218                [DCCPF_CCID]            = "CCID",
 219                [DCCPF_SHORT_SEQNOS]    = "Allow Short Seqnos",
 220                [DCCPF_SEQUENCE_WINDOW] = "Sequence Window",
 221                [DCCPF_ECN_INCAPABLE]   = "ECN Incapable",
 222                [DCCPF_ACK_RATIO]       = "Ack Ratio",
 223                [DCCPF_SEND_ACK_VECTOR] = "Send ACK Vector",
 224                [DCCPF_SEND_NDP_COUNT]  = "Send NDP Count",
 225                [DCCPF_MIN_CSUM_COVER]  = "Min. Csum Coverage",
 226                [DCCPF_DATA_CHECKSUM]   = "Send Data Checksum",
 227        };
 228        if (feat > DCCPF_DATA_CHECKSUM && feat < DCCPF_MIN_CCID_SPECIFIC)
 229                return feature_names[DCCPF_RESERVED];
 230
 231        if (feat ==  DCCPF_SEND_LEV_RATE)
 232                return "Send Loss Event Rate";
 233        if (feat >= DCCPF_MIN_CCID_SPECIFIC)
 234                return "CCID-specific";
 235
 236        return feature_names[feat];
 237}
 238
 239static const char *dccp_feat_sname[] = { "DEFAULT", "INITIALISING", "CHANGING",
 240                                         "UNSTABLE", "STABLE" };
 241
 242#ifdef CONFIG_IP_DCCP_DEBUG
 243static const char *dccp_feat_oname(const u8 opt)
 244{
 245        switch (opt) {
 246        case DCCPO_CHANGE_L:  return "Change_L";
 247        case DCCPO_CONFIRM_L: return "Confirm_L";
 248        case DCCPO_CHANGE_R:  return "Change_R";
 249        case DCCPO_CONFIRM_R: return "Confirm_R";
 250        }
 251        return NULL;
 252}
 253
 254static void dccp_feat_printval(u8 feat_num, dccp_feat_val const *val)
 255{
 256        u8 i, type = dccp_feat_type(feat_num);
 257
 258        if (val == NULL || (type == FEAT_SP && val->sp.vec == NULL))
 259                dccp_pr_debug_cat("(NULL)");
 260        else if (type == FEAT_SP)
 261                for (i = 0; i < val->sp.len; i++)
 262                        dccp_pr_debug_cat("%s%u", i ? " " : "", val->sp.vec[i]);
 263        else if (type == FEAT_NN)
 264                dccp_pr_debug_cat("%llu", (unsigned long long)val->nn);
 265        else
 266                dccp_pr_debug_cat("unknown type %u", type);
 267}
 268
 269static void dccp_feat_printvals(u8 feat_num, u8 *list, u8 len)
 270{
 271        u8 type = dccp_feat_type(feat_num);
 272        dccp_feat_val fval = { .sp.vec = list, .sp.len = len };
 273
 274        if (type == FEAT_NN)
 275                fval.nn = dccp_decode_value_var(list, len);
 276        dccp_feat_printval(feat_num, &fval);
 277}
 278
 279static void dccp_feat_print_entry(struct dccp_feat_entry const *entry)
 280{
 281        dccp_debug("   * %s %s = ", entry->is_local ? "local" : "remote",
 282                                    dccp_feat_fname(entry->feat_num));
 283        dccp_feat_printval(entry->feat_num, &entry->val);
 284        dccp_pr_debug_cat(", state=%s %s\n", dccp_feat_sname[entry->state],
 285                          entry->needs_confirm ? "(Confirm pending)" : "");
 286}
 287
 288#define dccp_feat_print_opt(opt, feat, val, len, mandatory)     do {          \
 289        dccp_pr_debug("%s(%s, ", dccp_feat_oname(opt), dccp_feat_fname(feat));\
 290        dccp_feat_printvals(feat, val, len);                                  \
 291        dccp_pr_debug_cat(") %s\n", mandatory ? "!" : "");      } while (0)
 292
 293#define dccp_feat_print_fnlist(fn_list)  {              \
 294        const struct dccp_feat_entry *___entry;         \
 295                                                        \
 296        dccp_pr_debug("List Dump:\n");                  \
 297        list_for_each_entry(___entry, fn_list, node)    \
 298                dccp_feat_print_entry(___entry);        \
 299}
 300#else   /* ! CONFIG_IP_DCCP_DEBUG */
 301#define dccp_feat_print_opt(opt, feat, val, len, mandatory)
 302#define dccp_feat_print_fnlist(fn_list)
 303#endif
 304
 305static int __dccp_feat_activate(struct sock *sk, const int idx,
 306                                const bool is_local, dccp_feat_val const *fval)
 307{
 308        bool rx;
 309        u64 val;
 310
 311        if (idx < 0 || idx >= DCCP_FEAT_SUPPORTED_MAX)
 312                return -1;
 313        if (dccp_feat_table[idx].activation_hdlr == NULL)
 314                return 0;
 315
 316        if (fval == NULL) {
 317                val = dccp_feat_table[idx].default_value;
 318        } else if (dccp_feat_table[idx].reconciliation == FEAT_SP) {
 319                if (fval->sp.vec == NULL) {
 320                        /*
 321                         * This can happen when an empty Confirm is sent
 322                         * for an SP (i.e. known) feature. In this case
 323                         * we would be using the default anyway.
 324                         */
 325                        DCCP_CRIT("Feature #%d undefined: using default", idx);
 326                        val = dccp_feat_table[idx].default_value;
 327                } else {
 328                        val = fval->sp.vec[0];
 329                }
 330        } else {
 331                val = fval->nn;
 332        }
 333
 334        /* Location is RX if this is a local-RX or remote-TX feature */
 335        rx = (is_local == (dccp_feat_table[idx].rxtx == FEAT_AT_RX));
 336
 337        dccp_debug("   -> activating %s %s, %sval=%llu\n", rx ? "RX" : "TX",
 338                   dccp_feat_fname(dccp_feat_table[idx].feat_num),
 339                   fval ? "" : "default ",  (unsigned long long)val);
 340
 341        return dccp_feat_table[idx].activation_hdlr(sk, val, rx);
 342}
 343
 344/* Test for "Req'd" feature (RFC 4340, 6.4) */
 345static inline int dccp_feat_must_be_understood(u8 feat_num)
 346{
 347        return  feat_num == DCCPF_CCID || feat_num == DCCPF_SHORT_SEQNOS ||
 348                feat_num == DCCPF_SEQUENCE_WINDOW;
 349}
 350
 351/* copy constructor, fval must not already contain allocated memory */
 352static int dccp_feat_clone_sp_val(dccp_feat_val *fval, u8 const *val, u8 len)
 353{
 354        fval->sp.len = len;
 355        if (fval->sp.len > 0) {
 356                fval->sp.vec = kmemdup(val, len, gfp_any());
 357                if (fval->sp.vec == NULL) {
 358                        fval->sp.len = 0;
 359                        return -ENOBUFS;
 360                }
 361        }
 362        return 0;
 363}
 364
 365static void dccp_feat_val_destructor(u8 feat_num, dccp_feat_val *val)
 366{
 367        if (unlikely(val == NULL))
 368                return;
 369        if (dccp_feat_type(feat_num) == FEAT_SP)
 370                kfree(val->sp.vec);
 371        memset(val, 0, sizeof(*val));
 372}
 373
 374static struct dccp_feat_entry *
 375              dccp_feat_clone_entry(struct dccp_feat_entry const *original)
 376{
 377        struct dccp_feat_entry *new;
 378        u8 type = dccp_feat_type(original->feat_num);
 379
 380        if (type == FEAT_UNKNOWN)
 381                return NULL;
 382
 383        new = kmemdup(original, sizeof(struct dccp_feat_entry), gfp_any());
 384        if (new == NULL)
 385                return NULL;
 386
 387        if (type == FEAT_SP && dccp_feat_clone_sp_val(&new->val,
 388                                                      original->val.sp.vec,
 389                                                      original->val.sp.len)) {
 390                kfree(new);
 391                return NULL;
 392        }
 393        return new;
 394}
 395
 396static void dccp_feat_entry_destructor(struct dccp_feat_entry *entry)
 397{
 398        if (entry != NULL) {
 399                dccp_feat_val_destructor(entry->feat_num, &entry->val);
 400                kfree(entry);
 401        }
 402}
 403
 404/*
 405 * List management functions
 406 *
 407 * Feature negotiation lists rely on and maintain the following invariants:
 408 * - each feat_num in the list is known, i.e. we know its type and default value
 409 * - each feat_num/is_local combination is unique (old entries are overwritten)
 410 * - SP values are always freshly allocated
 411 * - list is sorted in increasing order of feature number (faster lookup)
 412 */
 413static struct dccp_feat_entry *dccp_feat_list_lookup(struct list_head *fn_list,
 414                                                     u8 feat_num, bool is_local)
 415{
 416        struct dccp_feat_entry *entry;
 417
 418        list_for_each_entry(entry, fn_list, node) {
 419                if (entry->feat_num == feat_num && entry->is_local == is_local)
 420                        return entry;
 421                else if (entry->feat_num > feat_num)
 422                        break;
 423        }
 424        return NULL;
 425}
 426
 427/**
 428 * dccp_feat_entry_new  -  Central list update routine (called by all others)
 429 * @head:  list to add to
 430 * @feat:  feature number
 431 * @local: whether the local (1) or remote feature with number @feat is meant
 432 * This is the only constructor and serves to ensure the above invariants.
 433 */
 434static struct dccp_feat_entry *
 435              dccp_feat_entry_new(struct list_head *head, u8 feat, bool local)
 436{
 437        struct dccp_feat_entry *entry;
 438
 439        list_for_each_entry(entry, head, node)
 440                if (entry->feat_num == feat && entry->is_local == local) {
 441                        dccp_feat_val_destructor(entry->feat_num, &entry->val);
 442                        return entry;
 443                } else if (entry->feat_num > feat) {
 444                        head = &entry->node;
 445                        break;
 446                }
 447
 448        entry = kmalloc(sizeof(*entry), gfp_any());
 449        if (entry != NULL) {
 450                entry->feat_num = feat;
 451                entry->is_local = local;
 452                list_add_tail(&entry->node, head);
 453        }
 454        return entry;
 455}
 456
 457/**
 458 * dccp_feat_push_change  -  Add/overwrite a Change option in the list
 459 * @fn_list: feature-negotiation list to update
 460 * @feat: one of %dccp_feature_numbers
 461 * @local: whether local (1) or remote (0) @feat_num is meant
 462 * @needs_mandatory: whether to use Mandatory feature negotiation options
 463 * @fval: pointer to NN/SP value to be inserted (will be copied)
 464 */
 465static int dccp_feat_push_change(struct list_head *fn_list, u8 feat, u8 local,
 466                                 u8 mandatory, dccp_feat_val *fval)
 467{
 468        struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
 469
 470        if (new == NULL)
 471                return -ENOMEM;
 472
 473        new->feat_num        = feat;
 474        new->is_local        = local;
 475        new->state           = FEAT_INITIALISING;
 476        new->needs_confirm   = 0;
 477        new->empty_confirm   = 0;
 478        new->val             = *fval;
 479        new->needs_mandatory = mandatory;
 480
 481        return 0;
 482}
 483
 484/**
 485 * dccp_feat_push_confirm  -  Add a Confirm entry to the FN list
 486 * @fn_list: feature-negotiation list to add to
 487 * @feat: one of %dccp_feature_numbers
 488 * @local: whether local (1) or remote (0) @feat_num is being confirmed
 489 * @fval: pointer to NN/SP value to be inserted or NULL
 490 * Returns 0 on success, a Reset code for further processing otherwise.
 491 */
 492static int dccp_feat_push_confirm(struct list_head *fn_list, u8 feat, u8 local,
 493                                  dccp_feat_val *fval)
 494{
 495        struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
 496
 497        if (new == NULL)
 498                return DCCP_RESET_CODE_TOO_BUSY;
 499
 500        new->feat_num        = feat;
 501        new->is_local        = local;
 502        new->state           = FEAT_STABLE;     /* transition in 6.6.2 */
 503        new->needs_confirm   = 1;
 504        new->empty_confirm   = (fval == NULL);
 505        new->val.nn          = 0;               /* zeroes the whole structure */
 506        if (!new->empty_confirm)
 507                new->val     = *fval;
 508        new->needs_mandatory = 0;
 509
 510        return 0;
 511}
 512
 513static int dccp_push_empty_confirm(struct list_head *fn_list, u8 feat, u8 local)
 514{
 515        return dccp_feat_push_confirm(fn_list, feat, local, NULL);
 516}
 517
 518static inline void dccp_feat_list_pop(struct dccp_feat_entry *entry)
 519{
 520        list_del(&entry->node);
 521        dccp_feat_entry_destructor(entry);
 522}
 523
 524void dccp_feat_list_purge(struct list_head *fn_list)
 525{
 526        struct dccp_feat_entry *entry, *next;
 527
 528        list_for_each_entry_safe(entry, next, fn_list, node)
 529                dccp_feat_entry_destructor(entry);
 530        INIT_LIST_HEAD(fn_list);
 531}
 532EXPORT_SYMBOL_GPL(dccp_feat_list_purge);
 533
 534/* generate @to as full clone of @from - @to must not contain any nodes */
 535int dccp_feat_clone_list(struct list_head const *from, struct list_head *to)
 536{
 537        struct dccp_feat_entry *entry, *new;
 538
 539        INIT_LIST_HEAD(to);
 540        list_for_each_entry(entry, from, node) {
 541                new = dccp_feat_clone_entry(entry);
 542                if (new == NULL)
 543                        goto cloning_failed;
 544                list_add_tail(&new->node, to);
 545        }
 546        return 0;
 547
 548cloning_failed:
 549        dccp_feat_list_purge(to);
 550        return -ENOMEM;
 551}
 552
 553/**
 554 * dccp_feat_valid_nn_length  -  Enforce length constraints on NN options
 555 * Length is between 0 and %DCCP_OPTVAL_MAXLEN. Used for outgoing packets only,
 556 * incoming options are accepted as long as their values are valid.
 557 */
 558static u8 dccp_feat_valid_nn_length(u8 feat_num)
 559{
 560        if (feat_num == DCCPF_ACK_RATIO)        /* RFC 4340, 11.3 and 6.6.8 */
 561                return 2;
 562        if (feat_num == DCCPF_SEQUENCE_WINDOW)  /* RFC 4340, 7.5.2 and 6.5  */
 563                return 6;
 564        return 0;
 565}
 566
 567static u8 dccp_feat_is_valid_nn_val(u8 feat_num, u64 val)
 568{
 569        switch (feat_num) {
 570        case DCCPF_ACK_RATIO:
 571                return val <= DCCPF_ACK_RATIO_MAX;
 572        case DCCPF_SEQUENCE_WINDOW:
 573                return val >= DCCPF_SEQ_WMIN && val <= DCCPF_SEQ_WMAX;
 574        }
 575        return 0;       /* feature unknown - so we can't tell */
 576}
 577
 578/* check that SP values are within the ranges defined in RFC 4340 */
 579static u8 dccp_feat_is_valid_sp_val(u8 feat_num, u8 val)
 580{
 581        switch (feat_num) {
 582        case DCCPF_CCID:
 583                return val == DCCPC_CCID2 || val == DCCPC_CCID3;
 584        /* Type-check Boolean feature values: */
 585        case DCCPF_SHORT_SEQNOS:
 586        case DCCPF_ECN_INCAPABLE:
 587        case DCCPF_SEND_ACK_VECTOR:
 588        case DCCPF_SEND_NDP_COUNT:
 589        case DCCPF_DATA_CHECKSUM:
 590        case DCCPF_SEND_LEV_RATE:
 591                return val < 2;
 592        case DCCPF_MIN_CSUM_COVER:
 593                return val < 16;
 594        }
 595        return 0;                       /* feature unknown */
 596}
 597
 598static u8 dccp_feat_sp_list_ok(u8 feat_num, u8 const *sp_list, u8 sp_len)
 599{
 600        if (sp_list == NULL || sp_len < 1)
 601                return 0;
 602        while (sp_len--)
 603                if (!dccp_feat_is_valid_sp_val(feat_num, *sp_list++))
 604                        return 0;
 605        return 1;
 606}
 607
 608/**
 609 * dccp_feat_insert_opts  -  Generate FN options from current list state
 610 * @skb: next sk_buff to be sent to the peer
 611 * @dp: for client during handshake and general negotiation
 612 * @dreq: used by the server only (all Changes/Confirms in LISTEN/RESPOND)
 613 */
 614int dccp_feat_insert_opts(struct dccp_sock *dp, struct dccp_request_sock *dreq,
 615                          struct sk_buff *skb)
 616{
 617        struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
 618        struct dccp_feat_entry *pos, *next;
 619        u8 opt, type, len, *ptr, nn_in_nbo[DCCP_OPTVAL_MAXLEN];
 620        bool rpt;
 621
 622        /* put entries into @skb in the order they appear in the list */
 623        list_for_each_entry_safe_reverse(pos, next, fn, node) {
 624                opt  = dccp_feat_genopt(pos);
 625                type = dccp_feat_type(pos->feat_num);
 626                rpt  = false;
 627
 628                if (pos->empty_confirm) {
 629                        len = 0;
 630                        ptr = NULL;
 631                } else {
 632                        if (type == FEAT_SP) {
 633                                len = pos->val.sp.len;
 634                                ptr = pos->val.sp.vec;
 635                                rpt = pos->needs_confirm;
 636                        } else if (type == FEAT_NN) {
 637                                len = dccp_feat_valid_nn_length(pos->feat_num);
 638                                ptr = nn_in_nbo;
 639                                dccp_encode_value_var(pos->val.nn, ptr, len);
 640                        } else {
 641                                DCCP_BUG("unknown feature %u", pos->feat_num);
 642                                return -1;
 643                        }
 644                }
 645                dccp_feat_print_opt(opt, pos->feat_num, ptr, len, 0);
 646
 647                if (dccp_insert_fn_opt(skb, opt, pos->feat_num, ptr, len, rpt))
 648                        return -1;
 649                if (pos->needs_mandatory && dccp_insert_option_mandatory(skb))
 650                        return -1;
 651                /*
 652                 * Enter CHANGING after transmitting the Change option (6.6.2).
 653                 */
 654                if (pos->state == FEAT_INITIALISING)
 655                        pos->state = FEAT_CHANGING;
 656        }
 657        return 0;
 658}
 659
 660/**
 661 * __feat_register_nn  -  Register new NN value on socket
 662 * @fn: feature-negotiation list to register with
 663 * @feat: an NN feature from %dccp_feature_numbers
 664 * @mandatory: use Mandatory option if 1
 665 * @nn_val: value to register (restricted to 4 bytes)
 666 * Note that NN features are local by definition (RFC 4340, 6.3.2).
 667 */
 668static int __feat_register_nn(struct list_head *fn, u8 feat,
 669                              u8 mandatory, u64 nn_val)
 670{
 671        dccp_feat_val fval = { .nn = nn_val };
 672
 673        if (dccp_feat_type(feat) != FEAT_NN ||
 674            !dccp_feat_is_valid_nn_val(feat, nn_val))
 675                return -EINVAL;
 676
 677        /* Don't bother with default values, they will be activated anyway. */
 678        if (nn_val - (u64)dccp_feat_default_value(feat) == 0)
 679                return 0;
 680
 681        return dccp_feat_push_change(fn, feat, 1, mandatory, &fval);
 682}
 683
 684/**
 685 * __feat_register_sp  -  Register new SP value/list on socket
 686 * @fn: feature-negotiation list to register with
 687 * @feat: an SP feature from %dccp_feature_numbers
 688 * @is_local: whether the local (1) or the remote (0) @feat is meant
 689 * @mandatory: use Mandatory option if 1
 690 * @sp_val: SP value followed by optional preference list
 691 * @sp_len: length of @sp_val in bytes
 692 */
 693static int __feat_register_sp(struct list_head *fn, u8 feat, u8 is_local,
 694                              u8 mandatory, u8 const *sp_val, u8 sp_len)
 695{
 696        dccp_feat_val fval;
 697
 698        if (dccp_feat_type(feat) != FEAT_SP ||
 699            !dccp_feat_sp_list_ok(feat, sp_val, sp_len))
 700                return -EINVAL;
 701
 702        /* Avoid negotiating alien CCIDs by only advertising supported ones */
 703        if (feat == DCCPF_CCID && !ccid_support_check(sp_val, sp_len))
 704                return -EOPNOTSUPP;
 705
 706        if (dccp_feat_clone_sp_val(&fval, sp_val, sp_len))
 707                return -ENOMEM;
 708
 709        return dccp_feat_push_change(fn, feat, is_local, mandatory, &fval);
 710}
 711
 712/**
 713 * dccp_feat_register_sp  -  Register requests to change SP feature values
 714 * @sk: client or listening socket
 715 * @feat: one of %dccp_feature_numbers
 716 * @is_local: whether the local (1) or remote (0) @feat is meant
 717 * @list: array of preferred values, in descending order of preference
 718 * @len: length of @list in bytes
 719 */
 720int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
 721                          u8 const *list, u8 len)
 722{        /* any changes must be registered before establishing the connection */
 723        if (sk->sk_state != DCCP_CLOSED)
 724                return -EISCONN;
 725        if (dccp_feat_type(feat) != FEAT_SP)
 726                return -EINVAL;
 727        return __feat_register_sp(&dccp_sk(sk)->dccps_featneg, feat, is_local,
 728                                  0, list, len);
 729}
 730
 731/* Analogous to dccp_feat_register_sp(), but for non-negotiable values */
 732int dccp_feat_register_nn(struct sock *sk, u8 feat, u64 val)
 733{
 734        /* any changes must be registered before establishing the connection */
 735        if (sk->sk_state != DCCP_CLOSED)
 736                return -EISCONN;
 737        if (dccp_feat_type(feat) != FEAT_NN)
 738                return -EINVAL;
 739        return __feat_register_nn(&dccp_sk(sk)->dccps_featneg, feat, 0, val);
 740}
 741
 742/*
 743 *      Tracking features whose value depend on the choice of CCID
 744 *
 745 * This is designed with an extension in mind so that a list walk could be done
 746 * before activating any features. However, the existing framework was found to
 747 * work satisfactorily up until now, the automatic verification is left open.
 748 * When adding new CCIDs, add a corresponding dependency table here.
 749 */
 750static const struct ccid_dependency *dccp_feat_ccid_deps(u8 ccid, bool is_local)
 751{
 752        static const struct ccid_dependency ccid2_dependencies[2][2] = {
 753                /*
 754                 * CCID2 mandates Ack Vectors (RFC 4341, 4.): as CCID is a TX
 755                 * feature and Send Ack Vector is an RX feature, `is_local'
 756                 * needs to be reversed.
 757                 */
 758                {       /* Dependencies of the receiver-side (remote) CCID2 */
 759                        {
 760                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 761                                .is_local       = true,
 762                                .is_mandatory   = true,
 763                                .val            = 1
 764                        },
 765                        { 0, 0, 0, 0 }
 766                },
 767                {       /* Dependencies of the sender-side (local) CCID2 */
 768                        {
 769                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 770                                .is_local       = false,
 771                                .is_mandatory   = true,
 772                                .val            = 1
 773                        },
 774                        { 0, 0, 0, 0 }
 775                }
 776        };
 777        static const struct ccid_dependency ccid3_dependencies[2][5] = {
 778                {       /*
 779                         * Dependencies of the receiver-side CCID3
 780                         */
 781                        {       /* locally disable Ack Vectors */
 782                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 783                                .is_local       = true,
 784                                .is_mandatory   = false,
 785                                .val            = 0
 786                        },
 787                        {       /* see below why Send Loss Event Rate is on */
 788                                .dependent_feat = DCCPF_SEND_LEV_RATE,
 789                                .is_local       = true,
 790                                .is_mandatory   = true,
 791                                .val            = 1
 792                        },
 793                        {       /* NDP Count is needed as per RFC 4342, 6.1.1 */
 794                                .dependent_feat = DCCPF_SEND_NDP_COUNT,
 795                                .is_local       = false,
 796                                .is_mandatory   = true,
 797                                .val            = 1
 798                        },
 799                        { 0, 0, 0, 0 },
 800                },
 801                {       /*
 802                         * CCID3 at the TX side: we request that the HC-receiver
 803                         * will not send Ack Vectors (they will be ignored, so
 804                         * Mandatory is not set); we enable Send Loss Event Rate
 805                         * (Mandatory since the implementation does not support
 806                         * the Loss Intervals option of RFC 4342, 8.6).
 807                         * The last two options are for peer's information only.
 808                        */
 809                        {
 810                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 811                                .is_local       = false,
 812                                .is_mandatory   = false,
 813                                .val            = 0
 814                        },
 815                        {
 816                                .dependent_feat = DCCPF_SEND_LEV_RATE,
 817                                .is_local       = false,
 818                                .is_mandatory   = true,
 819                                .val            = 1
 820                        },
 821                        {       /* this CCID does not support Ack Ratio */
 822                                .dependent_feat = DCCPF_ACK_RATIO,
 823                                .is_local       = true,
 824                                .is_mandatory   = false,
 825                                .val            = 0
 826                        },
 827                        {       /* tell receiver we are sending NDP counts */
 828                                .dependent_feat = DCCPF_SEND_NDP_COUNT,
 829                                .is_local       = true,
 830                                .is_mandatory   = false,
 831                                .val            = 1
 832                        },
 833                        { 0, 0, 0, 0 }
 834                }
 835        };
 836        switch (ccid) {
 837        case DCCPC_CCID2:
 838                return ccid2_dependencies[is_local];
 839        case DCCPC_CCID3:
 840                return ccid3_dependencies[is_local];
 841        default:
 842                return NULL;
 843        }
 844}
 845
 846/**
 847 * dccp_feat_propagate_ccid - Resolve dependencies of features on choice of CCID
 848 * @fn: feature-negotiation list to update
 849 * @id: CCID number to track
 850 * @is_local: whether TX CCID (1) or RX CCID (0) is meant
 851 * This function needs to be called after registering all other features.
 852 */
 853static int dccp_feat_propagate_ccid(struct list_head *fn, u8 id, bool is_local)
 854{
 855        const struct ccid_dependency *table = dccp_feat_ccid_deps(id, is_local);
 856        int i, rc = (table == NULL);
 857
 858        for (i = 0; rc == 0 && table[i].dependent_feat != DCCPF_RESERVED; i++)
 859                if (dccp_feat_type(table[i].dependent_feat) == FEAT_SP)
 860                        rc = __feat_register_sp(fn, table[i].dependent_feat,
 861                                                    table[i].is_local,
 862                                                    table[i].is_mandatory,
 863                                                    &table[i].val, 1);
 864                else
 865                        rc = __feat_register_nn(fn, table[i].dependent_feat,
 866                                                    table[i].is_mandatory,
 867                                                    table[i].val);
 868        return rc;
 869}
 870
 871/**
 872 * dccp_feat_finalise_settings  -  Finalise settings before starting negotiation
 873 * @dp: client or listening socket (settings will be inherited)
 874 * This is called after all registrations (socket initialisation, sysctls, and
 875 * sockopt calls), and before sending the first packet containing Change options
 876 * (ie. client-Request or server-Response), to ensure internal consistency.
 877 */
 878int dccp_feat_finalise_settings(struct dccp_sock *dp)
 879{
 880        struct list_head *fn = &dp->dccps_featneg;
 881        struct dccp_feat_entry *entry;
 882        int i = 2, ccids[2] = { -1, -1 };
 883
 884        /*
 885         * Propagating CCIDs:
 886         * 1) not useful to propagate CCID settings if this host advertises more
 887         *    than one CCID: the choice of CCID  may still change - if this is
 888         *    the client, or if this is the server and the client sends
 889         *    singleton CCID values.
 890         * 2) since is that propagate_ccid changes the list, we defer changing
 891         *    the sorted list until after the traversal.
 892         */
 893        list_for_each_entry(entry, fn, node)
 894                if (entry->feat_num == DCCPF_CCID && entry->val.sp.len == 1)
 895                        ccids[entry->is_local] = entry->val.sp.vec[0];
 896        while (i--)
 897                if (ccids[i] > 0 && dccp_feat_propagate_ccid(fn, ccids[i], i))
 898                        return -1;
 899        dccp_feat_print_fnlist(fn);
 900        return 0;
 901}
 902
 903/**
 904 * dccp_feat_server_ccid_dependencies  -  Resolve CCID-dependent features
 905 * It is the server which resolves the dependencies once the CCID has been
 906 * fully negotiated. If no CCID has been negotiated, it uses the default CCID.
 907 */
 908int dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq)
 909{
 910        struct list_head *fn = &dreq->dreq_featneg;
 911        struct dccp_feat_entry *entry;
 912        u8 is_local, ccid;
 913
 914        for (is_local = 0; is_local <= 1; is_local++) {
 915                entry = dccp_feat_list_lookup(fn, DCCPF_CCID, is_local);
 916
 917                if (entry != NULL && !entry->empty_confirm)
 918                        ccid = entry->val.sp.vec[0];
 919                else
 920                        ccid = dccp_feat_default_value(DCCPF_CCID);
 921
 922                if (dccp_feat_propagate_ccid(fn, ccid, is_local))
 923                        return -1;
 924        }
 925        return 0;
 926}
 927
 928/* Select the first entry in @servlist that also occurs in @clilist (6.3.1) */
 929static int dccp_feat_preflist_match(u8 *servlist, u8 slen, u8 *clilist, u8 clen)
 930{
 931        u8 c, s;
 932
 933        for (s = 0; s < slen; s++)
 934                for (c = 0; c < clen; c++)
 935                        if (servlist[s] == clilist[c])
 936                                return servlist[s];
 937        return -1;
 938}
 939
 940/**
 941 * dccp_feat_prefer  -  Move preferred entry to the start of array
 942 * Reorder the @array_len elements in @array so that @preferred_value comes
 943 * first. Returns >0 to indicate that @preferred_value does occur in @array.
 944 */
 945static u8 dccp_feat_prefer(u8 preferred_value, u8 *array, u8 array_len)
 946{
 947        u8 i, does_occur = 0;
 948
 949        if (array != NULL) {
 950                for (i = 0; i < array_len; i++)
 951                        if (array[i] == preferred_value) {
 952                                array[i] = array[0];
 953                                does_occur++;
 954                        }
 955                if (does_occur)
 956                        array[0] = preferred_value;
 957        }
 958        return does_occur;
 959}
 960
 961/**
 962 * dccp_feat_reconcile  -  Reconcile SP preference lists
 963 *  @fval: SP list to reconcile into
 964 *  @arr: received SP preference list
 965 *  @len: length of @arr in bytes
 966 *  @is_server: whether this side is the server (and @fv is the server's list)
 967 *  @reorder: whether to reorder the list in @fv after reconciling with @arr
 968 * When successful, > 0 is returned and the reconciled list is in @fval.
 969 * A value of 0 means that negotiation failed (no shared entry).
 970 */
 971static int dccp_feat_reconcile(dccp_feat_val *fv, u8 *arr, u8 len,
 972                               bool is_server, bool reorder)
 973{
 974        int rc;
 975
 976        if (!fv->sp.vec || !arr) {
 977                DCCP_CRIT("NULL feature value or array");
 978                return 0;
 979        }
 980
 981        if (is_server)
 982                rc = dccp_feat_preflist_match(fv->sp.vec, fv->sp.len, arr, len);
 983        else
 984                rc = dccp_feat_preflist_match(arr, len, fv->sp.vec, fv->sp.len);
 985
 986        if (!reorder)
 987                return rc;
 988        if (rc < 0)
 989                return 0;
 990
 991        /*
 992         * Reorder list: used for activating features and in dccp_insert_fn_opt.
 993         */
 994        return dccp_feat_prefer(rc, fv->sp.vec, fv->sp.len);
 995}
 996
 997/**
 998 * dccp_feat_change_recv  -  Process incoming ChangeL/R options
 999 * @fn: feature-negotiation list to update
1000 * @is_mandatory: whether the Change was preceded by a Mandatory option
1001 * @opt: %DCCPO_CHANGE_L or %DCCPO_CHANGE_R
1002 * @feat: one of %dccp_feature_numbers
1003 * @val: NN value or SP value/preference list
1004 * @len: length of @val in bytes
1005 * @server: whether this node is the server (1) or the client (0)
1006 */
1007static u8 dccp_feat_change_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
1008                                u8 feat, u8 *val, u8 len, const bool server)
1009{
1010        u8 defval, type = dccp_feat_type(feat);
1011        const bool local = (opt == DCCPO_CHANGE_R);
1012        struct dccp_feat_entry *entry;
1013        dccp_feat_val fval;
1014
1015        if (len == 0 || type == FEAT_UNKNOWN)           /* 6.1 and 6.6.8 */
1016                goto unknown_feature_or_value;
1017
1018        dccp_feat_print_opt(opt, feat, val, len, is_mandatory);
1019
1020        /*
1021         *      Negotiation of NN features: Change R is invalid, so there is no
1022         *      simultaneous negotiation; hence we do not look up in the list.
1023         */
1024        if (type == FEAT_NN) {
1025                if (local || len > sizeof(fval.nn))
1026                        goto unknown_feature_or_value;
1027
1028                /* 6.3.2: "The feature remote MUST accept any valid value..." */
1029                fval.nn = dccp_decode_value_var(val, len);
1030                if (!dccp_feat_is_valid_nn_val(feat, fval.nn))
1031                        goto unknown_feature_or_value;
1032
1033                return dccp_feat_push_confirm(fn, feat, local, &fval);
1034        }
1035
1036        /*
1037         *      Unidirectional/simultaneous negotiation of SP features (6.3.1)
1038         */
1039        entry = dccp_feat_list_lookup(fn, feat, local);
1040        if (entry == NULL) {
1041                /*
1042                 * No particular preferences have been registered. We deal with
1043                 * this situation by assuming that all valid values are equally
1044                 * acceptable, and apply the following checks:
1045                 * - if the peer's list is a singleton, we accept a valid value;
1046                 * - if we are the server, we first try to see if the peer (the
1047                 *   client) advertises the default value. If yes, we use it,
1048                 *   otherwise we accept the preferred value;
1049                 * - else if we are the client, we use the first list element.
1050                 */
1051                if (dccp_feat_clone_sp_val(&fval, val, 1))
1052                        return DCCP_RESET_CODE_TOO_BUSY;
1053
1054                if (len > 1 && server) {
1055                        defval = dccp_feat_default_value(feat);
1056                        if (dccp_feat_preflist_match(&defval, 1, val, len) > -1)
1057                                fval.sp.vec[0] = defval;
1058                } else if (!dccp_feat_is_valid_sp_val(feat, fval.sp.vec[0])) {
1059                        kfree(fval.sp.vec);
1060                        goto unknown_feature_or_value;
1061                }
1062
1063                /* Treat unsupported CCIDs like invalid values */
1064                if (feat == DCCPF_CCID && !ccid_support_check(fval.sp.vec, 1)) {
1065                        kfree(fval.sp.vec);
1066                        goto not_valid_or_not_known;
1067                }
1068
1069                return dccp_feat_push_confirm(fn, feat, local, &fval);
1070
1071        } else if (entry->state == FEAT_UNSTABLE) {     /* 6.6.2 */
1072                return 0;
1073        }
1074
1075        if (dccp_feat_reconcile(&entry->val, val, len, server, true)) {
1076                entry->empty_confirm = 0;
1077        } else if (is_mandatory) {
1078                return DCCP_RESET_CODE_MANDATORY_ERROR;
1079        } else if (entry->state == FEAT_INITIALISING) {
1080                /*
1081                 * Failed simultaneous negotiation (server only): try to `save'
1082                 * the connection by checking whether entry contains the default
1083                 * value for @feat. If yes, send an empty Confirm to signal that
1084                 * the received Change was not understood - which implies using
1085                 * the default value.
1086                 * If this also fails, we use Reset as the last resort.
1087                 */
1088                WARN_ON(!server);
1089                defval = dccp_feat_default_value(feat);
1090                if (!dccp_feat_reconcile(&entry->val, &defval, 1, server, true))
1091                        return DCCP_RESET_CODE_OPTION_ERROR;
1092                entry->empty_confirm = 1;
1093        }
1094        entry->needs_confirm   = 1;
1095        entry->needs_mandatory = 0;
1096        entry->state           = FEAT_STABLE;
1097        return 0;
1098
1099unknown_feature_or_value:
1100        if (!is_mandatory)
1101                return dccp_push_empty_confirm(fn, feat, local);
1102
1103not_valid_or_not_known:
1104        return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1105                            : DCCP_RESET_CODE_OPTION_ERROR;
1106}
1107
1108/**
1109 * dccp_feat_confirm_recv  -  Process received Confirm options
1110 * @fn: feature-negotiation list to update
1111 * @is_mandatory: whether @opt was preceded by a Mandatory option
1112 * @opt: %DCCPO_CONFIRM_L or %DCCPO_CONFIRM_R
1113 * @feat: one of %dccp_feature_numbers
1114 * @val: NN value or SP value/preference list
1115 * @len: length of @val in bytes
1116 * @server: whether this node is server (1) or client (0)
1117 */
1118static u8 dccp_feat_confirm_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
1119                                 u8 feat, u8 *val, u8 len, const bool server)
1120{
1121        u8 *plist, plen, type = dccp_feat_type(feat);
1122        const bool local = (opt == DCCPO_CONFIRM_R);
1123        struct dccp_feat_entry *entry = dccp_feat_list_lookup(fn, feat, local);
1124
1125        dccp_feat_print_opt(opt, feat, val, len, is_mandatory);
1126
1127        if (entry == NULL) {    /* nothing queued: ignore or handle error */
1128                if (is_mandatory && type == FEAT_UNKNOWN)
1129                        return DCCP_RESET_CODE_MANDATORY_ERROR;
1130
1131                if (!local && type == FEAT_NN)          /* 6.3.2 */
1132                        goto confirmation_failed;
1133                return 0;
1134        }
1135
1136        if (entry->state != FEAT_CHANGING)              /* 6.6.2 */
1137                return 0;
1138
1139        if (len == 0) {
1140                if (dccp_feat_must_be_understood(feat)) /* 6.6.7 */
1141                        goto confirmation_failed;
1142                /*
1143                 * Empty Confirm during connection setup: this means reverting
1144                 * to the `old' value, which in this case is the default. Since
1145                 * we handle default values automatically when no other values
1146                 * have been set, we revert to the old value by removing this
1147                 * entry from the list.
1148                 */
1149                dccp_feat_list_pop(entry);
1150                return 0;
1151        }
1152
1153        if (type == FEAT_NN) {
1154                if (len > sizeof(entry->val.nn))
1155                        goto confirmation_failed;
1156
1157                if (entry->val.nn == dccp_decode_value_var(val, len))
1158                        goto confirmation_succeeded;
1159
1160                DCCP_WARN("Bogus Confirm for non-existing value\n");
1161                goto confirmation_failed;
1162        }
1163
1164        /*
1165         * Parsing SP Confirms: the first element of @val is the preferred
1166         * SP value which the peer confirms, the remainder depends on @len.
1167         * Note that only the confirmed value need to be a valid SP value.
1168         */
1169        if (!dccp_feat_is_valid_sp_val(feat, *val))
1170                goto confirmation_failed;
1171
1172        if (len == 1) {         /* peer didn't supply a preference list */
1173                plist = val;
1174                plen  = len;
1175        } else {                /* preferred value + preference list */
1176                plist = val + 1;
1177                plen  = len - 1;
1178        }
1179
1180        /* Check whether the peer got the reconciliation right (6.6.8) */
1181        if (dccp_feat_reconcile(&entry->val, plist, plen, server, 0) != *val) {
1182                DCCP_WARN("Confirm selected the wrong value %u\n", *val);
1183                return DCCP_RESET_CODE_OPTION_ERROR;
1184        }
1185        entry->val.sp.vec[0] = *val;
1186
1187confirmation_succeeded:
1188        entry->state = FEAT_STABLE;
1189        return 0;
1190
1191confirmation_failed:
1192        DCCP_WARN("Confirmation failed\n");
1193        return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1194                            : DCCP_RESET_CODE_OPTION_ERROR;
1195}
1196
1197/**
1198 * dccp_feat_parse_options  -  Process Feature-Negotiation Options
1199 * @sk: for general use and used by the client during connection setup
1200 * @dreq: used by the server during connection setup
1201 * @mandatory: whether @opt was preceded by a Mandatory option
1202 * @opt: %DCCPO_CHANGE_L | %DCCPO_CHANGE_R | %DCCPO_CONFIRM_L | %DCCPO_CONFIRM_R
1203 * @feat: one of %dccp_feature_numbers
1204 * @val: value contents of @opt
1205 * @len: length of @val in bytes
1206 * Returns 0 on success, a Reset code for ending the connection otherwise.
1207 */
1208int dccp_feat_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
1209                            u8 mandatory, u8 opt, u8 feat, u8 *val, u8 len)
1210{
1211        struct dccp_sock *dp = dccp_sk(sk);
1212        struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
1213        bool server = false;
1214
1215        switch (sk->sk_state) {
1216        /*
1217         *      Negotiation during connection setup
1218         */
1219        case DCCP_LISTEN:
1220                server = true;                  /* fall through */
1221        case DCCP_REQUESTING:
1222                switch (opt) {
1223                case DCCPO_CHANGE_L:
1224                case DCCPO_CHANGE_R:
1225                        return dccp_feat_change_recv(fn, mandatory, opt, feat,
1226                                                     val, len, server);
1227                case DCCPO_CONFIRM_R:
1228                case DCCPO_CONFIRM_L:
1229                        return dccp_feat_confirm_recv(fn, mandatory, opt, feat,
1230                                                      val, len, server);
1231                }
1232        }
1233        return 0;       /* ignore FN options in all other states */
1234}
1235
1236/**
1237 * dccp_feat_init  -  Seed feature negotiation with host-specific defaults
1238 * This initialises global defaults, depending on the value of the sysctls.
1239 * These can later be overridden by registering changes via setsockopt calls.
1240 * The last link in the chain is finalise_settings, to make sure that between
1241 * here and the start of actual feature negotiation no inconsistencies enter.
1242 *
1243 * All features not appearing below use either defaults or are otherwise
1244 * later adjusted through dccp_feat_finalise_settings().
1245 */
1246int dccp_feat_init(struct sock *sk)
1247{
1248        struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
1249        u8 on = 1, off = 0;
1250        int rc;
1251        struct {
1252                u8 *val;
1253                u8 len;
1254        } tx, rx;
1255
1256        /* Non-negotiable (NN) features */
1257        rc = __feat_register_nn(fn, DCCPF_SEQUENCE_WINDOW, 0,
1258                                    sysctl_dccp_sequence_window);
1259        if (rc)
1260                return rc;
1261
1262        /* Server-priority (SP) features */
1263
1264        /* Advertise that short seqnos are not supported (7.6.1) */
1265        rc = __feat_register_sp(fn, DCCPF_SHORT_SEQNOS, true, true, &off, 1);
1266        if (rc)
1267                return rc;
1268
1269        /* RFC 4340 12.1: "If a DCCP is not ECN capable, ..." */
1270        rc = __feat_register_sp(fn, DCCPF_ECN_INCAPABLE, true, true, &on, 1);
1271        if (rc)
1272                return rc;
1273
1274        /*
1275         * We advertise the available list of CCIDs and reorder according to
1276         * preferences, to avoid failure resulting from negotiating different
1277         * singleton values (which always leads to failure).
1278         * These settings can still (later) be overridden via sockopts.
1279         */
1280        if (ccid_get_builtin_ccids(&tx.val, &tx.len) ||
1281            ccid_get_builtin_ccids(&rx.val, &rx.len))
1282                return -ENOBUFS;
1283
1284        if (!dccp_feat_prefer(sysctl_dccp_tx_ccid, tx.val, tx.len) ||
1285            !dccp_feat_prefer(sysctl_dccp_rx_ccid, rx.val, rx.len))
1286                goto free_ccid_lists;
1287
1288        rc = __feat_register_sp(fn, DCCPF_CCID, true, false, tx.val, tx.len);
1289        if (rc)
1290                goto free_ccid_lists;
1291
1292        rc = __feat_register_sp(fn, DCCPF_CCID, false, false, rx.val, rx.len);
1293
1294free_ccid_lists:
1295        kfree(tx.val);
1296        kfree(rx.val);
1297        return rc;
1298}
1299
1300int dccp_feat_activate_values(struct sock *sk, struct list_head *fn_list)
1301{
1302        struct dccp_sock *dp = dccp_sk(sk);
1303        struct dccp_feat_entry *cur, *next;
1304        int idx;
1305        dccp_feat_val *fvals[DCCP_FEAT_SUPPORTED_MAX][2] = {
1306                 [0 ... DCCP_FEAT_SUPPORTED_MAX-1] = { NULL, NULL }
1307        };
1308
1309        list_for_each_entry(cur, fn_list, node) {
1310                /*
1311                 * An empty Confirm means that either an unknown feature type
1312                 * or an invalid value was present. In the first case there is
1313                 * nothing to activate, in the other the default value is used.
1314                 */
1315                if (cur->empty_confirm)
1316                        continue;
1317
1318                idx = dccp_feat_index(cur->feat_num);
1319                if (idx < 0) {
1320                        DCCP_BUG("Unknown feature %u", cur->feat_num);
1321                        goto activation_failed;
1322                }
1323                if (cur->state != FEAT_STABLE) {
1324                        DCCP_CRIT("Negotiation of %s %s failed in state %s",
1325                                  cur->is_local ? "local" : "remote",
1326                                  dccp_feat_fname(cur->feat_num),
1327                                  dccp_feat_sname[cur->state]);
1328                        goto activation_failed;
1329                }
1330                fvals[idx][cur->is_local] = &cur->val;
1331        }
1332
1333        /*
1334         * Activate in decreasing order of index, so that the CCIDs are always
1335         * activated as the last feature. This avoids the case where a CCID
1336         * relies on the initialisation of one or more features that it depends
1337         * on (e.g. Send NDP Count, Send Ack Vector, and Ack Ratio features).
1338         */
1339        for (idx = DCCP_FEAT_SUPPORTED_MAX; --idx >= 0;)
1340                if (__dccp_feat_activate(sk, idx, 0, fvals[idx][0]) ||
1341                    __dccp_feat_activate(sk, idx, 1, fvals[idx][1])) {
1342                        DCCP_CRIT("Could not activate %d", idx);
1343                        goto activation_failed;
1344                }
1345
1346        /* Clean up Change options which have been confirmed already */
1347        list_for_each_entry_safe(cur, next, fn_list, node)
1348                if (!cur->needs_confirm)
1349                        dccp_feat_list_pop(cur);
1350
1351        dccp_pr_debug("Activation OK\n");
1352        return 0;
1353
1354activation_failed:
1355        /*
1356         * We clean up everything that may have been allocated, since
1357         * it is difficult to track at which stage negotiation failed.
1358         * This is ok, since all allocation functions below are robust
1359         * against NULL arguments.
1360         */
1361        ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
1362        ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
1363        dp->dccps_hc_rx_ccid = dp->dccps_hc_tx_ccid = NULL;
1364        dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
1365        dp->dccps_hc_rx_ackvec = NULL;
1366        return -1;
1367}
1368