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 Changing non-negotiable (NN) values is supported in state OPEN/PARTOPEN.
  16 *  o All currently known SP features have 1-byte quantities. If in the future
  17 *    extensions of RFCs 4340..42 define features with item lengths larger than
  18 *    one byte, a feature-specific extension of the code will be required.
  19 *
  20 *  This program is free software; you can redistribute it and/or
  21 *  modify it under the terms of the GNU General Public License
  22 *  as published by the Free Software Foundation; either version
  23 *  2 of the License, or (at your option) any later version.
  24 */
  25#include <linux/module.h>
  26#include <linux/slab.h>
  27#include "ccid.h"
  28#include "feat.h"
  29
  30/* feature-specific sysctls - initialised to the defaults from RFC 4340, 6.4 */
  31unsigned long   sysctl_dccp_sequence_window __read_mostly = 100;
  32int             sysctl_dccp_rx_ccid         __read_mostly = 2,
  33                sysctl_dccp_tx_ccid         __read_mostly = 2;
  34
  35/*
  36 * Feature activation handlers.
  37 *
  38 * These all use an u64 argument, to provide enough room for NN/SP features. At
  39 * this stage the negotiated values have been checked to be within their range.
  40 */
  41static int dccp_hdlr_ccid(struct sock *sk, u64 ccid, bool rx)
  42{
  43        struct dccp_sock *dp = dccp_sk(sk);
  44        struct ccid *new_ccid = ccid_new(ccid, sk, rx);
  45
  46        if (new_ccid == NULL)
  47                return -ENOMEM;
  48
  49        if (rx) {
  50                ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
  51                dp->dccps_hc_rx_ccid = new_ccid;
  52        } else {
  53                ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
  54                dp->dccps_hc_tx_ccid = new_ccid;
  55        }
  56        return 0;
  57}
  58
  59static int dccp_hdlr_seq_win(struct sock *sk, u64 seq_win, bool rx)
  60{
  61        struct dccp_sock *dp = dccp_sk(sk);
  62
  63        if (rx) {
  64                dp->dccps_r_seq_win = seq_win;
  65                /* propagate changes to update SWL/SWH */
  66                dccp_update_gsr(sk, dp->dccps_gsr);
  67        } else {
  68                dp->dccps_l_seq_win = seq_win;
  69                /* propagate changes to update AWL */
  70                dccp_update_gss(sk, dp->dccps_gss);
  71        }
  72        return 0;
  73}
  74
  75static int dccp_hdlr_ack_ratio(struct sock *sk, u64 ratio, bool rx)
  76{
  77        if (rx)
  78                dccp_sk(sk)->dccps_r_ack_ratio = ratio;
  79        else
  80                dccp_sk(sk)->dccps_l_ack_ratio = ratio;
  81        return 0;
  82}
  83
  84static int dccp_hdlr_ackvec(struct sock *sk, u64 enable, bool rx)
  85{
  86        struct dccp_sock *dp = dccp_sk(sk);
  87
  88        if (rx) {
  89                if (enable && dp->dccps_hc_rx_ackvec == NULL) {
  90                        dp->dccps_hc_rx_ackvec = dccp_ackvec_alloc(gfp_any());
  91                        if (dp->dccps_hc_rx_ackvec == NULL)
  92                                return -ENOMEM;
  93                } else if (!enable) {
  94                        dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
  95                        dp->dccps_hc_rx_ackvec = NULL;
  96                }
  97        }
  98        return 0;
  99}
 100
 101static int dccp_hdlr_ndp(struct sock *sk, u64 enable, bool rx)
 102{
 103        if (!rx)
 104                dccp_sk(sk)->dccps_send_ndp_count = (enable > 0);
 105        return 0;
 106}
 107
 108/*
 109 * Minimum Checksum Coverage is located at the RX side (9.2.1). This means that
 110 * `rx' holds when the sending peer informs about his partial coverage via a
 111 * ChangeR() option. In the other case, we are the sender and the receiver
 112 * announces its coverage via ChangeL() options. The policy here is to honour
 113 * such communication by enabling the corresponding partial coverage - but only
 114 * if it has not been set manually before; the warning here means that all
 115 * packets will be dropped.
 116 */
 117static int dccp_hdlr_min_cscov(struct sock *sk, u64 cscov, bool rx)
 118{
 119        struct dccp_sock *dp = dccp_sk(sk);
 120
 121        if (rx)
 122                dp->dccps_pcrlen = cscov;
 123        else {
 124                if (dp->dccps_pcslen == 0)
 125                        dp->dccps_pcslen = cscov;
 126                else if (cscov > dp->dccps_pcslen)
 127                        DCCP_WARN("CsCov %u too small, peer requires >= %u\n",
 128                                  dp->dccps_pcslen, (u8)cscov);
 129        }
 130        return 0;
 131}
 132
 133static const struct {
 134        u8                      feat_num;               /* DCCPF_xxx */
 135        enum dccp_feat_type     rxtx;                   /* RX or TX  */
 136        enum dccp_feat_type     reconciliation;         /* SP or NN  */
 137        u8                      default_value;          /* as in 6.4 */
 138        int (*activation_hdlr)(struct sock *sk, u64 val, bool rx);
 139/*
 140 *    Lookup table for location and type of features (from RFC 4340/4342)
 141 *  +--------------------------+----+-----+----+----+---------+-----------+
 142 *  | Feature                  | Location | Reconc. | Initial |  Section  |
 143 *  |                          | RX | TX  | SP | NN |  Value  | Reference |
 144 *  +--------------------------+----+-----+----+----+---------+-----------+
 145 *  | DCCPF_CCID               |    |  X  | X  |    |   2     | 10        |
 146 *  | DCCPF_SHORT_SEQNOS       |    |  X  | X  |    |   0     |  7.6.1    |
 147 *  | DCCPF_SEQUENCE_WINDOW    |    |  X  |    | X  | 100     |  7.5.2    |
 148 *  | DCCPF_ECN_INCAPABLE      | X  |     | X  |    |   0     | 12.1      |
 149 *  | DCCPF_ACK_RATIO          |    |  X  |    | X  |   2     | 11.3      |
 150 *  | DCCPF_SEND_ACK_VECTOR    | X  |     | X  |    |   0     | 11.5      |
 151 *  | DCCPF_SEND_NDP_COUNT     |    |  X  | X  |    |   0     |  7.7.2    |
 152 *  | DCCPF_MIN_CSUM_COVER     | X  |     | X  |    |   0     |  9.2.1    |
 153 *  | DCCPF_DATA_CHECKSUM      | X  |     | X  |    |   0     |  9.3.1    |
 154 *  | DCCPF_SEND_LEV_RATE      | X  |     | X  |    |   0     | 4342/8.4  |
 155 *  +--------------------------+----+-----+----+----+---------+-----------+
 156 */
 157} dccp_feat_table[] = {
 158        { DCCPF_CCID,            FEAT_AT_TX, FEAT_SP, 2,   dccp_hdlr_ccid     },
 159        { DCCPF_SHORT_SEQNOS,    FEAT_AT_TX, FEAT_SP, 0,   NULL },
 160        { DCCPF_SEQUENCE_WINDOW, FEAT_AT_TX, FEAT_NN, 100, dccp_hdlr_seq_win  },
 161        { DCCPF_ECN_INCAPABLE,   FEAT_AT_RX, FEAT_SP, 0,   NULL },
 162        { DCCPF_ACK_RATIO,       FEAT_AT_TX, FEAT_NN, 2,   dccp_hdlr_ack_ratio},
 163        { DCCPF_SEND_ACK_VECTOR, FEAT_AT_RX, FEAT_SP, 0,   dccp_hdlr_ackvec   },
 164        { DCCPF_SEND_NDP_COUNT,  FEAT_AT_TX, FEAT_SP, 0,   dccp_hdlr_ndp      },
 165        { DCCPF_MIN_CSUM_COVER,  FEAT_AT_RX, FEAT_SP, 0,   dccp_hdlr_min_cscov},
 166        { DCCPF_DATA_CHECKSUM,   FEAT_AT_RX, FEAT_SP, 0,   NULL },
 167        { DCCPF_SEND_LEV_RATE,   FEAT_AT_RX, FEAT_SP, 0,   NULL },
 168};
 169#define DCCP_FEAT_SUPPORTED_MAX         ARRAY_SIZE(dccp_feat_table)
 170
 171/**
 172 * dccp_feat_index  -  Hash function to map feature number into array position
 173 * Returns consecutive array index or -1 if the feature is not understood.
 174 */
 175static int dccp_feat_index(u8 feat_num)
 176{
 177        /* The first 9 entries are occupied by the types from RFC 4340, 6.4 */
 178        if (feat_num > DCCPF_RESERVED && feat_num <= DCCPF_DATA_CHECKSUM)
 179                return feat_num - 1;
 180
 181        /*
 182         * Other features: add cases for new feature types here after adding
 183         * them to the above table.
 184         */
 185        switch (feat_num) {
 186        case DCCPF_SEND_LEV_RATE:
 187                        return DCCP_FEAT_SUPPORTED_MAX - 1;
 188        }
 189        return -1;
 190}
 191
 192static u8 dccp_feat_type(u8 feat_num)
 193{
 194        int idx = dccp_feat_index(feat_num);
 195
 196        if (idx < 0)
 197                return FEAT_UNKNOWN;
 198        return dccp_feat_table[idx].reconciliation;
 199}
 200
 201static int dccp_feat_default_value(u8 feat_num)
 202{
 203        int idx = dccp_feat_index(feat_num);
 204        /*
 205         * There are no default values for unknown features, so encountering a
 206         * negative index here indicates a serious problem somewhere else.
 207         */
 208        DCCP_BUG_ON(idx < 0);
 209
 210        return idx < 0 ? 0 : dccp_feat_table[idx].default_value;
 211}
 212
 213/*
 214 *      Debugging and verbose-printing section
 215 */
 216static const char *dccp_feat_fname(const u8 feat)
 217{
 218        static const char *const feature_names[] = {
 219                [DCCPF_RESERVED]        = "Reserved",
 220                [DCCPF_CCID]            = "CCID",
 221                [DCCPF_SHORT_SEQNOS]    = "Allow Short Seqnos",
 222                [DCCPF_SEQUENCE_WINDOW] = "Sequence Window",
 223                [DCCPF_ECN_INCAPABLE]   = "ECN Incapable",
 224                [DCCPF_ACK_RATIO]       = "Ack Ratio",
 225                [DCCPF_SEND_ACK_VECTOR] = "Send ACK Vector",
 226                [DCCPF_SEND_NDP_COUNT]  = "Send NDP Count",
 227                [DCCPF_MIN_CSUM_COVER]  = "Min. Csum Coverage",
 228                [DCCPF_DATA_CHECKSUM]   = "Send Data Checksum",
 229        };
 230        if (feat > DCCPF_DATA_CHECKSUM && feat < DCCPF_MIN_CCID_SPECIFIC)
 231                return feature_names[DCCPF_RESERVED];
 232
 233        if (feat ==  DCCPF_SEND_LEV_RATE)
 234                return "Send Loss Event Rate";
 235        if (feat >= DCCPF_MIN_CCID_SPECIFIC)
 236                return "CCID-specific";
 237
 238        return feature_names[feat];
 239}
 240
 241static const char *const dccp_feat_sname[] = {
 242        "DEFAULT", "INITIALISING", "CHANGING", "UNSTABLE", "STABLE",
 243};
 244
 245#ifdef CONFIG_IP_DCCP_DEBUG
 246static const char *dccp_feat_oname(const u8 opt)
 247{
 248        switch (opt) {
 249        case DCCPO_CHANGE_L:  return "Change_L";
 250        case DCCPO_CONFIRM_L: return "Confirm_L";
 251        case DCCPO_CHANGE_R:  return "Change_R";
 252        case DCCPO_CONFIRM_R: return "Confirm_R";
 253        }
 254        return NULL;
 255}
 256
 257static void dccp_feat_printval(u8 feat_num, dccp_feat_val const *val)
 258{
 259        u8 i, type = dccp_feat_type(feat_num);
 260
 261        if (val == NULL || (type == FEAT_SP && val->sp.vec == NULL))
 262                dccp_pr_debug_cat("(NULL)");
 263        else if (type == FEAT_SP)
 264                for (i = 0; i < val->sp.len; i++)
 265                        dccp_pr_debug_cat("%s%u", i ? " " : "", val->sp.vec[i]);
 266        else if (type == FEAT_NN)
 267                dccp_pr_debug_cat("%llu", (unsigned long long)val->nn);
 268        else
 269                dccp_pr_debug_cat("unknown type %u", type);
 270}
 271
 272static void dccp_feat_printvals(u8 feat_num, u8 *list, u8 len)
 273{
 274        u8 type = dccp_feat_type(feat_num);
 275        dccp_feat_val fval = { .sp.vec = list, .sp.len = len };
 276
 277        if (type == FEAT_NN)
 278                fval.nn = dccp_decode_value_var(list, len);
 279        dccp_feat_printval(feat_num, &fval);
 280}
 281
 282static void dccp_feat_print_entry(struct dccp_feat_entry const *entry)
 283{
 284        dccp_debug("   * %s %s = ", entry->is_local ? "local" : "remote",
 285                                    dccp_feat_fname(entry->feat_num));
 286        dccp_feat_printval(entry->feat_num, &entry->val);
 287        dccp_pr_debug_cat(", state=%s %s\n", dccp_feat_sname[entry->state],
 288                          entry->needs_confirm ? "(Confirm pending)" : "");
 289}
 290
 291#define dccp_feat_print_opt(opt, feat, val, len, mandatory)     do {          \
 292        dccp_pr_debug("%s(%s, ", dccp_feat_oname(opt), dccp_feat_fname(feat));\
 293        dccp_feat_printvals(feat, val, len);                                  \
 294        dccp_pr_debug_cat(") %s\n", mandatory ? "!" : "");      } while (0)
 295
 296#define dccp_feat_print_fnlist(fn_list)  {              \
 297        const struct dccp_feat_entry *___entry;         \
 298                                                        \
 299        dccp_pr_debug("List Dump:\n");                  \
 300        list_for_each_entry(___entry, fn_list, node)    \
 301                dccp_feat_print_entry(___entry);        \
 302}
 303#else   /* ! CONFIG_IP_DCCP_DEBUG */
 304#define dccp_feat_print_opt(opt, feat, val, len, mandatory)
 305#define dccp_feat_print_fnlist(fn_list)
 306#endif
 307
 308static int __dccp_feat_activate(struct sock *sk, const int idx,
 309                                const bool is_local, dccp_feat_val const *fval)
 310{
 311        bool rx;
 312        u64 val;
 313
 314        if (idx < 0 || idx >= DCCP_FEAT_SUPPORTED_MAX)
 315                return -1;
 316        if (dccp_feat_table[idx].activation_hdlr == NULL)
 317                return 0;
 318
 319        if (fval == NULL) {
 320                val = dccp_feat_table[idx].default_value;
 321        } else if (dccp_feat_table[idx].reconciliation == FEAT_SP) {
 322                if (fval->sp.vec == NULL) {
 323                        /*
 324                         * This can happen when an empty Confirm is sent
 325                         * for an SP (i.e. known) feature. In this case
 326                         * we would be using the default anyway.
 327                         */
 328                        DCCP_CRIT("Feature #%d undefined: using default", idx);
 329                        val = dccp_feat_table[idx].default_value;
 330                } else {
 331                        val = fval->sp.vec[0];
 332                }
 333        } else {
 334                val = fval->nn;
 335        }
 336
 337        /* Location is RX if this is a local-RX or remote-TX feature */
 338        rx = (is_local == (dccp_feat_table[idx].rxtx == FEAT_AT_RX));
 339
 340        dccp_debug("   -> activating %s %s, %sval=%llu\n", rx ? "RX" : "TX",
 341                   dccp_feat_fname(dccp_feat_table[idx].feat_num),
 342                   fval ? "" : "default ",  (unsigned long long)val);
 343
 344        return dccp_feat_table[idx].activation_hdlr(sk, val, rx);
 345}
 346
 347/**
 348 * dccp_feat_activate  -  Activate feature value on socket
 349 * @sk: fully connected DCCP socket (after handshake is complete)
 350 * @feat_num: feature to activate, one of %dccp_feature_numbers
 351 * @local: whether local (1) or remote (0) @feat_num is meant
 352 * @fval: the value (SP or NN) to activate, or NULL to use the default value
 353 *
 354 * For general use this function is preferable over __dccp_feat_activate().
 355 */
 356static int dccp_feat_activate(struct sock *sk, u8 feat_num, bool local,
 357                              dccp_feat_val const *fval)
 358{
 359        return __dccp_feat_activate(sk, dccp_feat_index(feat_num), local, fval);
 360}
 361
 362/* Test for "Req'd" feature (RFC 4340, 6.4) */
 363static inline int dccp_feat_must_be_understood(u8 feat_num)
 364{
 365        return  feat_num == DCCPF_CCID || feat_num == DCCPF_SHORT_SEQNOS ||
 366                feat_num == DCCPF_SEQUENCE_WINDOW;
 367}
 368
 369/* copy constructor, fval must not already contain allocated memory */
 370static int dccp_feat_clone_sp_val(dccp_feat_val *fval, u8 const *val, u8 len)
 371{
 372        fval->sp.len = len;
 373        if (fval->sp.len > 0) {
 374                fval->sp.vec = kmemdup(val, len, gfp_any());
 375                if (fval->sp.vec == NULL) {
 376                        fval->sp.len = 0;
 377                        return -ENOBUFS;
 378                }
 379        }
 380        return 0;
 381}
 382
 383static void dccp_feat_val_destructor(u8 feat_num, dccp_feat_val *val)
 384{
 385        if (unlikely(val == NULL))
 386                return;
 387        if (dccp_feat_type(feat_num) == FEAT_SP)
 388                kfree(val->sp.vec);
 389        memset(val, 0, sizeof(*val));
 390}
 391
 392static struct dccp_feat_entry *
 393              dccp_feat_clone_entry(struct dccp_feat_entry const *original)
 394{
 395        struct dccp_feat_entry *new;
 396        u8 type = dccp_feat_type(original->feat_num);
 397
 398        if (type == FEAT_UNKNOWN)
 399                return NULL;
 400
 401        new = kmemdup(original, sizeof(struct dccp_feat_entry), gfp_any());
 402        if (new == NULL)
 403                return NULL;
 404
 405        if (type == FEAT_SP && dccp_feat_clone_sp_val(&new->val,
 406                                                      original->val.sp.vec,
 407                                                      original->val.sp.len)) {
 408                kfree(new);
 409                return NULL;
 410        }
 411        return new;
 412}
 413
 414static void dccp_feat_entry_destructor(struct dccp_feat_entry *entry)
 415{
 416        if (entry != NULL) {
 417                dccp_feat_val_destructor(entry->feat_num, &entry->val);
 418                kfree(entry);
 419        }
 420}
 421
 422/*
 423 * List management functions
 424 *
 425 * Feature negotiation lists rely on and maintain the following invariants:
 426 * - each feat_num in the list is known, i.e. we know its type and default value
 427 * - each feat_num/is_local combination is unique (old entries are overwritten)
 428 * - SP values are always freshly allocated
 429 * - list is sorted in increasing order of feature number (faster lookup)
 430 */
 431static struct dccp_feat_entry *dccp_feat_list_lookup(struct list_head *fn_list,
 432                                                     u8 feat_num, bool is_local)
 433{
 434        struct dccp_feat_entry *entry;
 435
 436        list_for_each_entry(entry, fn_list, node) {
 437                if (entry->feat_num == feat_num && entry->is_local == is_local)
 438                        return entry;
 439                else if (entry->feat_num > feat_num)
 440                        break;
 441        }
 442        return NULL;
 443}
 444
 445/**
 446 * dccp_feat_entry_new  -  Central list update routine (called by all others)
 447 * @head:  list to add to
 448 * @feat:  feature number
 449 * @local: whether the local (1) or remote feature with number @feat is meant
 450 *
 451 * This is the only constructor and serves to ensure the above invariants.
 452 */
 453static struct dccp_feat_entry *
 454              dccp_feat_entry_new(struct list_head *head, u8 feat, bool local)
 455{
 456        struct dccp_feat_entry *entry;
 457
 458        list_for_each_entry(entry, head, node)
 459                if (entry->feat_num == feat && entry->is_local == local) {
 460                        dccp_feat_val_destructor(entry->feat_num, &entry->val);
 461                        return entry;
 462                } else if (entry->feat_num > feat) {
 463                        head = &entry->node;
 464                        break;
 465                }
 466
 467        entry = kmalloc(sizeof(*entry), gfp_any());
 468        if (entry != NULL) {
 469                entry->feat_num = feat;
 470                entry->is_local = local;
 471                list_add_tail(&entry->node, head);
 472        }
 473        return entry;
 474}
 475
 476/**
 477 * dccp_feat_push_change  -  Add/overwrite a Change option in the list
 478 * @fn_list: feature-negotiation list to update
 479 * @feat: one of %dccp_feature_numbers
 480 * @local: whether local (1) or remote (0) @feat_num is meant
 481 * @needs_mandatory: whether to use Mandatory feature negotiation options
 482 * @fval: pointer to NN/SP value to be inserted (will be copied)
 483 */
 484static int dccp_feat_push_change(struct list_head *fn_list, u8 feat, u8 local,
 485                                 u8 mandatory, dccp_feat_val *fval)
 486{
 487        struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
 488
 489        if (new == NULL)
 490                return -ENOMEM;
 491
 492        new->feat_num        = feat;
 493        new->is_local        = local;
 494        new->state           = FEAT_INITIALISING;
 495        new->needs_confirm   = false;
 496        new->empty_confirm   = false;
 497        new->val             = *fval;
 498        new->needs_mandatory = mandatory;
 499
 500        return 0;
 501}
 502
 503/**
 504 * dccp_feat_push_confirm  -  Add a Confirm entry to the FN list
 505 * @fn_list: feature-negotiation list to add to
 506 * @feat: one of %dccp_feature_numbers
 507 * @local: whether local (1) or remote (0) @feat_num is being confirmed
 508 * @fval: pointer to NN/SP value to be inserted or NULL
 509 *
 510 * Returns 0 on success, a Reset code for further processing otherwise.
 511 */
 512static int dccp_feat_push_confirm(struct list_head *fn_list, u8 feat, u8 local,
 513                                  dccp_feat_val *fval)
 514{
 515        struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
 516
 517        if (new == NULL)
 518                return DCCP_RESET_CODE_TOO_BUSY;
 519
 520        new->feat_num        = feat;
 521        new->is_local        = local;
 522        new->state           = FEAT_STABLE;     /* transition in 6.6.2 */
 523        new->needs_confirm   = true;
 524        new->empty_confirm   = (fval == NULL);
 525        new->val.nn          = 0;               /* zeroes the whole structure */
 526        if (!new->empty_confirm)
 527                new->val     = *fval;
 528        new->needs_mandatory = false;
 529
 530        return 0;
 531}
 532
 533static int dccp_push_empty_confirm(struct list_head *fn_list, u8 feat, u8 local)
 534{
 535        return dccp_feat_push_confirm(fn_list, feat, local, NULL);
 536}
 537
 538static inline void dccp_feat_list_pop(struct dccp_feat_entry *entry)
 539{
 540        list_del(&entry->node);
 541        dccp_feat_entry_destructor(entry);
 542}
 543
 544void dccp_feat_list_purge(struct list_head *fn_list)
 545{
 546        struct dccp_feat_entry *entry, *next;
 547
 548        list_for_each_entry_safe(entry, next, fn_list, node)
 549                dccp_feat_entry_destructor(entry);
 550        INIT_LIST_HEAD(fn_list);
 551}
 552EXPORT_SYMBOL_GPL(dccp_feat_list_purge);
 553
 554/* generate @to as full clone of @from - @to must not contain any nodes */
 555int dccp_feat_clone_list(struct list_head const *from, struct list_head *to)
 556{
 557        struct dccp_feat_entry *entry, *new;
 558
 559        INIT_LIST_HEAD(to);
 560        list_for_each_entry(entry, from, node) {
 561                new = dccp_feat_clone_entry(entry);
 562                if (new == NULL)
 563                        goto cloning_failed;
 564                list_add_tail(&new->node, to);
 565        }
 566        return 0;
 567
 568cloning_failed:
 569        dccp_feat_list_purge(to);
 570        return -ENOMEM;
 571}
 572
 573/**
 574 * dccp_feat_valid_nn_length  -  Enforce length constraints on NN options
 575 * Length is between 0 and %DCCP_OPTVAL_MAXLEN. Used for outgoing packets only,
 576 * incoming options are accepted as long as their values are valid.
 577 */
 578static u8 dccp_feat_valid_nn_length(u8 feat_num)
 579{
 580        if (feat_num == DCCPF_ACK_RATIO)        /* RFC 4340, 11.3 and 6.6.8 */
 581                return 2;
 582        if (feat_num == DCCPF_SEQUENCE_WINDOW)  /* RFC 4340, 7.5.2 and 6.5  */
 583                return 6;
 584        return 0;
 585}
 586
 587static u8 dccp_feat_is_valid_nn_val(u8 feat_num, u64 val)
 588{
 589        switch (feat_num) {
 590        case DCCPF_ACK_RATIO:
 591                return val <= DCCPF_ACK_RATIO_MAX;
 592        case DCCPF_SEQUENCE_WINDOW:
 593                return val >= DCCPF_SEQ_WMIN && val <= DCCPF_SEQ_WMAX;
 594        }
 595        return 0;       /* feature unknown - so we can't tell */
 596}
 597
 598/* check that SP values are within the ranges defined in RFC 4340 */
 599static u8 dccp_feat_is_valid_sp_val(u8 feat_num, u8 val)
 600{
 601        switch (feat_num) {
 602        case DCCPF_CCID:
 603                return val == DCCPC_CCID2 || val == DCCPC_CCID3;
 604        /* Type-check Boolean feature values: */
 605        case DCCPF_SHORT_SEQNOS:
 606        case DCCPF_ECN_INCAPABLE:
 607        case DCCPF_SEND_ACK_VECTOR:
 608        case DCCPF_SEND_NDP_COUNT:
 609        case DCCPF_DATA_CHECKSUM:
 610        case DCCPF_SEND_LEV_RATE:
 611                return val < 2;
 612        case DCCPF_MIN_CSUM_COVER:
 613                return val < 16;
 614        }
 615        return 0;                       /* feature unknown */
 616}
 617
 618static u8 dccp_feat_sp_list_ok(u8 feat_num, u8 const *sp_list, u8 sp_len)
 619{
 620        if (sp_list == NULL || sp_len < 1)
 621                return 0;
 622        while (sp_len--)
 623                if (!dccp_feat_is_valid_sp_val(feat_num, *sp_list++))
 624                        return 0;
 625        return 1;
 626}
 627
 628/**
 629 * dccp_feat_insert_opts  -  Generate FN options from current list state
 630 * @skb: next sk_buff to be sent to the peer
 631 * @dp: for client during handshake and general negotiation
 632 * @dreq: used by the server only (all Changes/Confirms in LISTEN/RESPOND)
 633 */
 634int dccp_feat_insert_opts(struct dccp_sock *dp, struct dccp_request_sock *dreq,
 635                          struct sk_buff *skb)
 636{
 637        struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
 638        struct dccp_feat_entry *pos, *next;
 639        u8 opt, type, len, *ptr, nn_in_nbo[DCCP_OPTVAL_MAXLEN];
 640        bool rpt;
 641
 642        /* put entries into @skb in the order they appear in the list */
 643        list_for_each_entry_safe_reverse(pos, next, fn, node) {
 644                opt  = dccp_feat_genopt(pos);
 645                type = dccp_feat_type(pos->feat_num);
 646                rpt  = false;
 647
 648                if (pos->empty_confirm) {
 649                        len = 0;
 650                        ptr = NULL;
 651                } else {
 652                        if (type == FEAT_SP) {
 653                                len = pos->val.sp.len;
 654                                ptr = pos->val.sp.vec;
 655                                rpt = pos->needs_confirm;
 656                        } else if (type == FEAT_NN) {
 657                                len = dccp_feat_valid_nn_length(pos->feat_num);
 658                                ptr = nn_in_nbo;
 659                                dccp_encode_value_var(pos->val.nn, ptr, len);
 660                        } else {
 661                                DCCP_BUG("unknown feature %u", pos->feat_num);
 662                                return -1;
 663                        }
 664                }
 665                dccp_feat_print_opt(opt, pos->feat_num, ptr, len, 0);
 666
 667                if (dccp_insert_fn_opt(skb, opt, pos->feat_num, ptr, len, rpt))
 668                        return -1;
 669                if (pos->needs_mandatory && dccp_insert_option_mandatory(skb))
 670                        return -1;
 671
 672                if (skb->sk->sk_state == DCCP_OPEN &&
 673                    (opt == DCCPO_CONFIRM_R || opt == DCCPO_CONFIRM_L)) {
 674                        /*
 675                         * Confirms don't get retransmitted (6.6.3) once the
 676                         * connection is in state OPEN
 677                         */
 678                        dccp_feat_list_pop(pos);
 679                } else {
 680                        /*
 681                         * Enter CHANGING after transmitting the Change
 682                         * option (6.6.2).
 683                         */
 684                        if (pos->state == FEAT_INITIALISING)
 685                                pos->state = FEAT_CHANGING;
 686                }
 687        }
 688        return 0;
 689}
 690
 691/**
 692 * __feat_register_nn  -  Register new NN value on socket
 693 * @fn: feature-negotiation list to register with
 694 * @feat: an NN feature from %dccp_feature_numbers
 695 * @mandatory: use Mandatory option if 1
 696 * @nn_val: value to register (restricted to 4 bytes)
 697 *
 698 * Note that NN features are local by definition (RFC 4340, 6.3.2).
 699 */
 700static int __feat_register_nn(struct list_head *fn, u8 feat,
 701                              u8 mandatory, u64 nn_val)
 702{
 703        dccp_feat_val fval = { .nn = nn_val };
 704
 705        if (dccp_feat_type(feat) != FEAT_NN ||
 706            !dccp_feat_is_valid_nn_val(feat, nn_val))
 707                return -EINVAL;
 708
 709        /* Don't bother with default values, they will be activated anyway. */
 710        if (nn_val - (u64)dccp_feat_default_value(feat) == 0)
 711                return 0;
 712
 713        return dccp_feat_push_change(fn, feat, 1, mandatory, &fval);
 714}
 715
 716/**
 717 * __feat_register_sp  -  Register new SP value/list on socket
 718 * @fn: feature-negotiation list to register with
 719 * @feat: an SP feature from %dccp_feature_numbers
 720 * @is_local: whether the local (1) or the remote (0) @feat is meant
 721 * @mandatory: use Mandatory option if 1
 722 * @sp_val: SP value followed by optional preference list
 723 * @sp_len: length of @sp_val in bytes
 724 */
 725static int __feat_register_sp(struct list_head *fn, u8 feat, u8 is_local,
 726                              u8 mandatory, u8 const *sp_val, u8 sp_len)
 727{
 728        dccp_feat_val fval;
 729
 730        if (dccp_feat_type(feat) != FEAT_SP ||
 731            !dccp_feat_sp_list_ok(feat, sp_val, sp_len))
 732                return -EINVAL;
 733
 734        /* Avoid negotiating alien CCIDs by only advertising supported ones */
 735        if (feat == DCCPF_CCID && !ccid_support_check(sp_val, sp_len))
 736                return -EOPNOTSUPP;
 737
 738        if (dccp_feat_clone_sp_val(&fval, sp_val, sp_len))
 739                return -ENOMEM;
 740
 741        return dccp_feat_push_change(fn, feat, is_local, mandatory, &fval);
 742}
 743
 744/**
 745 * dccp_feat_register_sp  -  Register requests to change SP feature values
 746 * @sk: client or listening socket
 747 * @feat: one of %dccp_feature_numbers
 748 * @is_local: whether the local (1) or remote (0) @feat is meant
 749 * @list: array of preferred values, in descending order of preference
 750 * @len: length of @list in bytes
 751 */
 752int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
 753                          u8 const *list, u8 len)
 754{        /* any changes must be registered before establishing the connection */
 755        if (sk->sk_state != DCCP_CLOSED)
 756                return -EISCONN;
 757        if (dccp_feat_type(feat) != FEAT_SP)
 758                return -EINVAL;
 759        return __feat_register_sp(&dccp_sk(sk)->dccps_featneg, feat, is_local,
 760                                  0, list, len);
 761}
 762
 763/**
 764 * dccp_feat_nn_get  -  Query current/pending value of NN feature
 765 * @sk: DCCP socket of an established connection
 766 * @feat: NN feature number from %dccp_feature_numbers
 767 *
 768 * For a known NN feature, returns value currently being negotiated, or
 769 * current (confirmed) value if no negotiation is going on.
 770 */
 771u64 dccp_feat_nn_get(struct sock *sk, u8 feat)
 772{
 773        if (dccp_feat_type(feat) == FEAT_NN) {
 774                struct dccp_sock *dp = dccp_sk(sk);
 775                struct dccp_feat_entry *entry;
 776
 777                entry = dccp_feat_list_lookup(&dp->dccps_featneg, feat, 1);
 778                if (entry != NULL)
 779                        return entry->val.nn;
 780
 781                switch (feat) {
 782                case DCCPF_ACK_RATIO:
 783                        return dp->dccps_l_ack_ratio;
 784                case DCCPF_SEQUENCE_WINDOW:
 785                        return dp->dccps_l_seq_win;
 786                }
 787        }
 788        DCCP_BUG("attempt to look up unsupported feature %u", feat);
 789        return 0;
 790}
 791EXPORT_SYMBOL_GPL(dccp_feat_nn_get);
 792
 793/**
 794 * dccp_feat_signal_nn_change  -  Update NN values for an established connection
 795 * @sk: DCCP socket of an established connection
 796 * @feat: NN feature number from %dccp_feature_numbers
 797 * @nn_val: the new value to use
 798 *
 799 * This function is used to communicate NN updates out-of-band.
 800 */
 801int dccp_feat_signal_nn_change(struct sock *sk, u8 feat, u64 nn_val)
 802{
 803        struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
 804        dccp_feat_val fval = { .nn = nn_val };
 805        struct dccp_feat_entry *entry;
 806
 807        if (sk->sk_state != DCCP_OPEN && sk->sk_state != DCCP_PARTOPEN)
 808                return 0;
 809
 810        if (dccp_feat_type(feat) != FEAT_NN ||
 811            !dccp_feat_is_valid_nn_val(feat, nn_val))
 812                return -EINVAL;
 813
 814        if (nn_val == dccp_feat_nn_get(sk, feat))
 815                return 0;       /* already set or negotiation under way */
 816
 817        entry = dccp_feat_list_lookup(fn, feat, 1);
 818        if (entry != NULL) {
 819                dccp_pr_debug("Clobbering existing NN entry %llu -> %llu\n",
 820                              (unsigned long long)entry->val.nn,
 821                              (unsigned long long)nn_val);
 822                dccp_feat_list_pop(entry);
 823        }
 824
 825        inet_csk_schedule_ack(sk);
 826        return dccp_feat_push_change(fn, feat, 1, 0, &fval);
 827}
 828EXPORT_SYMBOL_GPL(dccp_feat_signal_nn_change);
 829
 830/*
 831 *      Tracking features whose value depend on the choice of CCID
 832 *
 833 * This is designed with an extension in mind so that a list walk could be done
 834 * before activating any features. However, the existing framework was found to
 835 * work satisfactorily up until now, the automatic verification is left open.
 836 * When adding new CCIDs, add a corresponding dependency table here.
 837 */
 838static const struct ccid_dependency *dccp_feat_ccid_deps(u8 ccid, bool is_local)
 839{
 840        static const struct ccid_dependency ccid2_dependencies[2][2] = {
 841                /*
 842                 * CCID2 mandates Ack Vectors (RFC 4341, 4.): as CCID is a TX
 843                 * feature and Send Ack Vector is an RX feature, `is_local'
 844                 * needs to be reversed.
 845                 */
 846                {       /* Dependencies of the receiver-side (remote) CCID2 */
 847                        {
 848                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 849                                .is_local       = true,
 850                                .is_mandatory   = true,
 851                                .val            = 1
 852                        },
 853                        { 0, 0, 0, 0 }
 854                },
 855                {       /* Dependencies of the sender-side (local) CCID2 */
 856                        {
 857                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 858                                .is_local       = false,
 859                                .is_mandatory   = true,
 860                                .val            = 1
 861                        },
 862                        { 0, 0, 0, 0 }
 863                }
 864        };
 865        static const struct ccid_dependency ccid3_dependencies[2][5] = {
 866                {       /*
 867                         * Dependencies of the receiver-side CCID3
 868                         */
 869                        {       /* locally disable Ack Vectors */
 870                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 871                                .is_local       = true,
 872                                .is_mandatory   = false,
 873                                .val            = 0
 874                        },
 875                        {       /* see below why Send Loss Event Rate is on */
 876                                .dependent_feat = DCCPF_SEND_LEV_RATE,
 877                                .is_local       = true,
 878                                .is_mandatory   = true,
 879                                .val            = 1
 880                        },
 881                        {       /* NDP Count is needed as per RFC 4342, 6.1.1 */
 882                                .dependent_feat = DCCPF_SEND_NDP_COUNT,
 883                                .is_local       = false,
 884                                .is_mandatory   = true,
 885                                .val            = 1
 886                        },
 887                        { 0, 0, 0, 0 },
 888                },
 889                {       /*
 890                         * CCID3 at the TX side: we request that the HC-receiver
 891                         * will not send Ack Vectors (they will be ignored, so
 892                         * Mandatory is not set); we enable Send Loss Event Rate
 893                         * (Mandatory since the implementation does not support
 894                         * the Loss Intervals option of RFC 4342, 8.6).
 895                         * The last two options are for peer's information only.
 896                        */
 897                        {
 898                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
 899                                .is_local       = false,
 900                                .is_mandatory   = false,
 901                                .val            = 0
 902                        },
 903                        {
 904                                .dependent_feat = DCCPF_SEND_LEV_RATE,
 905                                .is_local       = false,
 906                                .is_mandatory   = true,
 907                                .val            = 1
 908                        },
 909                        {       /* this CCID does not support Ack Ratio */
 910                                .dependent_feat = DCCPF_ACK_RATIO,
 911                                .is_local       = true,
 912                                .is_mandatory   = false,
 913                                .val            = 0
 914                        },
 915                        {       /* tell receiver we are sending NDP counts */
 916                                .dependent_feat = DCCPF_SEND_NDP_COUNT,
 917                                .is_local       = true,
 918                                .is_mandatory   = false,
 919                                .val            = 1
 920                        },
 921                        { 0, 0, 0, 0 }
 922                }
 923        };
 924        switch (ccid) {
 925        case DCCPC_CCID2:
 926                return ccid2_dependencies[is_local];
 927        case DCCPC_CCID3:
 928                return ccid3_dependencies[is_local];
 929        default:
 930                return NULL;
 931        }
 932}
 933
 934/**
 935 * dccp_feat_propagate_ccid - Resolve dependencies of features on choice of CCID
 936 * @fn: feature-negotiation list to update
 937 * @id: CCID number to track
 938 * @is_local: whether TX CCID (1) or RX CCID (0) is meant
 939 *
 940 * This function needs to be called after registering all other features.
 941 */
 942static int dccp_feat_propagate_ccid(struct list_head *fn, u8 id, bool is_local)
 943{
 944        const struct ccid_dependency *table = dccp_feat_ccid_deps(id, is_local);
 945        int i, rc = (table == NULL);
 946
 947        for (i = 0; rc == 0 && table[i].dependent_feat != DCCPF_RESERVED; i++)
 948                if (dccp_feat_type(table[i].dependent_feat) == FEAT_SP)
 949                        rc = __feat_register_sp(fn, table[i].dependent_feat,
 950                                                    table[i].is_local,
 951                                                    table[i].is_mandatory,
 952                                                    &table[i].val, 1);
 953                else
 954                        rc = __feat_register_nn(fn, table[i].dependent_feat,
 955                                                    table[i].is_mandatory,
 956                                                    table[i].val);
 957        return rc;
 958}
 959
 960/**
 961 * dccp_feat_finalise_settings  -  Finalise settings before starting negotiation
 962 * @dp: client or listening socket (settings will be inherited)
 963 *
 964 * This is called after all registrations (socket initialisation, sysctls, and
 965 * sockopt calls), and before sending the first packet containing Change options
 966 * (ie. client-Request or server-Response), to ensure internal consistency.
 967 */
 968int dccp_feat_finalise_settings(struct dccp_sock *dp)
 969{
 970        struct list_head *fn = &dp->dccps_featneg;
 971        struct dccp_feat_entry *entry;
 972        int i = 2, ccids[2] = { -1, -1 };
 973
 974        /*
 975         * Propagating CCIDs:
 976         * 1) not useful to propagate CCID settings if this host advertises more
 977         *    than one CCID: the choice of CCID  may still change - if this is
 978         *    the client, or if this is the server and the client sends
 979         *    singleton CCID values.
 980         * 2) since is that propagate_ccid changes the list, we defer changing
 981         *    the sorted list until after the traversal.
 982         */
 983        list_for_each_entry(entry, fn, node)
 984                if (entry->feat_num == DCCPF_CCID && entry->val.sp.len == 1)
 985                        ccids[entry->is_local] = entry->val.sp.vec[0];
 986        while (i--)
 987                if (ccids[i] > 0 && dccp_feat_propagate_ccid(fn, ccids[i], i))
 988                        return -1;
 989        dccp_feat_print_fnlist(fn);
 990        return 0;
 991}
 992
 993/**
 994 * dccp_feat_server_ccid_dependencies  -  Resolve CCID-dependent features
 995 * It is the server which resolves the dependencies once the CCID has been
 996 * fully negotiated. If no CCID has been negotiated, it uses the default CCID.
 997 */
 998int dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq)
 999{
1000        struct list_head *fn = &dreq->dreq_featneg;
1001        struct dccp_feat_entry *entry;
1002        u8 is_local, ccid;
1003
1004        for (is_local = 0; is_local <= 1; is_local++) {
1005                entry = dccp_feat_list_lookup(fn, DCCPF_CCID, is_local);
1006
1007                if (entry != NULL && !entry->empty_confirm)
1008                        ccid = entry->val.sp.vec[0];
1009                else
1010                        ccid = dccp_feat_default_value(DCCPF_CCID);
1011
1012                if (dccp_feat_propagate_ccid(fn, ccid, is_local))
1013                        return -1;
1014        }
1015        return 0;
1016}
1017
1018/* Select the first entry in @servlist that also occurs in @clilist (6.3.1) */
1019static int dccp_feat_preflist_match(u8 *servlist, u8 slen, u8 *clilist, u8 clen)
1020{
1021        u8 c, s;
1022
1023        for (s = 0; s < slen; s++)
1024                for (c = 0; c < clen; c++)
1025                        if (servlist[s] == clilist[c])
1026                                return servlist[s];
1027        return -1;
1028}
1029
1030/**
1031 * dccp_feat_prefer  -  Move preferred entry to the start of array
1032 * Reorder the @array_len elements in @array so that @preferred_value comes
1033 * first. Returns >0 to indicate that @preferred_value does occur in @array.
1034 */
1035static u8 dccp_feat_prefer(u8 preferred_value, u8 *array, u8 array_len)
1036{
1037        u8 i, does_occur = 0;
1038
1039        if (array != NULL) {
1040                for (i = 0; i < array_len; i++)
1041                        if (array[i] == preferred_value) {
1042                                array[i] = array[0];
1043                                does_occur++;
1044                        }
1045                if (does_occur)
1046                        array[0] = preferred_value;
1047        }
1048        return does_occur;
1049}
1050
1051/**
1052 * dccp_feat_reconcile  -  Reconcile SP preference lists
1053 *  @fval: SP list to reconcile into
1054 *  @arr: received SP preference list
1055 *  @len: length of @arr in bytes
1056 *  @is_server: whether this side is the server (and @fv is the server's list)
1057 *  @reorder: whether to reorder the list in @fv after reconciling with @arr
1058 * When successful, > 0 is returned and the reconciled list is in @fval.
1059 * A value of 0 means that negotiation failed (no shared entry).
1060 */
1061static int dccp_feat_reconcile(dccp_feat_val *fv, u8 *arr, u8 len,
1062                               bool is_server, bool reorder)
1063{
1064        int rc;
1065
1066        if (!fv->sp.vec || !arr) {
1067                DCCP_CRIT("NULL feature value or array");
1068                return 0;
1069        }
1070
1071        if (is_server)
1072                rc = dccp_feat_preflist_match(fv->sp.vec, fv->sp.len, arr, len);
1073        else
1074                rc = dccp_feat_preflist_match(arr, len, fv->sp.vec, fv->sp.len);
1075
1076        if (!reorder)
1077                return rc;
1078        if (rc < 0)
1079                return 0;
1080
1081        /*
1082         * Reorder list: used for activating features and in dccp_insert_fn_opt.
1083         */
1084        return dccp_feat_prefer(rc, fv->sp.vec, fv->sp.len);
1085}
1086
1087/**
1088 * dccp_feat_change_recv  -  Process incoming ChangeL/R options
1089 * @fn: feature-negotiation list to update
1090 * @is_mandatory: whether the Change was preceded by a Mandatory option
1091 * @opt: %DCCPO_CHANGE_L or %DCCPO_CHANGE_R
1092 * @feat: one of %dccp_feature_numbers
1093 * @val: NN value or SP value/preference list
1094 * @len: length of @val in bytes
1095 * @server: whether this node is the server (1) or the client (0)
1096 */
1097static u8 dccp_feat_change_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
1098                                u8 feat, u8 *val, u8 len, const bool server)
1099{
1100        u8 defval, type = dccp_feat_type(feat);
1101        const bool local = (opt == DCCPO_CHANGE_R);
1102        struct dccp_feat_entry *entry;
1103        dccp_feat_val fval;
1104
1105        if (len == 0 || type == FEAT_UNKNOWN)           /* 6.1 and 6.6.8 */
1106                goto unknown_feature_or_value;
1107
1108        dccp_feat_print_opt(opt, feat, val, len, is_mandatory);
1109
1110        /*
1111         *      Negotiation of NN features: Change R is invalid, so there is no
1112         *      simultaneous negotiation; hence we do not look up in the list.
1113         */
1114        if (type == FEAT_NN) {
1115                if (local || len > sizeof(fval.nn))
1116                        goto unknown_feature_or_value;
1117
1118                /* 6.3.2: "The feature remote MUST accept any valid value..." */
1119                fval.nn = dccp_decode_value_var(val, len);
1120                if (!dccp_feat_is_valid_nn_val(feat, fval.nn))
1121                        goto unknown_feature_or_value;
1122
1123                return dccp_feat_push_confirm(fn, feat, local, &fval);
1124        }
1125
1126        /*
1127         *      Unidirectional/simultaneous negotiation of SP features (6.3.1)
1128         */
1129        entry = dccp_feat_list_lookup(fn, feat, local);
1130        if (entry == NULL) {
1131                /*
1132                 * No particular preferences have been registered. We deal with
1133                 * this situation by assuming that all valid values are equally
1134                 * acceptable, and apply the following checks:
1135                 * - if the peer's list is a singleton, we accept a valid value;
1136                 * - if we are the server, we first try to see if the peer (the
1137                 *   client) advertises the default value. If yes, we use it,
1138                 *   otherwise we accept the preferred value;
1139                 * - else if we are the client, we use the first list element.
1140                 */
1141                if (dccp_feat_clone_sp_val(&fval, val, 1))
1142                        return DCCP_RESET_CODE_TOO_BUSY;
1143
1144                if (len > 1 && server) {
1145                        defval = dccp_feat_default_value(feat);
1146                        if (dccp_feat_preflist_match(&defval, 1, val, len) > -1)
1147                                fval.sp.vec[0] = defval;
1148                } else if (!dccp_feat_is_valid_sp_val(feat, fval.sp.vec[0])) {
1149                        kfree(fval.sp.vec);
1150                        goto unknown_feature_or_value;
1151                }
1152
1153                /* Treat unsupported CCIDs like invalid values */
1154                if (feat == DCCPF_CCID && !ccid_support_check(fval.sp.vec, 1)) {
1155                        kfree(fval.sp.vec);
1156                        goto not_valid_or_not_known;
1157                }
1158
1159                return dccp_feat_push_confirm(fn, feat, local, &fval);
1160
1161        } else if (entry->state == FEAT_UNSTABLE) {     /* 6.6.2 */
1162                return 0;
1163        }
1164
1165        if (dccp_feat_reconcile(&entry->val, val, len, server, true)) {
1166                entry->empty_confirm = false;
1167        } else if (is_mandatory) {
1168                return DCCP_RESET_CODE_MANDATORY_ERROR;
1169        } else if (entry->state == FEAT_INITIALISING) {
1170                /*
1171                 * Failed simultaneous negotiation (server only): try to `save'
1172                 * the connection by checking whether entry contains the default
1173                 * value for @feat. If yes, send an empty Confirm to signal that
1174                 * the received Change was not understood - which implies using
1175                 * the default value.
1176                 * If this also fails, we use Reset as the last resort.
1177                 */
1178                WARN_ON(!server);
1179                defval = dccp_feat_default_value(feat);
1180                if (!dccp_feat_reconcile(&entry->val, &defval, 1, server, true))
1181                        return DCCP_RESET_CODE_OPTION_ERROR;
1182                entry->empty_confirm = true;
1183        }
1184        entry->needs_confirm   = true;
1185        entry->needs_mandatory = false;
1186        entry->state           = FEAT_STABLE;
1187        return 0;
1188
1189unknown_feature_or_value:
1190        if (!is_mandatory)
1191                return dccp_push_empty_confirm(fn, feat, local);
1192
1193not_valid_or_not_known:
1194        return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1195                            : DCCP_RESET_CODE_OPTION_ERROR;
1196}
1197
1198/**
1199 * dccp_feat_confirm_recv  -  Process received Confirm options
1200 * @fn: feature-negotiation list to update
1201 * @is_mandatory: whether @opt was preceded by a Mandatory option
1202 * @opt: %DCCPO_CONFIRM_L or %DCCPO_CONFIRM_R
1203 * @feat: one of %dccp_feature_numbers
1204 * @val: NN value or SP value/preference list
1205 * @len: length of @val in bytes
1206 * @server: whether this node is server (1) or client (0)
1207 */
1208static u8 dccp_feat_confirm_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
1209                                 u8 feat, u8 *val, u8 len, const bool server)
1210{
1211        u8 *plist, plen, type = dccp_feat_type(feat);
1212        const bool local = (opt == DCCPO_CONFIRM_R);
1213        struct dccp_feat_entry *entry = dccp_feat_list_lookup(fn, feat, local);
1214
1215        dccp_feat_print_opt(opt, feat, val, len, is_mandatory);
1216
1217        if (entry == NULL) {    /* nothing queued: ignore or handle error */
1218                if (is_mandatory && type == FEAT_UNKNOWN)
1219                        return DCCP_RESET_CODE_MANDATORY_ERROR;
1220
1221                if (!local && type == FEAT_NN)          /* 6.3.2 */
1222                        goto confirmation_failed;
1223                return 0;
1224        }
1225
1226        if (entry->state != FEAT_CHANGING)              /* 6.6.2 */
1227                return 0;
1228
1229        if (len == 0) {
1230                if (dccp_feat_must_be_understood(feat)) /* 6.6.7 */
1231                        goto confirmation_failed;
1232                /*
1233                 * Empty Confirm during connection setup: this means reverting
1234                 * to the `old' value, which in this case is the default. Since
1235                 * we handle default values automatically when no other values
1236                 * have been set, we revert to the old value by removing this
1237                 * entry from the list.
1238                 */
1239                dccp_feat_list_pop(entry);
1240                return 0;
1241        }
1242
1243        if (type == FEAT_NN) {
1244                if (len > sizeof(entry->val.nn))
1245                        goto confirmation_failed;
1246
1247                if (entry->val.nn == dccp_decode_value_var(val, len))
1248                        goto confirmation_succeeded;
1249
1250                DCCP_WARN("Bogus Confirm for non-existing value\n");
1251                goto confirmation_failed;
1252        }
1253
1254        /*
1255         * Parsing SP Confirms: the first element of @val is the preferred
1256         * SP value which the peer confirms, the remainder depends on @len.
1257         * Note that only the confirmed value need to be a valid SP value.
1258         */
1259        if (!dccp_feat_is_valid_sp_val(feat, *val))
1260                goto confirmation_failed;
1261
1262        if (len == 1) {         /* peer didn't supply a preference list */
1263                plist = val;
1264                plen  = len;
1265        } else {                /* preferred value + preference list */
1266                plist = val + 1;
1267                plen  = len - 1;
1268        }
1269
1270        /* Check whether the peer got the reconciliation right (6.6.8) */
1271        if (dccp_feat_reconcile(&entry->val, plist, plen, server, 0) != *val) {
1272                DCCP_WARN("Confirm selected the wrong value %u\n", *val);
1273                return DCCP_RESET_CODE_OPTION_ERROR;
1274        }
1275        entry->val.sp.vec[0] = *val;
1276
1277confirmation_succeeded:
1278        entry->state = FEAT_STABLE;
1279        return 0;
1280
1281confirmation_failed:
1282        DCCP_WARN("Confirmation failed\n");
1283        return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1284                            : DCCP_RESET_CODE_OPTION_ERROR;
1285}
1286
1287/**
1288 * dccp_feat_handle_nn_established  -  Fast-path reception of NN options
1289 * @sk:         socket of an established DCCP connection
1290 * @mandatory:  whether @opt was preceded by a Mandatory option
1291 * @opt:        %DCCPO_CHANGE_L | %DCCPO_CONFIRM_R (NN only)
1292 * @feat:       NN number, one of %dccp_feature_numbers
1293 * @val:        NN value
1294 * @len:        length of @val in bytes
1295 *
1296 * This function combines the functionality of change_recv/confirm_recv, with
1297 * the following differences (reset codes are the same):
1298 *    - cleanup after receiving the Confirm;
1299 *    - values are directly activated after successful parsing;
1300 *    - deliberately restricted to NN features.
1301 * The restriction to NN features is essential since SP features can have non-
1302 * predictable outcomes (depending on the remote configuration), and are inter-
1303 * dependent (CCIDs for instance cause further dependencies).
1304 */
1305static u8 dccp_feat_handle_nn_established(struct sock *sk, u8 mandatory, u8 opt,
1306                                          u8 feat, u8 *val, u8 len)
1307{
1308        struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
1309        const bool local = (opt == DCCPO_CONFIRM_R);
1310        struct dccp_feat_entry *entry;
1311        u8 type = dccp_feat_type(feat);
1312        dccp_feat_val fval;
1313
1314        dccp_feat_print_opt(opt, feat, val, len, mandatory);
1315
1316        /* Ignore non-mandatory unknown and non-NN features */
1317        if (type == FEAT_UNKNOWN) {
1318                if (local && !mandatory)
1319                        return 0;
1320                goto fast_path_unknown;
1321        } else if (type != FEAT_NN) {
1322                return 0;
1323        }
1324
1325        /*
1326         * We don't accept empty Confirms, since in fast-path feature
1327         * negotiation the values are enabled immediately after sending
1328         * the Change option.
1329         * Empty Changes on the other hand are invalid (RFC 4340, 6.1).
1330         */
1331        if (len == 0 || len > sizeof(fval.nn))
1332                goto fast_path_unknown;
1333
1334        if (opt == DCCPO_CHANGE_L) {
1335                fval.nn = dccp_decode_value_var(val, len);
1336                if (!dccp_feat_is_valid_nn_val(feat, fval.nn))
1337                        goto fast_path_unknown;
1338
1339                if (dccp_feat_push_confirm(fn, feat, local, &fval) ||
1340                    dccp_feat_activate(sk, feat, local, &fval))
1341                        return DCCP_RESET_CODE_TOO_BUSY;
1342
1343                /* set the `Ack Pending' flag to piggyback a Confirm */
1344                inet_csk_schedule_ack(sk);
1345
1346        } else if (opt == DCCPO_CONFIRM_R) {
1347                entry = dccp_feat_list_lookup(fn, feat, local);
1348                if (entry == NULL || entry->state != FEAT_CHANGING)
1349                        return 0;
1350
1351                fval.nn = dccp_decode_value_var(val, len);
1352                /*
1353                 * Just ignore a value that doesn't match our current value.
1354                 * If the option changes twice within two RTTs, then at least
1355                 * one CONFIRM will be received for the old value after a
1356                 * new CHANGE was sent.
1357                 */
1358                if (fval.nn != entry->val.nn)
1359                        return 0;
1360
1361                /* Only activate after receiving the Confirm option (6.6.1). */
1362                dccp_feat_activate(sk, feat, local, &fval);
1363
1364                /* It has been confirmed - so remove the entry */
1365                dccp_feat_list_pop(entry);
1366
1367        } else {
1368                DCCP_WARN("Received illegal option %u\n", opt);
1369                goto fast_path_failed;
1370        }
1371        return 0;
1372
1373fast_path_unknown:
1374        if (!mandatory)
1375                return dccp_push_empty_confirm(fn, feat, local);
1376
1377fast_path_failed:
1378        return mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
1379                         : DCCP_RESET_CODE_OPTION_ERROR;
1380}
1381
1382/**
1383 * dccp_feat_parse_options  -  Process Feature-Negotiation Options
1384 * @sk: for general use and used by the client during connection setup
1385 * @dreq: used by the server during connection setup
1386 * @mandatory: whether @opt was preceded by a Mandatory option
1387 * @opt: %DCCPO_CHANGE_L | %DCCPO_CHANGE_R | %DCCPO_CONFIRM_L | %DCCPO_CONFIRM_R
1388 * @feat: one of %dccp_feature_numbers
1389 * @val: value contents of @opt
1390 * @len: length of @val in bytes
1391 *
1392 * Returns 0 on success, a Reset code for ending the connection otherwise.
1393 */
1394int dccp_feat_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
1395                            u8 mandatory, u8 opt, u8 feat, u8 *val, u8 len)
1396{
1397        struct dccp_sock *dp = dccp_sk(sk);
1398        struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
1399        bool server = false;
1400
1401        switch (sk->sk_state) {
1402        /*
1403         *      Negotiation during connection setup
1404         */
1405        case DCCP_LISTEN:
1406                server = true;                  /* fall through */
1407        case DCCP_REQUESTING:
1408                switch (opt) {
1409                case DCCPO_CHANGE_L:
1410                case DCCPO_CHANGE_R:
1411                        return dccp_feat_change_recv(fn, mandatory, opt, feat,
1412                                                     val, len, server);
1413                case DCCPO_CONFIRM_R:
1414                case DCCPO_CONFIRM_L:
1415                        return dccp_feat_confirm_recv(fn, mandatory, opt, feat,
1416                                                      val, len, server);
1417                }
1418                break;
1419        /*
1420         *      Support for exchanging NN options on an established connection.
1421         */
1422        case DCCP_OPEN:
1423        case DCCP_PARTOPEN:
1424                return dccp_feat_handle_nn_established(sk, mandatory, opt, feat,
1425                                                       val, len);
1426        }
1427        return 0;       /* ignore FN options in all other states */
1428}
1429
1430/**
1431 * dccp_feat_init  -  Seed feature negotiation with host-specific defaults
1432 * This initialises global defaults, depending on the value of the sysctls.
1433 * These can later be overridden by registering changes via setsockopt calls.
1434 * The last link in the chain is finalise_settings, to make sure that between
1435 * here and the start of actual feature negotiation no inconsistencies enter.
1436 *
1437 * All features not appearing below use either defaults or are otherwise
1438 * later adjusted through dccp_feat_finalise_settings().
1439 */
1440int dccp_feat_init(struct sock *sk)
1441{
1442        struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
1443        u8 on = 1, off = 0;
1444        int rc;
1445        struct {
1446                u8 *val;
1447                u8 len;
1448        } tx, rx;
1449
1450        /* Non-negotiable (NN) features */
1451        rc = __feat_register_nn(fn, DCCPF_SEQUENCE_WINDOW, 0,
1452                                    sysctl_dccp_sequence_window);
1453        if (rc)
1454                return rc;
1455
1456        /* Server-priority (SP) features */
1457
1458        /* Advertise that short seqnos are not supported (7.6.1) */
1459        rc = __feat_register_sp(fn, DCCPF_SHORT_SEQNOS, true, true, &off, 1);
1460        if (rc)
1461                return rc;
1462
1463        /* RFC 4340 12.1: "If a DCCP is not ECN capable, ..." */
1464        rc = __feat_register_sp(fn, DCCPF_ECN_INCAPABLE, true, true, &on, 1);
1465        if (rc)
1466                return rc;
1467
1468        /*
1469         * We advertise the available list of CCIDs and reorder according to
1470         * preferences, to avoid failure resulting from negotiating different
1471         * singleton values (which always leads to failure).
1472         * These settings can still (later) be overridden via sockopts.
1473         */
1474        if (ccid_get_builtin_ccids(&tx.val, &tx.len) ||
1475            ccid_get_builtin_ccids(&rx.val, &rx.len))
1476                return -ENOBUFS;
1477
1478        if (!dccp_feat_prefer(sysctl_dccp_tx_ccid, tx.val, tx.len) ||
1479            !dccp_feat_prefer(sysctl_dccp_rx_ccid, rx.val, rx.len))
1480                goto free_ccid_lists;
1481
1482        rc = __feat_register_sp(fn, DCCPF_CCID, true, false, tx.val, tx.len);
1483        if (rc)
1484                goto free_ccid_lists;
1485
1486        rc = __feat_register_sp(fn, DCCPF_CCID, false, false, rx.val, rx.len);
1487
1488free_ccid_lists:
1489        kfree(tx.val);
1490        kfree(rx.val);
1491        return rc;
1492}
1493
1494int dccp_feat_activate_values(struct sock *sk, struct list_head *fn_list)
1495{
1496        struct dccp_sock *dp = dccp_sk(sk);
1497        struct dccp_feat_entry *cur, *next;
1498        int idx;
1499        dccp_feat_val *fvals[DCCP_FEAT_SUPPORTED_MAX][2] = {
1500                 [0 ... DCCP_FEAT_SUPPORTED_MAX-1] = { NULL, NULL }
1501        };
1502
1503        list_for_each_entry(cur, fn_list, node) {
1504                /*
1505                 * An empty Confirm means that either an unknown feature type
1506                 * or an invalid value was present. In the first case there is
1507                 * nothing to activate, in the other the default value is used.
1508                 */
1509                if (cur->empty_confirm)
1510                        continue;
1511
1512                idx = dccp_feat_index(cur->feat_num);
1513                if (idx < 0) {
1514                        DCCP_BUG("Unknown feature %u", cur->feat_num);
1515                        goto activation_failed;
1516                }
1517                if (cur->state != FEAT_STABLE) {
1518                        DCCP_CRIT("Negotiation of %s %s failed in state %s",
1519                                  cur->is_local ? "local" : "remote",
1520                                  dccp_feat_fname(cur->feat_num),
1521                                  dccp_feat_sname[cur->state]);
1522                        goto activation_failed;
1523                }
1524                fvals[idx][cur->is_local] = &cur->val;
1525        }
1526
1527        /*
1528         * Activate in decreasing order of index, so that the CCIDs are always
1529         * activated as the last feature. This avoids the case where a CCID
1530         * relies on the initialisation of one or more features that it depends
1531         * on (e.g. Send NDP Count, Send Ack Vector, and Ack Ratio features).
1532         */
1533        for (idx = DCCP_FEAT_SUPPORTED_MAX; --idx >= 0;)
1534                if (__dccp_feat_activate(sk, idx, 0, fvals[idx][0]) ||
1535                    __dccp_feat_activate(sk, idx, 1, fvals[idx][1])) {
1536                        DCCP_CRIT("Could not activate %d", idx);
1537                        goto activation_failed;
1538                }
1539
1540        /* Clean up Change options which have been confirmed already */
1541        list_for_each_entry_safe(cur, next, fn_list, node)
1542                if (!cur->needs_confirm)
1543                        dccp_feat_list_pop(cur);
1544
1545        dccp_pr_debug("Activation OK\n");
1546        return 0;
1547
1548activation_failed:
1549        /*
1550         * We clean up everything that may have been allocated, since
1551         * it is difficult to track at which stage negotiation failed.
1552         * This is ok, since all allocation functions below are robust
1553         * against NULL arguments.
1554         */
1555        ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
1556        ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
1557        dp->dccps_hc_rx_ccid = dp->dccps_hc_tx_ccid = NULL;
1558        dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
1559        dp->dccps_hc_rx_ackvec = NULL;
1560        return -1;
1561}
1562
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