/* * net/dccp/feat.c * * Feature negotiation for the DCCP protocol (RFC 4340, section 6) * * Copyright (c) 2008 Gerrit Renker <gerrit@erg.abdn.ac.uk> * Rewrote from scratch, some bits from earlier code by * Copyright (c) 2005 Andrea Bittau <a.bittau@cs.ucl.ac.uk> * * * ASSUMPTIONS * ----------- * o Feature negotiation is coordinated with connection setup (as in TCP), wild * changes of parameters of an established connection are not supported. * o All currently known SP features have 1-byte quantities. If in the future * extensions of RFCs 4340..42 define features with item lengths larger than * one byte, a feature-specific extension of the code will be required. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include <linux/module.h> #include <linux/slab.h> #include "ccid.h" #include "feat.h" /* feature-specific sysctls - initialised to the defaults from RFC 4340, 6.4 */ unsigned long sysctl_dccp_sequence_window __read_mostly = 100; int sysctl_dccp_rx_ccid __read_mostly = 2, sysctl_dccp_tx_ccid __read_mostly = 2; /* * Feature activation handlers. * * These all use an u64 argument, to provide enough room for NN/SP features. At * this stage the negotiated values have been checked to be within their range. */ static int dccp_hdlr_ccid(struct sock *sk, u64 ccid, bool rx) { struct dccp_sock *dp = dccp_sk(sk); struct ccid *new_ccid = ccid_new(ccid, sk, rx); if (new_ccid == NULL) return -ENOMEM; if (rx) { ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk); dp->dccps_hc_rx_ccid = new_ccid; } else { ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk); dp->dccps_hc_tx_ccid = new_ccid; } return 0; } static int dccp_hdlr_seq_win(struct sock *sk, u64 seq_win, bool rx) { struct dccp_sock *dp = dccp_sk(sk); if (rx) { dp->dccps_r_seq_win = seq_win; /* propagate changes to update SWL/SWH */ dccp_update_gsr(sk, dp->dccps_gsr); } else { dp->dccps_l_seq_win = seq_win; /* propagate changes to update AWL */ dccp_update_gss(sk, dp->dccps_gss); } return 0; } static int dccp_hdlr_ack_ratio(struct sock *sk, u64 ratio, bool rx) { if (rx) dccp_sk(sk)->dccps_r_ack_ratio = ratio; else dccp_sk(sk)->dccps_l_ack_ratio = ratio; return 0; } static int dccp_hdlr_ackvec(struct sock *sk, u64 enable, bool rx) { struct dccp_sock *dp = dccp_sk(sk); if (rx) { if (enable && dp->dccps_hc_rx_ackvec == NULL) { dp->dccps_hc_rx_ackvec = dccp_ackvec_alloc(gfp_any()); if (dp->dccps_hc_rx_ackvec == NULL) return -ENOMEM; } else if (!enable) { dccp_ackvec_free(dp->dccps_hc_rx_ackvec); dp->dccps_hc_rx_ackvec = NULL; } } return 0; } static int dccp_hdlr_ndp(struct sock *sk, u64 enable, bool rx) { if (!rx) dccp_sk(sk)->dccps_send_ndp_count = (enable > 0); return 0; } /* * Minimum Checksum Coverage is located at the RX side (9.2.1). This means that * `rx' holds when the sending peer informs about his partial coverage via a * ChangeR() option. In the other case, we are the sender and the receiver * announces its coverage via ChangeL() options. The policy here is to honour * such communication by enabling the corresponding partial coverage - but only * if it has not been set manually before; the warning here means that all * packets will be dropped. */ static int dccp_hdlr_min_cscov(struct sock *sk, u64 cscov, bool rx) { struct dccp_sock *dp = dccp_sk(sk); if (rx) dp->dccps_pcrlen = cscov; else { if (dp->dccps_pcslen == 0) dp->dccps_pcslen = cscov; else if (cscov > dp->dccps_pcslen) DCCP_WARN("CsCov %u too small, peer requires >= %u\n", dp->dccps_pcslen, (u8)cscov); } return 0; } static const struct { u8 feat_num; /* DCCPF_xxx */ enum dccp_feat_type rxtx; /* RX or TX */ enum dccp_feat_type reconciliation; /* SP or NN */ u8 default_value; /* as in 6.4 */ int (*activation_hdlr)(struct sock *sk, u64 val, bool rx); /* * Lookup table for location and type of features (from RFC 4340/4342) * +--------------------------+----+-----+----+----+---------+-----------+ * | Feature | Location | Reconc. | Initial | Section | * | | RX | TX | SP | NN | Value | Reference | * +--------------------------+----+-----+----+----+---------+-----------+ * | DCCPF_CCID | | X | X | | 2 | 10 | * | DCCPF_SHORT_SEQNOS | | X | X | | 0 | 7.6.1 | * | DCCPF_SEQUENCE_WINDOW | | X | | X | 100 | 7.5.2 | * | DCCPF_ECN_INCAPABLE | X | | X | | 0 | 12.1 | * | DCCPF_ACK_RATIO | | X | | X | 2 | 11.3 | * | DCCPF_SEND_ACK_VECTOR | X | | X | | 0 | 11.5 | * | DCCPF_SEND_NDP_COUNT | | X | X | | 0 | 7.7.2 | * | DCCPF_MIN_CSUM_COVER | X | | X | | 0 | 9.2.1 | * | DCCPF_DATA_CHECKSUM | X | | X | | 0 | 9.3.1 | * | DCCPF_SEND_LEV_RATE | X | | X | | 0 | 4342/8.4 | * +--------------------------+----+-----+----+----+---------+-----------+ */ } dccp_feat_table[] = { { DCCPF_CCID, FEAT_AT_TX, FEAT_SP, 2, dccp_hdlr_ccid }, { DCCPF_SHORT_SEQNOS, FEAT_AT_TX, FEAT_SP, 0, NULL }, { DCCPF_SEQUENCE_WINDOW, FEAT_AT_TX, FEAT_NN, 100, dccp_hdlr_seq_win }, { DCCPF_ECN_INCAPABLE, FEAT_AT_RX, FEAT_SP, 0, NULL }, { DCCPF_ACK_RATIO, FEAT_AT_TX, FEAT_NN, 2, dccp_hdlr_ack_ratio}, { DCCPF_SEND_ACK_VECTOR, FEAT_AT_RX, FEAT_SP, 0, dccp_hdlr_ackvec }, { DCCPF_SEND_NDP_COUNT, FEAT_AT_TX, FEAT_SP, 0, dccp_hdlr_ndp }, { DCCPF_MIN_CSUM_COVER, FEAT_AT_RX, FEAT_SP, 0, dccp_hdlr_min_cscov}, { DCCPF_DATA_CHECKSUM, FEAT_AT_RX, FEAT_SP, 0, NULL }, { DCCPF_SEND_LEV_RATE, FEAT_AT_RX, FEAT_SP, 0, NULL }, }; #define DCCP_FEAT_SUPPORTED_MAX ARRAY_SIZE(dccp_feat_table) /** * dccp_feat_index - Hash function to map feature number into array position * Returns consecutive array index or -1 if the feature is not understood. */ static int dccp_feat_index(u8 feat_num) { /* The first 9 entries are occupied by the types from RFC 4340, 6.4 */ if (feat_num > DCCPF_RESERVED && feat_num <= DCCPF_DATA_CHECKSUM) return feat_num - 1; /* * Other features: add cases for new feature types here after adding * them to the above table. */ switch (feat_num) { case DCCPF_SEND_LEV_RATE: return DCCP_FEAT_SUPPORTED_MAX - 1; } return -1; } static u8 dccp_feat_type(u8 feat_num) { int idx = dccp_feat_index(feat_num); if (idx < 0) return FEAT_UNKNOWN; return dccp_feat_table[idx].reconciliation; } static int dccp_feat_default_value(u8 feat_num) { int idx = dccp_feat_index(feat_num); /* * There are no default values for unknown features, so encountering a * negative index here indicates a serious problem somewhere else. */ DCCP_BUG_ON(idx < 0); return idx < 0 ? 0 : dccp_feat_table[idx].default_value; } /* * Debugging and verbose-printing section */ static const char *dccp_feat_fname(const u8 feat) { static const char *const feature_names[] = { [DCCPF_RESERVED] = "Reserved", [DCCPF_CCID] = "CCID", [DCCPF_SHORT_SEQNOS] = "Allow Short Seqnos", [DCCPF_SEQUENCE_WINDOW] = "Sequence Window", [DCCPF_ECN_INCAPABLE] = "ECN Incapable", [DCCPF_ACK_RATIO] = "Ack Ratio", [DCCPF_SEND_ACK_VECTOR] = "Send ACK Vector", [DCCPF_SEND_NDP_COUNT] = "Send NDP Count", [DCCPF_MIN_CSUM_COVER] = "Min. Csum Coverage", [DCCPF_DATA_CHECKSUM] = "Send Data Checksum", }; if (feat > DCCPF_DATA_CHECKSUM && feat < DCCPF_MIN_CCID_SPECIFIC) return feature_names[DCCPF_RESERVED]; if (feat == DCCPF_SEND_LEV_RATE) return "Send Loss Event Rate"; if (feat >= DCCPF_MIN_CCID_SPECIFIC) return "CCID-specific"; return feature_names[feat]; } static const char *const dccp_feat_sname[] = { "DEFAULT", "INITIALISING", "CHANGING", "UNSTABLE", "STABLE", }; #ifdef CONFIG_IP_DCCP_DEBUG static const char *dccp_feat_oname(const u8 opt) { switch (opt) { case DCCPO_CHANGE_L: return "Change_L"; case DCCPO_CONFIRM_L: return "Confirm_L"; case DCCPO_CHANGE_R: return "Change_R"; case DCCPO_CONFIRM_R: return "Confirm_R"; } return NULL; } static void dccp_feat_printval(u8 feat_num, dccp_feat_val const *val) { u8 i, type = dccp_feat_type(feat_num); if (val == NULL || (type == FEAT_SP && val->sp.vec == NULL)) dccp_pr_debug_cat("(NULL)"); else if (type == FEAT_SP) for (i = 0; i < val->sp.len; i++) dccp_pr_debug_cat("%s%u", i ? " " : "", val->sp.vec[i]); else if (type == FEAT_NN) dccp_pr_debug_cat("%llu", (unsigned long long)val->nn); else dccp_pr_debug_cat("unknown type %u", type); } static void dccp_feat_printvals(u8 feat_num, u8 *list, u8 len) { u8 type = dccp_feat_type(feat_num); dccp_feat_val fval = { .sp.vec = list, .sp.len = len }; if (type == FEAT_NN) fval.nn = dccp_decode_value_var(list, len); dccp_feat_printval(feat_num, &fval); } static void dccp_feat_print_entry(struct dccp_feat_entry const *entry) { dccp_debug(" * %s %s = ", entry->is_local ? "local" : "remote", dccp_feat_fname(entry->feat_num)); dccp_feat_printval(entry->feat_num, &entry->val); dccp_pr_debug_cat(", state=%s %s\n", dccp_feat_sname[entry->state], entry->needs_confirm ? "(Confirm pending)" : ""); } #define dccp_feat_print_opt(opt, feat, val, len, mandatory) do { \ dccp_pr_debug("%s(%s, ", dccp_feat_oname(opt), dccp_feat_fname(feat));\ dccp_feat_printvals(feat, val, len); \ dccp_pr_debug_cat(") %s\n", mandatory ? "!" : ""); } while (0) #define dccp_feat_print_fnlist(fn_list) { \ const struct dccp_feat_entry *___entry; \ \ dccp_pr_debug("List Dump:\n"); \ list_for_each_entry(___entry, fn_list, node) \ dccp_feat_print_entry(___entry); \ } #else /* ! CONFIG_IP_DCCP_DEBUG */ #define dccp_feat_print_opt(opt, feat, val, len, mandatory) #define dccp_feat_print_fnlist(fn_list) #endif static int __dccp_feat_activate(struct sock *sk, const int idx, const bool is_local, dccp_feat_val const *fval) { bool rx; u64 val; if (idx < 0 || idx >= DCCP_FEAT_SUPPORTED_MAX) return -1; if (dccp_feat_table[idx].activation_hdlr == NULL) return 0; if (fval == NULL) { val = dccp_feat_table[idx].default_value; } else if (dccp_feat_table[idx].reconciliation == FEAT_SP) { if (fval->sp.vec == NULL) { /* * This can happen when an empty Confirm is sent * for an SP (i.e. known) feature. In this case * we would be using the default anyway. */ DCCP_CRIT("Feature #%d undefined: using default", idx); val = dccp_feat_table[idx].default_value; } else { val = fval->sp.vec[0]; } } else { val = fval->nn; } /* Location is RX if this is a local-RX or remote-TX feature */ rx = (is_local == (dccp_feat_table[idx].rxtx == FEAT_AT_RX)); dccp_debug(" -> activating %s %s, %sval=%llu\n", rx ? "RX" : "TX", dccp_feat_fname(dccp_feat_table[idx].feat_num), fval ? "" : "default ", (unsigned long long)val); return dccp_feat_table[idx].activation_hdlr(sk, val, rx); } /* Test for "Req'd" feature (RFC 4340, 6.4) */ static inline int dccp_feat_must_be_understood(u8 feat_num) { return feat_num == DCCPF_CCID || feat_num == DCCPF_SHORT_SEQNOS || feat_num == DCCPF_SEQUENCE_WINDOW; } /* copy constructor, fval must not already contain allocated memory */ static int dccp_feat_clone_sp_val(dccp_feat_val *fval, u8 const *val, u8 len) { fval->sp.len = len; if (fval->sp.len > 0) { fval->sp.vec = kmemdup(val, len, gfp_any()); if (fval->sp.vec == NULL) { fval->sp.len = 0; return -ENOBUFS; } } return 0; } static void dccp_feat_val_destructor(u8 feat_num, dccp_feat_val *val) { if (unlikely(val == NULL)) return; if (dccp_feat_type(feat_num) == FEAT_SP) kfree(val->sp.vec); memset(val, 0, sizeof(*val)); } static struct dccp_feat_entry * dccp_feat_clone_entry(struct dccp_feat_entry const *original) { struct dccp_feat_entry *new; u8 type = dccp_feat_type(original->feat_num); if (type == FEAT_UNKNOWN) return NULL; new = kmemdup(original, sizeof(struct dccp_feat_entry), gfp_any()); if (new == NULL) return NULL; if (type == FEAT_SP && dccp_feat_clone_sp_val(&new->val, original->val.sp.vec, original->val.sp.len)) { kfree(new); return NULL; } return new; } static void dccp_feat_entry_destructor(struct dccp_feat_entry *entry) { if (entry != NULL) { dccp_feat_val_destructor(entry->feat_num, &entry->val); kfree(entry); } } /* * List management functions * * Feature negotiation lists rely on and maintain the following invariants: * - each feat_num in the list is known, i.e. we know its type and default value * - each feat_num/is_local combination is unique (old entries are overwritten) * - SP values are always freshly allocated * - list is sorted in increasing order of feature number (faster lookup) */ static struct dccp_feat_entry *dccp_feat_list_lookup(struct list_head *fn_list, u8 feat_num, bool is_local) { struct dccp_feat_entry *entry; list_for_each_entry(entry, fn_list, node) { if (entry->feat_num == feat_num && entry->is_local == is_local) return entry; else if (entry->feat_num > feat_num) break; } return NULL; } /** * dccp_feat_entry_new - Central list update routine (called by all others) * @head: list to add to * @feat: feature number * @local: whether the local (1) or remote feature with number @feat is meant * This is the only constructor and serves to ensure the above invariants. */ static struct dccp_feat_entry * dccp_feat_entry_new(struct list_head *head, u8 feat, bool local) { struct dccp_feat_entry *entry; list_for_each_entry(entry, head, node) if (entry->feat_num == feat && entry->is_local == local) { dccp_feat_val_destructor(entry->feat_num, &entry->val); return entry; } else if (entry->feat_num > feat) { head = &entry->node; break; } entry = kmalloc(sizeof(*entry), gfp_any()); if (entry != NULL) { entry->feat_num = feat; entry->is_local = local; list_add_tail(&entry->node, head); } return entry; } /** * dccp_feat_push_change - Add/overwrite a Change option in the list * @fn_list: feature-negotiation list to update * @feat: one of %dccp_feature_numbers * @local: whether local (1) or remote (0) @feat_num is meant * @needs_mandatory: whether to use Mandatory feature negotiation options * @fval: pointer to NN/SP value to be inserted (will be copied) */ static int dccp_feat_push_change(struct list_head *fn_list, u8 feat, u8 local, u8 mandatory, dccp_feat_val *fval) { struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local); if (new == NULL) return -ENOMEM; new->feat_num = feat; new->is_local = local; new->state = FEAT_INITIALISING; new->needs_confirm = 0; new->empty_confirm = 0; new->val = *fval; new->needs_mandatory = mandatory; return 0; } /** * dccp_feat_push_confirm - Add a Confirm entry to the FN list * @fn_list: feature-negotiation list to add to * @feat: one of %dccp_feature_numbers * @local: whether local (1) or remote (0) @feat_num is being confirmed * @fval: pointer to NN/SP value to be inserted or NULL * Returns 0 on success, a Reset code for further processing otherwise. */ static int dccp_feat_push_confirm(struct list_head *fn_list, u8 feat, u8 local, dccp_feat_val *fval) { struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local); if (new == NULL) return DCCP_RESET_CODE_TOO_BUSY; new->feat_num = feat; new->is_local = local; new->state = FEAT_STABLE; /* transition in 6.6.2 */ new->needs_confirm = 1; new->empty_confirm = (fval == NULL); new->val.nn = 0; /* zeroes the whole structure */ if (!new->empty_confirm) new->val = *fval; new->needs_mandatory = 0; return 0; } static int dccp_push_empty_confirm(struct list_head *fn_list, u8 feat, u8 local) { return dccp_feat_push_confirm(fn_list, feat, local, NULL); } static inline void dccp_feat_list_pop(struct dccp_feat_entry *entry) { list_del(&entry->node); dccp_feat_entry_destructor(entry); } void dccp_feat_list_purge(struct list_head *fn_list) { struct dccp_feat_entry *entry, *next; list_for_each_entry_safe(entry, next, fn_list, node) dccp_feat_entry_destructor(entry); INIT_LIST_HEAD(fn_list); } EXPORT_SYMBOL_GPL(dccp_feat_list_purge); /* generate @to as full clone of @from - @to must not contain any nodes */ int dccp_feat_clone_list(struct list_head const *from, struct list_head *to) { struct dccp_feat_entry *entry, *new; INIT_LIST_HEAD(to); list_for_each_entry(entry, from, node) { new = dccp_feat_clone_entry(entry); if (new == NULL) goto cloning_failed; list_add_tail(&new->node, to); } return 0; cloning_failed: dccp_feat_list_purge(to); return -ENOMEM; } /** * dccp_feat_valid_nn_length - Enforce length constraints on NN options * Length is between 0 and %DCCP_OPTVAL_MAXLEN. Used for outgoing packets only, * incoming options are accepted as long as their values are valid. */ static u8 dccp_feat_valid_nn_length(u8 feat_num) { if (feat_num == DCCPF_ACK_RATIO) /* RFC 4340, 11.3 and 6.6.8 */ return 2; if (feat_num == DCCPF_SEQUENCE_WINDOW) /* RFC 4340, 7.5.2 and 6.5 */ return 6; return 0; } static u8 dccp_feat_is_valid_nn_val(u8 feat_num, u64 val) { switch (feat_num) { case DCCPF_ACK_RATIO: return val <= DCCPF_ACK_RATIO_MAX; case DCCPF_SEQUENCE_WINDOW: return val >= DCCPF_SEQ_WMIN && val <= DCCPF_SEQ_WMAX; } return 0; /* feature unknown - so we can't tell */ } /* check that SP values are within the ranges defined in RFC 4340 */ static u8 dccp_feat_is_valid_sp_val(u8 feat_num, u8 val) { switch (feat_num) { case DCCPF_CCID: return val == DCCPC_CCID2 || val == DCCPC_CCID3; /* Type-check Boolean feature values: */ case DCCPF_SHORT_SEQNOS: case DCCPF_ECN_INCAPABLE: case DCCPF_SEND_ACK_VECTOR: case DCCPF_SEND_NDP_COUNT: case DCCPF_DATA_CHECKSUM: case DCCPF_SEND_LEV_RATE: return val < 2; case DCCPF_MIN_CSUM_COVER: return val < 16; } return 0; /* feature unknown */ } static u8 dccp_feat_sp_list_ok(u8 feat_num, u8 const *sp_list, u8 sp_len) { if (sp_list == NULL || sp_len < 1) return 0; while (sp_len--) if (!dccp_feat_is_valid_sp_val(feat_num, *sp_list++)) return 0; return 1; } /** * dccp_feat_insert_opts - Generate FN options from current list state * @skb: next sk_buff to be sent to the peer * @dp: for client during handshake and general negotiation * @dreq: used by the server only (all Changes/Confirms in LISTEN/RESPOND) */ int dccp_feat_insert_opts(struct dccp_sock *dp, struct dccp_request_sock *dreq, struct sk_buff *skb) { struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg; struct dccp_feat_entry *pos, *next; u8 opt, type, len, *ptr, nn_in_nbo[DCCP_OPTVAL_MAXLEN]; bool rpt; /* put entries into @skb in the order they appear in the list */ list_for_each_entry_safe_reverse(pos, next, fn, node) { opt = dccp_feat_genopt(pos); type = dccp_feat_type(pos->feat_num); rpt = false; if (pos->empty_confirm) { len = 0; ptr = NULL; } else { if (type == FEAT_SP) { len = pos->val.sp.len; ptr = pos->val.sp.vec; rpt = pos->needs_confirm; } else if (type == FEAT_NN) { len = dccp_feat_valid_nn_length(pos->feat_num); ptr = nn_in_nbo; dccp_encode_value_var(pos->val.nn, ptr, len); } else { DCCP_BUG("unknown feature %u", pos->feat_num); return -1; } } dccp_feat_print_opt(opt, pos->feat_num, ptr, len, 0); if (dccp_insert_fn_opt(skb, opt, pos->feat_num, ptr, len, rpt)) return -1; if (pos->needs_mandatory && dccp_insert_option_mandatory(skb)) return -1; /* * Enter CHANGING after transmitting the Change option (6.6.2). */ if (pos->state == FEAT_INITIALISING) pos->state = FEAT_CHANGING; } return 0; } /** * __feat_register_nn - Register new NN value on socket * @fn: feature-negotiation list to register with * @feat: an NN feature from %dccp_feature_numbers * @mandatory: use Mandatory option if 1 * @nn_val: value to register (restricted to 4 bytes) * Note that NN features are local by definition (RFC 4340, 6.3.2). */ static int __feat_register_nn(struct list_head *fn, u8 feat, u8 mandatory, u64 nn_val) { dccp_feat_val fval = { .nn = nn_val }; if (dccp_feat_type(feat) != FEAT_NN || !dccp_feat_is_valid_nn_val(feat, nn_val)) return -EINVAL; /* Don't bother with default values, they will be activated anyway. */ if (nn_val - (u64)dccp_feat_default_value(feat) == 0) return 0; return dccp_feat_push_change(fn, feat, 1, mandatory, &fval); } /** * __feat_register_sp - Register new SP value/list on socket * @fn: feature-negotiation list to register with * @feat: an SP feature from %dccp_feature_numbers * @is_local: whether the local (1) or the remote (0) @feat is meant * @mandatory: use Mandatory option if 1 * @sp_val: SP value followed by optional preference list * @sp_len: length of @sp_val in bytes */ static int __feat_register_sp(struct list_head *fn, u8 feat, u8 is_local, u8 mandatory, u8 const *sp_val, u8 sp_len) { dccp_feat_val fval; if (dccp_feat_type(feat) != FEAT_SP || !dccp_feat_sp_list_ok(feat, sp_val, sp_len)) return -EINVAL; /* Avoid negotiating alien CCIDs by only advertising supported ones */ if (feat == DCCPF_CCID && !ccid_support_check(sp_val, sp_len)) return -EOPNOTSUPP; if (dccp_feat_clone_sp_val(&fval, sp_val, sp_len)) return -ENOMEM; return dccp_feat_push_change(fn, feat, is_local, mandatory, &fval); } /** * dccp_feat_register_sp - Register requests to change SP feature values * @sk: client or listening socket * @feat: one of %dccp_feature_numbers * @is_local: whether the local (1) or remote (0) @feat is meant * @list: array of preferred values, in descending order of preference * @len: length of @list in bytes */ int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local, u8 const *list, u8 len) { /* any changes must be registered before establishing the connection */ if (sk->sk_state != DCCP_CLOSED) return -EISCONN; if (dccp_feat_type(feat) != FEAT_SP) return -EINVAL; return __feat_register_sp(&dccp_sk(sk)->dccps_featneg, feat, is_local, 0, list, len); } /* Analogous to dccp_feat_register_sp(), but for non-negotiable values */ int dccp_feat_register_nn(struct sock *sk, u8 feat, u64 val) { /* any changes must be registered before establishing the connection */ if (sk->sk_state != DCCP_CLOSED) return -EISCONN; if (dccp_feat_type(feat) != FEAT_NN) return -EINVAL; return __feat_register_nn(&dccp_sk(sk)->dccps_featneg, feat, 0, val); } /* * Tracking features whose value depend on the choice of CCID * * This is designed with an extension in mind so that a list walk could be done * before activating any features. However, the existing framework was found to * work satisfactorily up until now, the automatic verification is left open. * When adding new CCIDs, add a corresponding dependency table here. */ static const struct ccid_dependency *dccp_feat_ccid_deps(u8 ccid, bool is_local) { static const struct ccid_dependency ccid2_dependencies[2][2] = { /* * CCID2 mandates Ack Vectors (RFC 4341, 4.): as CCID is a TX * feature and Send Ack Vector is an RX feature, `is_local' * needs to be reversed. */ { /* Dependencies of the receiver-side (remote) CCID2 */ { .dependent_feat = DCCPF_SEND_ACK_VECTOR, .is_local = true, .is_mandatory = true, .val = 1 }, { 0, 0, 0, 0 } }, { /* Dependencies of the sender-side (local) CCID2 */ { .dependent_feat = DCCPF_SEND_ACK_VECTOR, .is_local = false, .is_mandatory = true, .val = 1 }, { 0, 0, 0, 0 } } }; static const struct ccid_dependency ccid3_dependencies[2][5] = { { /* * Dependencies of the receiver-side CCID3 */ { /* locally disable Ack Vectors */ .dependent_feat = DCCPF_SEND_ACK_VECTOR, .is_local = true, .is_mandatory = false, .val = 0 }, { /* see below why Send Loss Event Rate is on */ .dependent_feat = DCCPF_SEND_LEV_RATE, .is_local = true, .is_mandatory = true, .val = 1 }, { /* NDP Count is needed as per RFC 4342, 6.1.1 */ .dependent_feat = DCCPF_SEND_NDP_COUNT, .is_local = false, .is_mandatory = true, .val = 1 }, { 0, 0, 0, 0 }, }, { /* * CCID3 at the TX side: we request that the HC-receiver * will not send Ack Vectors (they will be ignored, so * Mandatory is not set); we enable Send Loss Event Rate * (Mandatory since the implementation does not support * the Loss Intervals option of RFC 4342, 8.6). * The last two options are for peer's information only. */ { .dependent_feat = DCCPF_SEND_ACK_VECTOR, .is_local = false, .is_mandatory = false, .val = 0 }, { .dependent_feat = DCCPF_SEND_LEV_RATE, .is_local = false, .is_mandatory = true, .val = 1 }, { /* this CCID does not support Ack Ratio */ .dependent_feat = DCCPF_ACK_RATIO, .is_local = true, .is_mandatory = false, .val = 0 }, { /* tell receiver we are sending NDP counts */ .dependent_feat = DCCPF_SEND_NDP_COUNT, .is_local = true, .is_mandatory = false, .val = 1 }, { 0, 0, 0, 0 } } }; switch (ccid) { case DCCPC_CCID2: return ccid2_dependencies[is_local]; case DCCPC_CCID3: return ccid3_dependencies[is_local]; default: return NULL; } } /** * dccp_feat_propagate_ccid - Resolve dependencies of features on choice of CCID * @fn: feature-negotiation list to update * @id: CCID number to track * @is_local: whether TX CCID (1) or RX CCID (0) is meant * This function needs to be called after registering all other features. */ static int dccp_feat_propagate_ccid(struct list_head *fn, u8 id, bool is_local) { const struct ccid_dependency *table = dccp_feat_ccid_deps(id, is_local); int i, rc = (table == NULL); for (i = 0; rc == 0 && table[i].dependent_feat != DCCPF_RESERVED; i++) if (dccp_feat_type(table[i].dependent_feat) == FEAT_SP) rc = __feat_register_sp(fn, table[i].dependent_feat, table[i].is_local, table[i].is_mandatory, &table[i].val, 1); else rc = __feat_register_nn(fn, table[i].dependent_feat, table[i].is_mandatory, table[i].val); return rc; } /** * dccp_feat_finalise_settings - Finalise settings before starting negotiation * @dp: client or listening socket (settings will be inherited) * This is called after all registrations (socket initialisation, sysctls, and * sockopt calls), and before sending the first packet containing Change options * (ie. client-Request or server-Response), to ensure internal consistency. */ int dccp_feat_finalise_settings(struct dccp_sock *dp) { struct list_head *fn = &dp->dccps_featneg; struct dccp_feat_entry *entry; int i = 2, ccids[2] = { -1, -1 }; /* * Propagating CCIDs: * 1) not useful to propagate CCID settings if this host advertises more * than one CCID: the choice of CCID may still change - if this is * the client, or if this is the server and the client sends * singleton CCID values. * 2) since is that propagate_ccid changes the list, we defer changing * the sorted list until after the traversal. */ list_for_each_entry(entry, fn, node) if (entry->feat_num == DCCPF_CCID && entry->val.sp.len == 1) ccids[entry->is_local] = entry->val.sp.vec[0]; while (i--) if (ccids[i] > 0 && dccp_feat_propagate_ccid(fn, ccids[i], i)) return -1; dccp_feat_print_fnlist(fn); return 0; } /** * dccp_feat_server_ccid_dependencies - Resolve CCID-dependent features * It is the server which resolves the dependencies once the CCID has been * fully negotiated. If no CCID has been negotiated, it uses the default CCID. */ int dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq) { struct list_head *fn = &dreq->dreq_featneg; struct dccp_feat_entry *entry; u8 is_local, ccid; for (is_local = 0; is_local <= 1; is_local++) { entry = dccp_feat_list_lookup(fn, DCCPF_CCID, is_local); if (entry != NULL && !entry->empty_confirm) ccid = entry->val.sp.vec[0]; else ccid = dccp_feat_default_value(DCCPF_CCID); if (dccp_feat_propagate_ccid(fn, ccid, is_local)) return -1; } return 0; } /* Select the first entry in @servlist that also occurs in @clilist (6.3.1) */ static int dccp_feat_preflist_match(u8 *servlist, u8 slen, u8 *clilist, u8 clen) { u8 c, s; for (s = 0; s < slen; s++) for (c = 0; c < clen; c++) if (servlist[s] == clilist[c]) return servlist[s]; return -1; } /** * dccp_feat_prefer - Move preferred entry to the start of array * Reorder the @array_len elements in @array so that @preferred_value comes * first. Returns >0 to indicate that @preferred_value does occur in @array. */ static u8 dccp_feat_prefer(u8 preferred_value, u8 *array, u8 array_len) { u8 i, does_occur = 0; if (array != NULL) { for (i = 0; i < array_len; i++) if (array[i] == preferred_value) { array[i] = array[0]; does_occur++; } if (does_occur) array[0] = preferred_value; } return does_occur; } /** * dccp_feat_reconcile - Reconcile SP preference lists * @fval: SP list to reconcile into * @arr: received SP preference list * @len: length of @arr in bytes * @is_server: whether this side is the server (and @fv is the server's list) * @reorder: whether to reorder the list in @fv after reconciling with @arr * When successful, > 0 is returned and the reconciled list is in @fval. * A value of 0 means that negotiation failed (no shared entry). */ static int dccp_feat_reconcile(dccp_feat_val *fv, u8 *arr, u8 len, bool is_server, bool reorder) { int rc; if (!fv->sp.vec || !arr) { DCCP_CRIT("NULL feature value or array"); return 0; } if (is_server) rc = dccp_feat_preflist_match(fv->sp.vec, fv->sp.len, arr, len); else rc = dccp_feat_preflist_match(arr, len, fv->sp.vec, fv->sp.len); if (!reorder) return rc; if (rc < 0) return 0; /* * Reorder list: used for activating features and in dccp_insert_fn_opt. */ return dccp_feat_prefer(rc, fv->sp.vec, fv->sp.len); } /** * dccp_feat_change_recv - Process incoming ChangeL/R options * @fn: feature-negotiation list to update * @is_mandatory: whether the Change was preceded by a Mandatory option * @opt: %DCCPO_CHANGE_L or %DCCPO_CHANGE_R * @feat: one of %dccp_feature_numbers * @val: NN value or SP value/preference list * @len: length of @val in bytes * @server: whether this node is the server (1) or the client (0) */ static u8 dccp_feat_change_recv(struct list_head *fn, u8 is_mandatory, u8 opt, u8 feat, u8 *val, u8 len, const bool server) { u8 defval, type = dccp_feat_type(feat); const bool local = (opt == DCCPO_CHANGE_R); struct dccp_feat_entry *entry; dccp_feat_val fval; if (len == 0 || type == FEAT_UNKNOWN) /* 6.1 and 6.6.8 */ goto unknown_feature_or_value; dccp_feat_print_opt(opt, feat, val, len, is_mandatory); /* * Negotiation of NN features: Change R is invalid, so there is no * simultaneous negotiation; hence we do not look up in the list. */ if (type == FEAT_NN) { if (local || len > sizeof(fval.nn)) goto unknown_feature_or_value; /* 6.3.2: "The feature remote MUST accept any valid value..." */ fval.nn = dccp_decode_value_var(val, len); if (!dccp_feat_is_valid_nn_val(feat, fval.nn)) goto unknown_feature_or_value; return dccp_feat_push_confirm(fn, feat, local, &fval); } /* * Unidirectional/simultaneous negotiation of SP features (6.3.1) */ entry = dccp_feat_list_lookup(fn, feat, local); if (entry == NULL) { /* * No particular preferences have been registered. We deal with * this situation by assuming that all valid values are equally * acceptable, and apply the following checks: * - if the peer's list is a singleton, we accept a valid value; * - if we are the server, we first try to see if the peer (the * client) advertises the default value. If yes, we use it, * otherwise we accept the preferred value; * - else if we are the client, we use the first list element. */ if (dccp_feat_clone_sp_val(&fval, val, 1)) return DCCP_RESET_CODE_TOO_BUSY; if (len > 1 && server) { defval = dccp_feat_default_value(feat); if (dccp_feat_preflist_match(&defval, 1, val, len) > -1) fval.sp.vec[0] = defval; } else if (!dccp_feat_is_valid_sp_val(feat, fval.sp.vec[0])) { kfree(fval.sp.vec); goto unknown_feature_or_value; } /* Treat unsupported CCIDs like invalid values */ if (feat == DCCPF_CCID && !ccid_support_check(fval.sp.vec, 1)) { kfree(fval.sp.vec); goto not_valid_or_not_known; } return dccp_feat_push_confirm(fn, feat, local, &fval); } else if (entry->state == FEAT_UNSTABLE) { /* 6.6.2 */ return 0; } if (dccp_feat_reconcile(&entry->val, val, len, server, true)) { entry->empty_confirm = 0; } else if (is_mandatory) { return DCCP_RESET_CODE_MANDATORY_ERROR; } else if (entry->state == FEAT_INITIALISING) { /* * Failed simultaneous negotiation (server only): try to `save' * the connection by checking whether entry contains the default * value for @feat. If yes, send an empty Confirm to signal that * the received Change was not understood - which implies using * the default value. * If this also fails, we use Reset as the last resort. */ WARN_ON(!server); defval = dccp_feat_default_value(feat); if (!dccp_feat_reconcile(&entry->val, &defval, 1, server, true)) return DCCP_RESET_CODE_OPTION_ERROR; entry->empty_confirm = 1; } entry->needs_confirm = 1; entry->needs_mandatory = 0; entry->state = FEAT_STABLE; return 0; unknown_feature_or_value: if (!is_mandatory) return dccp_push_empty_confirm(fn, feat, local); not_valid_or_not_known: return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR : DCCP_RESET_CODE_OPTION_ERROR; } /** * dccp_feat_confirm_recv - Process received Confirm options * @fn: feature-negotiation list to update * @is_mandatory: whether @opt was preceded by a Mandatory option * @opt: %DCCPO_CONFIRM_L or %DCCPO_CONFIRM_R * @feat: one of %dccp_feature_numbers * @val: NN value or SP value/preference list * @len: length of @val in bytes * @server: whether this node is server (1) or client (0) */ static u8 dccp_feat_confirm_recv(struct list_head *fn, u8 is_mandatory, u8 opt, u8 feat, u8 *val, u8 len, const bool server) { u8 *plist, plen, type = dccp_feat_type(feat); const bool local = (opt == DCCPO_CONFIRM_R); struct dccp_feat_entry *entry = dccp_feat_list_lookup(fn, feat, local); dccp_feat_print_opt(opt, feat, val, len, is_mandatory); if (entry == NULL) { /* nothing queued: ignore or handle error */ if (is_mandatory && type == FEAT_UNKNOWN) return DCCP_RESET_CODE_MANDATORY_ERROR; if (!local && type == FEAT_NN) /* 6.3.2 */ goto confirmation_failed; return 0; } if (entry->state != FEAT_CHANGING) /* 6.6.2 */ return 0; if (len == 0) { if (dccp_feat_must_be_understood(feat)) /* 6.6.7 */ goto confirmation_failed; /* * Empty Confirm during connection setup: this means reverting * to the `old' value, which in this case is the default. Since * we handle default values automatically when no other values * have been set, we revert to the old value by removing this * entry from the list. */ dccp_feat_list_pop(entry); return 0; } if (type == FEAT_NN) { if (len > sizeof(entry->val.nn)) goto confirmation_failed; if (entry->val.nn == dccp_decode_value_var(val, len)) goto confirmation_succeeded; DCCP_WARN("Bogus Confirm for non-existing value\n"); goto confirmation_failed; } /* * Parsing SP Confirms: the first element of @val is the preferred * SP value which the peer confirms, the remainder depends on @len. * Note that only the confirmed value need to be a valid SP value. */ if (!dccp_feat_is_valid_sp_val(feat, *val)) goto confirmation_failed; if (len == 1) { /* peer didn't supply a preference list */ plist = val; plen = len; } else { /* preferred value + preference list */ plist = val + 1; plen = len - 1; } /* Check whether the peer got the reconciliation right (6.6.8) */ if (dccp_feat_reconcile(&entry->val, plist, plen, server, 0) != *val) { DCCP_WARN("Confirm selected the wrong value %u\n", *val); return DCCP_RESET_CODE_OPTION_ERROR; } entry->val.sp.vec[0] = *val; confirmation_succeeded: entry->state = FEAT_STABLE; return 0; confirmation_failed: DCCP_WARN("Confirmation failed\n"); return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR : DCCP_RESET_CODE_OPTION_ERROR; } /** * dccp_feat_parse_options - Process Feature-Negotiation Options * @sk: for general use and used by the client during connection setup * @dreq: used by the server during connection setup * @mandatory: whether @opt was preceded by a Mandatory option * @opt: %DCCPO_CHANGE_L | %DCCPO_CHANGE_R | %DCCPO_CONFIRM_L | %DCCPO_CONFIRM_R * @feat: one of %dccp_feature_numbers * @val: value contents of @opt * @len: length of @val in bytes * Returns 0 on success, a Reset code for ending the connection otherwise. */ int dccp_feat_parse_options(struct sock *sk, struct dccp_request_sock *dreq, u8 mandatory, u8 opt, u8 feat, u8 *val, u8 len) { struct dccp_sock *dp = dccp_sk(sk); struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg; bool server = false; switch (sk->sk_state) { /* * Negotiation during connection setup */ case DCCP_LISTEN: server = true; /* fall through */ case DCCP_REQUESTING: switch (opt) { case DCCPO_CHANGE_L: case DCCPO_CHANGE_R: return dccp_feat_change_recv(fn, mandatory, opt, feat, val, len, server); case DCCPO_CONFIRM_R: case DCCPO_CONFIRM_L: return dccp_feat_confirm_recv(fn, mandatory, opt, feat, val, len, server); } } return 0; /* ignore FN options in all other states */ } /** * dccp_feat_init - Seed feature negotiation with host-specific defaults * This initialises global defaults, depending on the value of the sysctls. * These can later be overridden by registering changes via setsockopt calls. * The last link in the chain is finalise_settings, to make sure that between * here and the start of actual feature negotiation no inconsistencies enter. * * All features not appearing below use either defaults or are otherwise * later adjusted through dccp_feat_finalise_settings(). */ int dccp_feat_init(struct sock *sk) { struct list_head *fn = &dccp_sk(sk)->dccps_featneg; u8 on = 1, off = 0; int rc; struct { u8 *val; u8 len; } tx, rx; /* Non-negotiable (NN) features */ rc = __feat_register_nn(fn, DCCPF_SEQUENCE_WINDOW, 0, sysctl_dccp_sequence_window); if (rc) return rc; /* Server-priority (SP) features */ /* Advertise that short seqnos are not supported (7.6.1) */ rc = __feat_register_sp(fn, DCCPF_SHORT_SEQNOS, true, true, &off, 1); if (rc) return rc; /* RFC 4340 12.1: "If a DCCP is not ECN capable, ..." */ rc = __feat_register_sp(fn, DCCPF_ECN_INCAPABLE, true, true, &on, 1); if (rc) return rc; /* * We advertise the available list of CCIDs and reorder according to * preferences, to avoid failure resulting from negotiating different * singleton values (which always leads to failure). * These settings can still (later) be overridden via sockopts. */ if (ccid_get_builtin_ccids(&tx.val, &tx.len) || ccid_get_builtin_ccids(&rx.val, &rx.len)) return -ENOBUFS; if (!dccp_feat_prefer(sysctl_dccp_tx_ccid, tx.val, tx.len) || !dccp_feat_prefer(sysctl_dccp_rx_ccid, rx.val, rx.len)) goto free_ccid_lists; rc = __feat_register_sp(fn, DCCPF_CCID, true, false, tx.val, tx.len); if (rc) goto free_ccid_lists; rc = __feat_register_sp(fn, DCCPF_CCID, false, false, rx.val, rx.len); free_ccid_lists: kfree(tx.val); kfree(rx.val); return rc; } int dccp_feat_activate_values(struct sock *sk, struct list_head *fn_list) { struct dccp_sock *dp = dccp_sk(sk); struct dccp_feat_entry *cur, *next; int idx; dccp_feat_val *fvals[DCCP_FEAT_SUPPORTED_MAX][2] = { [0 ... DCCP_FEAT_SUPPORTED_MAX-1] = { NULL, NULL } }; list_for_each_entry(cur, fn_list, node) { /* * An empty Confirm means that either an unknown feature type * or an invalid value was present. In the first case there is * nothing to activate, in the other the default value is used. */ if (cur->empty_confirm) continue; idx = dccp_feat_index(cur->feat_num); if (idx < 0) { DCCP_BUG("Unknown feature %u", cur->feat_num); goto activation_failed; } if (cur->state != FEAT_STABLE) { DCCP_CRIT("Negotiation of %s %s failed in state %s", cur->is_local ? "local" : "remote", dccp_feat_fname(cur->feat_num), dccp_feat_sname[cur->state]); goto activation_failed; } fvals[idx][cur->is_local] = &cur->val; } /* * Activate in decreasing order of index, so that the CCIDs are always * activated as the last feature. This avoids the case where a CCID * relies on the initialisation of one or more features that it depends * on (e.g. Send NDP Count, Send Ack Vector, and Ack Ratio features). */ for (idx = DCCP_FEAT_SUPPORTED_MAX; --idx >= 0;) if (__dccp_feat_activate(sk, idx, 0, fvals[idx][0]) || __dccp_feat_activate(sk, idx, 1, fvals[idx][1])) { DCCP_CRIT("Could not activate %d", idx); goto activation_failed; } /* Clean up Change options which have been confirmed already */ list_for_each_entry_safe(cur, next, fn_list, node) if (!cur->needs_confirm) dccp_feat_list_pop(cur); dccp_pr_debug("Activation OK\n"); return 0; activation_failed: /* * We clean up everything that may have been allocated, since * it is difficult to track at which stage negotiation failed. * This is ok, since all allocation functions below are robust * against NULL arguments. */ ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk); ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk); dp->dccps_hc_rx_ccid = dp->dccps_hc_tx_ccid = NULL; dccp_ackvec_free(dp->dccps_hc_rx_ackvec); dp->dccps_hc_rx_ackvec = NULL; return -1; }