v4.19.13 snapshot.
diff --git a/net/dccp/feat.c b/net/dccp/feat.c
new file mode 100644
index 0000000..f227f00
--- /dev/null
+++ b/net/dccp/feat.c
@@ -0,0 +1,1564 @@
+/*
+ * 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 Changing non-negotiable (NN) values is supported in state OPEN/PARTOPEN.
+ * 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);
+}
+
+/**
+ * dccp_feat_activate - Activate feature value on socket
+ * @sk: fully connected DCCP socket (after handshake is complete)
+ * @feat_num: feature to activate, one of %dccp_feature_numbers
+ * @local: whether local (1) or remote (0) @feat_num is meant
+ * @fval: the value (SP or NN) to activate, or NULL to use the default value
+ *
+ * For general use this function is preferable over __dccp_feat_activate().
+ */
+static int dccp_feat_activate(struct sock *sk, u8 feat_num, bool local,
+ dccp_feat_val const *fval)
+{
+ return __dccp_feat_activate(sk, dccp_feat_index(feat_num), local, fval);
+}
+
+/* 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
+ * @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 = false;
+ new->empty_confirm = false;
+ 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 = true;
+ new->empty_confirm = (fval == NULL);
+ new->val.nn = 0; /* zeroes the whole structure */
+ if (!new->empty_confirm)
+ new->val = *fval;
+ new->needs_mandatory = false;
+
+ 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;
+
+ if (skb->sk->sk_state == DCCP_OPEN &&
+ (opt == DCCPO_CONFIRM_R || opt == DCCPO_CONFIRM_L)) {
+ /*
+ * Confirms don't get retransmitted (6.6.3) once the
+ * connection is in state OPEN
+ */
+ dccp_feat_list_pop(pos);
+ } else {
+ /*
+ * 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);
+}
+
+/**
+ * dccp_feat_nn_get - Query current/pending value of NN feature
+ * @sk: DCCP socket of an established connection
+ * @feat: NN feature number from %dccp_feature_numbers
+ *
+ * For a known NN feature, returns value currently being negotiated, or
+ * current (confirmed) value if no negotiation is going on.
+ */
+u64 dccp_feat_nn_get(struct sock *sk, u8 feat)
+{
+ if (dccp_feat_type(feat) == FEAT_NN) {
+ struct dccp_sock *dp = dccp_sk(sk);
+ struct dccp_feat_entry *entry;
+
+ entry = dccp_feat_list_lookup(&dp->dccps_featneg, feat, 1);
+ if (entry != NULL)
+ return entry->val.nn;
+
+ switch (feat) {
+ case DCCPF_ACK_RATIO:
+ return dp->dccps_l_ack_ratio;
+ case DCCPF_SEQUENCE_WINDOW:
+ return dp->dccps_l_seq_win;
+ }
+ }
+ DCCP_BUG("attempt to look up unsupported feature %u", feat);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(dccp_feat_nn_get);
+
+/**
+ * dccp_feat_signal_nn_change - Update NN values for an established connection
+ * @sk: DCCP socket of an established connection
+ * @feat: NN feature number from %dccp_feature_numbers
+ * @nn_val: the new value to use
+ *
+ * This function is used to communicate NN updates out-of-band.
+ */
+int dccp_feat_signal_nn_change(struct sock *sk, u8 feat, u64 nn_val)
+{
+ struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
+ dccp_feat_val fval = { .nn = nn_val };
+ struct dccp_feat_entry *entry;
+
+ if (sk->sk_state != DCCP_OPEN && sk->sk_state != DCCP_PARTOPEN)
+ return 0;
+
+ if (dccp_feat_type(feat) != FEAT_NN ||
+ !dccp_feat_is_valid_nn_val(feat, nn_val))
+ return -EINVAL;
+
+ if (nn_val == dccp_feat_nn_get(sk, feat))
+ return 0; /* already set or negotiation under way */
+
+ entry = dccp_feat_list_lookup(fn, feat, 1);
+ if (entry != NULL) {
+ dccp_pr_debug("Clobbering existing NN entry %llu -> %llu\n",
+ (unsigned long long)entry->val.nn,
+ (unsigned long long)nn_val);
+ dccp_feat_list_pop(entry);
+ }
+
+ inet_csk_schedule_ack(sk);
+ return dccp_feat_push_change(fn, feat, 1, 0, &fval);
+}
+EXPORT_SYMBOL_GPL(dccp_feat_signal_nn_change);
+
+/*
+ * 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
+ * @fv: 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 = false;
+ } 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 = true;
+ }
+ entry->needs_confirm = true;
+ entry->needs_mandatory = false;
+ 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_handle_nn_established - Fast-path reception of NN options
+ * @sk: socket of an established DCCP connection
+ * @mandatory: whether @opt was preceded by a Mandatory option
+ * @opt: %DCCPO_CHANGE_L | %DCCPO_CONFIRM_R (NN only)
+ * @feat: NN number, one of %dccp_feature_numbers
+ * @val: NN value
+ * @len: length of @val in bytes
+ *
+ * This function combines the functionality of change_recv/confirm_recv, with
+ * the following differences (reset codes are the same):
+ * - cleanup after receiving the Confirm;
+ * - values are directly activated after successful parsing;
+ * - deliberately restricted to NN features.
+ * The restriction to NN features is essential since SP features can have non-
+ * predictable outcomes (depending on the remote configuration), and are inter-
+ * dependent (CCIDs for instance cause further dependencies).
+ */
+static u8 dccp_feat_handle_nn_established(struct sock *sk, u8 mandatory, u8 opt,
+ u8 feat, u8 *val, u8 len)
+{
+ struct list_head *fn = &dccp_sk(sk)->dccps_featneg;
+ const bool local = (opt == DCCPO_CONFIRM_R);
+ struct dccp_feat_entry *entry;
+ u8 type = dccp_feat_type(feat);
+ dccp_feat_val fval;
+
+ dccp_feat_print_opt(opt, feat, val, len, mandatory);
+
+ /* Ignore non-mandatory unknown and non-NN features */
+ if (type == FEAT_UNKNOWN) {
+ if (local && !mandatory)
+ return 0;
+ goto fast_path_unknown;
+ } else if (type != FEAT_NN) {
+ return 0;
+ }
+
+ /*
+ * We don't accept empty Confirms, since in fast-path feature
+ * negotiation the values are enabled immediately after sending
+ * the Change option.
+ * Empty Changes on the other hand are invalid (RFC 4340, 6.1).
+ */
+ if (len == 0 || len > sizeof(fval.nn))
+ goto fast_path_unknown;
+
+ if (opt == DCCPO_CHANGE_L) {
+ fval.nn = dccp_decode_value_var(val, len);
+ if (!dccp_feat_is_valid_nn_val(feat, fval.nn))
+ goto fast_path_unknown;
+
+ if (dccp_feat_push_confirm(fn, feat, local, &fval) ||
+ dccp_feat_activate(sk, feat, local, &fval))
+ return DCCP_RESET_CODE_TOO_BUSY;
+
+ /* set the `Ack Pending' flag to piggyback a Confirm */
+ inet_csk_schedule_ack(sk);
+
+ } else if (opt == DCCPO_CONFIRM_R) {
+ entry = dccp_feat_list_lookup(fn, feat, local);
+ if (entry == NULL || entry->state != FEAT_CHANGING)
+ return 0;
+
+ fval.nn = dccp_decode_value_var(val, len);
+ /*
+ * Just ignore a value that doesn't match our current value.
+ * If the option changes twice within two RTTs, then at least
+ * one CONFIRM will be received for the old value after a
+ * new CHANGE was sent.
+ */
+ if (fval.nn != entry->val.nn)
+ return 0;
+
+ /* Only activate after receiving the Confirm option (6.6.1). */
+ dccp_feat_activate(sk, feat, local, &fval);
+
+ /* It has been confirmed - so remove the entry */
+ dccp_feat_list_pop(entry);
+
+ } else {
+ DCCP_WARN("Received illegal option %u\n", opt);
+ goto fast_path_failed;
+ }
+ return 0;
+
+fast_path_unknown:
+ if (!mandatory)
+ return dccp_push_empty_confirm(fn, feat, local);
+
+fast_path_failed:
+ return 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);
+ }
+ break;
+ /*
+ * Support for exchanging NN options on an established connection.
+ */
+ case DCCP_OPEN:
+ case DCCP_PARTOPEN:
+ return dccp_feat_handle_nn_established(sk, mandatory, opt, feat,
+ val, len);
+ }
+ 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))
+ return -ENOBUFS;
+ if (ccid_get_builtin_ccids(&rx.val, &rx.len)) {
+ kfree(tx.val);
+ 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;
+}