/*
* 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);
}
/*
* 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;
}