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dccp: Implement lookup table for feature-negotiation information 

A lookup table for feature-negotiation information, extracted from RFC 4340/42,
is provided by this patch. All currently known features can be found in this 
table, along with their feature location, their default value, and type.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
This commit is contained in:
Gerrit Renker 2008-09-04 07:30:19 +02:00
parent 5c7c9451f1
commit b4eec20637
2 changed files with 120 additions and 4 deletions
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9
include/linux/dccp.h
View File

@ -176,19 +176,20 @@ enum {
};
/* DCCP features (RFC 4340 section 6.4) */
enum {
enum dccp_feature_numbers {
DCCPF_RESERVED = 0,
DCCPF_CCID = 1,
DCCPF_SHORT_SEQNOS = 2, /* XXX: not yet implemented */
DCCPF_SHORT_SEQNOS = 2,
DCCPF_SEQUENCE_WINDOW = 3,
DCCPF_ECN_INCAPABLE = 4, /* XXX: not yet implemented */
DCCPF_ECN_INCAPABLE = 4,
DCCPF_ACK_RATIO = 5,
DCCPF_SEND_ACK_VECTOR = 6,
DCCPF_SEND_NDP_COUNT = 7,
DCCPF_MIN_CSUM_COVER = 8,
DCCPF_DATA_CHECKSUM = 9, /* XXX: not yet implemented */
DCCPF_DATA_CHECKSUM = 9,
/* 10-127 reserved */
DCCPF_MIN_CCID_SPECIFIC = 128,
DCCPF_SEND_LEV_RATE = 192, /* RFC 4342, sec. 8.4 */
DCCPF_MAX_CCID_SPECIFIC = 255,
};

115
net/dccp/feat.c
View File

@ -23,6 +23,80 @@
#define DCCP_FEAT_SP_NOAGREE (-123)
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 */
/*
* 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 },
{ DCCPF_SHORT_SEQNOS, FEAT_AT_TX, FEAT_SP, 0 },
{ DCCPF_SEQUENCE_WINDOW, FEAT_AT_TX, FEAT_NN, 100 },
{ DCCPF_ECN_INCAPABLE, FEAT_AT_RX, FEAT_SP, 0 },
{ DCCPF_ACK_RATIO, FEAT_AT_TX, FEAT_NN, 2 },
{ DCCPF_SEND_ACK_VECTOR, FEAT_AT_RX, FEAT_SP, 0 },
{ DCCPF_SEND_NDP_COUNT, FEAT_AT_TX, FEAT_SP, 0 },
{ DCCPF_MIN_CSUM_COVER, FEAT_AT_RX, FEAT_SP, 0 },
{ DCCPF_DATA_CHECKSUM, FEAT_AT_RX, FEAT_SP, 0 },
{ DCCPF_SEND_LEV_RATE, FEAT_AT_RX, FEAT_SP, 0 },
};
#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);
return idx < 0 ? : dccp_feat_table[idx].default_value;
}
/* 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)
{
@ -37,6 +111,45 @@ static int dccp_feat_clone_sp_val(dccp_feat_val *fval, u8 const *val, u8 len)
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);
}
}
int dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,
u8 *val, u8 len, gfp_t gfp)
{
@ -653,6 +766,8 @@ const char *dccp_feat_name(const u8 feat)
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";