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Commit b4eec206 authored by Gerrit Renker's avatar Gerrit Renker
Browse files

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: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: default avatarIan McDonald <ian.mcdonald@jandi.co.nz>
parent 5c7c9451

include/linux/dccp.h

+5 −4
Original line number Diff line number Diff line
@@ -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,

};

net/dccp/feat.c

+115 −0
Original line number Diff line number Diff line
@@ -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";