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[TLV] extend TLV parser with support for TvLV 

Tag-variableLength-Value is an encoding scheme used in the GPRS NS
and BSSGP protocols, where the length value can be 8 or 16 bits,
depending on actual demand.
This commit is contained in:
Harald Welte 2009-10-24 10:04:02 +02:00
parent ca0fcbe157
commit 73310c3c83
2 changed files with 69 additions and 0 deletions
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46
openbsc/include/openbsc/tlv.h
View File

@ -6,11 +6,33 @@
#include <openbsc/msgb.h>
/* Terminology / wording
tag length value (in bits)
V - - 8
LV - 8 N * 8
TLV 8 8 N * 8
TL16V 8 16 N * 8
TLV16 8 8 N * 16
TvLV 8 8/16 N * 8
*/
#define LV_GROSS_LEN(x) (x+1)
#define TLV_GROSS_LEN(x) (x+2)
#define TLV16_GROSS_LEN(x) ((2*x)+2)
#define TL16V_GROSS_LEN(x) (x+3)
#define TVLV_MAX_ONEBYTE 0x7f
static inline u_int16_t TVLV_GROSS_LEN(u_int16_t len)
{
if (len <= TVLV_MAX_ONEBYTE)
return TLV_GROSS_LEN(len);
else
return TL16V_GROSS_LEN(len);
}
/* TLV generation */
static inline u_int8_t *lv_put(u_int8_t *buf, u_int8_t len,
@ -49,6 +71,20 @@ static inline u_int8_t *tl16v_put(u_int8_t *buf, u_int8_t tag, u_int16_t len,
return buf + len*2;
}
static inline u_int8_t *tvlv_put(u_int8_t *buf, u_int8_t tag, u_int16_t len,
const u_int8_t *val)
{
u_int8_t *ret;
if (len <= TVLV_MAX_ONEBYTE) {
ret = tlv_put(buf, tag, len, val);
buf[1] |= 0x80;
} else
ret = tl16v_put(buf, tag, len, val);
return ret;
}
static inline u_int8_t *msgb_tlv16_put(struct msgb *msg, u_int8_t tag, u_int8_t len, const u_int16_t *val)
{
u_int8_t *buf = msgb_put(msg, TLV16_GROSS_LEN(len));
@ -62,6 +98,13 @@ static inline u_int8_t *msgb_tl16v_put(struct msgb *msg, u_int8_t tag, u_int16_t
return tl16v_put(buf, tag, len, val);
}
static inline u_int8_t *msgb_tvlv_put(struct msgb *msg, u_int8_t tag, u_int16_t len,
const u_int8_t *val)
{
u_int8_t *buf = msgb_put(msg, TVLV_GROSS_LEN(len));
return tvlv_put(buf, tag, len, val);
}
static inline u_int8_t *v_put(u_int8_t *buf, u_int8_t val)
{
*buf++ = val;
@ -146,6 +189,7 @@ enum tlv_type {
TLV_TYPE_TV,
TLV_TYPE_TLV,
TLV_TYPE_TL16V,
TLV_TYPE_TvLV,
};
struct tlv_def {
@ -161,6 +205,8 @@ struct tlv_parsed {
struct tlv_p_entry lv[0xff];
};
extern struct tlv_definition tvlv_att_def;
int tlv_parse(struct tlv_parsed *dec, const struct tlv_definition *def,
const u_int8_t *buf, int buf_len, u_int8_t lv_tag, u_int8_t lv_tag2);

23
openbsc/src/tlv_parser.c
View File

@ -1,5 +1,8 @@
#include <stdio.h>
#include <openbsc/tlv.h>
#include <openbsc/gsm_data.h>
struct tlv_definition tvlv_att_def;
int tlv_dump(struct tlv_parsed *dec)
{
@ -87,6 +90,20 @@ int tlv_parse(struct tlv_parsed *dec, const struct tlv_definition *def,
return -2;
num_parsed++;
break;
case TLV_TYPE_TvLV:
if (*(pos+1) & 0x80) {
/* like TLV, but without highest bit of len */
if (pos + 1 > buf + buf_len)
return -1;
dec->lv[tag].val = pos+2;
dec->lv[tag].len = *(pos+1) & 0x7f;
len = dec->lv[tag].len + 2;
if (pos + len > buf + buf_len)
return -2;
num_parsed++;
break;
}
/* like TL16V, fallthrough */
case TLV_TYPE_TL16V:
if (pos + 2 > buf + buf_len)
return -1;
@ -103,3 +120,9 @@ int tlv_parse(struct tlv_parsed *dec, const struct tlv_definition *def,
return num_parsed;
}
static __attribute__((constructor)) void on_dso_load_tlv(void)
{
int i;
for (i = 0; i < ARRAY_SIZE(tvlv_att_def.def); i++)
tvlv_att_def.def[i].type = TLV_TYPE_TvLV;
}