osmocom
/
libosmo-gprs
mirror of https://gerrit.osmocom.org/libosmo-gprs
11
0
Fork 0
Code Releases Wiki Activity
libosmo-gprs/src/rlcmac/rlcmac_dec.c

425 lines
12 KiB
C
Raw Blame History

/* RLC/MAC encoding helpers, 3GPP TS 44.060 */
/*
* (C) 2023 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
*
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include <stdint.h>
#include <osmocom/core/logging.h>
#include <osmocom/gprs/rlcmac/rlcmac_private.h>
#include <osmocom/gprs/rlcmac/rlcmac_dec.h>
#include <osmocom/gprs/rlcmac/rlc.h>
#include <osmocom/gprs/rlcmac/rlc_window_ul.h>
#define LENGTH_TO_END 255
/*!
* \returns num extensions fields (num frames == offset) on success,
* -errno otherwise.
*/
static int parse_extensions_egprs(const uint8_t *data, unsigned int data_len,
unsigned int *offs, bool is_last_block,
struct gprs_rlcmac_rlc_llc_chunk *chunks,
unsigned int chunks_size)
{
const struct gprs_rlcmac_rlc_li_field_egprs *li;
uint8_t e;
unsigned int num_chunks = 0;
e = 0;
while (!e) {
if (*offs > data_len) {
LOGRLCMAC(LOGL_NOTICE, "DL DATA LI extended, but no more data\n");
return -EINVAL;
}
/* get new E */
li = (struct gprs_rlcmac_rlc_li_field_egprs *)&data[*offs];
e = li->e;
*offs += 1;
if (!chunks)
continue;
if (num_chunks == chunks_size) {
LOGRLCMAC(LOGL_NOTICE, "DL DATA LI extended, but no more chunks possible\n");
return -ENOSPC;
}
if (li->li == 0 && num_chunks == 0) {
/* TS 44.060, table 10.4.14a.1, row 2a */
/* TS 44.060, table 10.4.14a.1, row 4 */
chunks[num_chunks].length = 0;
chunks[num_chunks].is_complete = true;
} else if (li->li == 127 && li->e == 1) {
/* TS 44.060, table 10.4.14a.1, row 3 & 5 */
/* only filling bytes left */
LOGRLCMAC(LOGL_DEBUG, "DL DATA LI contains only filling bytes with extension octet: LI=%d, E=%d, count=%d\n",
li->li, li->e, num_chunks);
break;
} else if (li->li > 0) {
/* TS 44.060, table 10.4.14a.1, row 1 & 2b */
chunks[num_chunks].length = li->li;
chunks[num_chunks].is_complete = true;
} else {
LOGRLCMAC(LOGL_NOTICE, "DL DATA LI contains invalid extension octet: LI=%d, E=%d, count=%d\n",
li->li, li->e, num_chunks);
return -EINVAL;
}
LOGRLCMAC(LOGL_DEBUG, "DL DATA LI contains extension octet: LI=%d, E=%d, count=%d\n",
li->li, li->e, num_chunks);
num_chunks += 1;
if (e == 1) {
/* There is space after the last chunk, add a final one */
if (num_chunks == chunks_size) {
LOGRLCMAC(LOGL_NOTICE, "DL DATA LI possibly extended, but no more chunks possible\n");
return -ENOSPC;
}
chunks[num_chunks].length = LENGTH_TO_END;
chunks[num_chunks].is_complete = is_last_block;
num_chunks += 1;
}
}
return num_chunks;
}
static int parse_extensions_gprs(const uint8_t *data, unsigned int data_len,
unsigned int *offs, bool is_last_block,
struct gprs_rlcmac_rlc_llc_chunk *chunks,
unsigned int chunks_size)
{
const struct gprs_rlcmac_rlc_li_field *li;
uint8_t m, e;
unsigned int num_chunks = 0;
e = 0;
while (!e) {
if (*offs > data_len) {
LOGRLCMAC(LOGL_NOTICE, "DL DATA LI extended, but no more data\n");
return -EINVAL;
}
/* get new E */
li = (const struct gprs_rlcmac_rlc_li_field *)&data[*offs];
e = li->e;
m = li->m;
*offs += 1;
if (li->li == 0) {
/* TS 44.060, 10.4.14, par 6 */
e = 1;
m = 0;
}
/* TS 44.060, table 10.4.13.1 */
if (m == 0 && e == 0) {
LOGRLCMAC(LOGL_NOTICE, "DL DATA ignored, because M='0' and E='0'.\n");
return 0;
}
if (!chunks)
continue;
if (num_chunks == chunks_size) {
LOGRLCMAC(LOGL_NOTICE, "DL DATA LI extended, but no more chunks possible\n");
return -ENOSPC;
}
if (li->li == 0)
/* e is 1 here */
chunks[num_chunks].length = LENGTH_TO_END;
else
chunks[num_chunks].length = li->li;
chunks[num_chunks].is_complete = li->li || is_last_block;
LOGRLCMAC(LOGL_DEBUG, "DL DATA LI contains extension octet: LI=%d, M=%d, E=%d, count=%d\n",
li->li, li->m, li->e, num_chunks);
num_chunks += 1;
if (e == 1 && m == 1) {
if (num_chunks == chunks_size) {
LOGRLCMAC(LOGL_NOTICE, "DL DATA LI extended, but no more chunks possible\n");
return -ENOSPC;
}
/* TS 44.060, 10.4.13.1, row 4 */
chunks[num_chunks].length = LENGTH_TO_END;
chunks[num_chunks].is_complete = is_last_block;
num_chunks += 1;
}
}
return num_chunks;
}
int gprs_rlcmac_rlc_data_from_dl_data(const struct gprs_rlcmac_rlc_block_info *rdbi,
enum gprs_rlcmac_coding_scheme cs,
const uint8_t *data,
struct gprs_rlcmac_rlc_llc_chunk *chunks,
unsigned int chunks_size)
{
uint8_t e;
unsigned int data_len = rdbi->data_len;
int num_chunks = 0, i;
unsigned int offs = 0;
bool is_last_block = (rdbi->cv == 0);
if (!chunks)
chunks_size = 0;
e = rdbi->e;
if (e) {
if (chunks_size > 0) {
/* Block without LI means it only contains data of one LLC PDU */
chunks[num_chunks].offset = offs;
chunks[num_chunks].length = LENGTH_TO_END;
chunks[num_chunks].is_complete = is_last_block;
num_chunks += 1;
} else if (chunks) {
LOGRLCMAC(LOGL_NOTICE, "No extension, but no more chunks possible\n");
return -ENOSPC;
}
} else if (gprs_rlcmac_mcs_is_edge(cs)) {
/* if E is not set (LI follows), EGPRS */
num_chunks = parse_extensions_egprs(data, data_len, &offs,
is_last_block,
chunks, chunks_size);
} else {
/* if E is not set (LI follows), GPRS */
num_chunks = parse_extensions_gprs(data, data_len, &offs,
is_last_block,
chunks, chunks_size);
}
if (num_chunks < 0)
return num_chunks;
if (chunks_size == 0)
return num_chunks;
/* LLC */
for (i = 0; i < num_chunks; i++) {
chunks[i].offset = offs;
if (chunks[i].length == LENGTH_TO_END) {
if (offs == data_len) {
/* There is no place for an additional chunk,
* so drop it (this may happen with EGPRS since
* there is no M flag. */
num_chunks -= 1;
break;
}
chunks[i].length = data_len - offs;
}
offs += chunks[i].length;
if (offs > data_len) {
LOGRLCMAC(LOGL_NOTICE, "DL DATA out of block border, "
"chunk idx: %d, offset: %u, size: %d, data_len: %u\n",
i, offs, chunks[i].length, data_len);
return -EINVAL;
}
}
return num_chunks;
}
int gprs_rlcmac_rlc_parse_dl_data_header_gprs(struct gprs_rlcmac_rlc_data_info *rlc,
const uint8_t *data, enum gprs_rlcmac_coding_scheme cs)
{
const struct gprs_rlcmac_rlc_dl_data_header *gprs = (const struct gprs_rlcmac_rlc_dl_data_header *)data;
unsigned int cur_bit = 0;
gprs_rlcmac_rlc_data_info_init_dl(rlc, cs, false);
rlc->usf = gprs->usf;
rlc->es_p = gprs->s_p;
rlc->rrbp = gprs->rrbp;
rlc->tfi = gprs->tfi;
rlc->pr = gprs->pr;
rlc->num_data_blocks = 1;
rlc->block_info[0].cv = gprs->fbi ? 0 : 0xff;
rlc->block_info[0].pi = 0;
rlc->block_info[0].bsn = gprs->bsn;
rlc->block_info[0].e = gprs->e;
rlc->block_info[0].ti = 0;
rlc->block_info[0].spb = 0;
cur_bit += rlc->data_offs_bits[0];
/* skip data area */
cur_bit += gprs_rlcmac_mcs_max_data_block_bytes(cs) * 8;
return cur_bit;
}
int gprs_rlcmac_rlc_parse_dl_data_header(struct gprs_rlcmac_rlc_data_info *rlc,
const uint8_t *data,
enum gprs_rlcmac_coding_scheme cs)
{
unsigned int cur_bit = 0;
switch (gprs_rlcmac_mcs_header_type(cs)) {
case GPRS_RLCMAC_HEADER_GPRS_DATA:
cur_bit = gprs_rlcmac_rlc_parse_dl_data_header_gprs(rlc, data, cs);
break;
case GPRS_RLCMAC_HEADER_EGPRS_DATA_TYPE_3:
case GPRS_RLCMAC_HEADER_EGPRS_DATA_TYPE_2:
case GPRS_RLCMAC_HEADER_EGPRS_DATA_TYPE_1:
/* TODO: EGPRS. See osmo-pcu.git rlc_parse_ul_data_header_egprs_type_*() */
default:
LOGRLCMAC(LOGL_ERROR, "Decoding of DL %s data blocks not yet supported.\n",
gprs_rlcmac_mcs_name(cs));
return -ENOTSUP;
};
return cur_bit;
}
/**
* Copy LSB bitstream RLC data block to byte aligned buffer.
*
* Note that the bitstream is encoded in LSB first order, so the two octets
* 654321xx xxxxxx87 contain the octet 87654321 starting at bit position 3
* (LSB has bit position 1). This is a different order than the one used by
* CSN.1.
*
* \param data_block_idx The block index, 0..1 for header type 1, 0 otherwise
* \param src A pointer to the start of the RLC block (incl. the header)
* \param buffer A data area of a least the size of the RLC block
* \returns the number of bytes copied
*/
unsigned int gprs_rlcmac_rlc_copy_to_aligned_buffer(
const struct gprs_rlcmac_rlc_data_info *rlc,
unsigned int data_block_idx,
const uint8_t *src, uint8_t *buffer)
{
unsigned int hdr_bytes;
unsigned int extra_bits;
unsigned int i;
uint8_t c, last_c;
uint8_t *dst;
const struct gprs_rlcmac_rlc_block_info *rdbi;
OSMO_ASSERT(data_block_idx < rlc->num_data_blocks);
rdbi = &rlc->block_info[data_block_idx];
hdr_bytes = rlc->data_offs_bits[data_block_idx] >> 3;
extra_bits = (rlc->data_offs_bits[data_block_idx] & 7);
if (extra_bits == 0) {
/* It is aligned already */
memmove(buffer, src + hdr_bytes, rdbi->data_len);
return rdbi->data_len;
}
dst = buffer;
src = src + hdr_bytes;
last_c = *(src++);
for (i = 0; i < rdbi->data_len; i++) {
c = src[i];
*(dst++) = (last_c >> extra_bits) | (c << (8 - extra_bits));
last_c = c;
}
return rdbi->data_len;
}
/**
* show_rbb needs to be an array with 65 elements
* The index of the array is the bit position in the rbb
* (show_rbb[63] relates to BSN ssn-1)
*/
void gprs_rlcmac_extract_rbb(const struct bitvec *rbb, char *show_rbb)
{
unsigned int i;
for (i = 0; i < rbb->cur_bit; i++) {
uint8_t bit;
bit = bitvec_get_bit_pos(rbb, i);
show_rbb[i] = bit == 1 ? 'R' : 'I';
}
show_rbb[i] = '\0';
}
static int handle_final_ack(struct bitvec *bits, int *bsn_begin, int *bsn_end,
struct gprs_rlcmac_rlc_ul_window *ulw)
{
int num_blocks, i;
uint16_t v_a = gprs_rlcmac_rlc_ul_window_v_a(ulw);
num_blocks = gprs_rlcmac_rlc_window_mod_sns_bsn(rlc_ulw_as_w(ulw),
gprs_rlcmac_rlc_ul_window_v_s(ulw) - v_a);
for (i = 0; i < num_blocks; i++)
bitvec_set_bit(bits, ONE);
*bsn_begin = v_a;
*bsn_end = gprs_rlcmac_rlc_window_mod_sns_bsn(rlc_ulw_as_w(ulw), *bsn_begin + num_blocks);
return num_blocks;
}
int gprs_rlcmac_decode_gprs_acknack_bits(const Ack_Nack_Description_t *desc,
struct bitvec *bits, int *bsn_begin, int *bsn_end,
struct gprs_rlcmac_rlc_ul_window *ulw)
{
int urbb_len = GPRS_RLCMAC_GPRS_WS;
int num_blocks;
struct bitvec urbb;
if (desc->FINAL_ACK_INDICATION)
return handle_final_ack(bits, bsn_begin, bsn_end, ulw);
*bsn_begin = gprs_rlcmac_rlc_ul_window_v_a(ulw);
*bsn_end = desc->STARTING_SEQUENCE_NUMBER;
num_blocks = gprs_rlcmac_rlc_window_mod_sns_bsn(rlc_ulw_as_w(ulw), *bsn_end - *bsn_begin);
if (num_blocks < 0 || num_blocks > urbb_len) {
*bsn_end = *bsn_begin;
LOGRLCMAC(LOGL_NOTICE, "Invalid GPRS Ack/Nack window %d:%d (length %d)\n",
*bsn_begin, *bsn_end, num_blocks);
return -EINVAL;
}
urbb.cur_bit = 0;
urbb.data = (uint8_t *)desc->RECEIVED_BLOCK_BITMAP;
urbb.data_len = sizeof(desc->RECEIVED_BLOCK_BITMAP);
/*
* TS 44.060, 12.3:
* BSN = (SSN - bit_number) modulo 128, for bit_number = 1 to 64.
* The BSN values represented range from (SSN - 1) mod 128 to (SSN - 64) mod 128.
*
* We are only interested in the range from V(A) to SSN-1 which is
* num_blocks large. The RBB is laid out as
* [SSN-1] [SSN-2] ... [V(A)] ... [SSN-64]
* so we want to start with [V(A)] and go backwards until we reach
* [SSN-1] to get the needed BSNs in an increasing order. Note that
* the bit numbers are counted from the end of the buffer.
*/
for (int i = num_blocks; i > 0; i--) {
int is_ack = bitvec_get_bit_pos(&urbb, urbb_len - i);
bitvec_set_bit(bits, is_ack == 1 ? ONE : ZERO);
}
return num_blocks;
}
View Git Blame Copy Permalink