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lib,rlc_am_nr: re-factored code for retx'ing with and without segmentation.

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master
Pedro Alvarez 3 years ago
parent 8c53c74c86
commit 5e8b7b5ebe
3 changed files with 274 additions and 20 deletions
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1
lib/include/srsran/rlc/rlc_am_data_structs.h
Unescape Escape View File

@ -302,6 +302,7 @@ private:
struct rlc_amd_retx_t {
uint32_t sn;
uint32_t sdu_end;
bool is_segment;
uint32_t so_start;
uint32_t so_end;

4
lib/include/srsran/rlc/rlc_am_nr.h
Unescape Escape View File

@ -108,10 +108,14 @@ public:
uint32_t build_new_sdu_segment(rlc_amd_tx_pdu_nr& tx_pdu, uint8_t* payload, uint32_t nof_bytes);
uint32_t build_continuation_sdu_segment(rlc_amd_tx_pdu_nr& tx_pdu, uint8_t* payload, uint32_t nof_bytes);
uint32_t build_retx_pdu(uint8_t* payload, uint32_t nof_bytes);
uint32_t build_retx_pdu_without_segmentation(rlc_amd_retx_t& retx, uint8_t* payload, uint32_t nof_bytes);
uint32_t build_retx_pdu_with_segmentation(rlc_amd_retx_t& retx, uint8_t* payload, uint32_t nof_bytes);
uint32_t build_retx_pdu_from_full_sdu(rlc_amd_retx_t& retx, uint8_t* payload, uint32_t nof_bytes);
uint32_t build_retx_segment_from_full_sdu(rlc_amd_retx_t& retx, uint8_t* payload, uint32_t nof_bytes);
uint32_t build_retx_pdu_from_sdu_segment(rlc_amd_retx_t& retx, uint8_t* payload, uint32_t nof_bytes);
uint32_t build_retx_segment_from_sdu_segment(rlc_amd_retx_t& retx, uint8_t* payload, uint32_t nof_bytes);
bool is_retx_segmentation_required(const rlc_amd_retx_t& retx, uint32_t nof_bytes);
uint32_t get_retx_expected_hdr_len(const rlc_amd_retx_t& retx);
/*
* uint32_t build_retx_sdu_segment(rlc_amd_retx_t& retx, rlc_amd_tx_pdu_nr& tx_pdu, uint8_t* payload, uint32_t
* nof_bytes);

289
lib/src/rlc/rlc_am_nr.cc
Unescape Escape View File

@ -417,17 +417,218 @@ uint32_t rlc_am_nr_tx::build_retx_pdu(uint8_t* payload, uint32_t nof_bytes)
}
}
RlcDebug("RETX - is_segment=%s, current_so=%d, so_start=%d, so_end=%d",
RlcDebug("RETX - SDU len=%d, is_segment=%s, current_so=%d, so_start=%d, so_end=%d",
retx.sdu_end,
retx.is_segment ? "true" : "false",
retx.current_so,
retx.so_start,
retx.so_end);
// Is segmentation/re-segmentation required?
bool segmentation_required = is_retx_segmentation_required(retx, nof_bytes);
if (segmentation_required) {
return build_retx_pdu_with_segmentation(retx, payload, nof_bytes);
}
return build_retx_pdu_without_segmentation(retx, payload, nof_bytes);
}
/**
* Builds a retx RLC PDU, without requiring (re-)segmentation.
*
* The RETX PDU may be transporting a full SDU or an SDU segment.
*
* \param [retx] is the retx info contained in the retx_queue.
* \param [payload] is a pointer to the MAC buffer that will hold the PDU segment.
* \param [nof_bytes] is the number of bytes the RLC is allowed to fill.
*
* \returns the number of bytes written to the payload buffer.
* \remark this function will not update the SI. This means that if the retx is of the last
* SDU segment, the SI should already be of the `last_segment` type.
*/
uint32_t rlc_am_nr_tx::build_retx_pdu_without_segmentation(rlc_amd_retx_t& retx, uint8_t* payload, uint32_t nof_bytes)
{
srsran_assert(tx_window.has_sn(retx.sn), "Called %s without checking retx SN", __FUNCTION__);
srsran_assert(not is_retx_segmentation_required(retx, nof_bytes),
"Called %s without checking if segmentation was required",
__FUNCTION__);
// Get tx_pdu info from tx_window
rlc_amd_tx_pdu_nr& tx_pdu = tx_window[retx.sn];
// Get expected header and payload len
uint32_t expected_hdr_len = get_retx_expected_hdr_len(retx);
uint32_t retx_payload_len = retx.is_segment ? (retx.so_end - retx.current_so) : tx_window[retx.sn].sdu_buf->N_bytes;
srsran_assert(nof_bytes >= (expected_hdr_len + retx_payload_len),
"Called %s but segmentation is required. nof_bytes=%d, expeced_hdr_len=%d, retx_payload_len=%d",
__FUNCTION__,
nof_bytes,
expected_hdr_len,
retx_payload_len);
// Update SI, if necessary
rlc_nr_si_field_t si = rlc_nr_si_field_t::full_sdu;
if (retx.is_segment) {
RlcDebug("SDU segment can be fully transmitted. SN=%d, nof_bytes=%d, expected_hdr_len=%d, "
"current_so=%d, so_start=%d, so_end=%d",
retx.sn,
nof_bytes,
expected_hdr_len,
retx.current_so,
retx.so_start,
retx.so_end);
if (retx.current_so == 0) {
si = rlc_nr_si_field_t::first_segment;
} else if ((retx.current_so + retx_payload_len) < tx_pdu.sdu_buf->N_bytes) {
si = rlc_nr_si_field_t::neither_first_nor_last_segment;
} else {
si = rlc_nr_si_field_t::last_segment;
}
}
// Update & write header
rlc_am_nr_pdu_header_t new_header = tx_pdu.header;
new_header.si = si;
new_header.p = 0;
if (retx.is_segment) {
return build_retx_pdu_from_sdu_segment(retx, payload, nof_bytes);
new_header.so = retx.current_so;
}
uint32_t hdr_len = rlc_am_nr_write_data_pdu_header(new_header, payload);
uint32_t pdu_bytes = 0;
if (not retx.is_segment) {
// RETX full SDU
memcpy(&payload[hdr_len], tx_window[retx.sn].sdu_buf->msg, tx_window[retx.sn].sdu_buf->N_bytes);
pdu_bytes = hdr_len + tx_window[retx.sn].sdu_buf->N_bytes;
} else {
// RETX SDU segment
uint32_t retx_pdu_payload_size = (retx.so_end - retx.current_so);
pdu_bytes = hdr_len + retx_pdu_payload_size;
memcpy(&payload[hdr_len], &tx_pdu.sdu_buf->msg[retx.current_so], retx_pdu_payload_size);
}
return build_retx_pdu_from_full_sdu(retx, payload, nof_bytes);
retx_queue.pop();
RlcHexInfo(tx_window[retx.sn].sdu_buf->msg,
tx_window[retx.sn].sdu_buf->N_bytes,
"Original SDU SN=%d (%d B) (attempt %d/%d)",
retx.sn,
tx_window[retx.sn].sdu_buf->N_bytes,
tx_window[retx.sn].retx_count + 1,
cfg.max_retx_thresh);
RlcHexInfo(payload, nof_bytes, "retx PDU SN=%d (%d B)", retx.sn, nof_bytes);
log_rlc_am_nr_pdu_header_to_string(logger.debug, new_header);
debug_state();
return pdu_bytes;
}
/**
* Builds a retx RLC PDU that requires (re-)segmentation.
*
* \param [tx_pdu] is the tx_pdu info contained in the tx_window.
* \param [payload] is a pointer to the MAC buffer that will hold the PDU segment.
* \param [nof_bytes] is the number of bytes the RLC is allowed to fill.
*
* \returns the number of bytes written to the payload buffer.
* \remark: This functions assumes that the SDU has already been copied to tx_pdu.sdu_buf.
*/
uint32_t rlc_am_nr_tx::build_retx_pdu_with_segmentation(rlc_amd_retx_t& retx, uint8_t* payload, uint32_t nof_bytes)
{
// Get tx_pdu info from tx_window
srsran_assert(tx_window.has_sn(retx.sn), "Called %s without checking retx SN", __FUNCTION__);
srsran_assert(is_retx_segmentation_required(retx, nof_bytes),
"Called %s without checking if segmentation was not required",
__FUNCTION__);
rlc_amd_tx_pdu_nr& tx_pdu = tx_window[retx.sn];
// Is this an SDU segment or a full SDU?
if (not retx.is_segment) {
RlcDebug("Creating SDU segment from full SDU. SN=%d Tx SDU (%d B), nof_bytes=%d B ",
retx.sn,
tx_pdu.sdu_buf->N_bytes,
nof_bytes);
} else {
RlcDebug("Creating SDU segment from SDU segment. SN=%d, current_so=%d, so_start=%d, so_end=%d",
__FUNCTION__,
retx.sn,
retx.current_so,
retx.so_start,
retx.so_end);
}
uint32_t expected_hdr_len = min_hdr_size;
rlc_nr_si_field_t si = rlc_nr_si_field_t::first_segment;
if (retx.current_so != 0) {
si = rlc_nr_si_field_t::neither_first_nor_last_segment;
expected_hdr_len = max_hdr_size;
}
// Sanity check: are there enough bytes for header plus data?
if (nof_bytes <= expected_hdr_len) {
RlcError("called %s, but there are not enough bytes for data plus header. SN=%d", __FUNCTION__, retx.sn);
return 0;
}
// Sanity check: could this have been transmitted without segmentation?
if (nof_bytes > (tx_pdu.sdu_buf->N_bytes + expected_hdr_len)) {
RlcError("called %s, but there are enough bytes to avoid segmentation. SN=%d", __FUNCTION__, retx.sn);
return 0;
}
// Can the RETX PDU be transmitted in a single PDU?
uint32_t retx_pdu_payload_size = nof_bytes - expected_hdr_len;
// Write header
rlc_am_nr_pdu_header_t hdr = tx_pdu.header;
hdr.so = retx.current_so;
hdr.si = si;
uint32_t hdr_len = rlc_am_nr_write_data_pdu_header(hdr, payload);
if (hdr_len >= nof_bytes || hdr_len != expected_hdr_len) {
log_rlc_am_nr_pdu_header_to_string(logger.error, hdr);
RlcError("Error writing AMD PDU header. nof_bytes=%d, hdr_len=%d", nof_bytes, hdr_len);
return 0;
}
log_rlc_am_nr_pdu_header_to_string(logger.info, hdr);
// Copy SDU segment into payload
srsran_assert((hdr_len + retx_pdu_payload_size) <= nof_bytes, "Error calculating hdr_len and segment_payload_len");
memcpy(&payload[hdr_len], tx_pdu.sdu_buf->msg, retx_pdu_payload_size);
// Update retx queue
retx.is_segment = true;
retx.current_so = retx.current_so + retx_pdu_payload_size;
RlcDebug("Updated RETX info. is_segment=%s, current_so=%d, so_start=%d, so_end=%d",
retx.is_segment ? "true" : "false",
retx.current_so,
retx.so_start,
retx.so_end);
if (retx.current_so >= tx_pdu.sdu_buf->N_bytes) {
RlcError("Current SO larger or equal to SDU size when creating SDU segment. SN=%d, current SO=%d, SO_start=%d, "
"SO_end=%d",
retx.sn,
retx.current_so,
retx.so_start,
retx.so_end);
return 0;
}
if (retx.current_so >= retx.so_end) {
RlcError("Current SO larger than SO end. SN=%d, current SO=%d, SO_start=%d, SO_end=%s",
retx.sn,
retx.current_so,
retx.so_start,
retx.so_end);
return 0;
}
// Update SDU segment info
// TODO
return hdr_len + retx_pdu_payload_size;
}
/**
* Builds a retx RLC PDU from a full SDU.
*
@ -777,6 +978,33 @@ uint32_t rlc_am_nr_tx::build_retx_segment_from_sdu_segment(rlc_amd_retx_t& retx,
return 0;
}
bool rlc_am_nr_tx::is_retx_segmentation_required(const rlc_amd_retx_t& retx, uint32_t nof_bytes)
{
bool segmentation_required = false;
if (retx.is_segment) {
uint32_t expected_hdr_size = retx.current_so == 0 ? min_hdr_size : max_hdr_size;
if (nof_bytes < ((retx.so_end - retx.current_so) + expected_hdr_size)) {
RlcInfo("Re-segmentation required for RETX. SN=%d", retx.sn);
segmentation_required = true;
}
} else {
if (nof_bytes < (tx_window[retx.sn].sdu_buf->N_bytes + min_hdr_size)) {
RlcInfo("Segmentation required for RETX. SN=%d", retx.sn);
segmentation_required = true;
}
}
return segmentation_required;
}
uint32_t rlc_am_nr_tx::get_retx_expected_hdr_len(const rlc_amd_retx_t& retx)
{
uint32_t expected_hdr_len = min_hdr_size;
if (retx.is_segment && retx.current_so != 0) {
expected_hdr_len = max_hdr_size;
}
return expected_hdr_len;
}
uint32_t rlc_am_nr_tx::build_status_pdu(byte_buffer_t* payload, uint32_t nof_bytes)
{
RlcInfo("generating status PDU. Bytes available:%d", nof_bytes);
@ -817,7 +1045,7 @@ void rlc_am_nr_tx::handle_control_pdu(uint8_t* payload, uint32_t nof_bytes)
// Process ACKs
uint32_t stop_sn = status.N_nack == 0
? status.ack_sn
: status.nacks[0].nack_sn - 1; // Stop processing ACKs at the first NACK, if it exists.
: status.nacks[0].nack_sn; // Stop processing ACKs at the first NACK, if it exists.
if (stop_sn > st.tx_next) {
RlcError("Received ACK or NACK larger than TX_NEXT. Ignoring status report");
return;
@ -836,25 +1064,46 @@ void rlc_am_nr_tx::handle_control_pdu(uint8_t* payload, uint32_t nof_bytes)
// Process N_acks
for (uint32_t nack_idx = 0; nack_idx < status.N_nack; nack_idx++) {
if (st.tx_next_ack <= status.nacks[nack_idx].nack_sn && status.nacks[nack_idx].nack_sn <= st.tx_next) {
uint32_t nack_sn = status.nacks[nack_idx].nack_sn;
auto nack = status.nacks[nack_idx];
uint32_t nack_sn = nack.nack_sn;
if (tx_window.has_sn(nack_sn)) {
auto& pdu = tx_window[nack_sn];
// add to retx queue if it's not already there
if (not retx_queue.has_sn(nack_sn)) {
// increment Retx counter and inform upper layers if needed
pdu.retx_count++;
// check_sn_reached_max_retx(nack_sn);
rlc_amd_retx_t& retx = retx_queue.push();
srsran_expect(tx_window[nack_sn].rlc_sn == nack_sn,
"Incorrect RLC SN=%d!=%d being accessed",
tx_window[nack_sn].rlc_sn,
nack_sn);
retx.sn = nack_sn;
retx.is_segment = false;
retx.so_start = 0;
retx.so_end = pdu.sdu_buf->N_bytes;
if (nack.has_so) {
// NACK'ing missing bytes in SDU segment.
// Retransmit all SDU segments within those missing bytes.
if (pdu.segment_list.empty()) {
RlcError("Received NACK with SO, but there is no segment information");
}
for (std::list<rlc_amd_tx_pdu_nr::pdu_segment>::iterator segm = pdu.segment_list.begin();
segm != pdu.segment_list.end();
segm++) {
if (segm->so >= nack.so_start && nack.so_end <= (segm->so + segm->payload_len)) {
rlc_amd_retx_t& retx = retx_queue.push();
retx.sn = nack_sn;
retx.sdu_end = pdu.sdu_buf->N_bytes;
retx.is_segment = true;
retx.so_start = segm->so;
retx.current_so = segm->so;
retx.so_end = segm->so + segm->payload_len;
}
}
} else {
// NACK'ing full SDU.
// add to retx queue if it's not already there
if (not retx_queue.has_sn(nack_sn)) {
// increment Retx counter and inform upper layers if needed
pdu.retx_count++;
// check_sn_reached_max_retx(nack_sn);
rlc_amd_retx_t& retx = retx_queue.push();
retx.sn = nack_sn;
retx.sdu_end = pdu.sdu_buf->N_bytes;
retx.is_segment = false;
retx.so_start = 0;
retx.current_so = 0;
retx.so_end = pdu.sdu_buf->N_bytes;
}
}
}
}

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