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rlc_um: fix PDU packing when newly added SDU segment was too large 

during the PDU packing it could happen that a new SDU segment
was added but the resulting larger header was so big that not even
a single byte of the new PDU could be added. because this
corner case wasn't handled correctly an invalid PDU was transmitted.

the solution is to revert the addition of the new SDU.
This commit is contained in:
Andre Puschmann 2020-06-25 17:05:34 +02:00
parent fc3cd24177
commit 86025cf390
2 changed files with 12 additions and 7 deletions
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2
lib/src/upper/rlc_um_base.cc
View File

@ -289,7 +289,7 @@ int rlc_um_base::rlc_um_base_tx::build_data_pdu(uint8_t* payload, uint32_t nof_b
std::lock_guard<std::mutex> lock(mutex);
log->debug("MAC opportunity - %d bytes\n", nof_bytes);
if (!tx_sdu && tx_sdu_queue.size() == 0) {
if (tx_sdu == nullptr && tx_sdu_queue.is_empty()) {
log->info("No data available to be sent\n");
return 0;
}

17
lib/src/upper/rlc_um_lte.cc
View File

@ -167,12 +167,18 @@ int rlc_um_lte::rlc_um_lte_tx::build_data_pdu(unique_byte_buffer_t pdu, uint8_t*
// Pull SDUs from queue
while (pdu_space > head_len + 1 && tx_sdu_queue.size() > 0) {
log->debug("pdu_space=%d, head_len=%d\n", pdu_space, head_len);
if (last_li > 0)
if (last_li > 0) {
header.li[header.N_li++] = last_li;
}
head_len = rlc_um_packed_length(&header);
tx_sdu = tx_sdu_queue.read();
uint32_t space = pdu_space - head_len;
to_move = space >= tx_sdu->N_bytes ? tx_sdu->N_bytes : space;
if (space == 0) {
// we cannot even fit a single byte of the newly added SDU, remove it again
header.N_li--;
break;
}
tx_sdu = tx_sdu_queue.read();
to_move = (space >= tx_sdu->N_bytes) ? tx_sdu->N_bytes : space;
log->debug("%s adding new SDU segment - %d bytes of %d remaining\n", rb_name.c_str(), to_move, tx_sdu->N_bytes);
memcpy(pdu_ptr, tx_sdu->msg, to_move);
last_li = to_move;
@ -200,13 +206,12 @@ int rlc_um_lte::rlc_um_lte_tx::build_data_pdu(unique_byte_buffer_t pdu, uint8_t*
// Add header and TX
rlc_um_write_data_pdu_header(&header, pdu.get());
memcpy(payload, pdu->msg, pdu->N_bytes);
uint32_t ret = pdu->N_bytes;
log->info_hex(payload, ret, "%s Tx PDU SN=%d (%d B)\n", rb_name.c_str(), header.sn, pdu->N_bytes);
log->info_hex(payload, pdu->N_bytes, "%s Tx PDU SN=%d (%d B)\n", rb_name.c_str(), header.sn, pdu->N_bytes);
debug_state();
return ret;
return pdu->N_bytes;
}
void rlc_um_lte::rlc_um_lte_tx::debug_state()