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srsLTE
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rlc: fix stopping of poll retx timer (#2006) 

* rlc_am: add TC for pollRetx timer handling

* rlc_am: fix stopping of pollRetx timer

stopping the pollRetx timer when receiving a status PDU
without checking the acknowledged PDUs is wrong.

if an ACK for another PDU, for which the polling bit has been set,
is still pending, it won't be rescheduled until another
PDU is transmitted that again starts the pollRetx timer.

this fixes the issue with missing RLC AM segment retx in #1992,
and #2003
This commit is contained in:
Andre Puschmann 2020-11-09 10:53:14 +01:00
parent 7cf919e2af
commit f155b7a5d5
2 changed files with 121 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
lib/src/upper/rlc_am_lte.cc
View File

@ -442,7 +442,7 @@ void rlc_am_lte::rlc_am_lte_tx::timer_expired(uint32_t timeout_id)
{
pthread_mutex_lock(&mutex);
if (poll_retx_timer.is_valid() && poll_retx_timer.id() == timeout_id) {
log->debug("Poll reTx timer expired for LCID=%d after %d ms\n", parent->lcid, poll_retx_timer.duration());
log->debug("%s Poll reTx timer expired after %dms\n", RB_NAME, poll_retx_timer.duration());
// Section 5.2.2.3 in TS 36.311, schedule random PDU for retransmission if
// (a) both tx and retx buffer are empty, or
// (b) no new data PDU can be transmitted (tx window is full)
@ -599,8 +599,8 @@ int rlc_am_lte::rlc_am_lte_tx::build_retx_pdu(uint8_t* payload, uint32_t nof_byt
log->info("%s pdu_without_poll: %d\n", RB_NAME, pdu_without_poll);
log->info("%s byte_without_poll: %d\n", RB_NAME, byte_without_poll);
if (poll_required()) {
new_header.p = 1;
poll_sn = vt_s;
new_header.p = 1;
// vt_s won't change for reTx, so don't update poll_sn
pdu_without_poll = 0;
byte_without_poll = 0;
if (poll_retx_timer.is_valid()) {
@ -657,8 +657,8 @@ int rlc_am_lte::rlc_am_lte_tx::build_segment(uint8_t* payload, uint32_t nof_byte
new_header.p = 0;
if (poll_required()) {
log->debug("%s setting poll bit to request status\n", RB_NAME);
new_header.p = 1;
poll_sn = vt_s;
new_header.p = 1;
// vt_s won't change for reTx, so don't update poll_sn
pdu_without_poll = 0;
byte_without_poll = 0;
if (poll_retx_timer.is_valid()) {
@ -960,7 +960,10 @@ void rlc_am_lte::rlc_am_lte_tx::handle_control_pdu(uint8_t* payload, uint32_t no
log->info("%s Rx Status PDU: %s\n", RB_NAME, rlc_am_status_pdu_to_string(&status).c_str());
if (poll_retx_timer.is_valid()) {
// Sec 5.2.2.2, stop poll reTx timer if status PDU comprises a positive _or_ negative acknowledgement
// for the RLC data PDU with sequence number poll_sn
if (poll_retx_timer.is_valid() && (TX_MOD_BASE(poll_sn) < TX_MOD_BASE(status.ack_sn))) {
log->debug("%s Stopping pollRetx timer\n", RB_NAME);
poll_retx_timer.stop();
}

114
lib/test/upper/rlc_am_test.cc
View File

@ -145,7 +145,7 @@ void basic_test_tx(rlc_am_lte* rlc, byte_buffer_t pdu_bufs[NBUFS])
assert(0 == rlc->get_buffer_state());
}
bool meas_obj_test()
bool basic_test()
{
rlc_am_tester tester;
timer_handler timers(8);
@ -411,6 +411,110 @@ bool retx_test()
return 0;
}
// Purpose: test correct retx of lost segment and pollRetx timer expiration
bool segment_retx_test()
{
rlc_am_tester tester;
timer_handler timers(8);
int len = 0;
rlc_am_lte rlc1(rrc_log1, 1, &tester, &tester, &timers);
rlc_am_lte rlc2(rrc_log2, 1, &tester, &tester, &timers);
if (not rlc1.configure(rlc_config_t::default_rlc_am_config())) {
return -1;
}
if (not rlc2.configure(rlc_config_t::default_rlc_am_config())) {
return -1;
}
// Push SDU(s) into RLC1
byte_buffer_pool* pool = byte_buffer_pool::get_instance();
const uint32_t nof_sdus = 1; // just one SDU to make sure the transmitter sets polling bit
unique_byte_buffer_t sdu_bufs[nof_sdus];
for (uint32_t i = 0; i < nof_sdus; i++) {
sdu_bufs[i] = srslte::allocate_unique_buffer(*pool, true);
sdu_bufs[i]->msg[0] = i; // Write the index into the buffer
sdu_bufs[i]->N_bytes = 10; // Give each buffer a size of 1 byte
rlc1.write_sdu(std::move(sdu_bufs[i]));
}
// Read 2 PDUs from RLC1
const uint32_t nof_pdus = 2;
byte_buffer_t pdu_bufs[nof_pdus];
for (uint32_t i = 0; i < nof_pdus; i++) {
len = rlc1.read_pdu(pdu_bufs[i].msg, 7); // 2 byte header
pdu_bufs[i].N_bytes = len;
}
TESTASSERT(rlc1.get_buffer_state() == 0);
// Step timers until poll Retx timeout expires
int cnt = 5;
while (cnt--) {
timers.step_all();
}
uint32_t buffer_state = rlc1.get_buffer_state();
TESTASSERT(buffer_state == 7);
// Read retx PDU from RLC1
byte_buffer_t retx_pdu;
len = rlc1.read_pdu(retx_pdu.msg, buffer_state); // provide exactly the reported buffer state
retx_pdu.N_bytes = len;
// Write retx segment to RLC2
rlc2.write_pdu(retx_pdu.msg, retx_pdu.N_bytes);
buffer_state = rlc2.get_buffer_state(); // Status PDU
TESTASSERT(buffer_state == 2);
// Read status PDU from RLC2
byte_buffer_t status_buf;
len = rlc2.read_pdu(status_buf.msg, 10); // 10 bytes is enough to hold the status
status_buf.N_bytes = len;
// Write status PDU to RLC1
rlc1.write_pdu(status_buf.msg, status_buf.N_bytes);
// Step timers again until poll Retx timeout expires
cnt = 5;
while (cnt--) {
timers.step_all();
}
// read buffer state from RLC1 again to see if it has rescheduled SN=1 for retx
buffer_state = rlc1.get_buffer_state(); // Status PDU
TESTASSERT(buffer_state == 7);
// Read 2nd retx PDU from RLC1
byte_buffer_t retx_pdu2;
len = rlc1.read_pdu(retx_pdu2.msg, buffer_state); // provide exactly the reported buffer state
retx_pdu2.N_bytes = len;
// Write retx segment to RLC2
rlc2.write_pdu(retx_pdu2.msg, retx_pdu2.N_bytes);
// read Status PDU from RLC2 again
len = rlc2.read_pdu(status_buf.msg, 10); // 10 bytes is enough to hold the status
status_buf.N_bytes = len;
rlc1.write_pdu(status_buf.msg, status_buf.N_bytes);
TESTASSERT(tester.n_sdus == nof_sdus);
for (int i = 0; i < tester.n_sdus; i++) {
if (tester.sdus[i]->N_bytes != 10) {
return SRSLTE_ERROR;
}
if (*(tester.sdus[i]->msg) != i) {
return SRSLTE_ERROR;
}
}
return SRSLTE_SUCCESS;
}
bool resegment_test_1()
{
// SDUs: | 10 | 10 | 10 | 10 | 10 |
@ -1549,7 +1653,7 @@ int main(int argc, char** argv)
rrc_log1->set_hex_limit(-1);
rrc_log2->set_hex_limit(-1);
if (meas_obj_test()) {
if (basic_test()) {
printf("basic_test failed\n");
exit(-1);
};
@ -1579,6 +1683,12 @@ int main(int argc, char** argv)
};
byte_buffer_pool::get_instance()->cleanup();
if (segment_retx_test()) {
printf("segment_retx_test failed\n");
exit(-1);
};
byte_buffer_pool::get_instance()->cleanup();
if (resegment_test_1()) {
printf("resegment_test_1 failed\n");
exit(-1);