Fix Dl EGPRS data blocks being generated occasionally on GPRS TBFs
Under some circumstances, it could happen that a DL TBF is created as a
GPRS TBF due to not yet having enough information of the MS, and only
after the TBF is created the PCU gains that information and upgrades the
MS mode to "EGPRS". Hence, there's the possibility to run into a
situation where a GPRS TBF is attached to a EGPRS MS.
It may also happen sometimes that despite the TBF and the MS be EGPRS,
there's need to further limit the DL MCS to use, eg. MCS1-4 (GMSK).
As a result, when asking for the current DL (M)CS to use, we must tell
the MS which kind of limitations we want to apply. The later reasoning
was already implemented when GPRS+EGPRS multiplexing was added, but the
former was not being checked. Hence, by further spreading through the
call stack the "req_kind_mode" we match both cases.
Related: OS#4973
Change-Id: Ic0276ce045660713129f0c72f1158a3321c5977f
diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index de43349..9562d86 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -448,29 +448,24 @@
{
int bsn;
int data_len2, force_data_len = -1;
- enum CodingScheme force_cs = UNKNOWN;
+ enum CodingScheme tx_cs;
+
+ /* Scheduler may be fine with sending any kind of data, but if
+ the selected TBF is GPRS-only, then let's filter out EGPRS
+ here */
+ if (!is_egprs_enabled())
+ req_mcs_kind = GPRS;
/* search for a nacked or resend marked bsn */
bsn = m_window.resend_needed();
if (previous_bsn >= 0) {
- force_cs = m_rlc.block(previous_bsn)->cs_current_trans;
- if (!mcs_is_edge(force_cs))
+ tx_cs = m_rlc.block(previous_bsn)->cs_current_trans;
+ if (!mcs_is_edge(tx_cs))
return -1;
force_data_len = m_rlc.block(previous_bsn)->len;
- } else if (bsn < 0 && is_egprs_enabled() && req_mcs_kind == EGPRS_GMSK) {
- /* New data to be sent for EGPRS TBF but we are required to downgrade to
- * MCS1-4, because USF for GPRS-only MS will be sent */
- force_cs = ms_current_cs_dl(m_ms);
- if (force_cs > MCS4) {
- force_cs = bts_cs_dl_is_supported(bts, MCS4) ? MCS4 :
- bts_cs_dl_is_supported(bts, MCS3) ? MCS3 :
- bts_cs_dl_is_supported(bts, MCS2) ? MCS2 :
- MCS1;
- LOGPTBFDL(this, LOGL_DEBUG,
- "Force downgrading DL %s -> %s due to USF for GPRS-only MS\n",
- mcs_name(ms_current_cs_dl(m_ms)), mcs_name(force_cs));
- }
+ } else {
+ tx_cs = ms_current_cs_dl(ms(), req_mcs_kind);
}
if (bsn >= 0) {
@@ -484,15 +479,14 @@
if (is_egprs_enabled()) {
/* Table 8.1.1.2 and Table 8.1.1.1 of 44.060 */
- m_rlc.block(bsn)->cs_current_trans = get_retx_mcs(m_rlc.block(bsn)->cs_init,
- ms_current_cs_dl(ms()),
+ m_rlc.block(bsn)->cs_current_trans = get_retx_mcs(m_rlc.block(bsn)->cs_init, tx_cs,
bts->pcu->vty.dl_arq_type == EGPRS_ARQ1);
LOGPTBFDL(this, LOGL_DEBUG,
"initial_cs_dl(%s) last_mcs(%s) demanded_mcs(%s) cs_trans(%s) arq_type(%d) bsn(%d)\n",
mcs_name(m_rlc.block(bsn)->cs_init),
mcs_name(m_rlc.block(bsn)->cs_last),
- mcs_name(ms_current_cs_dl(ms())),
+ mcs_name(tx_cs),
mcs_name(m_rlc.block(bsn)->cs_current_trans),
the_pcu->vty.dl_arq_type, bsn);
@@ -537,14 +531,12 @@
return take_next_bsn(fn, previous_bsn, req_mcs_kind, may_combine);
} else if (have_data()) {
/* The window has space left, generate new bsn */
- enum CodingScheme new_cs;
- new_cs = force_cs ? force_cs : current_cs();
LOGPTBFDL(this, LOGL_DEBUG,
"Sending new block at BSN %d, CS=%s%s\n",
- m_window.v_s(), mcs_name(new_cs),
- force_cs ? " (forced)" : "");
+ m_window.v_s(), mcs_name(tx_cs),
+ force_data_len != -1 ? " (forced)" : "");
- bsn = create_new_bsn(fn, new_cs);
+ bsn = create_new_bsn(fn, tx_cs);
} else if (bts->pcu->vty.dl_tbf_preemptive_retransmission && !m_window.window_empty()) {
/* The window contains unacked packages, but not acked.
* Mark unacked bsns as RESEND */
@@ -558,8 +550,8 @@
/* Nothing left to send, create dummy LLC commands */
LOGPTBFDL(this, LOGL_DEBUG,
"Sending new dummy block at BSN %d, CS=%s\n",
- m_window.v_s(), mcs_name(current_cs()));
- bsn = create_new_bsn(fn, current_cs());
+ m_window.v_s(), mcs_name(tx_cs));
+ bsn = create_new_bsn(fn, tx_cs);
/* Don't send a second block, so don't set cs_current_trans */
}