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osmo-pcu
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Error trying to obtain FN from RFN if curr_fn not known 

This may happen if a RACH.ind is received before any DATA.ind has been
received.
With usual osmo-bts-trx or osmo-bts-sysmo, this shouldn't happen
nowadays, but it is still a problem with osmo-bts-virtual, where lower
layers don't submit NOPE.ind in the absence of data, and hence it won't
sent DATA.ind to osmo-pcu all the time.

This change helps in showcasing confusing scenarios where the RFN
generated in the Imm Ass was wrong.

Change-Id: I29b7ba828fe890f90e35686bbb04d4abfe56b955
This commit is contained in:
Pau Espin 2023-05-31 19:36:41 +02:00
parent 33cb3d6175
commit f09056de46
1 changed files with 11 additions and 4 deletions
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15
src/bts.cpp
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@ -740,20 +740,27 @@ int bts_rcv_imm_ass_cnf(struct gprs_rlcmac_bts *bts, const uint8_t *data, uint32
/* Determine the full frame number from a relative frame number */
uint32_t bts_rfn_to_fn(const struct gprs_rlcmac_bts *bts, uint32_t rfn)
{
uint32_t m_cur_rfn;
uint32_t m_cur_fn, m_cur_rfn;
uint32_t fn_rounded;
/* Ensure that all following calculations are performed with the
* relative frame number */
OSMO_ASSERT(rfn < RFN_MODULUS);
m_cur_fn = bts_current_frame_number(bts);
if (m_cur_fn == FN_UNSET) {
LOGP(DRLCMAC, LOGL_ERROR, "Unable to calculate full FN from RFN %u: Current FN not known!\n",
rfn);
return rfn;
}
/* Compute an internal relative frame number from the full internal
frame number */
m_cur_rfn = fn2rfn(bts->cur_fn);
m_cur_rfn = fn2rfn(m_cur_fn);
/* Compute a "rounded" version of the internal frame number, which
* exactly fits in the RFN_MODULUS raster */
fn_rounded = GSM_TDMA_FN_SUB(bts->cur_fn, m_cur_rfn);
fn_rounded = GSM_TDMA_FN_SUB(m_cur_fn, m_cur_rfn);
/* If the delta between the internal and the external relative frame
* number exceeds a certain limit, we need to assume that the incoming
@ -762,7 +769,7 @@ uint32_t bts_rfn_to_fn(const struct gprs_rlcmac_bts *bts, uint32_t rfn)
if (GSM_TDMA_FN_DIFF(rfn, m_cur_rfn) > RFN_THRESHOLD) {
LOGP(DRLCMAC, LOGL_DEBUG,
"Race condition between rfn (%u) and m_cur_fn (%u) detected: rfn belongs to the previous modulus %u cycle, wrapping...\n",
rfn, bts->cur_fn, RFN_MODULUS);
rfn, m_cur_fn, RFN_MODULUS);
if (fn_rounded < RFN_MODULUS) {
LOGP(DRLCMAC, LOGL_DEBUG,
"Cornercase detected: wrapping crosses %u border\n",