Change in osmo-bts[master]: scheduler_trx.c: avoid division by zero when calculating BER

[dexter]

dexter has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bts/+/16067 )


Change subject: scheduler_trx.c: avoid division by zero when calculating BER
......................................................................

scheduler_trx.c: avoid division by zero when calculating BER

There is theoretical risk that when calculating the BER that a division
by zero occurrs. Lets add a check to avoid n_errors / n_bits_total when
n_bits_total is zero.

Related: CID#205696
Change-Id: I1c0731b9a60be4b8c0c84b85b4403168120ceacd
---
M src/osmo-bts-trx/scheduler_trx.c
1 file changed, 6 insertions(+), 3 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/67/16067/1

diff --git a/src/osmo-bts-trx/scheduler_trx.c b/src/osmo-bts-trx/scheduler_trx.c
index 9945b2c..0f1b233 100644
--- a/src/osmo-bts-trx/scheduler_trx.c
+++ b/src/osmo-bts-trx/scheduler_trx.c
@@ -1149,6 +1149,7 @@
 	struct gsm_lchan *lchan =
 		get_lchan_by_chan_nr(l1t->trx, trx_chan_desc[chan].chan_nr | bi->tn);
 	unsigned int fn_begin;
+	float ber;
 
 	/* handle rach, if handover rach detection is turned on */
 	if (chan_state->ho_rach_detect == 1)
@@ -1212,10 +1213,12 @@
 			(((bi->fn + 26 - 7) % 26) >> 2) & 1, chan_state->codec,
 			chan_state->codecs, &chan_state->ul_ft,
 			&chan_state->ul_cmr, &n_errors, &n_bits_total);
+		if (n_bits_total == 0)
+			ber = 1;
+		else
+			ber = (float)n_errors / (float)n_bits_total;
 		if (rc)
-			trx_loop_amr_input(l1t,
-				trx_chan_desc[chan].chan_nr | bi->tn, chan_state,
-				(float)n_errors/(float)n_bits_total);
+			trx_loop_amr_input(l1t, trx_chan_desc[chan].chan_nr | bi->tn, chan_state, ber);
 		amr = 2; /* we store tch_data + 2 header bytes */
 		/* only good speech frames get rtp header */
 		if (rc != GSM_MACBLOCK_LEN && rc >= 4) {

-- 
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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I1c0731b9a60be4b8c0c84b85b4403168120ceacd
Gerrit-Change-Number: 16067
Gerrit-PatchSet: 1
Gerrit-Owner: dexter <pmaier at sysmocom.de>
Gerrit-MessageType: newchange
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