fixeria has uploaded this change for review. (
https://gerrit.osmocom.org/c/osmo-bts/+/24594 )
Change subject: l1sap: fix TDMA frame number wrap in l1sap_info_time_ind()
......................................................................
l1sap: fix TDMA frame number wrap in l1sap_info_time_ind()
Using the normal arithmetic for TDMA frame numbers may result
in getting wrong values. Consider the following situation:
'info_time_ind->fn' is 0 (beginning of period)
'bts->gsm_time.fn' is 2715647 (end of period)
With these input values the following expression:
info_time_ind->fn - bts->gsm_time.fn
will be equal to:
0 - 2715647 or -2715647
In this case osmo-bts does not log an error, because:
if (-2715647 > 0) // is false
As a consequence, we do not increment number of RACH slots that
have passed by since the last time indication:
for (i = 0; i < -2715647; i++) // is false
This is why we introduced GSM_TDMA_FN_{SUB,SUM,DIFF,INC} API.
Change-Id: I6168dd75daea50bbe2e19338e637185ac9ac87ef
---
M src/common/l1sap.c
1 file changed, 4 insertions(+), 4 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/94/24594/1
diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index b17bf01..cd2af57 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -592,17 +592,17 @@
struct osmo_phsap_prim *l1sap,
struct info_time_ind_param *info_time_ind)
{
- int frames_expired;
- int i;
+ unsigned int frames_expired;
+ unsigned int i;
DEBUGPFN(DL1P, info_time_ind->fn, "Rx MPH_INFO time ind\n");
/* Calculate and check frame difference */
- frames_expired = info_time_ind->fn - bts->gsm_time.fn;
+ frames_expired = GSM_TDMA_FN_SUB(info_time_ind->fn, bts->gsm_time.fn);
if (frames_expired > 1) {
if (bts->gsm_time.fn)
LOGPFN(DL1P, LOGL_ERROR, info_time_ind->fn,
- "Invalid condition detected: Frame difference is
%"PRIu32"-%"PRIu32"=%d > 1!\n",
+ "Invalid condition detected: Frame difference is
%"PRIu32"-%"PRIu32"=%u > 1!\n",
info_time_ind->fn, bts->gsm_time.fn,
frames_expired);
}
--
To view, visit https://gerrit.osmocom.org/c/osmo-bts/+/24594
To unsubscribe, or for help writing mail filters, visit
https://gerrit.osmocom.org/settings
Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I6168dd75daea50bbe2e19338e637185ac9ac87ef
Gerrit-Change-Number: 24594
Gerrit-PatchSet: 1
Gerrit-Owner: fixeria <vyanits...@sysmocom.de>
Gerrit-MessageType: newchange
