aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorNeels Hofmeyr <nhofmeyr@sysmocom.de>2019-01-22 11:30:21 +0100
committerPhilipp Maier <pmaier@sysmocom.de>2019-01-22 11:37:42 +0100
commit8d9c3e7f303c9fdac0127bc56a99e1f4a9379cb1 (patch)
tree072364d460cdc7b4c13d0da6d99b7c7c999dc2e1
parent3035892d95424f17af64636bcba7ddb8f62c3207 (diff)
abis_rsl: Fix TCH-as-SDCCH allocation on Channel Request
On rsl_rx_chan_rqd(), so far osmo-bsc tried to preferably assign the lchan type that was asked for in the RACH. Firstly, this contained a bug, and secondly, it does not make sense to heed that preference, since we do late assignment. Ignore the preference for the MS' TCH kind. We do late assignment to avoid codec mismatches. In the "old days", we would heed the MS' TCH channel kind, even if the MSC or BSC didn't actually allow or prefer that channel kind. Hence, in the presence of both TCH/F and TCH/H, the MS could ask for TCH/F (which we would grant on the MO side) and the BSC or MSC could prefer TCH/H (which we would apply on the MT side), and hence fabricate a codec mismatch. Instead, since quite some time now, we *always* assign an SDCCH first, and only later on do another Assignment to hand out a proper voice lchan that heeds the MS capability bits as well as MSC's and BSC's preferences. By completely ignoring the channel kind the MS asked for in the RACH, we also eliminate this bug in rsl_rx_chan_rqd(): - If the first "lchan_select_by_type(GSM_LCHAN_SDDCH)" fails (all SDDCH in use), we should try to fall back to any TCH instead, to serve as SDCCH. - the first "if (!lchan && lctype != GSM_LCHAN_SDCCH)" was an attempt to prefer a fallback to the lchan type the MS requested. - the remaining two "if (!lchan && lctype == GSM_LCHAN_SDCCH)" were obviously only applied if the MS asked for an SDCCH, and skipped if the type was TCH/*. - hence, missing was: if the MS asked for a TCH, to also try the *other* TCH kind that the MS did not ask for. (Example: all SDCCH in use, MS asks for TCH/F, but BSC has only TCH/H lchans; we should assign TCH/H as SDCCH, instead we said "no resources") Change-Id: Ie3684cf071751f9528183d761c588102936e498c Related: OS#3503
-rw-r--r--src/osmo-bsc/abis_rsl.c18
1 files changed, 4 insertions, 14 deletions
diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c
index d67573f..fd6dbdb 100644
--- a/src/osmo-bsc/abis_rsl.c
+++ b/src/osmo-bsc/abis_rsl.c
@@ -1375,22 +1375,12 @@ static int rsl_rx_chan_rqd(struct msgb *msg)
/* check availability / allocate channel
*
* - First try to allocate SDCCH.
- * - If SDCCH is not available, try whatever MS requested, if not SDCCH.
- * - If there is still no channel available, reject channel request.
+ * - If SDCCH is not available, try a TCH/H (less bandwith).
+ * - If there is still no channel available, try a TCH/F.
*
- * Note: If the MS requests not TCH/H, we don't know if the phone
- * supports TCH/H, so we must assign TCH/F or SDCCH.
*/
lchan = lchan_select_by_type(bts, GSM_LCHAN_SDCCH);
- if (!lchan && lctype != GSM_LCHAN_SDCCH) {
- LOGP(DRSL, LOGL_NOTICE, "(bts=%d) CHAN RQD: no resources for %s "
- "0x%x, retrying with %s\n",
- msg->lchan->ts->trx->bts->nr,
- gsm_lchant_name(GSM_LCHAN_SDCCH), rqd_ref->ra,
- gsm_lchant_name(lctype));
- lchan = lchan_select_by_type(bts, lctype);
- }
- if (!lchan && lctype == GSM_LCHAN_SDCCH) {
+ if (!lchan) {
LOGP(DRSL, LOGL_NOTICE, "(bts=%d) CHAN RQD: no resources for %s "
"0x%x, retrying with %s\n",
msg->lchan->ts->trx->bts->nr,
@@ -1398,7 +1388,7 @@ static int rsl_rx_chan_rqd(struct msgb *msg)
gsm_lchant_name(GSM_LCHAN_TCH_H));
lchan = lchan_select_by_type(bts, GSM_LCHAN_TCH_H);
}
- if (!lchan && lctype == GSM_LCHAN_SDCCH) {
+ if (!lchan) {
LOGP(DRSL, LOGL_NOTICE, "(bts=%d) CHAN RQD: no resources for %s "
"0x%x, retrying with %s\n",
msg->lchan->ts->trx->bts->nr,