Change in osmo-bts[master]: osmo-bts-trx: fix trx_init(): do not send OPSTART ACK blindly

[laforge]

laforge has submitted this change. ( https://gerrit.osmocom.org/c/osmo-bts/+/19988 )

Change subject: osmo-bts-trx: fix trx_init(): do not send OPSTART ACK blindly
......................................................................

osmo-bts-trx: fix trx_init(): do not send OPSTART ACK blindly

It was reported that both osmo-bsc and osmo-bts-trx may end up
running in a half-broken state, when everything looks good and
the UEs can see the network, but all channel requests get
rejected due to "trx not usable" error:

  lchan_select.c:173 (bts=0) lchan_select_by_type(SDCCH)
  lchan_select.c:48 looking for lchan CCCH+SDCCH4: (bts=0,trx=0) trx not usable
  lchan_select.c:48 looking for lchan SDCCH8: (bts=0,trx=0) trx not usable
  lchan_select.c:239 (bts=0) Failed to select SDCCH channel

  lchan_select.c:173 (bts=0) lchan_select_by_type(TCH_H)
  lchan_select.c:48 looking for lchan TCH/H: (bts=0,trx=0) trx not usable
  lchan_select.c:239 (bts=0) Failed to select TCH_H channel

  lchan_select.c:173 (bts=0) lchan_select_by_type(TCH_F)
  lchan_select.c:48 looking for lchan TCH/F: (bts=0,trx=0) trx not usable
  lchan_select.c:239 (bts=0) Failed to select TCH_F channel

As was then figured out, this happens because the Radio Carrier
MO (Managed Object) remains Disabled even after the BSC has
sent OPSTART and the BTS ACKed it:

  oml.c:986 OC=RADIO-CARRIER(02) INST=(00,00,ff): Rx OPSTART
  l1_if.c:614 Rx OPSTART for RADIO-CARRIER MO
  l1_if.c:201 TRX_PROV(phy0-0)[0x1238c0]{OPEN_POWERON}:
              Event TRX_PROV_EV_CFG_ENABLE not permitted
  oml.c:144 OC=RADIO-CARRIER(02) INST=(00,00,ff): Tx Opstart Ack

It remains a mistery why the TRX_PROV FSM is already in state
OPEN_POWERON, while it's expected to be in state OPEN_POWEROFF,
but we definitely should not ACKnowledge the OPSTART if this
happens.  Send a NACK instead with cause NM_NACK_CANT_PERFORM.

Change-Id: I8727460acbf850b84df67a9cbdc25b47dee1fadd
Related: SYS#5063
---
M src/osmo-bts-trx/l1_if.c
1 file changed, 4 insertions(+), 1 deletion(-)

Approvals:
  Jenkins Builder: Verified
  pespin: Looks good to me, but someone else must approve
  laforge: Looks good to me, approved



diff --git a/src/osmo-bts-trx/l1_if.c b/src/osmo-bts-trx/l1_if.c
index 8cf0823..430d97e 100644
--- a/src/osmo-bts-trx/l1_if.c
+++ b/src/osmo-bts-trx/l1_if.c
@@ -197,8 +197,11 @@
 {
 	struct phy_instance *pinst = trx_phy_instance(trx);
 	struct trx_l1h *l1h = pinst->u.osmotrx.hdl;
+	int rc;
 
-	osmo_fsm_inst_dispatch(l1h->provision_fi, TRX_PROV_EV_CFG_ENABLE, (void*)(intptr_t)true);
+	rc = osmo_fsm_inst_dispatch(l1h->provision_fi, TRX_PROV_EV_CFG_ENABLE, (void*)(intptr_t)true);
+	if (rc != 0)
+		return oml_mo_opstart_nack(&trx->mo, NM_NACK_CANT_PERFORM);
 
 	if (trx == trx->bts->c0)
 		lchan_init_lapdm(&trx->ts[0].lchan[CCCH_LCHAN]);

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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I8727460acbf850b84df67a9cbdc25b47dee1fadd
Gerrit-Change-Number: 19988
Gerrit-PatchSet: 2
Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-Reviewer: neels <nhofmeyr at sysmocom.de>
Gerrit-Reviewer: pespin <pespin at sysmocom.de>
Gerrit-MessageType: merged
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