Add VTY option to avoid sending empty Full BCCH Info for disabled SI

According to 3GPP TS 08.58 §8.5.1 BCCH INFORMATION:
"If the Full BCCH information element is not included this indicates that
transmission of the indicated SYSTEM INFORMATION message shall be stopped."

However, some ipaccess nanoBTS firmware versions are known to not support
some SI elements and also to dislike receiving BCCH Information for those SI,
even if received with empty BCCH Information meaning they should not be used.

Upon receival of this kind of message, nanoBTS sends a Failure Report
with following text:
Type=processing failure, Severity=critical failure, Probable cause=Manufacturer specific values: Fatal software error, Additional Text=l2_bch.c:1149
****
** l2_bch.c#1149:BCHbcchSItypeValid( prim_p->infoType )
** IPA_SW_FATAL_ERROR
** In task "TRX Proc:L2_BCH" @ (325).
****

This kind of issue only appears with some fw versions, since it's known
to work fine in other ones, so let's not disable this kind of mesage by
default on all BTs of type "nanobts".

Instead, add a VTY command that allows disabling this kind of message in
order to be able to operate those nanoBTS units.

Fixes: OS#3707
Change-Id: Idec1daabc21de4eea5c55edd1dbb0e0775720fc7

1 files changed, 10 insertions, 6 deletions

diff --git a/src/osmo-bsc/bsc_init.c b/src/osmo-bsc/bsc_init.c
index 2f44b200a..7d29d4fbe 100644
--- a/src/osmo-bsc/bsc_init.c
+++ b/src/osmo-bsc/bsc_init.c
@@ -173,12 +173,16 @@ int gsm_bts_trx_set_system_infos(struct gsm_bts_trx *trx)
 
 	for (n = 0; n < n_si; n++) {
 		i = gen_si[n];
-		/* if we don't currently have this SI, we send a zero-length
-		 * RSL BCCH FILLING / SACCH FILLING * in order to deactivate
-		 * the SI, in case it might have previously been active */
-		if (!GSM_BTS_HAS_SI(bts, i))
-			rc = rsl_si(trx, i, 0);
-		else
+		/* 3GPP TS 08.58 §8.5.1 BCCH INFORMATION. If we don't currently
+		 * have this SI, we send a zero-length RSL BCCH FILLING /
+		 * SACCH FILLING in order to deactivate the SI, in case it
+		 * might have previously been active */
+		if (!GSM_BTS_HAS_SI(bts, i)) {
+			if (bts->si_unused_send_empty)
+				rc = rsl_si(trx, i, 0);
+			else
+				rc = 0; /* some nanoBTS fw don't like receiving empty unsupported SI */
+		} else
 			rc = rsl_si(trx, i, si_len[i]);
 		if (rc < 0)
 			return rc;