[o&m] Dispatch a signal for nacked O&M messages

When trying to operate a nanoBTS900 on channels for 1800
or the other way around the "SET BTS ATTRIBUTES" message
will be nacked. Dispatch all nacked messages from abis_nm
via signals. Handle this in bsc_hack.c, print a small hint
and exit the application as this is considered a fatal
unrecoverable error (the exit is in the app, so a library
can be more robust).

openbsc/include/openbsc/signal.h

@@ -54,6 +54,7 @@ enum signal_abisip {
 enum signal_nm {
 	S_NM_SW_ACTIV_REP,	/* GSM 12.21 software activated report */
 	S_NM_FAIL_REP,		/* GSM 12.21 failure event report */
+	S_NM_NACK,		/* GSM 12.21 various NM_MT_*_NACK happened */
 };
 
 /* SS_LCHAN signals */

openbsc/src/abis_nm.c

@@ -893,6 +893,9 @@ static int abis_nm_rcvmsg_fom(struct msgb *mb)
 				nack_cause_name(*TLVP_VAL(&tp, NM_ATT_NACK_CAUSES)));
 		else
 			DEBUGPC(DNM, "\n");
+
+		dispatch_signal(SS_NM, S_NM_NACK, (void*) ((long)mt));
+		return 0;
 	}
 #if 0
 	/* check if last message is to be acked */

openbsc/src/bsc_hack.c

@@ -454,6 +454,18 @@ static int sw_activ_rep(struct msgb *mb)
 	return 0;
 }
 
+/* Callback function for NACK on the OML NM */
+static int oml_msg_nack(int mt)
+{
+	if (mt == NM_MT_SET_BTS_ATTR_NACK) {
+		fprintf(stderr, "Failed to set BTS attributes. That is fatal. "
+				"Was the bts type and frequency properly specified?\n");
+		exit(-1);
+	}
+
+	return 0;
+}
+
 /* Callback function to be called every time we receive a signal from NM */
 static int nm_sig_cb(unsigned int subsys, unsigned int signal,
 		     void *handler_data, void *signal_data)
@@ -461,6 +473,8 @@ static int nm_sig_cb(unsigned int subsys, unsigned int signal,
 	switch (signal) {
 	case S_NM_SW_ACTIV_REP:
 		return sw_activ_rep(signal_data);
+	case S_NM_NACK:
+		return oml_msg_nack((int)signal_data);
 	default:
 		break;
 	}