sms: change rp err cause of smpp_try_deliver errors

smpp_try_deliver could fail with rc < 0. In such cases don't send the MS the rp
error sms rejected (cause 21). A rejected message should not be sent again. The
spec 04 11 recommends sending cause 41 Temporary failure in unknown cases.

Add also a log message and rate counter for such cases.

Tweaked-By: Neels Hofmeyr <nhofmeyr@sysmocom.de>
Change-Id: Ia03e50ce2bd9a7d1054cc5a6000fd73bd3497c03
diff --git a/openbsc/src/libmsc/gsm_04_11.c b/openbsc/src/libmsc/gsm_04_11.c
index 6d3f41b..d1fdfb9 100644
--- a/openbsc/src/libmsc/gsm_04_11.c
+++ b/openbsc/src/libmsc/gsm_04_11.c
@@ -40,6 +40,7 @@
 
 #include <osmocom/gsm/gsm_utils.h>
 #include <osmocom/gsm/gsm0411_utils.h>
+#include <osmocom/gsm/protocol/gsm_04_11.h>
 
 #include <openbsc/debug.h>
 #include <openbsc/gsm_data.h>
@@ -294,8 +295,12 @@
 		if (rc == 1)
 			goto try_local;
 		if (rc < 0) {
-			rc = 21; /* cause 21: short message transfer rejected */
-			/* FIXME: handle the error somehow? */
+	 		LOGP(DLSMS, LOGL_ERROR, "%s: SMS delivery error: %d.",
+			     subscr_name(conn->subscr), rc);
+	 		rc = GSM411_RP_CAUSE_MO_TEMP_FAIL;
+			/* rc will be logged by gsm411_send_rp_error() */
+	 		rate_ctr_inc(&conn->bts->network->msc_ctrs->ctr[
+					MSC_CTR_SMS_DELIVER_UNKNOWN_ERROR]);
 		}
 		return rc;
 	}
@@ -319,8 +324,12 @@
 			rc = 1; /* cause 1: unknown subscriber */
 			rate_ctr_inc(&conn->bts->network->msc_ctrs->ctr[MSC_CTR_SMS_NO_RECEIVER]);
 		} else if (rc < 0) {
-			rc = 21; /* cause 21: short message transfer rejected */
-			/* FIXME: handle the error somehow? */
+	 		LOGP(DLSMS, LOGL_ERROR, "%s: SMS delivery error: %d.",
+			     subscr_name(conn->subscr), rc);
+	 		rc = GSM411_RP_CAUSE_MO_TEMP_FAIL;
+			/* rc will be logged by gsm411_send_rp_error() */
+	 		rate_ctr_inc(&conn->bts->network->msc_ctrs->ctr[
+					MSC_CTR_SMS_DELIVER_UNKNOWN_ERROR]);
 		}
 #else
 		rc = 1; /* cause 1: unknown subscriber */