--- a/smsc-sendmt/smsc_addr.c	Sun Aug 27 13:39:51 2023 -0800
+++ b/smsc-sendmt/smsc_addr.c	Sun Aug 27 16:36:28 2023 -0800
@@ -1,21 +1,25 @@
 /*
- * This C module is being stashed here temporarily until we figure out
- * where this function ultimately needs to go.  The parsing of the SMSC
- * address is being moved out of proto-smsc-daemon to proto-smsc-sendmt,
- * but we haven't started putting together the latter program yet.
+ * This module handles the parsing and GSUP encoding of our SMSC address,
+ * which we need to send to the MSC and ultimately to the MS as SM-RP-OA.
  */
 
 #include <ctype.h>
 #include <string.h>
 #include <stdio.h>
+#include <stdint.h>
 #include <stdlib.h>
 
-char smsc_addr_num[21];		/* maximum of 20 digits per GSM 04.11 */
-uint8_t smsc_addr_ton_npi;
+#include <osmocom/gsm/gsm48_ie.h>
+#include <osmocom/gsm/gsup.h>
 
-void parse_smsc_addr_arg(char *arg)
+static char smsc_addr_num[21];	/* maximum of 20 digits per GSM 04.11 */
+static uint8_t smsc_addr_ton_npi;
+static uint8_t smsc_addr_bcd[12];
+
+void parse_smsc_addr_arg(const char *arg)
 {
-	char *cp, *dp, *endp;
+	const char *cp;
+	char *dp, *endp;
 	unsigned ndig;
 
 	cp = arg;
@@ -49,3 +53,11 @@
 	if (*endp)
 		goto invalid;
 }
+
+void encode_smsc_addr(struct osmo_gsup_message *gmsg)
+{
+	gsm48_encode_bcd_number(smsc_addr_bcd, 11, 1, smsc_addr_num);
+	smsc_addr_bcd[1] = smsc_addr_ton_npi;
+	gmsg->sm_rp_oa = smsc_addr_bcd + 1;
+	gmsg->sm_rp_oa_len = smsc_addr_bcd[0];
+}