Make random MSISDN assignment optional

Previously if subscriber was automatically created it got assigned
random MSISDN number. Make it optional (defaulting to previous behavior)
by adding following:

* new optional no-extension argument for subscriber-create-on-demand vty
  command
* db unit tests
* vty test

Note: using the db made with new code might result in subscribers with
empty extension. Such subscribers cannot be deleted using old
code. Make sure not to mix db versions or manually fix it by editing
sqlite with external program.

Fixes: OS#1658
Change-Id: Ibbc2e88e4722b08854ebc631485f19ed56443cbb
diff --git a/openbsc/src/libmsc/db.c b/openbsc/src/libmsc/db.c
index b367139..68eba3e 100644
--- a/openbsc/src/libmsc/db.c
+++ b/openbsc/src/libmsc/db.c
@@ -23,6 +23,7 @@
 #include <inttypes.h>
 #include <libgen.h>
 #include <stdio.h>
+#include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
@@ -519,7 +520,7 @@
 }
 
 struct gsm_subscriber *db_create_subscriber(const char *imsi, uint64_t smin,
-					    uint64_t smax)
+					    uint64_t smax, bool alloc_exten)
 {
 	dbi_result result;
 	struct gsm_subscriber *subscr;
@@ -551,7 +552,8 @@
 	strncpy(subscr->imsi, imsi, sizeof(subscr->imsi)-1);
 	dbi_result_free(result);
 	LOGP(DDB, LOGL_INFO, "New Subscriber: ID %llu, IMSI %s\n", subscr->id, subscr->imsi);
-	db_subscriber_alloc_exten(subscr, smin, smax);
+	if (alloc_exten)
+		db_subscriber_alloc_exten(subscr, smin, smax);
 	return subscr;
 }
 
@@ -956,8 +958,11 @@
 
 	dbi_conn_quote_string_copy(conn, 
 				   subscriber->name, &q_name);
-	dbi_conn_quote_string_copy(conn, 
-				   subscriber->extension, &q_extension);
+	if (subscriber->extension[0] != '\0')
+		dbi_conn_quote_string_copy(conn,
+					   subscriber->extension, &q_extension);
+	else
+		q_extension = strdup("NULL");
 	
 	if (subscriber->tmsi != GSM_RESERVED_TMSI) {
 		sprintf(tmsi, "%u", subscriber->tmsi);
@@ -1062,15 +1067,17 @@
 	}
 	dbi_result_free(result);
 
-	result = dbi_conn_queryf(conn,
-			"DELETE FROM SMS WHERE src_addr=%s OR dest_addr=%s",
-			subscr->extension, subscr->extension);
-	if (!result) {
-		LOGP(DDB, LOGL_ERROR,
-			"Failed to delete SMS for %llu\n", subscr->id);
-		return -1;
+	if (subscr->extension[0] != '\0') {
+		result = dbi_conn_queryf(conn,
+			    "DELETE FROM SMS WHERE src_addr=%s OR dest_addr=%s",
+					 subscr->extension, subscr->extension);
+		if (!result) {
+			LOGP(DDB, LOGL_ERROR,
+			     "Failed to delete SMS for %llu\n", subscr->id);
+			return -1;
+		}
+		dbi_result_free(result);
 	}
-	dbi_result_free(result);
 
 	result = dbi_conn_queryf(conn,
 			"DELETE FROM VLR WHERE subscriber_id=%llu",