Introduce initial unit test for db_sms_* API

Since OsmoMSC has built-in SMSC, it needs to store the messages
somewhere. Currently we use libdbi and SQLite3 back-end for that.

For a long time, the db_sms_* API remained uncovered by unit tests.
This change aims to fix that, and does cover the following calls:

  - db_sms_store(),
  - db_sms_get(),

  - db_sms_get_next_unsent(),
  - db_sms_mark_delivered(),

  - db_sms_delete_sent_message_by_id(),
  - db_sms_delete_by_msisdn(),
  - db_sms_delete_oldest_expired_message().

Due to performance reasons, the test database is initialized in
RAM using the magic filename ':memory:'. This is a feature of
SQLite3 (and not libdbi), see:

  https://www.sqlite.org/inmemorydb.html

Of course, this unit test helped to discover some problems:

  1) Storing an SMS with empty TP-User-Data (TP-UDL=0) causes
     buffer overruns in both db_sms_store() and db_sms_get().

  2) TP-User-Data-Length is always being interpreted in octets,
     regardless of DCS (Data Coding Scheme). This results in
     storing garbage in the database if the default 7-bit
     encoding is used. Fortunately, the 'user_data' buffer
     in structure 'gsm_sms' is large emough, so we don't
     experience buffer overruns.

  3) db_sms_delete_oldest_expired_message() doesn't work
     as expected. Instead of removing the *oldest* expired
     message, it tries to remove the *newest* one.

The current test expectations do reflect these problems.
All of them will be fixed in the follow-up patches.

Change-Id: Id94ad35b6f78f839137db2e17010fbf9b40111a3

1 files changed, 4 insertions, 1 deletions

diff --git a/src/libmsc/db.c b/src/libmsc/db.c
index c2d833939..b564697f9 100644
--- a/src/libmsc/db.c
+++ b/src/libmsc/db.c
@@ -772,7 +772,10 @@ static struct gsm_sms *sms_from_result(struct gsm_network *net, dbi_result resul
 	daddr = dbi_result_get_string(result, "dest_addr");
 	if (daddr)
 		OSMO_STRLCPY_ARRAY(sms->dst.addr, daddr);
-	sms->receiver = vlr_subscr_find_by_msisdn(net->vlr, sms->dst.addr, VSUB_USE_SMS_RECEIVER);
+
+	if (net != NULL) /* db_sms_test passes NULL, so we need to be tolerant */
+		sms->receiver = vlr_subscr_find_by_msisdn(net->vlr, sms->dst.addr,
+							  VSUB_USE_SMS_RECEIVER);
 
 	sms->src.npi = dbi_result_get_ulonglong(result, "src_npi");
 	sms->src.ton = dbi_result_get_ulonglong(result, "src_ton");