Add SGs Interface

Add an SGs interface (3GPP TS 29.118) to osmo-msc in order to support
SMS tunneling and Circuit Switched Fallback (CSFB)

Change-Id: I73359925fc1ca72b33a1466e6ac41307f2f0b11d
Related: OS#3615
diff --git a/tests/sms_queue/sms_queue_test.c b/tests/sms_queue/sms_queue_test.c
index 68819b9..e426377 100644
--- a/tests/sms_queue/sms_queue_test.c
+++ b/tests/sms_queue/sms_queue_test.c
@@ -237,3 +237,24 @@
 
 	return 0;
 }
+
+void osmo_stream_srv_link_set_data(struct osmo_stream_srv_link *link, void *data) {}
+struct osmo_fd *osmo_stream_srv_get_ofd(struct osmo_stream_srv *srv) { return NULL; }
+void osmo_stream_srv_destroy(struct osmo_stream_srv *conn) {}
+struct osmo_stream_srv *osmo_stream_srv_create(void *ctx, struct osmo_stream_srv_link *link,
+					       int fd, int (*cb)(struct osmo_stream_srv *conn),
+					       int (*closed_cb)(struct osmo_stream_srv *conn),
+					       void *data) { return NULL; }
+void osmo_stream_srv_send(struct osmo_stream_srv *conn, struct msgb *msg) {}
+void osmo_stream_srv_link_set_proto(struct osmo_stream_srv_link *link, uint16_t proto) {}
+struct osmo_fd *osmo_stream_srv_link_get_ofd(struct osmo_stream_srv_link *link) { return NULL; }
+struct osmo_stream_srv_link *osmo_stream_srv_link_create(void *ctx) { return NULL; }
+void *osmo_stream_srv_get_data(struct osmo_stream_srv *conn) { return NULL; }
+void osmo_stream_srv_link_set_nodelay(struct osmo_stream_srv_link *link, bool nodelay) {}
+void osmo_stream_srv_link_set_accept_cb(struct osmo_stream_srv_link *link, int (*accept_cb)
+					(struct osmo_stream_srv_link *link, int fd)) {}
+int osmo_stream_srv_link_open(struct osmo_stream_srv_link *link) { return 0; }
+void *osmo_stream_srv_link_get_data(struct osmo_stream_srv_link *link) { return NULL; }
+void osmo_stream_srv_link_set_port(struct osmo_stream_srv_link *link, uint16_t port) {}
+void osmo_stream_srv_link_set_addr(struct osmo_stream_srv_link *link, const char *addr) {}
+int sctp_recvmsg(int sd, void *msg, size_t len, void *from, void *fromlen, void *info, int *msg_flags) { return 0; }