ss7: Drop the input of packages as well

We don't want the input change any state on the linkset and will
drop them if we think our application is not reachable.
diff --git a/src/ss7_application.c b/src/ss7_application.c
index 0609603..831ae1e 100644
--- a/src/ss7_application.c
+++ b/src/ss7_application.c
@@ -398,3 +398,16 @@
 	rate_ctr_inc(&link->set->ctrg->ctr[MTP_LSET_TOTA_OUT_MSG]);
 	link->write(link, msg);
 }
+
+int mtp_link_set_data(struct mtp_link *link, struct msgb *msg)
+{
+	if (link->set->app && link->set->app->type == APP_STP) {
+		if (!link->set->app->route_src.up || !link->set->app->route_dst.up) {
+			LOGP(DINP, LOGL_NOTICE, "Not handling data as application is down %d/%s.\n",
+			     link->set->app->nr, link->set->app->name);
+			return -1;
+		}
+	}
+
+	return mtp_link_handle_data(link, msg);
+}