Index: trunk/src/libgrbs/route_common.c
===================================================================
--- trunk/src/libgrbs/route_common.c	(revision 1328)
+++ trunk/src/libgrbs/route_common.c	(revision 1329)
@@ -90,6 +90,40 @@
 	return best_arc;
 }
 
+/* Checks if convex-below-concave does not cross a concave arc. Returns 0 if
+   the concave arc 'from' is valid or non-zero on crossing */
+static int convex_below_concave_validate(grbs_t *grbs, grbs_2net_t *tn, grbs_addr_t *from, double new_da)
+{
+	int cnc_segi;
+
+	for(cnc_segi = 0; cnc_segi < GRBS_MAX_SEG; cnc_segi++) {
+		grbs_arc_t *cnc_sentinel = gdl_first(&from->obj.arc->parent_pt->arcs[1][cnc_segi]);
+		double enda;
+
+		if (cnc_sentinel == NULL) continue;
+
+	printf("sent: %f %f   convex: %f %f\n", cnc_sentinel->sa, cnc_sentinel->da, from->obj.arc->new_sa, new_da);
+
+		if (grbs_angle_in_arc(cnc_sentinel->sa, cnc_sentinel->da, from->obj.arc->new_sa, 0)) {
+			coll_report_arc(grbs, tn, cnc_sentinel->link_point.next);
+			tprintf("convex_below_concave_validate: start angle\n");
+			return 1;
+		}
+
+		enda = from->obj.arc->new_sa + new_da;
+		if (enda > 2*M_PI) enda -= 2*M_PI;
+		if (enda < 0) enda += 2*M_PI;
+
+		if (grbs_angle_in_arc(cnc_sentinel->sa, cnc_sentinel->da, enda, 0)) {
+			coll_report_arc(grbs, tn, cnc_sentinel->link_point.next);
+			tprintf("convex_below_concave_validate: end angle\n");
+			return 1;
+		}
+	}
+	return 0;
+}
+
+
 /* "from" is an existing arc with a start angle where the current route
    entered the orbit in its sector; "end_a" is where it should exit (the
    direction is known from "from"). This function checks wether this enter-exit
@@ -111,6 +145,10 @@
 		return -1;
 	}
 
+	if (!from_conc && convex_below_concave_validate(grbs, tn, from, nda))
+		return -1;
+
+
 	from->obj.arc->new_da = nda;
 
 	is_new_seg = ((from->obj.arc->link_point.next == NULL) && (from->obj.arc->link_point.prev == NULL) && !from->obj.arc->in_use);