Index: trunk/src/plugins/rt_topo/crbs.c
===================================================================
--- trunk/src/plugins/rt_topo/crbs.c	(revision 1318)
+++ trunk/src/plugins/rt_topo/crbs.c	(revision 1319)
@@ -38,6 +38,15 @@
 
 #include "crbs.h"
 
+static void crbs_coll_report_cb(grbs_t *grbs, grbs_2net_t *tn, grbs_2net_t *coll_tn, grbs_arc_t *coll_arc)
+{
+	crbs_t *crbs = grbs->user_data;
+	crbs_2net_t *ctn = tn->user_data, *coll_ctn = coll_tn->user_data;
+
+	printf("\n(COLLISION %s %s)\n", ctn->tn->net->hdr.oid, coll_ctn->tn->net->hdr.oid);
+}
+
+
 crbs_point_t *crbs_point_new(crbs_t *crbs)
 {
 	crbs_point_t *p = calloc(sizeof(crbs_point_t), 1);
@@ -55,6 +64,8 @@
 
 	grbs_init(&crbs->grbs);
 	crbs->ctx = ctx;
+	crbs->grbs.coll_report_cb = crbs_coll_report_cb;
+	crbs->grbs.user_data = crbs;
 	htad_init(&crbs->addrs, htad_hash, grbs_addr_hash_keyeq);
 
 	for(via = rtrnd_rtree_all_first(&it, &ctx->board->vias); via != NULL; via = rtrnd_rtree_all_next(&it)) {
Index: trunk/src/plugins/rt_topo/crbs_route.c
===================================================================
--- trunk/src/plugins/rt_topo/crbs_route.c	(revision 1318)
+++ trunk/src/plugins/rt_topo/crbs_route.c	(revision 1319)
@@ -344,6 +344,7 @@
 
 #warning TODO: per net wire thickness
 	crbs->routing_tn = grbs_2net_new(&crbs->grbs, rt_topo_cfg.wire_thick, rt_topo_cfg.wire_clr);
+	crbs->routing_tn->user_data = ctn;
 
 	printf(" route_net: from P%ld to P%ld\n",
 		((crbs_point_t *)(ctn->cstart->data))->gpt->uid,