route_bgp: find_conn_for_node prefers live links_up path, fallback to best any

src/route_bgp.c

@@ -495,14 +495,23 @@ struct ETCP_CONN* route_bgp_find_conn_for_node(struct ROUTE_BGP* bgp, uint64_t n
     struct NODEINFO_Q* nq = nodeinfo_find_by_id(bgp, node_id);
     if (!nq || !nq->paths || !nq->paths->head) return NULL;
     struct ll_entry* e = nq->paths->head;
-    struct NODEINFO_PATH* best = NULL;
-    uint8_t best_hops = 255;
+    struct NODEINFO_PATH* best_live = NULL;
+    uint8_t best_live_hops = 255;
+    struct NODEINFO_PATH* best_any = NULL;
+    uint8_t best_any_hops = 255;
     while (e) {
         struct NODEINFO_PATH* path = (struct NODEINFO_PATH*)e;
-        if (path->conn && path->hop_count < best_hops) { best = path; best_hops = path->hop_count; }
+        if (path->conn) {
+            if (path->conn->links_up && path->hop_count < best_live_hops) { best_live = path; best_live_hops = path->hop_count; }
+            if (path->hop_count < best_any_hops) { best_any = path; best_any_hops = path->hop_count; }
+        }
         e = e->next;
     }
-    return best ? best->conn : NULL;
+    if (!best_live && best_any) {
+        DEBUG_DEBUG(DEBUG_CATEGORY_BGP, "find_conn_for_node %016llx: no live paths, fallback to best (hops=%d links_up=%d)",
+                    (unsigned long long)node_id, best_any_hops, best_any->conn->links_up);
+    }
+    return best_live ? best_live->conn : (best_any ? best_any->conn : NULL);
 }
 
 int route_bgp_add_path(struct NODEINFO_Q* nq, struct ETCP_CONN* conn, uint64_t* hop_list, uint8_t hop_count) {