bgp: fix node removal when alternative paths exist

- route_bgp_process_nodeinfo: record alternative paths even when NODEINFO
  version hasn't changed (fixes nodes disappearing on link down despite
  having other active links)
- route_bgp_process_withdraw: only remove node when all paths gone (ret==1)
- route_bgp_remove_conn: broadcast withdraw for each removed node with
  correct wd_source

src/route_bgp.c

@@ -441,14 +441,12 @@ void route_bgp_remove_conn(struct ETCP_CONN* conn) {
     struct ROUTE_TABLE* rt = conn->instance->rt;
 
     // Remove this connection from all nodes' path lists
-    bool need_withdraw = false;
     int nodes_removed = 0;
     struct ll_entry* node_entry = bgp->nodes ? bgp->nodes->head : NULL;
     while (node_entry) {
         struct ll_entry* next = node_entry->next;
         struct NODEINFO_Q* nq = (struct NODEINFO_Q*)node_entry;
         if (route_bgp_remove_path(nq, conn) == 1) {
-            need_withdraw = true;
             if (rt) route_delete(rt, nq);
             if (conn->instance && conn->instance->control_srv)
                 control_server_notify_node_removed(conn->instance->control_srv, nq->node.node_id);
@@ -460,6 +458,8 @@ void route_bgp_remove_conn(struct ETCP_CONN* conn) {
             if (entry) { queue_remove_data(bgp->nodes, entry); queue_entry_free(entry); }
             nodes_removed++;
             etcp_router_conn_close_all_for_node(bgp->instance, key);
+            uint64_t wd_src = (key == conn->peer_node_id) ? conn->instance->node_id : conn->peer_node_id;
+            route_bgp_broadcast_withdraw(bgp, key, wd_src, NULL);
             DEBUG_DEBUG(DEBUG_CATEGORY_BGP, "Removed node %016llx after link down", (unsigned long long)key);
         }
         node_entry = next;
@@ -477,12 +477,8 @@ void route_bgp_remove_conn(struct ETCP_CONN* conn) {
         e = e->next;
     }
 
-    if (need_withdraw) {
+    DEBUG_INFO(DEBUG_CATEGORY_BGP, "BGP peer removed: %s nodes=%d",
-        route_bgp_broadcast_withdraw(bgp, conn->peer_node_id, conn->instance->node_id, NULL);
+               conn->log_name, nodes_removed);
-    }
-
-    DEBUG_INFO(DEBUG_CATEGORY_BGP, "BGP peer removed: %s nodes=%d withdraw=%d",
-               conn->log_name, nodes_removed, need_withdraw);
 }
 
 
@@ -755,7 +751,16 @@ int route_bgp_process_nodeinfo(struct ROUTE_BGP* bgp, struct ETCP_CONN* from, co
     uint8_t new_ver = ni->ver;
 
     if (nodeinfo1 && (int8_t)(nodeinfo1->last_ver-new_ver)>=0) {
-        DEBUG_TRACE(DEBUG_CATEGORY_BGP, "NODEINFO ignored old ver: node=%016llx ver=%d<=%d from=%s",
+        int new_hops = ni->hop_count + 1;
+        if (new_hops <= MAX_HOPS) {
+            uint64_t hop_list[MAX_HOPS];
+            uint64_t* pkt_hops = (uint64_t*)((uint8_t*)ni + sizeof(struct NODEINFO) + dyn_size);
+            memcpy(hop_list, pkt_hops, ni->hop_count * 8);
+            hop_list[ni->hop_count] = from->peer_node_id;
+            route_bgp_remove_path_by_hop(nodeinfo1, from->peer_node_id);
+            route_bgp_add_path(nodeinfo1, from, hop_list, new_hops);
+        }
+        DEBUG_TRACE(DEBUG_CATEGORY_BGP, "NODEINFO old ver: node=%016llx ver=%d<=%d from=%s (paths updated)",
                     (unsigned long long)node_id, new_ver, nodeinfo1->last_ver, from->log_name);
         return 0;
     }
@@ -887,7 +892,7 @@ int route_bgp_process_withdraw(struct ROUTE_BGP* bgp, struct ETCP_CONN* sender,
         return 0;
     }
     int ret=route_bgp_remove_path_by_hop(nq, wd_source);
-    if (ret>0 || !nq->paths || (nq->paths && queue_entry_count(nq->paths) == 0)) {
+    if (ret == 1) {
         if (bgp->instance && bgp->instance->rt) route_delete(bgp->instance->rt, nq);
         if (bgp->instance->control_srv) control_server_notify_node_removed(bgp->instance->control_srv, node_id);
         nq->dirty = 1;