--- /dev/null
+/*
+ graph.c -- graph algorithms
+ Copyright (C) 2001-2002 Guus Sliepen <guus@sliepen.warande.net>,
+ 2001-2002 Ivo Timmermans <itimmermans@bigfoot.com>
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ $Id: graph.c,v 1.1 2002/04/28 12:46:26 zarq Exp $
+*/
+
+/* We need to generate two trees from the graph:
+
+ 1. A minimum spanning tree for broadcasts,
+ 2. A single-source shortest path tree for unicasts.
+
+ Actually, the first one alone would suffice but would make unicast packets
+ take longer routes than necessary.
+
+ For the MST algorithm we can choose from Prim's or Kruskal's. I personally
+ favour Kruskal's, because we make an extra AVL tree of edges sorted on
+ weights (metric). That tree only has to be updated when an edge is added or
+ removed, and during the MST algorithm we just have go linearly through that
+ tree, adding safe edges until #edges = #nodes - 1. The implementation here
+ however is not so fast, because I tried to avoid having to make a forest and
+ merge trees.
+
+ For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
+ simple breadth-first search is presented here.
+
+ The SSSP algorithm will also be used to determine whether nodes are directly,
+ indirectly or not reachable from the source. It will also set the correct
+ destination address and port of a node if possible.
+*/
+
+#include "config.h"
+#include <string.h>
+#if defined(HAVE_FREEBSD) || defined(HAVE_OPENBSD)
+ #include <sys/param.h>
+#endif
+#include <netinet/in.h>
+
+#include <avl_tree.h>
+#include <hooks.h>
+#include <utils.h>
+
+#include "interface.h"
+#include "netutl.h"
+#include "node.h"
+#include "edge.h"
+#include "connection.h"
+#include "logging.h"
+
+#include "system.h"
+
+/* Implementation of Kruskal's algorithm.
+ Running time: O(EN)
+ Please note that sorting on weight is already done by add_edge().
+*/
+
+void mst_kruskal(void)
+{
+ avl_node_t *node, *next;
+ edge_t *e;
+ node_t *n;
+ connection_t *c;
+ int nodes = 0;
+ int safe_edges = 0;
+ int skipped;
+
+ /* Clear MST status on connections */
+
+ for(node = connection_tree->head; node; node = node->next)
+ {
+ c = (connection_t *)node->data;
+ c->status.mst = 0;
+ }
+
+ /* Do we have something to do at all? */
+
+ if(!edge_weight_tree->head)
+ return;
+
+ log(DEBUG_SCARY_THINGS, TLOG_DEBUG,
+ _("Running Kruskal's algorithm:"));
+
+ /* Clear visited status on nodes */
+
+ for(node = node_tree->head; node; node = node->next)
+ {
+ n = (node_t *)node->data;
+ n->status.visited = 0;
+ nodes++;
+ }
+
+ /* Starting point */
+
+ ((edge_t *)edge_weight_tree->head->data)->from.node->status.visited = 1;
+
+ /* Add safe edges */
+
+ for(skipped = 0, node = edge_weight_tree->head; node; node = next)
+ {
+ next = node->next;
+ e = (edge_t *)node->data;
+
+ if(e->from.node->status.visited == e->to.node->status.visited)
+ {
+ skipped = 1;
+ continue;
+ }
+
+ e->from.node->status.visited = 1;
+ e->to.node->status.visited = 1;
+ if(e->connection)
+ e->connection->status.mst = 1;
+
+ safe_edges++;
+
+ if(debug_lvl >= DEBUG_SCARY_THINGS)
+ syslog(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from.node->name, e->to.node->name, e->weight);
+
+ if(skipped)
+ {
+ next = edge_weight_tree->head;
+ continue;
+ }
+ }
+
+ if(debug_lvl >= DEBUG_SCARY_THINGS)
+ syslog(LOG_DEBUG, "Done, counted %d nodes and %d safe edges.", nodes, safe_edges);
+}
+
+/* Implementation of a simple breadth-first search algorithm.
+ Running time: O(E)
+*/
+
+void sssp_bfs(void)
+{
+ avl_node_t *node, *from, *next, *to;
+ edge_t *e;
+ node_t *n;
+ halfconnection_t to_hc, from_hc;
+ avl_tree_t *todo_tree;
+ int indirect;
+
+ todo_tree = avl_alloc_tree(NULL, NULL);
+
+ /* Clear visited status on nodes */
+
+ for(node = node_tree->head; node; node = node->next)
+ {
+ n = (node_t *)node->data;
+ n->status.visited = 0;
+ n->status.indirect = 1;
+ }
+
+ /* Begin with myself */
+
+ myself->status.visited = 1;
+ myself->status.indirect = 0;
+ myself->nexthop = myself;
+ myself->via = myself;
+ node = avl_alloc_node();
+ node->data = myself;
+ avl_insert_top(todo_tree, node);
+
+ /* Loop while todo_tree is filled */
+
+ while(todo_tree->head)
+ {
+ for(from = todo_tree->head; from; from = next) /* "from" is the node from which we start */
+ {
+ next = from->next;
+ n = (node_t *)from->data;
+
+ for(to = n->edge_tree->head; to; to = to->next) /* "to" is the edge connected to "from" */
+ {
+ e = (edge_t *)to->data;
+
+ if(e->from.node == n) /* "from_hc" is the halfconnection with .node == from */
+ to_hc = e->to, from_hc = e->from;
+ else
+ to_hc = e->from, from_hc = e->to;
+
+ /* Situation:
+
+ /
+ /
+ ------(n)from_hc-----to_hc
+ \
+ \
+
+ n->address is set to the to_hc.udpaddress of the edge left of n.
+ We are currently examining the edge right of n:
+
+ - If from_hc.udpaddress != n->address, then to_hc.node is probably
+ not reachable for the nodes left of n. We do as if the indirectdata
+ flag is set on edge e.
+ - If edge e provides for better reachability of to_hc.node, update
+ to_hc.node and (re)add it to the todo_tree to (re)examine the reachability
+ of nodes behind it.
+ */
+
+ indirect = n->status.indirect || e->options & OPTION_INDIRECT || ((n != myself) && sockaddrcmp(&n->address, &from_hc.udpaddress));
+
+ if(to_hc.node->status.visited && (!to_hc.node->status.indirect || indirect))
+ continue;
+
+ to_hc.node->status.visited = 1;
+ to_hc.node->status.indirect = indirect;
+ to_hc.node->nexthop = (n->nexthop == myself) ? to_hc.node : n->nexthop;
+ to_hc.node->via = indirect ? n->via : to_hc.node;
+ to_hc.node->options = e->options;
+ if(sockaddrcmp(&to_hc.node->address, &to_hc.udpaddress))
+ {
+ node = avl_unlink(node_udp_tree, to_hc.node);
+ to_hc.node->address = to_hc.udpaddress;
+ if(to_hc.node->hostname)
+ free(to_hc.node->hostname);
+ to_hc.node->hostname = sockaddr2hostname(&to_hc.udpaddress);
+ avl_insert_node(node_udp_tree, node);
+ }
+ node = avl_alloc_node();
+ node->data = to_hc.node;
+ avl_insert_before(todo_tree, from, node);
+ }
+
+ avl_delete_node(todo_tree, from);
+ }
+ }
+
+ avl_free_tree(todo_tree);
+
+ /* Check reachability status. */
+
+ for(node = node_tree->head; node; node = next)
+ {
+ next = node->next;
+ n = (node_t *)node->data;
+
+ if(n->status.visited)
+ {
+ if(!n->status.reachable)
+ {
+ if(debug_lvl >= DEBUG_TRAFFIC)
+ syslog(LOG_ERR, _("Node %s (%s) became reachable"), n->name, n->hostname);
+ n->status.reachable = 1;
+ run_hooks("node-visible", n);
+ }
+ }
+ else
+ {
+ if(n->status.reachable)
+ {
+ if(debug_lvl >= DEBUG_TRAFFIC)
+ syslog(LOG_DEBUG, _("Node %s (%s) became unreachable"), n->name, n->hostname);
+ n->status.reachable = 0;
+ n->status.validkey = 0;
+ n->status.waitingforkey = 0;
+ n->sent_seqno = 0;
+ run_hooks("node-invisible", n);
+ }
+ }
+ }
+}
+
+void graph(void)
+{
+ mst_kruskal();
+ sssp_bfs();
+}
projects / tinc / blobdiff