+++ /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