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- /*
- graph.c -- graph algorithms
- Copyright (C) 2001-2014 Guus Sliepen <guus@tinc-vpn.org>,
- 2001-2005 Ivo Timmermans
- 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.,
- 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- */
- /* 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 "system.h"
- #include "avl_tree.h"
- #include "conf.h"
- #include "connection.h"
- #include "device.h"
- #include "edge.h"
- #include "graph.h"
- #include "logger.h"
- #include "netutl.h"
- #include "node.h"
- #include "process.h"
- #include "protocol.h"
- #include "subnet.h"
- #include "utils.h"
- #include "xalloc.h"
- static bool graph_changed = true;
- /* Implementation of Kruskal's algorithm.
- Running time: O(EN)
- Please note that sorting on weight is already done by add_edge().
- */
- static 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;
- bool skipped;
- /* Clear MST status on connections */
- for(node = connection_tree->head; node; node = node->next) {
- c = node->data;
- c->status.mst = false;
- }
- /* Do we have something to do at all? */
- if(!edge_weight_tree->head)
- return;
- ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Running Kruskal's algorithm:");
- /* Clear visited status on nodes */
- for(node = node_tree->head; node; node = node->next) {
- n = node->data;
- n->status.visited = false;
- nodes++;
- }
- /* Starting point */
- for(node = edge_weight_tree->head; node; node = node->next) {
- e = node->data;
- if(e->from->status.reachable) {
- e->from->status.visited = true;
- break;
- }
- }
- /* Add safe edges */
- for(skipped = false, node = edge_weight_tree->head; node; node = next) {
- next = node->next;
- e = node->data;
- if(!e->reverse || e->from->status.visited == e->to->status.visited) {
- skipped = true;
- continue;
- }
- e->from->status.visited = true;
- e->to->status.visited = true;
- if(e->connection)
- e->connection->status.mst = true;
- if(e->reverse->connection)
- e->reverse->connection->status.mst = true;
- safe_edges++;
- ifdebug(SCARY_THINGS) logger(LOG_DEBUG, " Adding edge %s - %s weight %d", e->from->name,
- e->to->name, e->weight);
- if(skipped) {
- skipped = false;
- next = edge_weight_tree->head;
- continue;
- }
- }
- ifdebug(SCARY_THINGS) logger(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)
- */
- static void sssp_bfs(void) {
- avl_node_t *node, *next, *to;
- edge_t *e;
- node_t *n;
- list_t *todo_list;
- list_node_t *from, *todonext;
- bool indirect;
- char *name;
- char *address, *port;
- char *envp[8] = {NULL};
- int i;
- todo_list = list_alloc(NULL);
- /* Clear visited status on nodes */
- for(node = node_tree->head; node; node = node->next) {
- n = node->data;
- n->status.visited = false;
- n->status.indirect = true;
- }
- /* Begin with myself */
- myself->status.visited = true;
- myself->status.indirect = false;
- myself->nexthop = myself;
- myself->prevedge = NULL;
- myself->via = myself;
- list_insert_head(todo_list, myself);
- /* Loop while todo_list is filled */
- for(from = todo_list->head; from; from = todonext) { /* "from" is the node from which we start */
- n = from->data;
- for(to = n->edge_tree->head; to; to = to->next) { /* "to" is the edge connected to "from" */
- e = to->data;
- if(!e->reverse)
- continue;
- /* Situation:
- /
- /
- ----->(n)---e-->(e->to)
- \
- \
- Where e is an edge, (n) and (e->to) are nodes.
- n->address is set to the e->address of the edge left of n to n.
- We are currently examining the edge e right of n from n:
- - If edge e provides for better reachability of e->to, update
- e->to and (re)add it to the todo_list to (re)examine the reachability
- of nodes behind it.
- */
- indirect = n->status.indirect || e->options & OPTION_INDIRECT;
- if(e->to->status.visited
- && (!e->to->status.indirect || indirect))
- continue;
- // Only update nexthop the first time we visit this node.
- if(!e->to->status.visited)
- e->to->nexthop = (n->nexthop == myself) ? e->to : n->nexthop;
- e->to->status.visited = true;
- e->to->status.indirect = indirect;
- e->to->prevedge = e;
- e->to->via = indirect ? n->via : e->to;
- e->to->options = e->options;
- if(e->to->address.sa.sa_family == AF_UNSPEC && e->address.sa.sa_family != AF_UNKNOWN)
- update_node_udp(e->to, &e->address);
- list_insert_tail(todo_list, e->to);
- }
- todonext = from->next;
- list_delete_node(todo_list, from);
- }
- list_free(todo_list);
- /* Check reachability status. */
- for(node = node_tree->head; node; node = next) {
- next = node->next;
- n = node->data;
- if(n->status.visited != n->status.reachable) {
- n->status.reachable = !n->status.reachable;
- if(n->status.reachable) {
- ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became reachable",
- n->name, n->hostname);
- } else {
- ifdebug(TRAFFIC) logger(LOG_DEBUG, "Node %s (%s) became unreachable",
- n->name, n->hostname);
- }
- /* TODO: only clear status.validkey if node is unreachable? */
- n->status.validkey = false;
- n->last_req_key = 0;
- n->maxmtu = MTU;
- n->minmtu = 0;
- n->mtuprobes = 0;
- if(n->mtuevent) {
- event_del(n->mtuevent);
- n->mtuevent = NULL;
- }
- xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
- xasprintf(&envp[1], "DEVICE=%s", device ? : "");
- xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
- xasprintf(&envp[3], "NODE=%s", n->name);
- sockaddr2str(&n->address, &address, &port);
- xasprintf(&envp[4], "REMOTEADDRESS=%s", address);
- xasprintf(&envp[5], "REMOTEPORT=%s", port);
- xasprintf(&envp[6], "NAME=%s", myself->name);
- execute_script(n->status.reachable ? "host-up" : "host-down", envp);
- xasprintf(&name,
- n->status.reachable ? "hosts/%s-up" : "hosts/%s-down",
- n->name);
- execute_script(name, envp);
- free(name);
- free(address);
- free(port);
- for(i = 0; i < 7; i++)
- free(envp[i]);
- subnet_update(n, NULL, n->status.reachable);
- if(!n->status.reachable) {
- update_node_udp(n, NULL);
- memset(&n->status, 0, sizeof n->status);
- n->options = 0;
- } else if(n->connection) {
- send_ans_key(n);
- }
- }
- }
- }
- void graph(void) {
- subnet_cache_flush();
- sssp_bfs();
- mst_kruskal();
- graph_changed = true;
- }
- /* Dump nodes and edges to a graphviz file.
-
- The file can be converted to an image with
- dot -Tpng graph_filename -o image_filename.png -Gconcentrate=true
- */
- void dump_graph(void) {
- avl_node_t *node;
- node_t *n;
- edge_t *e;
- char *filename = NULL, *tmpname = NULL;
- FILE *file, *pipe = NULL;
-
- if(!graph_changed || !get_config_string(lookup_config(config_tree, "GraphDumpFile"), &filename))
- return;
- graph_changed = false;
- ifdebug(PROTOCOL) logger(LOG_NOTICE, "Dumping graph");
-
- if(filename[0] == '|') {
- file = pipe = popen(filename + 1, "w");
- } else {
- xasprintf(&tmpname, "%s.new", filename);
- file = fopen(tmpname, "w");
- }
- if(!file) {
- logger(LOG_ERR, "Unable to open graph dump file %s: %s", filename, strerror(errno));
- free(filename);
- free(tmpname);
- return;
- }
- fprintf(file, "digraph {\n");
-
- /* dump all nodes first */
- for(node = node_tree->head; node; node = node->next) {
- n = node->data;
- fprintf(file, " %s [label = \"%s\"];\n", n->name, n->name);
- }
- /* now dump all edges */
- for(node = edge_weight_tree->head; node; node = node->next) {
- e = node->data;
- fprintf(file, " %s -> %s;\n", e->from->name, e->to->name);
- }
- fprintf(file, "}\n");
-
- if(pipe) {
- pclose(pipe);
- } else {
- fclose(file);
- #ifdef HAVE_MINGW
- unlink(filename);
- #endif
- if(rename(tmpname, filename))
- logger(LOG_ERR, "Could not rename %s to %s: %s\n", tmpname, filename, strerror(errno));
- free(tmpname);
- }
- free(filename);
- }
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