Added graph dumping ability based on Markus Goetz's patch.

THANKS

@@ -18,6 +18,7 @@ We would like to thank the following people for their contributions to tinc:
 * Mads Kiilerich
 * Marc A. Lehmann
 * Mark Glines
+* Markus Goetz
 * Martin Kihlgren
 * Matias Carrasco
 * Miles Nordin

src/graph.c

@@ -47,6 +47,7 @@
 #include "system.h"
 
 #include "avl_tree.h"
+#include "config.h"
 #include "connection.h"
 #include "device.h"
 #include "edge.h"
@@ -57,6 +58,8 @@
 #include "subnet.h"
 #include "utils.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().
@@ -306,4 +309,65 @@ void graph(void)
 {
 	mst_kruskal();
 	sssp_bfs();
+	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;
+	
+	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 = popen(filename + 1, "w");
+	} else {
+		asprintf(&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(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");	
+	
+	fclose(file);
+
+	if(filename[0] != '|') {
+		rename(tmpname, filename);
+		free(tmpname);
+	}
 }

src/graph.h

@@ -26,5 +26,6 @@
 extern void graph(void);
 extern void mst_kruskal(void);
 extern void sssp_bfs(void);
+extern void dump_graph(void);
 
 #endif /* __TINC_GRAPH_H__ */

src/net.c

@@ -354,13 +354,15 @@ int main_loop(void)
 	fd_set readset, writeset;
 	struct timeval tv;
 	int r, maxfd;
-	time_t last_ping_check, last_config_check;
+	time_t last_ping_check, last_config_check, last_graph_dump;
 	event_t *event;
 
 	cp();
 
 	last_ping_check = now;
 	last_config_check = now;
+	last_graph_dump = now;
+	
 	srand(now);
 
 	running = true;
@@ -478,6 +480,13 @@ int main_loop(void)
 			
 			try_outgoing_connections();
 		}
+		
+		/* Dump graph if wanted every 60 seconds*/
+
+		if(last_graph_dump + 60 < now) {
+			dump_graph();
+			last_graph_dump = now;
+		}
 	}
 
 	return 0;