Detect and prevent two nodes with the same Name being on the VPN simultaneously.

In this situation, the two nodes will start fighting over the edges they announced.
When we have to contradict both ADD_EDGE and DEL_EDGE messages, we log a warning,
and with 25% chance per PingTimeout we quit.

src/net.c

@@ -44,6 +44,8 @@ bool do_purge = false;
 volatile bool running = false;
 
 time_t now = 0;
+int contradicting_add_edge = 0;
+int contradicting_del_edge = 0;
 
 /* Purge edges and subnets of unreachable nodes. Use carefully. */
 
@@ -415,6 +417,19 @@ int main_loop(void) {
 				send_key_changed(broadcast, myself);
 				keyexpires = now + keylifetime;
 			}
+
+			if(contradicting_del_edge && contradicting_add_edge) {
+				logger(LOG_WARNING, "Possible node with same Name as us!");
+
+				if(rand() % 3 == 0) {
+					logger(LOG_ERR, "Shutting down, check configuration of all nodes for duplicate Names!");
+					running = false;
+					break;
+				}
+
+				contradicting_add_edge = 0;
+				contradicting_del_edge = 0;
+			}
 		}
 
 		if(sigalrm) {

src/net.h

@@ -115,6 +115,8 @@ extern bool do_prune;
 extern bool do_purge;
 extern char *myport;
 extern time_t now;
+extern int contradicting_add_edge;
+extern int contradicting_del_edge;
 
 /* Yes, very strange placement indeed, but otherwise the typedefs get all tangled up */
 #include "connection.h"

src/protocol_edge.c

@@ -133,6 +133,7 @@ bool add_edge_h(connection_t *c) {
 	} else if(from == myself) {
 		ifdebug(PROTOCOL) logger(LOG_WARNING, "Got %s from %s (%s) for ourself which does not exist",
 				   "ADD_EDGE", c->name, c->hostname);
+		contradicting_add_edge++;
 		e = new_edge();
 		e->from = from;
 		e->to = to;
@@ -229,6 +230,7 @@ bool del_edge_h(connection_t *c) {
 	if(e->from == myself) {
 		ifdebug(PROTOCOL) logger(LOG_WARNING, "Got %s from %s (%s) for ourself",
 				   "DEL_EDGE", c->name, c->hostname);
+		contradicting_del_edge++;
 		send_add_edge(c, e);	/* Send back a correction */
 		return true;
 	}