Make code to detect two nodes with the same Name less triggerhappy.

First of all, if there really are two nodes with the same name, much
more than 10 contradicting ADD_EDGE and DEL_EDGE messages will be sent.
Also, we forgot to reset the counters when nothing happened.

In case there is a ADD_EDGE/DEL_EDGE storm, we do not shut down, but
sleep an increasing amount of time, allowing tinc to recover gracefully
from temporary failures.

diff --git a/src/net.c b/src/net.c
index c5193c5d67a3726213eac3c6971b712c674865bc..b3f924ad661232312427abf929aadc6b4af1e361 100644 (file)
--- a/src/net.c
+++ b/src/net.c
@@ -50,6 +50,7 @@ bool graph_dump = false;
 time_t now = 0;
 int contradicting_add_edge = 0;
 int contradicting_del_edge = 0;
+static int sleeptime = 10;
 
 /* Purge edges and subnets of unreachable nodes. Use carefully. */
 
@@ -464,18 +465,25 @@ int main_loop(void) {
                                keyexpires = now + keylifetime;
                        }
 
-                       if(contradicting_del_edge > 10 && contradicting_add_edge > 10) {
-                               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;
+                       /* Detect ADD_EDGE/DEL_EDGE storms that are caused when
+                        * two tinc daemons with the same name are on the VPN.
+                        * If so, sleep a while. If this happens multiple times
+                        * in a row, sleep longer. */
+
+                       if(contradicting_del_edge > 100 && contradicting_add_edge > 100) {
+                               logger(LOG_WARNING, "Possible node with same Name as us! Sleeping %d seconds.", sleeptime);
+                               sleep(sleeptime);
+                               sleeptime *= 2;
+                               if(sleeptime < 0)
+                                       sleeptime = 3600;
+                       } else {
+                               sleeptime /= 2;
+                               if(sleeptime < 10)
+                                       sleeptime = 10;
                        }
+
+                       contradicting_add_edge = 0;
+                       contradicting_del_edge = 0;
                }
 
                if(sigalrm) {