update-tunnelbroker: work around timing issue

Looks like fetch command has a timing issue with the tunnelbroker
endpoint... We have to try several times to work around this.
Consider the update failed on third error.

Author: eworm-de

update-tunnelbroker

@@ -32,17 +32,26 @@
   :local InterfaceVal [ /interface/6to4/get $Interface ];
 
   :if ($PublicAddress != $InterfaceVal->"local-address") do={
+    :local I 0;
+    :local Success false;
     :local Comment [ $ParseKeyValueStore ($InterfaceVal->"comment") ];
 
     :if ([ $CertificateAvailable "Starfield Secure Certificate Authority - G2" ] = false) do={
       $LogPrintExit2 error $0 ("Downloading required certificate failed.") true;
     }
     $LogPrintExit2 info $0 ("Local address changed, sending UPDATE to tunnelbroker! New address: " . $PublicAddress) false;
-    :do {
-      /tool/fetch check-certificate=yes-without-crl \
-          ("https://ipv4.tunnelbroker.net/nic/update\?hostname=" . $Comment->"id") \
-          user=($Comment->"user") password=($Comment->"pass") output=none as-value;
-    } on-error={
+    :while ($I < 3 && $Success = false) do={
+      :do {
+        /tool/fetch check-certificate=yes-without-crl \
+            ("https://ipv4.tunnelbroker.net/nic/update\?hostname=" . $Comment->"id") \
+            user=($Comment->"user") password=($Comment->"pass") output=none as-value;
+        :set Success true;
+      } on-error={
+        :delay 10s;
+        :set I ($I + 1);
+      }
+    }
+    :if ($Success = false) do={
       $LogPrintExit2 error $0 ("Failed sending the local address to tunnelbroker! Wrong credentials?") true;
     }
     /interface/6to4/set $Interface local-address=$PublicAddress;