Be slightly less agressive about sending requests in route_lost.

route.c

@@ -964,8 +964,12 @@ route_lost(struct source *src, unsigned oldmetric)
     if(new_route) {
         consider_route(new_route);
     } else if(oldmetric < INFINITY) {
-        /* Complain loudly. */
+        /* Avoid creating a blackhole. */
         send_update_resend(NULL, src->prefix, src->plen);
+        /* If the route was usable enough, try to get an alternate one.
+           If it was not, we could be dealing with oscillations around
+           the value of INFINITY. */
+        if(oldmetric <= INFINITY / 2)
             send_request_resend(NULL, src->prefix, src->plen,
                                 src->metric >= INFINITY ?
                                 src->seqno : seqno_plus(src->seqno, 1),