Implement poison routes.

We now distinguish between the timeout timer and the gc timer, and announce
infinity until gc time.  Timeout is set to 120 seconds, gc to 90.

babel.c

@@ -708,18 +708,19 @@ expire_routes(void)
     while(i < numroutes) {
         struct route *route = &routes[i];
 
-        if(route->time < now.tv_sec - 180) {
+        if(route->blackhole_time > 0 &&
+           route->blackhole_time < now.tv_sec - 65) {
             flush_route(route);
             continue;
         }
 
+        if(route->time < now.tv_sec - 120)
+            update_route(route->dest->address, ((route->seqno + 1) & 0xFF),
+                         INFINITY, route->nexthop, NULL, 0);
+        else
             update_route_metric(route);
 
-        if(route->refmetric >= INFINITY) {
-            flush_route(route);
-            continue;
-        }
-        if(route->installed) {
+        if(route->installed && route->refmetric < INFINITY) {
             if(route->time <= now.tv_sec - 90)
                 send_unicast_request(route->nexthop, route->dest);
         }

route.c

@@ -306,8 +306,13 @@ update_route(const unsigned char *d, int seqno, int refmetric,
         oldseqno = route->seqno;
         oldmetric = route->metric;
         route->time = now.tv_sec;
-        if(route->refmetric >= INFINITY && refmetric < INFINITY)
+        if(refmetric < INFINITY) {
+            route->blackhole_time = 0;
+            if(route->refmetric >= INFINITY)
                 route->origtime = now.tv_sec;
+        } else if(route->blackhole_time <= 0) {
+            route->blackhole_time = now.tv_sec;
+        }
         route->seqno = seqno;
         route->refmetric = refmetric;
         change_route_metric(route, metric);
@@ -342,6 +347,7 @@ update_route(const unsigned char *d, int seqno, int refmetric,
         route->nexthop = nexthop;
         route->time = now.tv_sec;
         route->origtime = now.tv_sec;
+        route->blackhole_time = 0;
         route->installed = 0;
         numroutes++;
         for(i = 0; i < numpxroutes; i++)

route.h

@@ -30,6 +30,7 @@ struct route {
     struct neighbour *nexthop;
     int time;
     int origtime;
+    int blackhole_time;
     int installed;
 };