Implement -u: keep unfeasible routes.

This is useful in order to provide extra information to a graphic
front-end.  In can cause the RIB to explode in some pathological cases,
so it is not the default.

babeld.c

@@ -125,7 +125,7 @@ main(int argc, char **argv)
     protocol_port = 6697;
 
     while(1) {
-        opt = getopt(argc, argv, "m:p:h:H:i:k:A:PsS:d:g:lwt:T:c:C:DL:I:");
+        opt = getopt(argc, argv, "m:p:h:H:i:k:A:PsuS:d:g:lwt:T:c:C:DL:I:");
         if(opt < 0)
             break;
 
@@ -180,6 +180,9 @@ main(int argc, char **argv)
         case 's':
             split_horizon = 0;
             break;
+        case 'u':
+            keep_unfeasible = 1;
+            break;
         case 'S':
             state_file = optarg;
             break;
@@ -776,11 +779,11 @@ main(int argc, char **argv)
             "                "
             "[-h hello] [-H wired_hello] [-i idle_hello]\n"
             "                "
-            "[-k metric] [-A metric] [-s] [-P] [-l] [-w] [-d level] [-g port]\n"
+            "[-k metric] [-A metric] [-s] [-P] [-l] [-w] [-u] [-g port]\n"
             "                "
             "[-t table] [-T table] [-c file] [-C statement]\n"
             "                "
-            "[-D] [-L logfile] [-I pidfile]\n"
+            "[-d level] [-D] [-L logfile] [-I pidfile]\n"
             "                "
             "[id] interface...\n",
             argv[0]);

route.c

@@ -44,6 +44,7 @@ struct route *routes = NULL;
 int numroutes = 0, maxroutes = 0;
 int kernel_metric = 0;
 int allow_duplicates = -1;
+int keep_unfeasible = 0;
 
 struct route *
 find_route(const unsigned char *prefix, unsigned char plen,
@@ -455,7 +456,7 @@ update_route(const unsigned char *a, const unsigned char *p, unsigned char plen,
         }
 
         route->src = src;
-        if(feasible && refmetric < INFINITY)
+        if((feasible || keep_unfeasible) && refmetric < INFINITY)
             route->time = now.tv_sec;
         route->seqno = seqno;
         route->refmetric = refmetric;
@@ -475,8 +476,10 @@ update_route(const unsigned char *a, const unsigned char *p, unsigned char plen,
             return NULL;
         if(!feasible) {
             send_unfeasible_request(neigh, 0, seqno, metric, src);
-            return NULL;
+            if(!keep_unfeasible)
+                return NULL;
         }
+
         if(numroutes >= maxroutes) {
             struct route *new_routes;
             int n = maxroutes < 1 ? 8 : 2 * maxroutes;

route.h

@@ -41,6 +41,7 @@ route_metric(const struct route *route)
 extern struct route *routes;
 extern int numroutes, maxroutes;
 extern int kernel_metric, allow_duplicates;
+extern int keep_unfeasible;
 
 struct route *find_route(const unsigned char *prefix, unsigned char plen,
                          struct neighbour *neigh, const unsigned char *nexthop);