Implement reflect-kernel-metric.

Thanks to Pierre Pfister.

CHANGES

+babeld-1.5.2 (unreleased):
+
+  * Added support for reflecting metrics as kernel priorities.  Thanks to
+    Pierre Pfister.
+
 4 July 2014: babeld-1.5.1:
 
   * Added support for reading multiple configuration files by specifying

babeld.man

@@ -164,6 +164,13 @@ This specifies the priority value used when installing routes into the
 kernel, and is equivalent to the command-line option
 .BR \-k .
 .TP
+.BR reflect-kernel-metric " {" true | false }
+Reflect route metrics as kernel priorities.  The priority effectively used
+is
+.B kernel-priority
++
+.BR metric .
+.TP
 .BI allow-duplicates " priority"
 This allows duplicating external routes when their kernel priority is
 at least

configuration.c

@@ -656,6 +656,8 @@ parse_option(int c, gnc_t gnc, void *closure, char *token)
             random_id = b;
         else if(strcmp(token, "daemonise") == 0)
             do_daemonise = b;
+        else if(strcmp(token, "reflect-kernel-metric") == 0)
+            reflect_kernel_metric = b;
         else
             abort();
     } else if(strcmp(token, "protocol-group") == 0) {

route.c

@@ -42,7 +42,7 @@ THE SOFTWARE.
 
 struct babel_route **routes = NULL;
 static int route_slots = 0, max_route_slots = 0;
-int kernel_metric = 0;
+int kernel_metric = 0, reflect_kernel_metric = 0;
 int allow_duplicates = -1;
 int diversity_kind = DIVERSITY_NONE;
 int diversity_factor = 256;     /* in units of 1/256 */
@@ -373,7 +373,14 @@ route_stream_done(struct route_stream *stream)
 static int
 metric_to_kernel(int metric)
 {
-    return metric < INFINITY ? kernel_metric : KERNEL_INFINITY;
+	if(metric >= INFINITY) {
+		return KERNEL_INFINITY;
+	} else if(reflect_kernel_metric) {
+		int r = kernel_metric + metric;
+		return r >= KERNEL_INFINITY ? KERNEL_INFINITY : r;
+	} else {
+		return kernel_metric;
+	}
 }
 
 /* This is used to maintain the invariant that the installed route is at

route.h

@@ -47,7 +47,7 @@ struct babel_route {
 struct route_stream;
 
 extern struct babel_route **routes;
-extern int kernel_metric, allow_duplicates;
+extern int kernel_metric, allow_duplicates, reflect_kernel_metric;
 extern int diversity_kind, diversity_factor;
 extern int keep_unfeasible;