Add reference counting to the source table.

This avoids the quadratic behaviour of expire_sources.

route.c

@@ -237,13 +237,17 @@ flush_route(struct route *route)
 
     if(lost)
         route_lost(src, oldmetric);
+
+    release_source(src);
 }
 
 void
 flush_all_routes()
 {
+    int i;
+
     /* Start from the end, to avoid shifting the table. */
-    int i = route_slots - 1;
+    i = route_slots - 1;
     while(i >= 0) {
         while(i < route_slots) {
         /* Uninstall first, to avoid calling route_lost. */
@@ -253,6 +257,8 @@ flush_all_routes()
         }
         i--;
     }
+
+    check_sources_released();
 }
 
 void
@@ -326,24 +332,6 @@ for_all_installed_routes(void (*f)(struct route*, void*), void *closure)
     }
 }
 
-/* Find any route with a given source.  This should go when we fix our
-   data structures. */
-struct route *
-find_route_with_source(struct source *src)
-{
-    int i;
-
-    for(i = 0; i < route_slots; i++) {
-        struct route *r = routes[i];
-        while(r) {
-            if(r->src == src)
-                return r;
-            r = r->next;
-        }
-    }
-    return NULL;
-}
-
 static int
 metric_to_kernel(int metric)
 {
@@ -723,7 +711,7 @@ update_route(const unsigned char *a, const unsigned char *p, unsigned char plen,
             }
         }
 
-        route->src = src;
+        route->src = retain_source(src);
         if((feasible || keep_unfeasible) && refmetric < INFINITY)
             route->time = now.tv_sec;
         route->seqno = seqno;
@@ -738,6 +726,7 @@ update_route(const unsigned char *a, const unsigned char *p, unsigned char plen,
         if(!feasible)
             send_unfeasible_request(neigh, route->installed && route_old(route),
                                     seqno, metric, src);
+        release_source(oldsrc);
     } else {
         struct route *new_route;
 
@@ -756,7 +745,7 @@ update_route(const unsigned char *a, const unsigned char *p, unsigned char plen,
             return NULL;
         }
 
-        route->src = src;
+        route->src = retain_source(src);
         route->refmetric = refmetric;
         route->cost = neighbour_cost(neigh);
         route->add_metric = add_metric;

route.h

@@ -75,7 +75,6 @@ void flush_neighbour_routes(struct neighbour *neigh);
 void flush_interface_routes(struct interface *ifp, int v4only);
 void for_all_routes(void (*f)(struct route*, void*), void *closure);
 void for_all_installed_routes(void (*f)(struct route*, void*), void *closure);
-struct route *find_route_with_source(struct source *src);
 void install_route(struct route *route);
 void uninstall_route(struct route *route);
 void switch_route(struct route *old, struct route *new);

source.c

@@ -24,6 +24,7 @@ THE SOFTWARE.
 #include <stdio.h>
 #include <string.h>
 #include <sys/time.h>
+#include <assert.h>
 
 #include "babeld.h"
 #include "util.h"
@@ -67,17 +68,32 @@ find_source(const unsigned char *id, const unsigned char *p, unsigned char plen,
     src->seqno = seqno;
     src->metric = INFINITY;
     src->time = now.tv_sec;
+    src->route_count = 0;
     src->next = srcs;
     srcs = src;
     return src;
 }
 
+struct source *
+retain_source(struct source *src)
+{
+    assert(src->route_count < 0xffff);
+    src->route_count++;
+    return src;
+}
+
+void
+release_source(struct source *src)
+{
+    assert(src->route_count > 0);
+    src->route_count--;
+}
+
 int
 flush_source(struct source *src)
 {
-    /* This is absolutely horrible -- it makes expire_sources quadratic.
-       But it's not called very often. */
-    if(find_route_with_source(src))
+    if(src->route_count > 0)
+        /* The source is in use by a route. */
         return 0;
 
     if(srcs == src) {
@@ -128,3 +144,17 @@ expire_sources()
         src = src->next;
     }
 }
+
+void
+check_sources_released(void)
+{
+    struct source *src;
+
+    for(src = srcs; src; src = src->next) {
+        if(src->route_count != 0)
+            fprintf(stderr, "Warning: source %s %s has refcount %d.\n",
+                    format_eui64(src->id),
+                    format_prefix(src->prefix, src->plen),
+                    (int)src->route_count);
+    }
+}

source.h

@@ -29,6 +29,7 @@ struct source {
     unsigned char plen;
     unsigned short seqno;
     unsigned short metric;
+    unsigned short route_count;
     time_t time;
 };
 
@@ -36,7 +37,10 @@ struct source *find_source(const unsigned char *id,
                            const unsigned char *p,
                            unsigned char plen,
                            int create, unsigned short seqno);
+struct source *retain_source(struct source *src);
+void release_source(struct source *src);
 int flush_source(struct source *src);
 void update_source(struct source *src,
                    unsigned short seqno, unsigned short metric);
 void expire_sources(void);
+void check_sources_released(void);