When there is a transition in permitted nodes, apply it to trackexithosts map

IOW, if we were using TrackExitHosts, and we added an excluded node or
removed a node from exitnodes, we wouldn't actually remove the mapping
that points us at the new node.

Also, note with an XXX022 comment a place that I think we are looking
at the wrong string.

src/or/config.c

@@ -1271,6 +1271,7 @@ options_act(or_options_t *old_options)
                "excluded node lists. Abandoning previous circuits.");
       circuit_mark_all_unused_circs();
       circuit_expire_all_dirty_circs();
+      addressmap_clear_excluded_trackexithosts(options);
     }
 
 /* How long should we delay counting bridge stats after becoming a bridge?

src/or/connection_edge.c

@@ -789,9 +789,6 @@ addressmap_ent_remove(const char *address, addressmap_entry_t *ent)
 static void
 clear_trackexithost_mappings(const char *exitname)
 {
-  /* XXXX022-1090 We need a variant of this that clears all mappings no longer
-     permitted because of changes to the ExcludeNodes, ExitNodes, or
-     ExcludeExitNodes settings. */
   char *suffix;
   size_t suffix_len;
   if (!addressmap || !exitname)
@@ -802,6 +799,7 @@ clear_trackexithost_mappings(const char *exitname)
   tor_strlower(suffix);
 
   STRMAP_FOREACH_MODIFY(addressmap, address, addressmap_entry_t *, ent) {
+    /* XXXX022 HEY!  Shouldn't this look at ent->new_address? */
     if (ent->source == ADDRMAPSRC_TRACKEXIT && !strcmpend(address, suffix)) {
       addressmap_ent_remove(address, ent);
       MAP_DEL_CURRENT(address);
@@ -811,6 +809,56 @@ clear_trackexithost_mappings(const char *exitname)
   tor_free(suffix);
 }
 
+/** Remove all TRACKEXIT mappings from the addressmap for which the target
+ * host is unknown or no longer allowed. */
+void
+addressmap_clear_excluded_trackexithosts(or_options_t *options)
+{
+  const routerset_t *allow_nodes = options->ExitNodes;
+  const routerset_t *exclude_nodes = options->_ExcludeExitNodesUnion;
+
+  if (!addressmap)
+    return;
+  if (routerset_is_empty(allow_nodes))
+    allow_nodes = NULL;
+  if (allow_nodes == NULL && routerset_is_empty(exclude_nodes))
+    return;
+
+  STRMAP_FOREACH_MODIFY(addressmap, address, addressmap_entry_t *, ent) {
+    size_t len;
+    const char *target = ent->new_address, *dot;
+    char *nodename;
+    routerinfo_t *ri; /* XXX023 Use node_t. */
+
+    if (strcmpend(target, ".exit")) {
+      /* Not a .exit mapping */
+      continue;
+    } else if (ent->source != ADDRMAPSRC_TRACKEXIT) {
+      /* Not a trackexit mapping. */
+      continue;
+    }
+    len = strlen(target);
+    if (len < 6)
+      continue; /* malformed. */
+    dot = target + len - 6; /* dot now points to just before .exit */
+    dot = strrchr(dot, '.'); /* dot now points to the . before .exit, or NULL */
+    if (!dot) {
+      nodename = tor_strndup(target, len-5);
+    } else {
+      nodename = tor_strndup(dot+1, strlen(dot+1)-5);
+    }
+    ri = router_get_by_nickname(nodename, 0);
+    tor_free(nodename);
+    if (!ri ||
+        (allow_nodes && !routerset_contains_router(allow_nodes, ri)) ||
+        routerset_contains_router(exclude_nodes, ri)) {
+      /* We don't know this one, or we want to be rid of it. */
+      addressmap_ent_remove(address, ent);
+      MAP_DEL_CURRENT(address);
+    }
+  } STRMAP_FOREACH_END;
+}
+
 /** Remove all entries from the addressmap that were set via the
  * configuration file or the command line. */
 void

src/or/connection_edge.h

@@ -62,6 +62,7 @@ int connection_ap_process_transparent(edge_connection_t *conn);
 int address_is_invalid_destination(const char *address, int client);
 
 void addressmap_init(void);
+void addressmap_clear_excluded_trackexithosts(or_options_t *options);
 void addressmap_clean(time_t now);
 void addressmap_clear_configured(void);
 void addressmap_clear_transient(void);

src/or/routerlist.c

@@ -5474,7 +5474,7 @@ routerset_needs_geoip(const routerset_t *set)
 }
 
 /** Return true iff there are no entries in <b>set</b>. */
-static int
+int
 routerset_is_empty(const routerset_t *set)
 {
   return !set || smartlist_len(set->list) == 0;

src/or/routerlist.h

@@ -167,6 +167,7 @@ int routerset_parse(routerset_t *target, const char *s,
 void routerset_union(routerset_t *target, const routerset_t *source);
 int routerset_is_list(const routerset_t *set);
 int routerset_needs_geoip(const routerset_t *set);
+int routerset_is_empty(const routerset_t *set);
 int routerset_contains_router(const routerset_t *set, routerinfo_t *ri);
 int routerset_contains_routerstatus(const routerset_t *set,
                                     routerstatus_t *rs);