When TrackExitHosts changes, remove all no-longer-valid mappings

This bug couldn't happen when TrackExitHosts changed in torrc, since
the SIGHUP to reload the torrc would clear out all the transient
addressmap entries before.  But if you used SETCONF to change
TrackExitHosts, old entries would be left alone: that's a bug, and so
this is a bugfix on Tor 0.1.0.1-rc.

changes/bug1345

@@ -1,4 +1,7 @@
   o Minor bugfixes:
-    - On SIGHUP, do not clear out all TrackExitHost mappings, client DNS
+    - On SIGHUP, do not clear out all TrackHostExits mappings, client DNS
       cache entries, and virtual address mappings: that's what NEWNYM is
       for.  Bugfix on Tor 0.1.0.1-rc; fixes bug 1345.
+    - When TrackHostExits is changed from a controller, remove any
+      mappings for hosts that should no longer have their exits tracked.
+      Bugfix on Tor 0.1.0.1-rc.

src/or/config.c

@@ -1264,6 +1264,7 @@ options_act(or_options_t *old_options)
 
   /* Check for transitions that need action. */
   if (old_options) {
+    int revise_trackexithosts = 0;
     if ((options->UseEntryGuards && !old_options->UseEntryGuards) ||
         !routerset_equal(old_options->ExcludeNodes,options->ExcludeNodes) ||
         !routerset_equal(old_options->ExcludeExitNodes,
@@ -1276,9 +1277,16 @@ 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);
+      revise_trackexithosts = 1;
     }
 
+    if (!smartlist_strings_eq(old_options->TrackHostExits,
+                              options->TrackHostExits))
+      revise_trackexithosts = 1;
+
+    if (revise_trackexithosts)
+      addressmap_clear_excluded_trackexithosts(options);
+
 /* How long should we delay counting bridge stats after becoming a bridge?
  * We use this so we don't count people who used our bridge thinking it is
  * a relay. If you change this, don't forget to change the log message

src/or/connection_edge.c

@@ -810,7 +810,8 @@ clear_trackexithost_mappings(const char *exitname)
 }
 
 /** Remove all TRACKEXIT mappings from the addressmap for which the target
- * host is unknown or no longer allowed. */
+ * host is unknown or no longer allowed, or for which the source address
+ * is no longer in trackexithosts. */
 void
 addressmap_clear_excluded_trackexithosts(or_options_t *options)
 {
@@ -851,7 +852,8 @@ addressmap_clear_excluded_trackexithosts(or_options_t *options)
     tor_free(nodename);
     if (!ri ||
         (allow_nodes && !routerset_contains_router(allow_nodes, ri)) ||
-        routerset_contains_router(exclude_nodes, ri)) {
+        routerset_contains_router(exclude_nodes, ri) ||
+        !hostname_in_track_host_exits(options, address)) {
       /* We don't know this one, or we want to be rid of it. */
       addressmap_ent_remove(address, ent);
       MAP_DEL_CURRENT(address);