Merge branch 'bug12844'

Conflicts:
	src/or/circuituse.c
	src/test/include.am
	src/test/test_entrynodes.c

14 files changed, 305 insertions, 70 deletions

diff --git a/changes/feature12844 b/changes/feature12844
new file mode 100644
index 0000000000..7b7276640a
--- /dev/null
+++ b/changes/feature12844
@@ -0,0 +1,5 @@
+  o Minor features:
+    - Introduce the config option Tor2webRendezvousPoints, which
+      allows clients in Tor2webMode to select a specific Rendezvous
+      Point to be used in HS circuits. This might allow better
+      performance for Tor2Web nodes. Implements ticket #12844.
diff --git a/doc/tor.1.txt b/doc/tor.1.txt
index 1349bf35b5..b646a4c6e0 100644
--- a/doc/tor.1.txt
+++ b/doc/tor.1.txt
@@ -1335,6 +1335,22 @@ The following options are useful only for clients (that is, if
     To enable this option the compile time flag --enable-tor2webmode must be
     specified. (Default: 0)
 
+[[Tor2webRendezvousPoints]] **Tor2webRendezvousPoints** __node__,__node__,__...__::
+    A list of identity fingerprints, nicknames, country codes and
+    address patterns of nodes that are allowed to be used as RPs
+    in HS circuits; any other nodes will not be used as RPs.
+    (Example:
+    Tor2webRendezvousPoints Fastyfasty, ABCD1234CDEF5678ABCD1234CDEF5678ABCD1234, \{cc}, 255.254.0.0/8) +
+ +
+    This feature can only be used if Tor2webMode is also enabled.
+ +
+    ExcludeNodes have higher priority than Tor2webRendezvousPoints,
+    which means that nodes specified in ExcludeNodes will not be
+    picked as RPs.
+ +
+    If no nodes in Tor2webRendezvousPoints are currently available for
+    use, Tor will choose a random node when building HS circuits.
+
 [[UseMicrodescriptors]] **UseMicrodescriptors** **0**|**1**|**auto**::
     Microdescriptors are a smaller version of the information that Tor needs
     in order to build its circuits.  Using microdescriptors makes Tor clients
diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c
index fa5a2f5242..57056b2a66 100644
--- a/src/or/circuitbuild.c
+++ b/src/or/circuitbuild.c
@@ -1737,6 +1737,83 @@ choose_good_exit_server_general(int need_uptime, int need_capacity)
   return NULL;
 }
 
+#if defined(ENABLE_TOR2WEB_MODE) || defined(TOR_UNIT_TESTS)
+/* The config option Tor2webRendezvousPoints has been set and we need
+ * to pick an RP out of that set. Make sure that the RP we choose is
+ * alive, and return it. Return NULL if no usable RP could be found in
+ * Tor2webRendezvousPoints. */
+STATIC const node_t *
+pick_tor2web_rendezvous_node(router_crn_flags_t flags,
+                             const or_options_t *options)
+{
+  const node_t *rp_node = NULL;
+  const int allow_invalid = (flags & CRN_ALLOW_INVALID) != 0;
+  const int need_desc = (flags & CRN_NEED_DESC) != 0;
+
+  smartlist_t *whitelisted_live_rps = smartlist_new();
+  smartlist_t *all_live_nodes = smartlist_new();
+
+  tor_assert(options->Tor2webRendezvousPoints);
+
+  /* Add all running nodes to all_live_nodes */
+  router_add_running_nodes_to_smartlist(all_live_nodes,
+                                        allow_invalid,
+                                        0, 0, 0,
+                                        need_desc);
+
+  /* Filter all_live_nodes to only add live *and* whitelisted RPs to
+   * the list whitelisted_live_rps. */
+  SMARTLIST_FOREACH_BEGIN(all_live_nodes, node_t *, live_node) {
+    if (routerset_contains_node(options->Tor2webRendezvousPoints, live_node)) {
+      smartlist_add(whitelisted_live_rps, live_node);
+    }
+  } SMARTLIST_FOREACH_END(live_node);
+
+  /* Honor ExcludeNodes */
+  if (options->ExcludeNodes) {
+    routerset_subtract_nodes(whitelisted_live_rps, options->ExcludeNodes);
+  }
+
+  /* Now pick randomly amongst the whitelisted RPs. No need to waste time
+     doing bandwidth load balancing, for most use cases
+     'whitelisted_live_rps' contains a single OR anyway. */
+  rp_node = smartlist_choose(whitelisted_live_rps);
+
+  if (!rp_node) {
+    log_warn(LD_REND, "Could not find a Rendezvous Point that suits "
+             "the purposes of Tor2webRendezvousPoints. Choosing random one.");
+  }
+
+  smartlist_free(whitelisted_live_rps);
+  smartlist_free(all_live_nodes);
+
+  return rp_node;
+}
+#endif
+
+/* Pick a Rendezvous Point for our HS circuits according to <b>flags</b>. */
+static const node_t *
+pick_rendezvous_node(router_crn_flags_t flags)
+{
+  const or_options_t *options = get_options();
+
+  if (options->AllowInvalid_ & ALLOW_INVALID_RENDEZVOUS)
+    flags |= CRN_ALLOW_INVALID;
+
+#ifdef ENABLE_TOR2WEB_MODE
+  /* The user wants us to pick specific RPs. */
+  if (options->Tor2webRendezvousPoints) {
+    const node_t *tor2web_rp = pick_tor2web_rendezvous_node(flags, options);
+    if (tor2web_rp) {
+      return tor2web_rp;
+    }
+    /* Else, if no tor2web RP was found, fall back to choosing a random node */
+  }
+#endif
+
+  return router_choose_random_node(NULL, options->ExcludeNodes, flags);
+}
+
 /** Return a pointer to a suitable router to be the exit node for the
  * circuit of purpose <b>purpose</b> that we're about to build (or NULL
  * if no router is suitable).
@@ -1767,9 +1844,13 @@ choose_good_exit_server(uint8_t purpose,
       else
         return choose_good_exit_server_general(need_uptime,need_capacity);
     case CIRCUIT_PURPOSE_C_ESTABLISH_REND:
-      if (options->AllowInvalid_ & ALLOW_INVALID_RENDEZVOUS)
-        flags |= CRN_ALLOW_INVALID;
-      return router_choose_random_node(NULL, options->ExcludeNodes, flags);
+      {
+        /* Pick a new RP */
+        const node_t *rendezvous_node = pick_rendezvous_node(flags);
+        log_info(LD_REND, "Picked new RP: %s",
+                 safe_str_client(node_describe(rendezvous_node)));
+        return rendezvous_node;
+      }
   }
   log_warn(LD_BUG,"Unhandled purpose %d", purpose);
   tor_fragile_assert();
diff --git a/src/or/circuitbuild.h b/src/or/circuitbuild.h
index c72016d530..ddf86416fc 100644
--- a/src/or/circuitbuild.h
+++ b/src/or/circuitbuild.h
@@ -61,6 +61,9 @@ const node_t *choose_good_entry_server(uint8_t purpose,
 
 #ifdef CIRCUITBUILD_PRIVATE
 STATIC circid_t get_unique_circ_id_by_chan(channel_t *chan);
+STATIC const node_t *pick_tor2web_rendezvous_node(router_crn_flags_t flags,
+                                                  const or_options_t *options);
+
 #endif
 
 #endif
diff --git a/src/or/circuituse.c b/src/or/circuituse.c
index 612b536bad..c463b0a40f 100644
--- a/src/or/circuituse.c
+++ b/src/or/circuituse.c
@@ -1677,6 +1677,7 @@ circuit_launch_by_extend_info(uint8_t purpose,
   origin_circuit_t *circ;
   int onehop_tunnel = (flags & CIRCLAUNCH_ONEHOP_TUNNEL) != 0;
   int have_path = have_enough_path_info(! (flags & CIRCLAUNCH_IS_INTERNAL) );
+  int need_specific_rp = 0;
 
   if (!onehop_tunnel && (!router_have_minimum_dir_info() || !have_path)) {
     log_debug(LD_CIRC,"Haven't %s yet; canceling "
@@ -1687,8 +1688,17 @@ circuit_launch_by_extend_info(uint8_t purpose,
     return NULL;
   }
 
+  /* If Tor2webRendezvousPoints is enabled and we are dealing with an
+     RP circuit, we want a specific RP node so we shouldn't canibalize
+     an already existing circuit. */
+  if (get_options()->Tor2webRendezvousPoints &&
+      purpose == CIRCUIT_PURPOSE_C_ESTABLISH_REND) {
+    need_specific_rp = 1;
+  }
+
   if ((extend_info || purpose != CIRCUIT_PURPOSE_C_GENERAL) &&
-      purpose != CIRCUIT_PURPOSE_TESTING && !onehop_tunnel) {
+      purpose != CIRCUIT_PURPOSE_TESTING &&
+      !onehop_tunnel && !need_specific_rp) {
     /* see if there are appropriate circs available to cannibalize. */
     /* XXX if we're planning to add a hop, perhaps we want to look for
      * internal circs rather than exit circs? -RD */
diff --git a/src/or/config.c b/src/or/config.c
index de0baa40d9..ad4fd45846 100644
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -80,6 +80,7 @@ static config_abbrev_t option_abbrevs_[] = {
   PLURAL(AuthDirRejectCC),
   PLURAL(EntryNode),
   PLURAL(ExcludeNode),
+  PLURAL(Tor2webRendezvousPoint),
   PLURAL(FirewallPort),
   PLURAL(LongLivedPort),
   PLURAL(HiddenServiceNode),
@@ -404,6 +405,7 @@ static config_var_t option_vars_[] = {
   V(TestSocks,                   BOOL,     "0"),
   V(TokenBucketRefillInterval,   MSEC_INTERVAL, "100 msec"),
   V(Tor2webMode,                 BOOL,     "0"),
+  V(Tor2webRendezvousPoints,      ROUTERSET, NULL),
   V(TLSECGroup,                  STRING,   NULL),
   V(TrackHostExits,              CSV,      NULL),
   V(TrackHostExitsExpire,        INTERVAL, "30 minutes"),
@@ -1262,7 +1264,8 @@ options_need_geoip_info(const or_options_t *options, const char **reason_out)
     routerset_needs_geoip(options->EntryNodes) ||
     routerset_needs_geoip(options->ExitNodes) ||
     routerset_needs_geoip(options->ExcludeExitNodes) ||
-    routerset_needs_geoip(options->ExcludeNodes);
+    routerset_needs_geoip(options->ExcludeNodes) ||
+    routerset_needs_geoip(options->Tor2webRendezvousPoints);
 
   if (routerset_usage && reason_out) {
     *reason_out = "We've been configured to use (or avoid) nodes in certain "
@@ -1395,7 +1398,7 @@ options_act(const or_options_t *old_options)
     log_err(LD_CONFIG, "This copy of Tor was not compiled to run in "
             "'tor2web mode'. It cannot be run with the Tor2webMode torrc "
             "option enabled. To enable Tor2webMode recompile with the "
-            "--enable-tor2webmode option.");
+            "--enable-tor2web-mode option.");
     return -1;
   }
 #endif
@@ -1651,6 +1654,8 @@ options_act(const or_options_t *old_options)
                          options->ExcludeExitNodes) ||
         !routerset_equal(old_options->EntryNodes, options->EntryNodes) ||
         !routerset_equal(old_options->ExitNodes, options->ExitNodes) ||
+        !routerset_equal(old_options->Tor2webRendezvousPoints,
+                         options->Tor2webRendezvousPoints) ||
         options->StrictNodes != old_options->StrictNodes) {
       log_info(LD_CIRC,
                "Changed to using entry guards or bridges, or changed "
@@ -3057,6 +3062,10 @@ options_validate(or_options_t *old_options, or_options_t *options,
     options->UseEntryGuards = 0;
   }
 
+  if (options->Tor2webRendezvousPoints && !options->Tor2webMode) {
+    REJECT("Tor2webRendezvousPoints cannot be set without Tor2webMode.");
+  }
+
   if (!(options->UseEntryGuards) &&
       (options->RendConfigLines != NULL)) {
     log_warn(LD_CONFIG,
diff --git a/src/or/or.h b/src/or/or.h
index 5d70798d8e..560f5ff5b7 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -3567,6 +3567,9 @@ typedef struct {
    * circuits.) */
   int Tor2webMode;
 
+  /** A routerset that should be used when picking RPs for HS circuits. */
+  routerset_t *Tor2webRendezvousPoints;
+
   /** Close hidden service client circuits immediately when they reach
    * the normal circuit-build timeout, even if they have already sent
    * an INTRODUCE1 cell on its way to the service. */
diff --git a/src/or/routerlist.c b/src/or/routerlist.c
index fe92ac0050..64c43c298b 100644
--- a/src/or/routerlist.c
+++ b/src/or/routerlist.c
@@ -1775,7 +1775,7 @@ routerlist_add_node_and_family(smartlist_t *sl, const routerinfo_t *router)
 /** Add every suitable node from our nodelist to <b>sl</b>, so that
  * we can pick a node for a circuit.
  */
-static void
+void
 router_add_running_nodes_to_smartlist(smartlist_t *sl, int allow_invalid,
                                       int need_uptime, int need_capacity,
                                       int need_guard, int need_desc)
diff --git a/src/or/routerlist.h b/src/or/routerlist.h
index f106ca2316..78c3fbb880 100644
--- a/src/or/routerlist.h
+++ b/src/or/routerlist.h
@@ -58,6 +58,10 @@ const routerstatus_t *router_pick_fallback_dirserver(dirinfo_type_t type,
 int router_get_my_share_of_directory_requests(double *v3_share_out);
 void router_reset_status_download_failures(void);
 int routers_have_same_or_addrs(const routerinfo_t *r1, const routerinfo_t *r2);
+void router_add_running_nodes_to_smartlist(smartlist_t *sl, int allow_invalid,
+                                           int need_uptime, int need_capacity,
+                                           int need_guard, int need_desc);
+
 const routerinfo_t *routerlist_find_my_routerinfo(void);
 uint32_t router_get_advertised_bandwidth(const routerinfo_t *router);
 uint32_t router_get_advertised_bandwidth_capped(const routerinfo_t *router);
diff --git a/src/test/include.am b/src/test/include.am
index 595be0b7c2..71041b1237 100644
--- a/src/test/include.am
+++ b/src/test/include.am
@@ -62,6 +62,7 @@ src_test_test_SOURCES = \
 	src/test/test_threads.c \
 	src/test/test_util.c \
 	src/test/testing_common.c \
+	src/test/testhelper.c \
 	src/ext/tinytest.c
 
 src_test_test_slow_SOURCES = \
@@ -119,10 +120,12 @@ src_test_test_workqueue_LDADD = src/or/libtor-testing.a \
 noinst_HEADERS+= \
 	src/test/fakechans.h \
 	src/test/test.h \
+	src/test/testhelper.h \
 	src/test/test_descriptors.inc \
 	src/test/example_extrainfo.inc \
 	src/test/failing_routerdescs.inc \
-	src/test/ed25519_vectors.inc
+	src/test/ed25519_vectors.inc \
+	src/test/test_descriptors.inc
 
 noinst_PROGRAMS+= src/test/test-ntor-cl
 src_test_test_ntor_cl_SOURCES  = src/test/test_ntor_cl.c
diff --git a/src/test/test_entrynodes.c b/src/test/test_entrynodes.c
index 19071a1550..5f2051c48f 100644
--- a/src/test/test_entrynodes.c
+++ b/src/test/test_entrynodes.c
@@ -18,7 +18,7 @@
 #include "statefile.h"
 #include "config.h"
 
-#include "test_descriptors.inc"
+#include "testhelper.h"
 
 /* TODO:
  * choose_random_entry() test with state set.
@@ -37,62 +37,6 @@ get_or_state_replacement(void)
   return dummy_state;
 }
 
-/* NOP replacement for router_descriptor_is_older_than() */
-static int
-router_descriptor_is_older_than_replacement(const routerinfo_t *router,
-                                            int seconds)
-{
-  (void) router;
-  (void) seconds;
-  return 0;
-}
-
-/* Number of descriptors contained in test_descriptors.txt. */
-#define NUMBER_OF_DESCRIPTORS 8
-
-/** Parse a file containing router descriptors and load them to our
-    routerlist. This function is used to setup an artificial network
-    so that we can conduct entry guard tests. */
-static void
-setup_fake_routerlist(void)
-{
-  int retval;
-  routerlist_t *our_routerlist = NULL;
-  smartlist_t *our_nodelist = NULL;
-
-  /* Read the file that contains our test descriptors. */
-
-  /* We need to mock this function otherwise the descriptors will not
-     accepted as they are too old. */
-  MOCK(router_descriptor_is_older_than,
-       router_descriptor_is_older_than_replacement);
-
-  /* Load all the test descriptors to the routerlist. */
-  retval = router_load_routers_from_string(TEST_DESCRIPTORS,
-                                           NULL, SAVED_IN_JOURNAL,
-                                           NULL, 0, NULL);
-  tt_int_op(retval, OP_EQ, NUMBER_OF_DESCRIPTORS);
-
-  /* Sanity checking of routerlist and nodelist. */
-  our_routerlist = router_get_routerlist();
-  tt_int_op(smartlist_len(our_routerlist->routers), OP_EQ,
-            NUMBER_OF_DESCRIPTORS);
-  routerlist_assert_ok(our_routerlist);
-
-  our_nodelist = nodelist_get_list();
-  tt_int_op(smartlist_len(our_nodelist), OP_EQ, NUMBER_OF_DESCRIPTORS);
-
-  /* Mark all routers as non-guards but up and running! */
-  SMARTLIST_FOREACH_BEGIN(our_nodelist, node_t *, node) {
-    node->is_running = 1;
-    node->is_valid = 1;
-    node->is_possible_guard = 0;
-  } SMARTLIST_FOREACH_END(node);
-
- done:
-  UNMOCK(router_descriptor_is_older_than);
-}
-
 /* Unittest cleanup function: Cleanup the fake network. */
 static int
 fake_network_cleanup(const struct testcase_t *testcase, void *ptr)
@@ -120,7 +64,7 @@ fake_network_setup(const struct testcase_t *testcase)
        get_or_state_replacement);
 
   /* Setup fake routerlist. */
-  setup_fake_routerlist();
+  helper_setup_fake_routerlist();
 
   /* Return anything but NULL (it's interpreted as test fail) */
   return dummy_state;
@@ -197,7 +141,7 @@ populate_live_entry_guards_test_helper(int num_needed)
 
   /* Walk the nodelist and add all nodes as entry guards. */
   our_nodelist = nodelist_get_list();
-  tt_int_op(smartlist_len(our_nodelist), OP_EQ, NUMBER_OF_DESCRIPTORS);
+  tt_int_op(smartlist_len(our_nodelist), OP_EQ, HELPER_NUMBER_OF_DESCRIPTORS);
 
   SMARTLIST_FOREACH_BEGIN(our_nodelist, const node_t *, node) {
     const node_t *node_tmp;
@@ -206,7 +150,7 @@ populate_live_entry_guards_test_helper(int num_needed)
   } SMARTLIST_FOREACH_END(node);
 
   /* Make sure the nodes were added as entry guards. */
-  tt_int_op(smartlist_len(all_entry_guards), OP_EQ, NUMBER_OF_DESCRIPTORS);
+  tt_int_op(smartlist_len(all_entry_guards), OP_EQ, HELPER_NUMBER_OF_DESCRIPTORS);
 
   /* Ensure that all the possible entry guards are enough to satisfy us. */
   tt_int_op(smartlist_len(all_entry_guards), OP_GE, num_needed);
@@ -647,7 +591,7 @@ test_entry_is_live(void *arg)
 
   /* Walk the nodelist and add all nodes as entry guards. */
   our_nodelist = nodelist_get_list();
-  tt_int_op(smartlist_len(our_nodelist), OP_EQ, NUMBER_OF_DESCRIPTORS);
+  tt_int_op(smartlist_len(our_nodelist), OP_EQ, HELPER_NUMBER_OF_DESCRIPTORS);
 
   SMARTLIST_FOREACH_BEGIN(our_nodelist, const node_t *, node) {
     const node_t *node_tmp;
@@ -659,7 +603,7 @@ test_entry_is_live(void *arg)
   } SMARTLIST_FOREACH_END(node);
 
   /* Make sure the nodes were added as entry guards. */
-  tt_int_op(smartlist_len(all_entry_guards), OP_EQ, NUMBER_OF_DESCRIPTORS);
+  tt_int_op(smartlist_len(all_entry_guards), OP_EQ, HELPER_NUMBER_OF_DESCRIPTORS);
 
   /* Now get a random test entry that we will use for this unit test. */
   which_node = 3;  /* (chosen by fair dice roll) */
diff --git a/src/test/test_hs.c b/src/test/test_hs.c
index 0246eaf648..e70ca5ee96 100644
--- a/src/test/test_hs.c
+++ b/src/test/test_hs.c
@@ -7,9 +7,15 @@
  **/
 
 #define CONTROL_PRIVATE
+#define CIRCUITBUILD_PRIVATE
+
 #include "or.h"
 #include "test.h"
 #include "control.h"
+#include "testhelper.h"
+#include "config.h"
+#include "routerset.h"
+#include "circuitbuild.h"
 
 /* mock ID digest and longname for node that's in nodelist */
 #define HSDIR_EXIST_ID "\xAA\xAA\xAA\xAA\xAA\xAA\xAA\xAA\xAA\xAA" \
@@ -123,9 +129,83 @@ test_hs_desc_event(void *arg)
   tor_free(received_msg);
 }
 
+/* Make sure we always pick the right RP, given a well formatted
+ * Tor2webRendezvousPoints value. */
+static void
+test_pick_tor2web_rendezvous_node(void *arg)
+{
+  or_options_t *options = get_options_mutable();
+  const node_t *chosen_rp = NULL;
+  router_crn_flags_t flags = CRN_NEED_DESC;
+  int retval, i;
+  const char *tor2web_rendezvous_str = "test003r";
+
+  (void) arg;
+
+  /* Setup fake routerlist. */
+  helper_setup_fake_routerlist();
+
+  /* Parse Tor2webRendezvousPoints as a routerset. */
+  options->Tor2webRendezvousPoints = routerset_new();
+  retval = routerset_parse(options->Tor2webRendezvousPoints,
+                           tor2web_rendezvous_str,
+                           "test_tor2web_rp");
+  tt_int_op(retval, >=, 0);
+
+  /* Pick rendezvous point. Make sure the correct one is
+     picked. Repeat many times to make sure it works properly. */
+  for (i = 0; i < 50 ; i++) {
+    chosen_rp = pick_tor2web_rendezvous_node(flags, options);
+    tt_assert(chosen_rp);
+    tt_str_op(chosen_rp->ri->nickname, ==, tor2web_rendezvous_str);
+  }
+
+ done:
+  routerset_free(options->Tor2webRendezvousPoints);
+}
+
+/* Make sure we never pick an RP if Tor2webRendezvousPoints doesn't
+ * correspond to an actual node. */
+static void
+test_pick_bad_tor2web_rendezvous_node(void *arg)
+{
+  or_options_t *options = get_options_mutable();
+  const node_t *chosen_rp = NULL;
+  router_crn_flags_t flags = CRN_NEED_DESC;
+  int retval, i;
+  const char *tor2web_rendezvous_str = "dummy";
+
+  (void) arg;
+
+  /* Setup fake routerlist. */
+  helper_setup_fake_routerlist();
+
+  /* Parse Tor2webRendezvousPoints as a routerset. */
+  options->Tor2webRendezvousPoints = routerset_new();
+  retval = routerset_parse(options->Tor2webRendezvousPoints,
+                           tor2web_rendezvous_str,
+                           "test_tor2web_rp");
+  tt_int_op(retval, >=, 0);
+
+  /* Pick rendezvous point. Since Tor2webRendezvousPoints was set to a
+     dummy value, we shouldn't find any eligible RPs. */
+  for (i = 0; i < 50 ; i++) {
+    chosen_rp = pick_tor2web_rendezvous_node(flags, options);
+    tt_assert(!chosen_rp);
+  }
+
+ done:
+  routerset_free(options->Tor2webRendezvousPoints);
+}
+
 struct testcase_t hs_tests[] = {
   { "hs_desc_event", test_hs_desc_event, TT_FORK,
     NULL, NULL },
+  { "pick_tor2web_rendezvous_node", test_pick_tor2web_rendezvous_node, TT_FORK,
+    NULL, NULL },
+  { "pick_bad_tor2web_rendezvous_node",
+    test_pick_bad_tor2web_rendezvous_node, TT_FORK,
+    NULL, NULL },
   END_OF_TESTCASES
 };
 
diff --git a/src/test/testhelper.c b/src/test/testhelper.c
new file mode 100644
index 0000000000..8bbc192a6c
--- /dev/null
+++ b/src/test/testhelper.c
@@ -0,0 +1,67 @@
+/* Copyright (c) 2014, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#define ROUTERLIST_PRIVATE
+
+#include "or.h"
+#include "routerlist.h"
+#include "testhelper.h"
+#include "nodelist.h"
+
+#include "test.h"
+
+#include "test_descriptors.inc"
+
+/* NOP replacement for router_descriptor_is_older_than() */
+static int
+router_descriptor_is_older_than_replacement(const routerinfo_t *router,
+                                            int seconds)
+{
+  (void) router;
+  (void) seconds;
+  return 0;
+}
+
+/** Parse a file containing router descriptors and load them to our
+    routerlist. This function is used to setup an artificial network
+    so that we can conduct tests on it. */
+void
+helper_setup_fake_routerlist(void)
+{
+  int retval;
+  routerlist_t *our_routerlist = NULL;
+  smartlist_t *our_nodelist = NULL;
+
+  /* Read the file that contains our test descriptors. */
+
+  /* We need to mock this function otherwise the descriptors will not
+     accepted as they are too old. */
+  MOCK(router_descriptor_is_older_than,
+       router_descriptor_is_older_than_replacement);
+
+  /* Load all the test descriptors to the routerlist. */
+  retval = router_load_routers_from_string(TEST_DESCRIPTORS,
+                                           NULL, SAVED_IN_JOURNAL,
+                                           NULL, 0, NULL);
+  tt_int_op(retval, ==, HELPER_NUMBER_OF_DESCRIPTORS);
+
+  /* Sanity checking of routerlist and nodelist. */
+  our_routerlist = router_get_routerlist();
+  tt_int_op(smartlist_len(our_routerlist->routers), ==,
+              HELPER_NUMBER_OF_DESCRIPTORS);
+  routerlist_assert_ok(our_routerlist);
+
+  our_nodelist = nodelist_get_list();
+  tt_int_op(smartlist_len(our_nodelist), ==, HELPER_NUMBER_OF_DESCRIPTORS);
+
+  /* Mark all routers as non-guards but up and running! */
+  SMARTLIST_FOREACH_BEGIN(our_nodelist, node_t *, node) {
+    node->is_running = 1;
+    node->is_valid = 1;
+    node->is_possible_guard = 0;
+  } SMARTLIST_FOREACH_END(node);
+
+ done:
+  UNMOCK(router_descriptor_is_older_than);
+}
+
diff --git a/src/test/testhelper.h b/src/test/testhelper.h
new file mode 100644
index 0000000000..6b1bde6822
--- /dev/null
+++ b/src/test/testhelper.h
@@ -0,0 +1,10 @@
+#ifndef TOR_TEST_HELPER_H
+#define TOR_TEST_HELPER_H
+
+/* Number of descriptors contained in test_descriptors.txt. */
+#define HELPER_NUMBER_OF_DESCRIPTORS 8
+
+void helper_setup_fake_routerlist(void);
+
+#endif
+