Add support for feature detection in transports.

src/feature/client/transports.c

@@ -131,6 +131,7 @@ static void parse_method_error(const char *line, int is_server_method);
 #define PROTO_PROXY_ERROR "PROXY-ERROR"
 #define PROTO_LOG "LOG"
 #define PROTO_STATUS "STATUS"
+#define PROTO_FEATURES "FEATURES"
 
 /** The first and only supported - at the moment - configuration
     protocol version. */
@@ -916,16 +917,20 @@ handle_proxy_line(const char *line, managed_proxy_t *mp)
     parse_proxy_error(line);
     goto err;
 
-    /* We check for the additional " " after the PROTO_LOG * PROTO_STATUS
-     * string to make sure we can later extend this big if/else-if table with
-     * something that begins with "LOG" without having to get the order right.
+    /* We check for the additional " " after the PROTO_LOG, PROTO_STATUS, and
+     * PROTO_FEATURES string to make sure we can later extend this big
+     * if/else-if table with something that begins with "LOG" without having to
+     * get the order right.
      * */
   } else if (!strcmpstart(line, PROTO_LOG " ")) {
     parse_log_line(line, mp);
     return;
   } else if (!strcmpstart(line, PROTO_STATUS " ")) {
     parse_status_line(line, mp);
     return;
+  } else if (!strcmpstart(line, PROTO_FEATURES " ")) {
+    parse_features_line(line, mp);
+    return;
   }
 
   log_notice(LD_GENERAL, "Unknown line received by managed proxy (%s).", line);
@@ -1213,6 +1218,46 @@ parse_log_line(const char *line, managed_proxy_t *mp)
   tor_free(log_message);
 }
 
+/** Parses a FEATURES <b>line</b> line for the given <b>mp</b>. */
+STATIC void
+parse_features_line(const char *line, managed_proxy_t *mp)
+{
+  tor_assert(line);
+  tor_assert(mp);
+
+  smartlist_t *features = NULL;
+
+  if (strlen(line) < (strlen(PROTO_FEATURES) + 1)) {
+    log_warn(LD_PT, "Managed proxy sent us a %s line "
+                    "with missing argument.", PROTO_FEATURES);
+    goto done;
+  }
+
+  if (mp->features_received) {
+    log_warn(LD_PT, "Managed proxy sent us a FEATURES line, "
+                    "but we already received one earlier.");
+    goto done;
+  }
+
+  /* Flag that we have received the FEATURES line. */
+  mp->features_received = true;
+
+  const char *data = line + strlen(PROTO_FEATURES) + 1;
+
+  features = smartlist_new();
+  smartlist_split_string(features, data, ",", 0, 0);
+
+  SMARTLIST_FOREACH_BEGIN(features, const char *, feature) {
+    /* Dormant mode feature extension. */
+    if (! strcmp(feature, "dormant")) {
+      mp->dormant_supported = true;
+    }
+  } SMARTLIST_FOREACH_END(feature);
+
+ done:
+  smartlist_free(features);
+}
+
 /** Parses a STATUS <b>line</b> and emit control events accordingly. */
 STATIC void
 parse_status_line(const char *line, managed_proxy_t *mp)
@@ -1439,6 +1484,9 @@ create_managed_proxy_environment(const managed_proxy_t *mp)
    */
   smartlist_add_asprintf(envs, "TOR_PT_EXIT_ON_STDIN_CLOSE=1");
 
+  /* Add a list of supported feature extensions. */
+  smartlist_add_asprintf(envs, "TOR_PT_FEATURES=dormant");
+
   SMARTLIST_FOREACH_BEGIN(envs, const char *, env_var) {
     set_environment_variable_in_smartlist(merged_env_vars, env_var,
                                           tor_free_, 1);

src/feature/client/transports.h

@@ -116,6 +116,12 @@ typedef struct {
   /* The 'transports' list contains all the transports this proxy has
      launched. */
   smartlist_t *transports;
+
+  /** Boolean: Have this PT announced its features? */
+  bool features_received:1;
+
+  /** Boolean: Does this PT support the Dormant feature extension? */
+  bool dormant_supported:1;
 } managed_proxy_t;
 
 STATIC transport_t *transport_new(const tor_addr_t *addr, uint16_t port,
@@ -129,6 +135,7 @@ STATIC void parse_env_error(const char *line);
 STATIC void parse_proxy_error(const char *line);
 STATIC void handle_proxy_line(const char *line, managed_proxy_t *mp);
 STATIC void parse_log_line(const char *line, managed_proxy_t *mp);
+STATIC void parse_features_line(const char *line, managed_proxy_t *mp);
 STATIC void parse_status_line(const char *line, managed_proxy_t *mp);
 STATIC char *get_transport_options_for_server_proxy(const managed_proxy_t *mp);
 

src/test/test_pt.c

@@ -238,6 +238,15 @@ test_pt_protocol(void *arg)
   handle_proxy_line(line, mp);
   tt_assert(mp->conf_state == PT_PROTO_CONFIGURED);
 
+  /* Check features support. */
+  tt_assert(! mp->features_received);
+  tt_assert(! mp->dormant_supported);
+
+  strlcpy(line,"FEATURES dormant", sizeof(line));
+  handle_proxy_line(line, mp);
+  tt_assert(mp->features_received);
+  tt_assert(mp->dormant_supported);
+
  done:
   reset_mp(mp);
   smartlist_free(mp->transports);