Split code for entry guards and bridges into a new module.

changes/split_circuitbuild

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+  o Code simplification and refactoring:
+    - Move the entry node code from circuitbuild.c to its own file.

src/or/entrynodes.h

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+/* Copyright (c) 2001 Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2012, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file guardnodes.h
+ * \brief Header file for circuitbuild.c.
+ **/
+
+#ifndef TOR_ENTRYNODES_H
+#define TOR_ENTRYNODES_H
+
+#if 1
+/* XXXX NM I would prefer that all of this stuff be private to
+ * entrynodes.c. */
+
+/** An entry_guard_t represents our information about a chosen long-term
+ * first hop, known as a "helper" node in the literature. We can't just
+ * use a node_t, since we want to remember these even when we
+ * don't have any directory info. */
+typedef struct entry_guard_t {
+  char nickname[MAX_NICKNAME_LEN+1];
+  char identity[DIGEST_LEN];
+  time_t chosen_on_date; /**< Approximately when was this guard added?
+                          * "0" if we don't know. */
+  char *chosen_by_version; /**< What tor version added this guard? NULL
+                            * if we don't know. */
+  unsigned int made_contact : 1; /**< 0 if we have never connected to this
+                                  * router, 1 if we have. */
+  unsigned int can_retry : 1; /**< Should we retry connecting to this entry,
+                               * in spite of having it marked as unreachable?*/
+  unsigned int path_bias_notice : 1; /**< Did we alert the user about path bias
+                                      * for this node already? */
+  unsigned int path_bias_disabled : 1; /**< Have we disabled this node because
+                                        * of path bias issues? */
+  time_t bad_since; /**< 0 if this guard is currently usable, or the time at
+                      * which it was observed to become (according to the
+                      * directory or the user configuration) unusable. */
+  time_t unreachable_since; /**< 0 if we can connect to this guard, or the
+                             * time at which we first noticed we couldn't
+                             * connect to it. */
+  time_t last_attempted; /**< 0 if we can connect to this guard, or the time
+                          * at which we last failed to connect to it. */
+
+  unsigned first_hops; /**< Number of first hops this guard has completed */
+  unsigned circuit_successes; /**< Number of successfully built circuits using
+                               * this guard as first hop. */
+} entry_guard_t;
+
+entry_guard_t *entry_guard_get_by_id_digest(const char *digest);
+void entry_guards_changed(void);
+const smartlist_t *get_entry_guards(void);
+
+#endif
+
+void entry_guards_compute_status(const or_options_t *options, time_t now);
+int entry_guard_register_connect_status(const char *digest, int succeeded,
+                                        int mark_relay_status, time_t now);
+void entry_nodes_should_be_added(void);
+int entry_list_is_constrained(const or_options_t *options);
+const node_t *choose_random_entry(cpath_build_state_t *state);
+int entry_guards_parse_state(or_state_t *state, int set, char **msg);
+void entry_guards_update_state(or_state_t *state);
+int getinfo_helper_entry_guards(control_connection_t *conn,
+                                const char *question, char **answer,
+                                const char **errmsg);
+
+void mark_bridge_list(void);
+void sweep_bridge_list(void);
+
+int routerinfo_is_a_configured_bridge(const routerinfo_t *ri);
+int node_is_a_configured_bridge(const node_t *node);
+void learned_router_identity(const tor_addr_t *addr, uint16_t port,
+                             const char *digest);
+void bridge_add_from_config(const tor_addr_t *addr, uint16_t port,
+                            const char *digest,
+                            const char *transport_name);
+void retry_bridge_descriptor_fetch_directly(const char *digest);
+void fetch_bridge_descriptors(const or_options_t *options, time_t now);
+void learned_bridge_descriptor(routerinfo_t *ri, int from_cache);
+int any_bridge_descriptors_known(void);
+int any_pending_bridge_descriptor_fetches(void);
+int entries_known_but_down(const or_options_t *options);
+void entries_retry_all(const or_options_t *options);
+
+int any_bridges_dont_support_microdescriptors(void);
+
+void entry_guards_free_all(void);
+
+const char *find_transport_name_by_bridge_addrport(const tor_addr_t *addr,
+                                                   uint16_t port);
+struct transport_t;
+int find_transport_by_bridge_addrport(const tor_addr_t *addr, uint16_t port,
+                                      const struct transport_t **transport);
+
+int validate_pluggable_transports_config(void);
+
+#endif
+