From 507c1257a4d9c629fefc2adbad8db73607749734 Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Mon, 30 May 2011 23:32:38 -0400
Subject: [PATCH] Add an "auto" option to UseBridges

UseBridges 1 now means "connect only to bridges; if you know no
bridges, don't make connections."  UseBridges auto means "Use bridges
if they are known, and we have no EntryNodes set, and we aren't a
server."  UseBridges 0 means "don't use bridges."
---
 src/or/config.c | 19 +++++++++++++++----
 src/or/or.h     | 12 +++++++++++-
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/or/config.c b/src/or/config.c
index 6635cac5d6..44cecf353b 100644
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -376,7 +376,7 @@ static config_var_t _option_vars[] = {
   V(TransPort,                   PORT,     "0"),
   V(TunnelDirConns,              BOOL,     "1"),
   V(UpdateBridgesFromAuthority,  BOOL,     "0"),
-  V(UseBridges,                  BOOL,     "0"),
+  VAR("UseBridges",              STRING,   UseBridges_, "auto"),
   V(UseEntryGuards,              BOOL,     "1"),
   V(User,                        STRING,   NULL),
   VAR("V1AuthoritativeDirectory",BOOL, V1AuthoritativeDir,   "0"),
@@ -3232,6 +3232,19 @@ options_validate(or_options_t *old_options, or_options_t *options,
            "of the Internet, so they must not set Reachable*Addresses "
            "or FascistFirewall.");
 
+  /* XXX023 use autobool instead. */
+  if (!strcmp(options->UseBridges_, "auto")) {
+    options->UseBridges = (options->Bridges &&
+                           !server_mode(options) &&
+                           !options->EntryNodes);
+  } else if (!strcmp(options->UseBridges_, "0")) {
+    options->UseBridges = 0;
+  } else if (!strcmp(options->UseBridges_, "1")) {
+    options->UseBridges = 1;
+  } else {
+    REJECT("UseBridges must be 0, 1, or auto");
+  }
+
   if (options->UseBridges &&
       server_mode(options))
     REJECT("Servers must be able to freely connect to the rest "
@@ -3566,10 +3579,8 @@ options_validate(or_options_t *old_options, or_options_t *options,
   if (validate_dir_authorities(options, old_options) < 0)
     REJECT("Directory authority line did not parse. See logs for details.");
 
-  if (options->UseBridges && !options->Bridges)
-    REJECT("If you set UseBridges, you must specify at least one bridge.");
   if (options->UseBridges && !options->TunnelDirConns)
-    REJECT("If you set UseBridges, you must set TunnelDirConns.");
+    REJECT("TunnelDirConns set to 0 only works with UseBridges set to 0");
   if (options->Bridges) {
     for (cl = options->Bridges; cl; cl = cl->next) {
       if (parse_bridge_line(cl->value, 1)<0)
diff --git a/src/or/or.h b/src/or/or.h
index 97fecd1500..456dce2be4 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -2480,7 +2480,17 @@ typedef struct {
    * when doing so. */
   char *BridgePassword;
 
-  int UseBridges; /**< Boolean: should we start all circuits with a bridge? */
+  /** Whether we should start all circuits with a bridge. "1" means strictly
+   * yes, "0" means strictly no, and "auto" means that we do iff any bridges
+   * are configured, we are not running a server and have not specified a list
+   * of entry nodes. */
+  char *UseBridges_;
+  /** Effective value of UseBridges. Will be set equally for UseBridges set to
+   * 1 or 0, but for 'auto' it will be set to 1 iff any bridges are
+   * configured, we are not running a server and have not specified a list of
+   * entry nodes. */
+  int UseBridges;
+
   config_line_t *Bridges; /**< List of bootstrap bridge addresses. */
 
   int BridgeRelay; /**< Boolean: are we acting as a bridge relay? We make