cleanups on r11258

svn:r11263

ChangeLog

@@ -4,6 +4,15 @@ Changes in version 0.2.0.6-alpha - 2007-??-??
       mean-times-between-failures. When we have 4 or more days of data,
       use measured MTBF rather than declared uptime to decide whether
       to call a router Stable. Implements proposal 108.
+    - When choosing nodes for non-guard positions, weight guards
+      proportionally less, since they already have enough load. Patch
+      from Mike Perry.
+    - Raise the "max believable bandwidth" from 1.5MB/s to 10MB/s. This
+      will allow fast Tor servers to get more attention. Also, when we're
+      upgrading from an old Tor version, forget our current guards and
+      pick new ones according to the new weightings. The resulting load
+      balancing improvement could raise effective network capacity by
+      a factor of four. Thanks to Mike Perry for measurements.
 
   o Major bugfixes:
     - Handle unexpected whitespace better in malformed descriptors. Bug

src/or/config.c

@@ -299,10 +299,12 @@ static config_var_t _state_vars[] = {
   VAR("AccountingExpectedUsage", MEMUNIT,     AccountingExpectedUsage, NULL),
   VAR("AccountingIntervalStart", ISOTIME,     AccountingIntervalStart, NULL),
   VAR("AccountingSecondsActive", INTERVAL,    AccountingSecondsActive, NULL),
+
   VAR("EntryGuard",              LINELIST_S,  EntryGuards,             NULL),
   VAR("EntryGuardDownSince",     LINELIST_S,  EntryGuards,             NULL),
   VAR("EntryGuardUnlistedSince", LINELIST_S,  EntryGuards,             NULL),
   VAR("EntryGuards",             LINELIST_V,  EntryGuards,             NULL),
+  VAR("GuardVersion",            UINT,        GuardVersion,            "0"),
 
   VAR("BWHistoryReadEnds",       ISOTIME,     BWHistoryReadEnds,      NULL),
   VAR("BWHistoryReadInterval",   UINT,        BWHistoryReadInterval,  "900"),
@@ -529,6 +531,8 @@ static config_var_description_t state_description[] = {
     "The last entry guard has been unreachable since this time." },
   { "EntryGuardUnlistedSince",
     "The last entry guard has been unusable since this time." },
+  { "GuardVersion", "Which algorithm did we use to pick these guards?" },
+
   { "LastRotatedOnionKey",
     "The last time at which we changed the medium-term private key used for "
     "building circuits." },
@@ -4332,6 +4336,12 @@ get_or_state_fname(void)
   return fname;
 }
 
+/** What's the newest known version for our guard-picking algorithm?
+ * If the version in the state file is older than this (or if there is
+ * no version listed in the state file), we want to ignore the guards
+ * in the state file and pick new ones. */
+#define RECOMMENDED_GUARD_VERSION 1
+
 /** Return 0 if every setting in <b>state</b> is reasonable, and a
  * permissible transition from <b>old_state</b>.  Else warn and return -1.
  * Should have no side effects, except for normalizing the contents of
@@ -4346,27 +4356,17 @@ or_state_validate(or_state_t *old_state, or_state_t *state,
    * signature. */
   (void) from_setconf;
   (void) old_state;
-  if (entry_guards_parse_state(state, 0, msg)<0) {
+
+  if (state->GuardVersion < RECOMMENDED_GUARD_VERSION) {
+    config_free_lines(state->EntryGuards);
+    state->EntryGuards = NULL;
+    log_notice(LD_CONFIG, "Detected state file from old version '%s'. "
+               "Choosing new entry guards for you.",
+               state->TorVersion ? state->TorVersion : "unknown");
+    state->GuardVersion = RECOMMENDED_GUARD_VERSION;
+  } else if (entry_guards_parse_state(state, 0, msg)<0) {
     return -1;
   }
-  if (state->TorVersion) {
-    tor_version_t v;
-    if (tor_version_parse(state->TorVersion, &v)) {
-      log_warn(LD_GENERAL, "Can't parse Tor version '%s' from your state "
-               "file. Proceeding anyway.", state->TorVersion);
-    } else { /* take action based on v */
-      if ((tor_version_as_new_as(state->TorVersion, "0.1.1.10-alpha") &&
-          !tor_version_as_new_as(state->TorVersion, "0.1.2.17-dev"))
-          || (tor_version_as_new_as(state->TorVersion, "0.2.0.0-alpha") &&
-          !tor_version_as_new_as(state->TorVersion, "0.2.0.6-alpha-dev"))) {
-        log_notice(LD_CONFIG, "Detected state file from buggy version '%s'. "
-                   "Enabling workaround to choose working entry guards.",
-                   state->TorVersion);
-        config_free_lines(state->EntryGuards);
-        state->EntryGuards = NULL;
-      }
-    }
-  }
   return 0;
 }
 

src/or/or.h

@@ -2111,6 +2111,11 @@ typedef struct {
 
   /** A list of Entry Guard-related configuration lines. */
   config_line_t *EntryGuards;
+  /** What algorithm did we use to select these guards? 0 if we didn't
+   * know about the GuardVersion concept when we picked them. We use
+   * this to expire and re-pick our guards if Tor knows about a newer
+   * version than the state file lists. */
+  int GuardVersion;
 
   /** These fields hold information on the history of bandwidth usage for
    * servers.  The "Ends" fields hold the time when we last updated the

src/or/routerlist.c

@@ -1262,7 +1262,18 @@ router_get_advertised_bandwidth(routerinfo_t *router)
 
 /** Do not weight any declared bandwidth more than this much when picking
  * routers by bandwidth. */
-#define MAX_BELIEVABLE_BANDWIDTH 10000000 /* 10 MB/sec */
+#define DEFAULT_MAX_BELIEVABLE_BANDWIDTH 10000000 /* 10 MB/sec */
+
+/** Eventually, the number we return will come from the directory
+ * consensus, so clients can dynamically update to better numbers.
+ *
+ * But for now, or in case there is no consensus available, just return
+ * a sufficient default. */
+static uint32_t
+get_max_believable_bandwidth(void)
+{
+  return DEFAULT_MAX_BELIEVABLE_BANDWIDTH;
+}
 
 /** Helper function:
  * choose a random element of smartlist <b>sl</b>, weighted by
@@ -1301,6 +1312,7 @@ smartlist_choose_by_bandwidth(smartlist_t *sl, int for_exit, int for_guard,
   int n_unknown = 0;
   bitarray_t *exit_bits;
   bitarray_t *guard_bits;
+  uint32_t max_believable_bw = get_max_believable_bandwidth();
 
   /* Can't choose exit and guard at same time */
   tor_assert(!(for_exit && for_guard));
@@ -1344,7 +1356,7 @@ smartlist_choose_by_bandwidth(smartlist_t *sl, int for_exit, int for_guard,
     if (is_guard)
       bitarray_set(guard_bits, i);
     /* if they claim something huge, don't believe it */
-    if (this_bw > MAX_BELIEVABLE_BANDWIDTH) {
+    if (this_bw > max_believable_bw) {
       char fp[HEX_DIGEST_LEN+1];
       if (status) {
           base16_encode(fp, sizeof(fp),
@@ -1357,8 +1369,8 @@ smartlist_choose_by_bandwidth(smartlist_t *sl, int for_exit, int for_guard,
           "Bandwidth %d for router %s (%s) exceeds allowed max %d, capping",
           this_bw, router ? router->nickname : "(null)",
           status || router ? fp : "0",
-          MAX_BELIEVABLE_BANDWIDTH);
-      this_bw = MAX_BELIEVABLE_BANDWIDTH;
+          max_believable_bw);
+      this_bw = max_believable_bw;
     }
     if (is_known) {
       bandwidths[i] = (int32_t) this_bw; // safe since MAX_BELIEVABLE<INT32_MAX