r13732@catbus: nickm | 2007-07-12 12:35:06 -0400

 Backport 10812: avoid roundoff-error-induced crash bugs when picking routers by bandwith.


svn:r10813

2 files changed, 9 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 3e198124bd..055244c965 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -27,6 +27,9 @@ Changes in version 0.1.2.15 - 2007-0?-??
   o Minor bugfixes (misc)
     - On Windows, we were preventing other processes from reading
       cached-routers while Tor was running.  (Reported by janbar)
+    - Fix a possible (but very unlikely) bug in picking routers by bandwidth.
+      Add a log message to confirm that it is in fact unlikely. (Patch from
+      lodger.)
     - Backport miscellaneous cosmetic bugfixes.
 
 
diff --git a/src/or/routerlist.c b/src/or/routerlist.c
index 9af9520844..4d6ed26ccb 100644
--- a/src/or/routerlist.c
+++ b/src/or/routerlist.c
@@ -1082,6 +1082,12 @@ smartlist_choose_by_bandwidth(smartlist_t *sl, int for_exit, int statuses)
     if (tmp >= rand_bw)
       break;
   }
+  if (i == smartlist_len(sl)) {
+    /* This is possible due to round-off error. */
+    --i;
+    log_warn(LD_BUG, "Round-off error in computing bandwidth had an effect on "
+             " which router we chose.  Please tell the developers.");
+  }
   tor_free(bandwidths);
   return smartlist_get(sl, i);
 }