From 68caa834f4ed9cae16a551c9fc63ea982c9f1904 Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Fri, 14 Sep 2012 10:10:16 -0400
Subject: [PATCH] document why we only allow 64 flags in votes

---
 src/or/routerparse.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/or/routerparse.c b/src/or/routerparse.c
index 496b90d4ad..43a95e88c1 100644
--- a/src/or/routerparse.c
+++ b/src/or/routerparse.c
@@ -3006,6 +3006,11 @@ networkstatus_parse_vote_from_string(const char *s, const char **eos_out,
   }
   if (ns->type != NS_TYPE_CONSENSUS &&
       smartlist_len(ns->known_flags) > MAX_KNOWN_FLAGS_IN_VOTE) {
+    /* If we allowed more than 64 flags in votes, then parsing them would make
+     * us invoke undefined behavior whenever we used 1<<flagnum to do a
+     * bit-shift. This is only for votes and opinions: consensus users don't
+     * care about flags they don't recognize, and so don't build a bitfield
+     * for them. */
     log_warn(LD_DIR, "Too many known-flags in consensus vote or opinion");
     goto err;
   }