Fix check_expired_networkstatus_callback() if condition

The condition was always true meaning that we would reconsider updating our
directory information every 2 minutes.

If valid_until is 6am today, then now - 24h == 1pm yesterday which means that
"valid_until < (now - 24h)" is false. But at 6:01am tomorrow, "valid_until <
(now - 24h)" becomes true which is that point that we shouldn't trust the
consensus anymore.

Fixes #23091

Signed-off-by: David Goulet <dgoulet@torproject.org>

changes/bug23091

@@ -0,0 +1,6 @@
+  o Minor bugfixes (consensus expiry):
+    - Tor would reconsider updating its directory information every 2 minutes
+      instead of only doing it for a consensus that is more than 24 hours old
+      (badly expired). This specific check is done in the tor main loop
+      callback that validates if we have an expired consensus. Fixes bug
+      23091; bugfix on tor-0.2.0.19-alpha.

src/or/main.c

@@ -1713,7 +1713,7 @@ check_expired_networkstatus_callback(time_t now, const or_options_t *options)
    * networkstatus_get_reasonably_live_consensus(), but that value is way
    * way too high.  Arma: is the bridge issue there resolved yet? -NM */
 #define NS_EXPIRY_SLOP (24*60*60)
-  if (ns && ns->valid_until < now+NS_EXPIRY_SLOP &&
+  if (ns && ns->valid_until < (now - NS_EXPIRY_SLOP) &&
       router_have_minimum_dir_info()) {
     router_dir_info_changed();
   }