Require fallback directories to have the same address and port for 7 days

7 days is a tradeoff between the expected time between major Tor releases,
which is 6 months, and the number of relays with enough stability.

Relays whose OnionOO stability timer is reset on restart by bug #18050
should upgrade to Tor 0.2.8.7 or later, which has a fix for this issue.

Closes ticket #20880; maintains short-term fix in e2202146 in tor-0.2.8.2-alpha.

changes/fallbacks-201612

@@ -5,10 +5,11 @@
       updateFallbackDirs.py.
       Closes ticket 20878.
     - Require fallback directories to have the same address and port for
-      6 months. (We expect to regenerate the fallback list each major Tor
-      release.) Relays whose OnionOO stability timer is reset on restart by
-      bug 18050 should upgrade to Tor 0.2.8.7 or later, which has a fix for
-      this issue.
+      4 months. (4 months is a tradeoff between the expected time between
+      major Tor releases, which is 6 months, and the number of relays with
+      enough stability.) Relays whose OnionOO stability timer is reset on
+      restart by bug 18050 should upgrade to Tor 0.2.8.7 or later, which has
+      a fix for this issue.
       Closes ticket 20880; removes short-term fix in e220214 in
       tor-0.2.8.2-alpha.
     - Make it easier to change the output sort order of fallbacks.

scripts/maint/updateFallbackDirs.py

@@ -137,10 +137,13 @@ MAX_LIST_FILE_SIZE = 1024 * 1024
 
 ## Eligibility Settings
 
-# Reduced due to a bug in tor where a relay submits a 0 DirPort when restarted
-# This causes OnionOO to (correctly) reset its stability timer
-# This issue will be fixed in 0.2.7.7 and 0.2.8.2
-# Until then, the CUTOFFs below ensure a decent level of stability.
+# Require fallbacks to have the same address and port for a set amount of time
+#
+# There was a bug in Tor 0.2.8.1-alpha and earlier where a relay temporarily
+# submits a 0 DirPort when restarted.
+# This causes OnionOO to (correctly) reset its stability timer.
+# Affected relays should upgrade to Tor 0.2.8.7 or later, which has a fix
+# for this issue.
 ADDRESS_AND_PORT_STABLE_DAYS = 7
 # What time-weighted-fraction of these flags must FallbackDirs
 # Equal or Exceed?