Drop the MaxMemInCellQueues lower limit down to 256 MB.

on #9686, gmorehose reports that the 500 MB lower limit is too high
for raspberry pi users.

This is a backport of 647248729fa65f0e51d062e2af8f4e8b38592bf5 to 0.2.4.

Note that in 0.2.4, the option is called MaxMemInCellQueues.

changes/bug9686_024

@@ -0,0 +1,5 @@
+  o Minor features (security):
+    - Decrease the lower limit of MaxMemInCellQueues to 256 MBytes (but leave
+      the default at 8GBytes), to better support Raspberry Pi users. Fixes
+      bug 9686; bugfix on 0.2.4.14-alpha.
+

src/or/config.c

@@ -2616,10 +2616,10 @@ options_validate(or_options_t *old_options, or_options_t *options,
     REJECT("If EntryNodes is set, UseEntryGuards must be enabled.");
   }
 
-  if (options->MaxMemInCellQueues < (500 << 20)) {
-    log_warn(LD_CONFIG, "MaxMemInCellQueues must be at least 500 MB for now. "
+  if (options->MaxMemInCellQueues < (256 << 20)) {
+    log_warn(LD_CONFIG, "MaxMemInCellQueues must be at least 256 MB for now. "
              "Ideally, have it as large as you can afford.");
-    options->MaxMemInCellQueues = (500 << 20);
+    options->MaxMemInCellQueues = (256 << 20);
   }
 
   options->AllowInvalid_ = 0;