Merge remote-tracking branch 'dgoulet/bug23751_032_01' into maint-0.3.2

changes/bug23751

@@ -0,0 +1,6 @@
+  o Minor bugfixes (scheduler, channel):
+    - Ignore channels that have been closed while flushing cells. This can
+      happen if the write on the connection fails leading to the channel being
+      closed while in the scheduler loop. This is not a complete fix, it is a
+      bandaid until we are able to refactor those interactions. Fixes bug
+      23751; bugfix on 0.3.2.1-alpha.

src/or/scheduler_kist.c

@@ -598,6 +598,15 @@ kist_scheduler_run(void)
     if (socket_can_write(&socket_table, chan)) {
       /* flush to channel queue/outbuf */
       flush_result = (int)channel_flush_some_cells(chan, 1); // 1 for num cells
+      /* XXX: While flushing cells, it is possible that the connection write
+       * fails leading to the channel to be closed which triggers a release
+       * and free its entry in the socket table. And because of a engineering
+       * design issue, the error is not propagated back so we don't get an
+       * error at this poin. So before we continue, make sure the channel is
+       * open and if not just ignore it. See #23751. */
+      if (!CHANNEL_IS_OPEN(chan)) {
+        continue;
+      }
       /* flush_result has the # cells flushed */
       if (flush_result > 0) {
         update_socket_written(&socket_table, chan, flush_result *