[PATCH v7 3/6] monitor: Clean up fd sets on monitor disconnect

[Corey Bryant <coreyb@xxxxxxxxxxxxxxxxxx>]

Fd sets are shared by all monitor connections.  Fd sets are considered
to be in use while at least one monitor is connected.  When the last
monitor disconnects, all fds that are members of an fd set with
refcount of zero are closed.  This prevents any fd leakage associated
with a client disconnect prior to using a passed fd.

Signed-off-by: Corey Bryant <coreyb@xxxxxxxxxxxxxxxxxx>
---
v5:
 -This patch is new in v5.
 -This support addresses concerns from v4 regarding fd leakage
  if the client disconnects unexpectedly. (eblake@xxxxxxxxxx,
  kwolf@xxxxxxxxxx, dberrange@xxxxxxxxxx)

v6:
 -No changes

v7:
 -Removed monitor_fdsets_set_in_use() function since we now use
  mon_refcount to determine if fdsets are in use.
 -Added monitor_fdsets_cleanup() function, and increment/decrement
  of mon_refcount when monitor connects/disconnects.

 monitor.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/monitor.c b/monitor.c
index 04b86b7..84eade8 100644
--- a/monitor.c
+++ b/monitor.c
@@ -2431,6 +2431,16 @@ static void monitor_fdset_cleanup(mon_fdset_t *mon_fdset)
     }
 }
 
+static void monitor_fdsets_cleanup(void)
+{
+    mon_fdset_t *mon_fdset;
+    mon_fdset_t *mon_fdset_next;
+
+    QLIST_FOREACH_SAFE(mon_fdset, &mon_fdsets, next, mon_fdset_next) {
+        monitor_fdset_cleanup(mon_fdset);
+    }
+}
+
 AddfdInfo *qmp_add_fd(bool has_fdset_id, int64_t fdset_id, Error **errp)
 {
     int fd;
@@ -4760,9 +4770,12 @@ static void monitor_control_event(void *opaque, int event)
         data = get_qmp_greeting();
         monitor_json_emitter(mon, data);
         qobject_decref(data);
+        mon_refcount++;
         break;
     case CHR_EVENT_CLOSED:
         json_message_parser_destroy(&mon->mc->parser);
+        mon_refcount--;
+        monitor_fdsets_cleanup();
         break;
     }
 }
@@ -4803,6 +4816,12 @@ static void monitor_event(void *opaque, int event)
             readline_show_prompt(mon->rs);
         }
         mon->reset_seen = 1;
+        mon_refcount++;
+        break;
+
+    case CHR_EVENT_CLOSED:
+        mon_refcount--;
+        monitor_fdsets_cleanup();
         break;
     }
 }
-- 
1.7.10.4

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