Prevent potential race condition in multiparty basic bridges.

For more details about the race condition see the linked review
at the bottom of this commit

(closes issue ASTERISK-21882)
Reported by Matt Jordan

Review: https://reviewboard.asterisk.org/r/2663

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@394232 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/main/bridging_basic.c b/main/bridging_basic.c
index c1c0045..844ff3c 100644 (file)
--- a/main/bridging_basic.c
+++ b/main/bridging_basic.c
@@ -99,9 +99,16 @@ struct ast_flags *ast_bridge_features_ds_get(struct ast_channel *chan)
  */
 static int basic_hangup_hook(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel, void *hook_pvt)
 {
-/* BUGBUG Race condition.  If all parties but one hangup at the same time, the bridge may not be dissolved on the remaining party. */
+       int bridge_count = 0;
+       struct ast_bridge_channel *iter;
+
        ast_bridge_channel_lock_bridge(bridge_channel);
-       if (2 < bridge_channel->bridge->num_channels) {
+       AST_LIST_TRAVERSE(&bridge->channels, iter, entry) {
+               if (iter != bridge_channel && iter->state == AST_BRIDGE_CHANNEL_STATE_WAIT) {
+                       ++bridge_count;
+               }
+       }
+       if (2 <= bridge_count) {
                /* Just allow this channel to leave the multi-party bridge. */
                ast_bridge_change_state(bridge_channel, AST_BRIDGE_CHANNEL_STATE_HANGUP);
        }