[GUACAMOLE-1846] Race condition can cause the first user for a connection to miss updates

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 1.5.4
• Component/s: guacamole-server
• Assignee: Unassigned
• Reporter: James Muehlner
• Created: 10/Aug/23 23:15
• Updated: 17/Apr/24 17:33
• Resolved: 30/Aug/23 22:47

Description

The changes in https://github.com/apache/guacamole-server/pull/39 seem to have introduced a potential race condition where the client thread may write updates to the broadcast socket before the first user (the owner) is added to the user list.

This change was made nearly 7 years ago, and I never noticed it before testing my changes in https://github.com/apache/guacamole-server/pull/454, so it's fair to say that it doesn't happen very often. I only see it maybe 10% of the time, and only with an RDP connection using the Cygwin build of guacamole-server.

The symptoms are that nothing but a blank screen is rendered.

Issue Links

• causes: GUACAMOLE-1940 rdp-connect failed when microphone input is enabled
• causes: GUACAMOLE-1892 Build fails with "undefined reference to 'timer_create'"
• causes: GUACAMOLE-1920 When the cumulative number of user connections reaches a certain amount, guacd will report an error. "RDP server closed/refused connection: Security negotiation failed (wrong security type?)”
• is related to: GUACAMOLE-1140 Starting/joining an RDP connection may segfault depending on timing of underlying RDP/SFTP connection(s)