GUACAMOLE-2221: fix RDP busy-loop on transport failure#635
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@pwgcz As discussed in the Jira ticket, I don't think we want to simply revert the previous patch, as that just reintroduces the issue that the commit resolves. You had suggested an alternate approach in the Jira issue - you're welcome to update this PR with that approach and we can see if that addresses the issue without (re)introducing other issues.
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@necouchman Sorry for not responding sooner. I've updated the code now. |
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Thanks for looking into this, @pwgcz! Please also:
-
Base this off
staging/1.6.1(so it can be included as part of 1.6.1) -
Rebase to get rid of the merge commit that snuck in here:
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When an RDP connection hits a transport-level failure (for example, a certificate error), the inner event loop in rdp.c can spin at 100% CPU. This happens because rdp_guac_client_wait_for_events() does not check FreeRDP's error state, so it keeps returning success even after a transport failure has been recorded. As a result, the loop never observes the error and continues polling indefinitely. Fix: check freerdp_get_last_error() in rdp_guac_client_wait_for_events() and return -1 when an error is recorded. This satisfies the function's contract to report errors and ensures the loop exits promptly.
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@mike-jumper Any other concerns?
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When an RDP connection hits a transport-level
failure (for example, a certificate error), the
inner event loop in rdp.c can spin at 100% CPU.
This happens because the error state in
wait_result gets overwritten. When the issue
occurs, guac_rdp_handle_events() sets wait_result
to -1, but the loop doesn’t exit immediately. In
the next iteration, the while condition assigns
wait_result from rdp_guac_client_wait_for_events()
effectively clearing the error flag. As a result,
the loop never observes the transport failure and
continues polling, spinning the CPU.
Fix: break out of the loop immediately after
guac_rdp_handle_events() fails, so we stop
processing when FreeRDP reports a connection
error.