#21765: PortForwardingHelper stdout/stderr log forwarding seems fragile ------------------------------+-------------------------------- Reporter: ahf | Owner: Type: defect | Status: new Priority: Low | Milestone: Tor: 0.3.1.x-final Component: Core Tor/Tor | Version: Tor: unspecified Severity: Normal | Keywords: Actual Points: | Parent ID: Points: | Reviewer: Sponsor: | ------------------------------+-------------------------------- While working on a fix for a regression I caused in #21757 I noticed that we had code in our utility module that could be affected by the same regression as I was trying to fix.
I've tried to list some of my observations while studying this code: - We use non-blocking I/O for stdout and stderr in the spawned `tor-fw- helper` child process, but we only call `log_from_pipe()` once immediately after spawning the process. From my quick observation the call to `log_form_pipe()` almost always result in a `EAGAIN` and we then return without processing any lines at all since we never actually try to read again. - We have duplicated code in `handle_fw_helper_line()` and `log_from_pipe()` to handle `SPAWN_ERROR_MESSAGE` error messages during child creation with a comment related to the first observation. I tried to test this with a simple dummy `PortForwardingHelper` script which outputs a set of lines on stdout and stderr, sleeps for a while, then continues to write some more content before it exits and only a subset of these lines are actually forwarded to tor's logging subsystem. The application seems to work correctly and contact my router, so this issue is purely related to the forwarding of stdout and stderr from the helper process. -- Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21765> Tor Bug Tracker & Wiki <https://trac.torproject.org/> The Tor Project: anonymity online _______________________________________________ tor-bugs mailing list tor-bugs@lists.torproject.org https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-bugs