Launching tor-fw-helper should untangle stderr for control, stdout for data?
Per discussion on #9781 (moved) :
back in cd05f35d2cdf50, we introduced a mismatch.
// In the child process: nbytes = write(STDOUT_FILENO, error_message, error_message_length); // In the parent: stderr_status = log_from_pipe(child_handle->stderr_handle, LOG_INFO, filename, &retval);
Note that we're writing the error message to stdout, but expecting to read it from stderr. To fix this for #9781 (moved), I had the code look for the error message in stdout too. But the code as it stands is still doing a silly thing by writing a message to one fd and expecting to read it from another.
(I tried to fix it by switching the child process to write to stderr, but that didn't work, so a cleverer fix may be needed.)