Commits on Oct 20, 2023

1. Revert "sshdriver: Prevent timeout from deadlock" …

   This reverts commit b8f059f.
   
   OpenSSH < 8.5 called with -f waits for the stderr pipe to be closed
   before forking. [1] fixes this behavior.
   The labgrid commit to be reverted calls communicate(), relying on a
   timely fork. Affected OpenSSH versions now run into a TimeoutExpired
   exception on communicate() leading to an ExecutionError being raised in
   labgrid.
   
   A wait() with timeout was used since the initial implementation [2].
   We wanted to make sure that we don't depend on the state of the pipes, so
   use of wait() was intentional, as it directly covers the interesting cases:
   
   - immediate abort (due to a config error or similar)
   - normal startup (parent process exits after fork)
   - hang (via wait() timeout)
   
   Reverting the problematic commit avoids the complexity of having to
   maintain two different ways to start SSH as suggested in [3].
   
   If timeouts still occur after the revert, we should implement this
   suggestion [4].
   
   Discussion that lead to this patch can be found in the PR introducing
   the problematic commit [5] as well as in [3].
   
   The other commit [6] in the PR [5] has a similar approach for
   `labgrid.util.SSHConnection._start_own_master()`. It shouldn't
   be problematic though: The ssh process is not expected to fork as it is
   not called with -f.
   
   [1] OpenSSH: 396d32f3a ("upstream: There are lots of place where we want to redirect stdin,")
   [2] e4862fa ("SSHDriver: ControlMaster & Driver")
   [3] labgrid-project#1278
   [4] labgrid-project#1265 (comment)
   [5] labgrid-project#1265
   [6] f9ca024 ("ssh: Prevent timeout from deadlock")
   
   Signed-off-by: Bastian Krause <[email protected]>

   

   Bastian-Krause committed Oct 20, 2023
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