Changed behavior of ControlPath too long errors

Jakub Jelen jjelen at
Wed May 3 18:27:10 AEST 2017

recently we noticed that the behavior of too long ControlPath sockets 
changed in OpenSSH 6.7 from non-fatal error to fatal. The change was 
brought in by the unix-domain socket forwarding [1] and is not 
completely clear if it is intentional or not. It can be simply 
reproduced by trying to set up long ControlPath (common in Ansible):

ssh -o 
-o ControlMaster=yes jenkins.localdomain hostname
too long for Unix domain socket

The OpenSSH 6.6p1 successfully falls back to not using MUX (goto 
disable_mux_master;), but newer versions interpret it as a fatal errors 
and exit.

I understand that I might be late for party and being strict about 
configuration options is a good thing, but having this functionality 
backward compatible would be very helpful for existing scripts.

Is this intentional change? Can we stick back to the old behavior?


Jakub Jelen
Software Engineer
Security Technologies
Red Hat

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