Changed behavior of ControlPath too long errors

[Jakub Jelen]

Hello,
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 
ControlPath=/var/lib/very-long-installer/.ansible/cp/ansible-ssh-%h-%p-%r 
-o ControlMaster=yes jenkins.localdomain hostname
ControlPath 
"/var/lib/very-long-installer/.ansible/cp/ansible-ssh-jenkins-localdomain-22-installer.RpqsfHyo1aAYZIg2" 
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?

[1] https://github.com/Jakuje/openssh-portable/commit/7acefbbc

Thanks,
-- 
Jakub Jelen
Software Engineer
Security Technologies
Red Hat