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Message-ID:	<56ac586e-e754-4cf3-8a68-17e62152931a@acm.org>
Date:	Thu, 27 Mar 2025 16:11:03 -0700
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User-Agent:	Mozilla Thunderbird
To:	cygwin AT cygwin DOT com
Subject:	ssh with multiplexing fails after connection and leaves zombie ssh
	processes
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From:	Jim Garrison via Cygwin <cygwin AT cygwin DOT com>
Reply-To:	Jim Garrison <jhg AT acm DOT org>
Sender:	"Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>

I just learned about ssh multiplexing and tried to set it up (Cygwin 
client to Debian server), but it fails to work and each attempt leaves a 
zombie ssh process.

According to the ssh -vvv debug output, authentication is successful but 
then fails during setup of the control master with

     mm_receive_fd: no message header
     mux_master_process_new_session: failed to receive fd 0 from client

I found a StackOverflow post from over a decade ago indicating the 
problem is that Cygwin doesn't support file descriptor passing via 
unix-domain sockets.  https://stackoverflow.com/questions/20959792

Is it still true that ssh multiplexing is not available in Cygwin, or is 
there a way to make it work?

-- 
Jim Garrison
jhg AT acm DOT org


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