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Date: Thu, 15 Feb 2024 23:14:18 +0000
To: cygwin@cygwin.com
Subject: Re: ssh over stunnel hangs on second connection
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Here is some more strangeness:

1. (As before)
   - ssh first time -> succeeds
   - logout
   - ssh again -> hangs

2. Another sequence
   - SESSION 1: ssh first time -> succeeds
   - SESSION 2: ssh second time -> succeeds (without logging out session 1)
   - ...
   - SESSION N: ssh n'th time -> succeeds (without logging out any of the previous ones
   - logout of any of the first N-sessions
   - SESSION N+1: ssh -> FAILS
   - SESSION N+2: ssh -> FAILS
   - ...

So it seems like logging out of an 'ssh over stunnel' session somehow
causes 'stunnel' to hang on any succeeding sessions


"" wrote at about 14:23:30 -0500 on Thursday, February 15, 2024:
 > I am using Cygwin stunnel 5.71 on Windows 11 to connect to 'ssh' into my Ubuntu
 > server over 'stunnel'.
 > 
 > - The first time I ssh via stunnel it works fine The second time, I
 > - try to connect, it hangs with 'ssh -v' showing only the initial
 >   local steps of connection:
 > 
 > 	OpenSSH_9.5p1, OpenSSL 3.0.12 24 Oct 2023
 > 	debug1: Reading configuration data /home/myuser/.ssh/config
 > 	debug1: Reading configuration data /etc/ssh_config
 > 	debug1: Connecting to localhost [::1] port 2222.
 > 	debug1: Connection established.
 > 	debug1: identity file /home/myuser/.ssh/id_rsa type 0
 > 	debug1: identity file /home/myuser/.ssh/id_rsa-cert type -1
 > 	debug1: identity file /home/myuser/.ssh/id_ecdsa type -1
 > 	debug1: identity file /home/myuser/.ssh/id_ecdsa-cert type -1
 > 	debug1: identity file /home/myuser/.ssh/id_ecdsa_sk type -1
 > 	debug1: identity file /home/myuser/.ssh/id_ecdsa_sk-cert type -1
 > 	debug1: identity file /home/myuser/.ssh/id_ed25519 type -1
 > 	debug1: identity file /home/myuser/.ssh/id_ed25519-cert type -1
 > 	debug1: identity file /home/myuser/.ssh/id_ed25519_sk type -1
 > 	debug1: identity file /home/myuser/.ssh/id_ed25519_sk-cert type -1
 > 	debug1: identity file /home/myuser/.ssh/id_xmss type -1
 > 	debug1: identity file /home/myuser/.ssh/id_xmss-cert type -1
 > 	debug1: identity file /home/myuser/.ssh/id_dsa type -1
 > 	debug1: identity file /home/myuser/.ssh/id_dsa-cert type -1
 > 	debug1: Local version string SSH-2.0-OpenSSH_9.5
 > 
 >   and '/var/log/stunnel' on the Cygwin client failing early:
 > 
 >     LOG7[main]: Found 1 ready file descriptor(s)
 > 	LOG7[main]: FD=4 events=0x1 revents=0x0
 > 	LOG7[main]: FD=8 events=0x1 revents=0x1
 > 	LOG7[main]: FD=10 events=0x1 revents=0x0
 > 	LOG7[main]: Service [ssh] accepted (FD=3) from ::1:52718
 > 
 > 
 > - If I connect a *third* (or more times), 'ssh -v' hangs with the same
 >   output as above, but there is *no* additional logging in
 >   '/var/log/stunnel' on the client.
 > 
 > 
 > It thus is acting as if 'stunnel' on the Cygwin client itself somehow
 > hangs/becomes unresponsive early in the second 'ssh' connection
 > attempt.
 > 
 > Note that the client '/usr/bin/stunnel/ process continues to run so it
 > doesn't crash.
 > 
 > Killing and relaunching /usr/bin/stunnel restarts the situation
 > allowing me to ssh-over-stunel OK on the first attempt but again
 > hanging on the 2nd and subsequent 'ssh' attempts
 > 
 > Also, the 'stunnel' server on Ubuntu continues to run throughout since
 > I can continue to ssh-over-stunnel into it from other machines.
 > 
 > It doesn't *seem* to be a firewall problem, since it connects fine the
 > first time. Nor does it seem to be a network or 'stunnel' server
 > problem.
 > 
 > Any ideas on why this is happening?
 > 

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