mosh-client exits unexpectedly on Cygwin when using Windows console

[danrsc]

mosh-client is exiting unexpectedly for me after 10 seconds - 1 minute. This seems to happen regardless of what I type (though it seems I must type to cause the issue). I tried typing the alphabet and there does not seem to be a particular character that causes the problem. I am invoking mosh through the cygwin terminal (i.e. in bash). If I invoke script and then invoke mosh within the script session, then I do not reproduce the behavior (i.e. the mosh-client does not exit unexpectedly). I have attached a screen shot of how it looks when the session has exited (which does not have any useful information). I also have run mosh-server in debug mode and mosh-client with strace (for the same session). I have attached the output from both.

On the client I am running:
Windows 10 Pro (version 1511) build 10586.36
cygwin 2.3.1
and the mosh version that installs with the cygwin installer (1.2.5-1)

I have two different servers that I'm trying to connect to; both reproduce the issue. On the servers I built mosh myself. Mosh version 1.2.5 using protbuf version 2.6.1:
Linux 2.6.35.9-004-F14_64 #1 SMP PREEMPT Thu Sep 18 12:31:45 EDT 2014 x86_64 x86_64 x86_64 GNU/Linux
LSB Version: :core-4.0-amd64:core-4.0-noarch
Distributor ID: Fedora
Description: Fedora release 14 (Laughlin)
Release: 14
Codename: Laughlin

Linux 2.6.32-279.el6.x86_64 #1 SMP Fri Jun 22 12:19:21 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
LSB Version: :core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch
Distributor ID: CentOS
Description: CentOS release 6.2 (Final)
Release: 6.2
Codename: Final

mosh_server_debug.txt
mosh_strace_output.txt

[cgull]

OK, I've now managed to reproduce this on my personal Win7Pro laptop with development Mosh sources, talking to a server about 10ms away. Mosh exits with no notification of problems after I've been typing a little while. This is likely different enough from your system that I don't think it's related to Win10 or any particular configuration you have.

But I can only reproduce it in Windows console, not in mintty. In the terminal you're using (before you start mosh) can you type ps -p $PPID, and tell me what command is listed? (It might be none at all, in which case you're using Windows console.)

What's the exit status of mosh-client when it fails? (Type echo $? immediately after mosh exits.)

If you are using Windows console, please try using mintty, and report whether Mosh still exits unexpectedly. You need to use mintty or another fully-featured terminal emulator anyway, the primitive ANSI-terminal emulation in Windows console doesn't work well with Mosh and you'll get corrupted screens. Even if this fixes your problem, I still want to chase this problem down a little further in case there's a bug/weakness in Mosh in this area.

[danrsc]

Yes you're right. When I run ps -p $PPID I do not get anything back, and if I run with mintty then mosh-client seems to behave correctly. echo $ does not give anything.

Thanks for your help!

Dan

[cgull]

This appears to be a bug in Cygwin's select() coupled with poor error handling in mosh-client: https://cygwin.com/ml/cygwin/2015-12/msg00332.html

[cgull]

The Cygwin maintainer has finally fixed the Cygwin bug, see the linked email thread. I'll also commit a workaround for the bug, and changes to make our tests work under Cygwin (though they wouldn't have caught this issue, since tmux is not a Windows console).