Date: Wed, 10 Aug 2016 14:46:55 -0400 From: john hood <cgull+l-freebsd-current@glup.org> To: Peter Jeremy <peter@rulingia.com>, freebsd-ports@freebsd.org, freebsd-current@freebsd.org, mosh-devel@mit.edu, John Hood <cgull@glup.org> Subject: Re: Mosh regression between 10.x and 11-stable Message-ID: <0daf3b02-55dd-6397-d64d-10a525d4b478@glup.org> In-Reply-To: <20160810081831.GA65184@server.rulingia.com> References: <20160810081831.GA65184@server.rulingia.com>
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On 8/10/16 4:18 AM, Peter Jeremy wrote: > I recently updated one of my VPS hosts from 10.3-RELEASE-p5 to 11.0-BETA4 > r303811 and mosh to that host from my Linux laptop stopped working. All > I get on the laptop is: > $ mosh remotehost > Connection to remotehost closed. > /usr/bin/mosh: Did not find mosh server startup message. > > I've tried rebuilding mosh (and all dependencies) on the host to no avail. I'm a mosh maintainer. mosh 1.2.5 (from ports) and mosh master (just last night tagged as 1.2.6, alas) work fine for me on my two 11.0-BETA4 systems, one local and one remote. > This isn't the DSA change that's been discussed elsewhere: I can SSH from my > laptop to the host without problem. I can also manually invoke mosh-client > and mosh-server and it works. Unfortunately, mosh has no provision for > debugging. I've tried hacking the mosh perl script to make it more verbose > and that shows that: > 1) the "MOSH CONNECT" message isn't making it out of the local ssh process. Do you know if the message is getting out of mosh-server? into sshd? Do you know if mosh-server is actually running? (It will log utmp entries on startup.) Mosh's debugging/logging isn't very good, but 'mosh-server new -v 2> logfile' does produce some useful info (mostly logging of network traffic). > 2) it's racy because I can get it from "always fails" to "sometimes works". How do you get it there? > My suspicion is that something has changed in either sshd or TCP that > is resulting in the connection going away before the stdout from the > remote mosh-server makes it out from the local ssh process. mosh does 'ssh -t' and uses ptys. That's another potential point the message could get dropped. > I've looked at tcpdump's of both successful and failed SSH sessions > but don't see anything obviously different (encryption makes it > difficult to decode the session). > > Has anyone else seen this behaviour or have any ideas what might be > causing it? Common suspects include issues with shell login/invocation of mosh (are you making sure it's reachable in /usr/local/bin with $PATH or '--server=/usr/local/bin/mosh'? are your login shell and its login scripts unusual?) On Linux we've had issues with ecryptfs and systemd breaking mosh-server when the ssh session ends, but I don't think that applies here. regards, --jh
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