[mosh-devel] JuiceSSH STPClient Resuming

[Tom Maddox]

Hi Keith,

Brilliant, it looks like we're gonna be able to get this sussed out then.

So, the licensing stuff. We're building mosh-client from source on a
dedicated build server and then including that binary with our app to run
as a subprocess. We've also included (as of this release) an About page in
our Settings Menu which displays information and licenses of all open
source projects used, including the GPL notice.
Our application isn't open source as that would rather quickly make our
in-app purchase worthless however, mosh and other open source dependent
features are included within JuiceSSH's core functionality and will never
require a purchase. Whilst we don't want or expect to ever make a huge sum
of money through pro-pack purchases, we do have some hosting and test
device costs we'd like to cover.
If you feel that we're not meeting the requirements of mosh's license,
we'll be happy to do our best to make changes to that end.

I think I understand what you mean by only allowing a restore to happen
once from a serialised state. But just to check, if a session had been
restored in a new process successfully, would we then be able to repeat the
save state and resume later procedure?

The kill signal solution with the state printed stdout should definitely be
workable. It'll take a bit of work to intercept the io streams before it
reaches the terminal but it's certainly not impossible.

A couple of ideas that come to mind with this functionality:

   1. JuiceSSH has a pro feature called CloudSync which keeps devices in
   sync with AES-256 encrypted backups. There's the potential to use this or
   NFC to add some "Resume on tablet" functionality.
   2. Is there anything server side that would prevent a state being reused
   more than once? For example, if a connection is made where the client's
   state is older than that of the last recorded client state, then the new
   client (in the older state) is denied updates.

Thanks again,
Tom


Tom Maddox
*Co-founder, Sonelli Ltd*
tom at sonelli.com | https://sonelli.com
JuiceSSH - Free SSH client for
Android<https://play.google.com/store/apps/details?id=com.sonelli.juicessh>


On 4 August 2013 04:57, Keith Winstein <keithw at mit.edu> wrote:

> Hi Tom,
>
> Thanks for getting in touch. We can work with you to serialize the state
> of an STMClient object and restore it later. We are eager to see an Android
> Mosh client in the Play Store.
>
> The major major constraint here is that you can only restore from a
> serialized state *once*. We will want mosh-client to erase the serialized
> state before using it to make sure it can't be reused. The reason is that
> if you reuse a crypto sequence number (the nonce), that blows everything.
>
> How would you like to communicate with mosh-client that you want it to
> quit and dump state? You could just send us a SIGUSR1 or something and we
> could write it to stdout bracketed with something like BEGIN MOSH SAVED
> STATE if that works for you. And then if you give us a filename on startup
> (that we can erase), that would work fine to restore.
>
> I should ask -- are you running mosh-client as a separate binary or are
> you linking against it? (If linking against it, just to check, is your app
> under the GPL too?)
>
> Also, what sort of timeframe are you looking at for your release?
>
> Cheers,
> Keith
>
> On Sat, Aug 3, 2013 at 1:34 PM, Tom Maddox <tom at sonelli.com> wrote:
>
>> Hi,
>>
>> We're currently beta testing MOSH integration with our Android SSH
>> client, JuiceSSH, of which the progress can be followed in our G+
>> community <https://plus.google.com/u/0/communities/110428419162168502506>
>> .
>>
>> One issue that has been raised so far is battery usage. Currently when
>> JuiceSSH has any active connections, there is a service running which holds
>> a device wake lock and polls the connections for failures. Seeing as Mosh
>> sessions should always be resumable, and as Keith pointed out, this
>> shouldn't be necessary in the case of Mosh.
>>
>> Keith implied that he may be able to help us save the state of a
>> mosh-client process, allowing for it to be resumed in the future.
>>
>> I've planned the majority of how to exclude Mosh sessions from wake locks
>> and connection polling, and I'm confident that we'll be able to catch the
>> point that the state should be saved and then finally I know how we could
>> implement an "if-process-not-running-attempt-resume"-esque session.
>>
>> But the bit I'm not sure about is how to get the state, what form it will
>> be in, and then how to reuse it.
>>
>> Having looked through the research paper and checking out the
>> presentation, it would appear that this functionality is not yet in place.
>> If so, and this functionality is new, then one solution I can think of
>> would be the ability to run "mosh-client <IP> <Port> --resume-from-state
>> [<State-Related-Params>|<State-File>]" to resume the process and perhaps a
>> certain kill signal could result in mosh-client printing it's state just
>> before it finishes.
>>
>> Any thoughts or help would be really appreciated. We're both very excited
>> here about how convenient and nice this tool will be. As a couple of
>> SysAdmins that wrote JuiceSSH mostly during our commutes on trains, we
>> certainly appreciate the benefits!
>>
>> Thanks and regards,
>> Tom
>>
>> Tom Maddox
>> *Co-founder, Sonelli Ltd*
>> tom at sonelli.com | https://sonelli.com
>> JuiceSSH - Free SSH client for Android<https://play.google.com/store/apps/details?id=com.sonelli.juicessh>
>>
>> _______________________________________________
>> mosh-devel mailing list
>> mosh-devel at mit.edu
>> http://mailman.mit.edu/mailman/listinfo/mosh-devel
>>
>>
>
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