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Why does ssh keep hanging

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  Why does ssh keep hanging unruh <unruh@invalid.ca> - 2012-04-30 00:37 +0000
    Re: Why does ssh keep hanging "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2012-04-29 21:20 -0400
      Re: Why does ssh keep hanging Richard Kettlewell <rjk@greenend.org.uk> - 2012-04-30 09:06 +0100
    Re: Why does ssh keep hanging Chris Davies <chris-usenet@roaima.co.uk> - 2012-04-30 10:38 +0100
      Re: Why does ssh keep hanging unruh <unruh@invalid.ca> - 2012-04-30 14:46 +0000
        Re: Why does ssh keep hanging Chris Davies <chris-usenet@roaima.co.uk> - 2012-04-30 17:07 +0100
          Re: Why does ssh keep hanging unruh <unruh@invalid.ca> - 2012-04-30 16:53 +0000
        Re: Why does ssh keep hanging Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-04-30 19:53 +0000
          Re: Why does ssh keep hanging unruh <unruh@invalid.ca> - 2012-04-30 21:14 +0000
            Re: Why does ssh keep hanging Rick Jones <rick.jones2@hp.com> - 2012-04-30 22:33 +0000
              Re: Why does ssh keep hanging Bernhard Kupfer a.k.a. Compukiller <nntp@compukiller.net> - 2012-05-04 06:06 +0000
                Re: Why does ssh keep hanging Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-05-04 12:32 +0000
                Re: Why does ssh keep hanging Rick Jones <rick.jones2@hp.com> - 2012-05-04 18:29 +0000
                  Re: Why does ssh keep hanging Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-05-05 03:54 +0000
                    Re: Why does ssh keep hanging Rick Jones <rick.jones2@hp.com> - 2012-05-07 18:05 +0000
                      Re: Why does ssh keep hanging Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-05-08 00:06 +0000
                    Re: Why does ssh keep hanging Chris Davies <chris-usenet@roaima.co.uk> - 2012-05-09 09:44 +0100
                      Re: Why does ssh keep hanging Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-05-09 11:08 +0000
                        Re: Why does ssh keep hanging Chris Davies <chris-usenet@roaima.co.uk> - 2012-05-10 17:09 +0100
                          Re: Why does ssh keep hanging Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-05-10 21:33 +0000
                            Re: Why does ssh keep hanging Chris Davies <chris-usenet@roaima.co.uk> - 2012-05-10 23:38 +0100
                              Re: Why does ssh keep hanging Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-05-11 09:22 +0000
    Re: Why does ssh keep hanging Richard Kettlewell <rjk@greenend.org.uk> - 2012-04-30 15:49 +0100
      Re: Why does ssh keep hanging unruh <unruh@invalid.ca> - 2012-04-30 15:48 +0000
        Re: Why does ssh keep hanging Richard Kettlewell <rjk@greenend.org.uk> - 2012-04-30 17:11 +0100

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#1315 — Why does ssh keep hanging

I am connecting to the net via a home router wireless (Zoom)  and I am
discovering that if I leave an ssh session for more than a minute of
two, it freezes (ie the ssh session stops being connected and the screen
is frozen) The session is not disconnected according to either of the
machines-- they seem to think that the ssh session is still running--
but nothing I type gets to the other side and no information goes from
there to me. 
I can open a new ssh session in anther terminal window, but the old one
stays dead. 
This is annoying if I am for example answering a netnews session or
editing an email as I just have to close the window and try again. Ie,
thought is being penalized. Is there any way I can figure out what is
going on-- why the session is freezing?

Note that a ping to the remote machine I am sshing to in another
 window keeps going.

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#1316

On Sun, 29 Apr 2012 20:37:51 -0400, unruh <unruh@invalid.ca> wrote:

> I am connecting to the net via a home router wireless (Zoom)  and I am
> discovering that if I leave an ssh session for more than a minute of
> two, it freezes (ie the ssh session stops being connected

http://fredericiana.com/2009/10/21/keeping-ssh-from-disconnecting-automatically/

Regards, Dave Hodgins

-- 
Change nomail.afraid.org to ody.ca to reply by email.
(nomail.afraid.org has been set up specifically for
use in usenet. Feel free to use it yourself.)

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#1317

"David W. Hodgins" <dwhodgins@nomail.afraid.org> writes:

> http://fredericiana.com/2009/10/21/keeping-ssh-from-disconnecting-automatically/

| Unfortunately, OpenSSH servers in their default settings take this
| silence as a perfect excuse to cut the cord after 5 minutes.

This is nonsense.  The blog poster has misunderstood whatever their
problem is (which is most likely to be some intervening firewall or
NAT).

-- 
http://www.greenend.org.uk/rjk/

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#1321

unruh <unruh@invalid.ca> wrote:
> I am connecting to the net via a home router wireless (Zoom)  and I am
> discovering that if I leave an ssh session for more than a minute of
> two, it freezes (ie the ssh session stops being connected and the screen
> is frozen)

One (or more) of the firewall devices between you and the remote server
is timing out your session. To stop this happening you need to use the
ServerAliveInterval setting.

For example, drop this in your ~/.ssh/config, or if the file already
exists, tweak it appropriately:

    Host *
	ServerAliveInterval 60

I often have these two configuration items in there, too, but YMMV:
	ForwardX11 yes
	Compression yes

Chris

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#1324

On 2012-04-30, Chris Davies <chris-usenet@roaima.co.uk> wrote:
> unruh <unruh@invalid.ca> wrote:
>> I am connecting to the net via a home router wireless (Zoom)  and I am
>> discovering that if I leave an ssh session for more than a minute of
>> two, it freezes (ie the ssh session stops being connected and the screen
>> is frozen)
>
> One (or more) of the firewall devices between you and the remote server
> is timing out your session. To stop this happening you need to use the
> ServerAliveInterval setting.

I suppose that the zoom modem might have a firewall enabled, but I doubt
it. My computers on either end do not Note that this happens even if I
am connected to exactly the same machine in another window (also on ssh)
Ie, it seems to be a ssh session problem, not a general computer to
computer problem. I'll try the various Alive options. 
Thanks

( and it is not an ssh closing problem. On my side the session is to all
intents still open-- no logout, no closing. On the far side the program
that was running in the ssh session is still running so it thinks it is
still connected to something. It is just that no data passes between
them.
This is only happening as well on this one connection through this zoom
modem, and not at work where the session stays useable and open for
hours and days. So it is not the computers at either end.



>
> For example, drop this in your ~/.ssh/config, or if the file already
> exists, tweak it appropriately:
>
>     Host *
> 	ServerAliveInterval 60
>
> I often have these two configuration items in there, too, but YMMV:
> 	ForwardX11 yes
> 	Compression yes
>
> Chris

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#1329

>> unruh <unruh@invalid.ca> wrote:
>>> I am connecting to the net via a home router wireless (Zoom)  and I am
>>> discovering that if I leave an ssh session for more than a minute of
>>> two, it freezes (ie the ssh session stops being connected and the screen
>>> is frozen)

> On 2012-04-30, Chris Davies <chris-usenet@roaima.co.uk> wrote:
>> One (or more) of the firewall devices between you and the remote server
>> is timing out your session. To stop this happening you need to use the
>> ServerAliveInterval setting.

unruh <unruh@invalid.ca> wrote:
> I suppose that the zoom modem might have a firewall enabled, but I doubt
> it.

You described it as a wireless router and then a modem. On that basis
I'm going to continue to assume that it's performing NAT, and therefore
it's a strong candidate for triggering the fault as described.

Chris

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#1331

On 2012-04-30, Chris Davies <chris-usenet@roaima.co.uk> wrote:
>>> unruh <unruh@invalid.ca> wrote:
>>>> I am connecting to the net via a home router wireless (Zoom)  and I am
>>>> discovering that if I leave an ssh session for more than a minute of
>>>> two, it freezes (ie the ssh session stops being connected and the screen
>>>> is frozen)
>
>> On 2012-04-30, Chris Davies <chris-usenet@roaima.co.uk> wrote:
>>> One (or more) of the firewall devices between you and the remote server
>>> is timing out your session. To stop this happening you need to use the
>>> ServerAliveInterval setting.
>
> unruh <unruh@invalid.ca> wrote:
>> I suppose that the zoom modem might have a firewall enabled, but I doubt
>> it.
>
> You described it as a wireless router and then a modem. On that basis
> I'm going to continue to assume that it's performing NAT, and therefore
> it's a strong candidate for triggering the fault as described.

Sorry, yes, it is a wireless access point, a router. I have no idea how
it hooks into the network. 

I enabled ClientAliveInterval 15 on the host, and that seems to be
helpful. We will see. 


>
> Chris

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#1333

On Mon, 2012-04-30, unruh wrote:
> On 2012-04-30, Chris Davies <chris-usenet@roaima.co.uk> wrote:
>> unruh <unruh@invalid.ca> wrote:
>>> I am connecting to the net via a home router wireless (Zoom)  and I am
>>> discovering that if I leave an ssh session for more than a minute of
>>> two, it freezes (ie the ssh session stops being connected and the screen
>>> is frozen)
>>
>> One (or more) of the firewall devices between you and the remote server
>> is timing out your session. To stop this happening you need to use the
>> ServerAliveInterval setting.
>
> I suppose that the zoom modem might have a firewall enabled, but I doubt
> it. My computers on either end do not Note that this happens even if I
> am connected to exactly the same machine in another window (also on ssh)
> Ie, it seems to be a ssh session problem, not a general computer to
> computer problem.

I bet it's a general TCP problem. I.e. if you set e.g. netcat to
listen on one machine, use netcat to connect to it from the other, and
type a few lines once in a while, you'll see the exact same thing.

Like the others, I blame NAT. I am happy to say I have no such devices
-- killing TCP connections after mere minutes of inactivty is plain
broken. I'd demand my money back (and enable keepalives while waiting
for a replacement).

/Jorgen

-- 
  // Jorgen Grahn <grahn@  Oo  o.   .     .
\X/     snipabacken.se>   O  o   .

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#1335

On 2012-04-30, Jorgen Grahn <grahn+nntp@snipabacken.se> wrote:
> On Mon, 2012-04-30, unruh wrote:
>> On 2012-04-30, Chris Davies <chris-usenet@roaima.co.uk> wrote:
>>> unruh <unruh@invalid.ca> wrote:
>>>> I am connecting to the net via a home router wireless (Zoom)  and I am
>>>> discovering that if I leave an ssh session for more than a minute of
>>>> two, it freezes (ie the ssh session stops being connected and the screen
>>>> is frozen)
>>>
>>> One (or more) of the firewall devices between you and the remote server
>>> is timing out your session. To stop this happening you need to use the
>>> ServerAliveInterval setting.
>>
>> I suppose that the zoom modem might have a firewall enabled, but I doubt
>> it. My computers on either end do not Note that this happens even if I
>> am connected to exactly the same machine in another window (also on ssh)
>> Ie, it seems to be a ssh session problem, not a general computer to
>> computer problem.
>
> I bet it's a general TCP problem. I.e. if you set e.g. netcat to
> listen on one machine, use netcat to connect to it from the other, and
> type a few lines once in a while, you'll see the exact same thing.
>
> Like the others, I blame NAT. I am happy to say I have no such devices
> -- killing TCP connections after mere minutes of inactivty is plain
> broken. I'd demand my money back (and enable keepalives while waiting
> for a replacement).

Fortunately I am only here for a few weeks, so will soon be rid of the
problem. But it sure is annoying while it lasts. 

>
> /Jorgen
>

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#1337

unruh <unruh@invalid.ca> wrote:
> On 2012-04-30, Jorgen Grahn <grahn+nntp@snipabacken.se> wrote:
> > Like the others, I blame NAT. I am happy to say I have no such
> > devices -- killing TCP connections after mere minutes of inactivty
> > is plain broken. I'd demand my money back (and enable keepalives
> > while waiting for a replacement).

> Fortunately I am only here for a few weeks, so will soon be rid of
> the problem. But it sure is annoying while it lasts.

Oh! what a tangled web we wove
When NAT we sought to interpose!

(with apologies to Walter Scott)

rick jones
-- 
oxymoron n, Hummer H2 with California Save Our Coasts and Oceans plates
these opinions are mine, all mine; HP might not want them anyway... :)
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

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#1363

Rick Jones <rick.jones2@hp.com> wrote:
> 
> Oh! what a tangled web we wove
> When NAT we sought to interpose!
> 
> (with apologies to Walter Scott)
> 
> rick jones

Right ;)
And IPv6 is still not available for most customers :/ At least in
Germany...

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#1366

On Fri, 2012-05-04, Bernhard Kupfer a.k.a  Compukiller wrote:
> Rick Jones <rick.jones2@hp.com> wrote:
>> 
>> Oh! what a tangled web we wove
>> When NAT we sought to interpose!
>> 
>> (with apologies to Walter Scott)
>> 
>> rick jones
>
> Right ;)
> And IPv6 is still not available for most customers :/ At least in
> Germany...

It's available alright (free tunnels from e.g. Hurricane Electric)
-- there aren't too many peers to talk to ...

/Jorgen

-- 
  // Jorgen Grahn <grahn@  Oo  o.   .     .
\X/     snipabacken.se>   O  o   .

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#1367

Bernhard Kupfer a.k.a. Compukiller <nntp@compukiller.net> wrote:
> Rick Jones <rick.jones2@hp.com> wrote:
> > Oh! what a tangled web we wove
> > When NAT we sought to interpose!
> > 
> > (with apologies to Walter Scott)

> Right ;)
> And IPv6 is still not available for most customers :/ At least in
> Germany...

I don't think it has been lit-up by Uvers (AT&T) in Sunnyvale, CA
either.  Even so, does IPv6 really make NAT go away?  Yes, it may
address one of the first motivations for NAT - lack of address space
(assuming the providers are willing to provide sufficiently sized
address blocks to customers) but won't there still be a strong desire
to obfuscate what is going on on the customer premises?

rick jones
-- 
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

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#1368

On Fri, 2012-05-04, Rick Jones wrote:
> Bernhard Kupfer a.k.a. Compukiller <nntp@compukiller.net> wrote:
>> Rick Jones <rick.jones2@hp.com> wrote:
>> > Oh! what a tangled web we wove
>> > When NAT we sought to interpose!
>> > 
>> > (with apologies to Walter Scott)
>
>> Right ;)
>> And IPv6 is still not available for most customers :/ At least in
>> Germany...
>
> I don't think it has been lit-up by Uvers (AT&T) in Sunnyvale, CA
> either.  Even so, does IPv6 really make NAT go away?  Yes, it may
> address one of the first motivations for NAT - lack of address space
> (assuming the providers are willing to provide sufficiently sized
> address blocks to customers)

Why wouldn't they? As far as I can tell, giving the customers
something smaller than a /64 would just create more work for them,
and/or violate IPv6 itself.

> but won't there still be a strong desire
> to obfuscate what is going on on the customer premises?

There seems to be lots of people who think NAT is a vital part of
their privacy -- I don't quite understand why. Perhaps they will
reconsider when the rest of us start using real peer-to-peer
protocols without NAT workarounds.

/Jorgen

-- 
  // Jorgen Grahn <grahn@  Oo  o.   .     .
\X/     snipabacken.se>   O  o   .

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#1370

Jorgen Grahn <grahn+nntp@snipabacken.se> wrote:
> On Fri, 2012-05-04, Rick Jones wrote:
> > Even so, does IPv6 really make NAT go away?  Yes, it may address
> > one of the first motivations for NAT - lack of address space
> > (assuming the providers are willing to provide sufficiently sized
> > address blocks to customers)

> Why wouldn't they? As far as I can tell, giving the customers
> something smaller than a /64 would just create more work for them,
> and/or violate IPv6 itself.

I just wonder if they will try to monetize somehow.  Giving a customer
a large number of addresses without charging more for it is something
I suspect a number of green-eyeshades types look dimmly upon.

rick jones
-- 
Wisdom Teeth are impacted, people are affected by the effects of events.
these opinions are mine, all mine; HP might not want them anyway... :)
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

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#1371

On Mon, 2012-05-07, Rick Jones wrote:
> Jorgen Grahn <grahn+nntp@snipabacken.se> wrote:
>> On Fri, 2012-05-04, Rick Jones wrote:
>> > Even so, does IPv6 really make NAT go away?  Yes, it may address
>> > one of the first motivations for NAT - lack of address space
>> > (assuming the providers are willing to provide sufficiently sized
>> > address blocks to customers)
>
>> Why wouldn't they? As far as I can tell, giving the customers
>> something smaller than a /64 would just create more work for them,
>> and/or violate IPv6 itself.
>
> I just wonder if they will try to monetize somehow.  Giving a customer
> a large number of addresses without charging more for it is something
> I suspect a number of green-eyeshades types look dimmly upon.

Messing with that aspect of IPv6 would be astonishingly stupid and
counter-productive ... perhaps I'm not cynical enough, but I don't
think it will happen that way.

(On the other hand, when *will* it happen? ISPs around here
don't even /pretend/ to have IPv6 plans.)

/Jorgen

-- 
  // Jorgen Grahn <grahn@  Oo  o.   .     .
\X/     snipabacken.se>   O  o   .

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#1373

Jorgen Grahn <grahn+nntp@snipabacken.se> wrote:
> There seems to be lots of people who think NAT is a vital part of
> their privacy -- I don't quite understand why.

I'm currently sitting on the NAT side of the fence. (Just.) My
reasoning is this. It is the ISPs that issue the /64 netblocks for
end users/organisations. If I use that /64 directly on my network,
it's fine right up to the point that I want to switch ISP, but then I
need a mammoth renumber to fit the new /64 from the new ISP. This can
work for devices that use and understand DHCP but requires intensive
and coordinated intervention for everything else (routers, firewalls,
DHCP servers, dumber devices, etc.)

1:1 NAT would help tremendously in this situation, as I could keep my own
private number space internally, but still present the full address space
in the routable IPv6 world with every device potentially addressable -
just like you would expect.

Chris

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#1374

On Wed, 2012-05-09, Chris Davies wrote:
> Jorgen Grahn <grahn+nntp@snipabacken.se> wrote:
>> There seems to be lots of people who think NAT is a vital part of
>> their privacy -- I don't quite understand why.
>
> I'm currently sitting on the NAT side of the fence. (Just.)

Well, I wasn't arguing against optional NAT for any possible need.

> My reasoning is this. It is the ISPs that issue the /64 netblocks for
> end users/organisations. If I use that /64 directly on my network,
> it's fine right up to the point that I want to switch ISP, but then I
> need a mammoth renumber to fit the new /64 from the new ISP. This can
> work for devices that use and understand DHCP but requires intensive
> and coordinated intervention for everything else (routers, firewalls,
> DHCP servers, dumber devices, etc.)

In a large organization: yes, I guess so.

In a smaller home network, I'd expect stateless address autoconfig
plus DNS to make that fairly painless. Not that I have much experience
with this -- perhaps I'm overlooking something.

> 1:1 NAT would help tremendously in this situation, as I could keep my own
> private number space internally, but still present the full address space
> in the routable IPv6 world with every device potentially addressable -
> just like you would expect.

1:1 NAT would indeed be much less painful than what most of us suffer
from today. Done wrong it could still have the problem which caused
this thread, though. And it feels weird to have two different addresses
for a host depending on from where you're looking.

/Jorgen

-- 
  // Jorgen Grahn <grahn@  Oo  o.   .     .
\X/     snipabacken.se>   O  o   .

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#1376

Jorgen Grahn <grahn+nntp@snipabacken.se> wrote:
> it feels weird to have two different addresses for a host depending
> on from where you're looking.

This situation already exists today, and for most people they don't
even know about it as properly split and organised DNS hides the issue -
just like it should.

Chris

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#1377

On Thu, 2012-05-10, Chris Davies wrote:
> Jorgen Grahn <grahn+nntp@snipabacken.se> wrote:
>> it feels weird to have two different addresses for a host depending
>> on from where you're looking.
>
> This situation already exists today,

I know, but that doesn't make it less weird.

> and for most people they don't
> even know about it as properly split and organised DNS hides the issue -
> just like it should.

It may hide part of the issue, but they still cannot run any servers,
use protocols which aren't made to work with normal IPv4 NAT, and so
on.

/Jorgen

-- 
  // Jorgen Grahn <grahn@  Oo  o.   .     .
\X/     snipabacken.se>   O  o   .

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