Mailing List Archive: OpenSSH: Dev

CHANNEL SIZE.

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tshipclark at gmail

Apr 23, 2008, 9:22 AM

Post #1 of 4 (1008 views)
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CHANNEL SIZE.

Recently I updated to Hardy Heron(Ubuntu beta) and with it cam
openssh-client 4.7p1. In my environment we have alot of
Extreme(www.extremenetworks.com) switch devices which we access via
ssh.

4.7p1 would no longer allow me to connect to the switches, however 4.6p1
would. The error I received was.

' channel 0: open failed: resource shortage: Channel open failed'

I did some diggin and noticed these two constants where changed between
4.6 and 4.7

#define CHAN_SES_WINDOW_DEFAULT (4*CHAN_SES_PACKET_DEFAULT)
#define CHAN_TCP_WINDOW_DEFAULT (4*CHAN_TCP_PACKET_DEFAULT)

Changing the new value of 64*, back to 4*, solved the issue.

- markus [at] cvs 2007/06/11 09:14:00
[channels.h]
increase default channel windows; ok djm

Its probably an issue with our switches, but that is something I
probably cannot get rectified.

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djm at mindrot

Apr 23, 2008, 7:53 PM

Post #2 of 4 (959 views)
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Re: CHANNEL SIZE. [In reply to]

On Wed, 23 Apr 2008, Terry Shiplcark wrote:

> Recently I updated to Hardy Heron(Ubuntu beta) and with it cam
> openssh-client 4.7p1. In my environment we have alot of
> Extreme(www.extremenetworks.com) switch devices which we access via
> ssh.
>
> 4.7p1 would no longer allow me to connect to the switches, however 4.6p1
> would. The error I received was.
>
> ' channel 0: open failed: resource shortage: Channel open failed'
>
> I did some diggin and noticed these two constants where changed between
> 4.6 and 4.7
>
> #define CHAN_SES_WINDOW_DEFAULT (4*CHAN_SES_PACKET_DEFAULT)
> #define CHAN_TCP_WINDOW_DEFAULT (4*CHAN_TCP_PACKET_DEFAULT)
>
> Changing the new value of 64*, back to 4*, solved the issue.
>
> - markus [at] cvs 2007/06/11 09:14:00
> [channels.h]
> increase default channel windows; ok djm
>
> Its probably an issue with our switches, but that is something I
> probably cannot get rectified.

Please send a full debug trace (from "ssh -vvv ...") - I'm particularly
interested in the server banner. It appears in the debug trace like this:

debug1: Remote protocol version 2.0, remote software version OpenSSH_5.0

-d
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markus.r.friedl at arcor

Apr 24, 2008, 12:49 AM

Post #3 of 4 (965 views)
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Re: CHANNEL SIZE. [In reply to]

On Wed, Apr 23, 2008 at 12:22:53PM -0400, Terry Shiplcark wrote:
> 4.7p1 would no longer allow me to connect to the switches, however 4.6p1
> would. The error I received was.
>
> ' channel 0: open failed: resource shortage: Channel open failed'

yes, that's strange. it looks like a bug in the switch since
we only increased the size that openssh claims it can receive
and not the buffer sizes on the remote side.

do you have the ssh version string of the switch?

ssh -v prints it as
debug1: Remote protocol version X.Y, remote software version ZZZ

-m
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tshipclark at gmail

Apr 24, 2008, 5:50 AM

Post #4 of 4 (957 views)
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Re: CHANNEL SIZE. [In reply to]

debug1: Remote protocol version 2.0, remote software version 4.1.2 SSH
Secure Shell Toolkit
debug1: no match: 4.1.2 SSH Secure Shell Toolkit
debug1: Enabling compatibility mode for protocol 2.0

Is the one that doesnt connect. I did some more testing, and there older
hardware on the extremeware platform will still connect. Newer Hardware
will not.

old hardware

debug1: Remote protocol version 2.0, remote software version 2.0.12
(non-commercial)
debug1: match: 2.0.12 (non-commercial) pat 2.0.11*,2.0.12*
debug1: Enabling compatibility mode for protocol 2.0

Like I stated earlier changing the Default window size back to 4 solved the
issue, and everything else works fine. Full DEBUG output is attached

On Thu, Apr 24, 2008 at 3:49 AM, Markus Friedl <markus.r.friedl [at] arcor>
wrote:

> On Wed, Apr 23, 2008 at 12:22:53PM -0400, Terry Shiplcark wrote:
> > 4.7p1 would no longer allow me to connect to the switches, however 4.6p1
> > would. The error I received was.
> >
> > ' channel 0: open failed: resource shortage: Channel open failed'
>
> yes, that's strange. it looks like a bug in the switch since
> we only increased the size that openssh claims it can receive
> and not the buffer sizes on the remote side.
>
> do you have the ssh version string of the switch?
>
> ssh -v prints it as
> debug1: Remote protocol version X.Y, remote software version ZZZ
>
> -m
>

Attachments:

debug_output.txt (4.74 KB)

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