Re: SFTP client Expect 5.43 via PASE, maximum times allowed depending on remote OS.

We programmed an sFTP system using Expect because our sFTP partner will not allow key exchange.

We had to modify the Expect timeout on large files as Scott suggests below.

This could be done dynamically by checking the file size before initiating the Expect sFTP

Jerry

On 11/23/2015 3:13 PM, Scott Klement wrote:

Paul,

1) Expect is not "one of my products". It's a public domain program
available from NIST.

There are a lot of tools available for IBM i that fall into "my
products", HTTPAPI, FTPAPI, TN5250, HSSFR4, XLPARSER4, JDBCR4, etc.

2) I do not have any other versions of it, I haven't needed them. Feel
free to get the latest sources and build your own version for PASE if
you are so inclined.

3) I do not consider any of the behavior you mentioned to be a bug in
Expect. Your script for Expect can be modified to check the timeout in a
loop, thus allowing it to take much longer. Or to turn off the timeout
completely, etc as you like.

Also, it's more useful to know the version of Expect vs. the operating
system being used. As Expect is not part of the operating system, the
version of the OS really shouldn't come into play, here.

-SK


On 11/23/2015 10:45 AM, Steinmetz, Paul wrote:

Scott,

I want to clarify that this is an Expect 5.43 issue (one of your
products), which is not supported by IBM.
Second, majority of the SFTP and SSH documentation does not apply when
Expect is used.
Third, based on my testing and attempting to change config files, the
ssh_config and sshd_config files are not used.
ClinetAliveCountMax ; ClinetAliveInterval ; TCPKeepAlive had no impact.

The reason this product was installed years ago, we needed an SFTP
solution for when the remote site could/would NOT support the use of
keys, only user and password.
Originally, only one remote vendor.
Now we are using for seven vendors.

Could you confirm my findings?
Do you have a newer version of Expect?
Is there a fix or workaround for this issue?

I've been testing sending the same file(s) via Expect 5.43 to 3
different servers using V7R1 as the client.

1) Remote Vendor OS unknown
2) Remote Local Production i5 V7R1
3) Remote Local Linux CENTOS 6.7

CALL PGM(QP2SHELL) PARM('/QOpenSys/usr/bin/sh' +
'-c' +
'/home/SFTPXFER/PAULS/paulsP05.expect > +
/home/SFTPXFER/PAULS/paulsP05.output')

It appears Expect 5.43 has a default "set timeout" of 20 seconds when
no "set timeout" is coded.
Files taking longer than 20 seconds will not complete.
By adding a "set timeout NNN" to the script, longer/larger files can
be sent.
However, the "set timeout NNN" has different maximums depending on the
remote OS.
When the "set timeout NNN" is above the maximum, file never starts
sending, connection is closed.
Sending to the Remote Vendor OS unknown, "set timeout 290" works,
higher values fail.
Sending to the Remote Local V7R1 i5, "set timeout 120" works, higher
values fail.
Sending to the Remote Local Linux CENTOS 6.7, "set timeout 119"
works, higher values fail.

Below are my testing results, showing the maximums allowed, sending
from a V7R1 OS client to:


Remote Vendor OS unknown Rem Production i5 V7R1 Rem
Local Linux CENTOS 6.7
7mb 20 sec 12 sec 12 sec
10mb 23 sec 12 sec 12 sec
15mb 23 sec 12 sec 12 sec
20mb 49 sec with ST 30 12 sec 12 sec
25mb 49 sec with ST 30 12 sec 13 sec
50mb 1m 49 sec with ST 60 15 sec 15 sec
75mb 1m 52 sec with ST 60 17 sec 17 sec
100mb 2m 49 sec with ST 90 21 sec 19 sec
125mb 2m 54 sec with ST 90 44 sec with ST 30 41
sec with ST 30
150mb 3m 46 sec with ST 120 44 sec with ST 30 45
sec with ST 30
200mb 4m 50 sec with ST 150 50 sec with ST 30
58 sec with ST 30
300mb 7m 42 sec with ST 240 60 sec with ST 30 58
sec with ST 30
400mb 8m 38 sec with ST 290 1m 49 sec with ST 60
1m 44 sec with ST 60
500mb 8m 40 sec with ST 290 1m 49 sec with ST 60
1m 46 sec with ST 60
600mb 10m with ST 290 88% 1m 57 sec with ST 60 1m
47 sec with ST 60
700mb 2m 35 sec with ST 90 2m 33 sec
with ST 90
800mb 2m 57 sec with ST 90 2m 48 sec
with ST 90
900mb 3m 31 sec with ST 120 3m 14 sec
with ST 110
1gb 3m 39 sec with ST 120 3m 24 sec with
ST 110
1.1gb 3m 51 sec with ST 120 3m 24 sec
with ST 110
1.2gb 3m 55 sec with ST 120 3m 38 sec
with ST 110
1.3gb 4m 00 sec with ST120 98% 4m 00 sec
with ST 119 88%

Paul


-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of
Scott Klement
Sent: Wednesday, November 18, 2015 3:00 PM
To: Midrange Systems Technical Discussion
Subject: Re: SFTP client via PASE, large files possibly timing out

Paul,

The 'set timeout' in Expect makes perfect sense. That didn't occur to
me before seeing your recent messages, but it makes a lot of sense.

Expect is not part of SSH (like SFTP is). It is a generic program
that pretends to be a user at a terminal, and automates what the user
might do... so it keys in values, and sits and waits for responses to
be sent to the "screen" (the virtual screen it's reading under the
covers, not your actual display) and based on what it sees on the
screen, it does something in response, etc. It can be used to automate
any user interaction with a PASE command-line environment.

So if you've written your script to timeout during a put/get command,
it makes perfect sense that it's killing the file transfer when the
timeout occurs. It doesn't know what the command is doing under the
covers, it only knows what's displayed to the screen.

So, my question to you... why code expect to do a timeout during the
actual put/get command? are you having trouble with it 'freezing'
during file transfers and never completing?

Sorry this response was a bit slow... I was out of the office for a
few days.

-SK




On 11/14/2015 11:43 AM, Steinmetz, Paul wrote:

Scott,

Those were settings recommended to check by IBM support.
By increasing "Set Timeout" from 30 to 90 included in the .expect
input script, I was successful in resolving this issue.
I tested using higher values, successful up to 296.
297 and higher fails.
Why is this?
I'd like to confirm for future for large files or when times are longer.

Paul

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of
Scott Klement
Sent: Friday, November 13, 2015 12:49 AM
To: Midrange Systems Technical Discussion
Subject: Re: SFTP client via PASE, large files possibly timing out

Paul,

Unless I'm misunderstanding your symptoms, you're looking at the
wrong settings, here...

My understanding is that your file transfer is looking good,
transferring data successfully until all of the sudden, mysteriously,
the transfer is cut off after 45 seconds.

But, you are checking things related to "inactivity". Inactivity
means that NOTHING is sent for the timeout period. Inactivity would
never cut you off in the middle of a file transfer that's progressing!

I know the timeout settings are set higher, but let's use 45 seconds
as an example to explain what 'inactivity' timeouts mean... if you
had an inactivity timeout of 45 seconds that was affecting you, this
is what would happen: (1) You'd start the transfer. (2) At some
point (maybe right away, or maybe several minutes later) the transfer
would "freeze"
where no new data was transfering for some reason like a network
glitch or something. (3) 45 seconds after freezing up -- which is to
say, 45 seconds without a single byte being transferred -- the
timeout would
kick in and disconnect you. If the transfer never froze up, the
timeout would never occur (even if the file took hours to send)

That's what an inactivity timeout is... it means things are stalled.
Nothing at all is transferred in the timeout period, not even a
single byte. As long as at least one byte is sent in that 45
seconds, it would not occur.

However, that's not how I understand your symptom. I understood that
it was cutting you off while the transfer was successfully going..
So unless i'm misunderstnading, what you're experiencing cannot be an
inactivity timeout. It's a timeout that occurs even on an active
session... right?

The 4 settings you mentioned, however...

1- an INACTIVITY timeout on your router.

2- Keepalive... this is completely unrelated.

3- FTP server settings -- completely unrelated, you are not using FTP.
Even if you were, it's not the server.

4- SSH is the right tool to check for settings on... but again, this
is an INACTIVITY timeout.

Unfortunately, I have no clue what would cause the issue you're seeing.
I've never seen this happen before. But, unless the session _is_
stalling for 45 seconds, this isn't an "inactivity" timeout. It's a
"you only have 45 seconds total to use this connection before I cut
you off" timeout, which is very different.

It's like saying to your teenaged daughter "you can only be on the
phone for 10 minutes per day". (Time limit) That's very different
from "as long as you say at least one word every 10 minutes you can
stay on the phone, but if you don't say anything for 10 minutes i'll
cut you off"
(inactivity timeout)




On 11/12/2015 2:03 PM, Steinmetz, Paul wrote:

I discovered a new piece to this puzzle.
For this one specific remote server:
All files are successful that complete in 45 seconds or less.
All files taking longer than 45 seconds fail.

Somewhere, there must be a 45 second timer/timeout setting.
These have been checked and confirmed.

1- It could be at the firewall/router's idle timeout level. - 5
minutes.
2- Verify the TCP keepalive on the iSeries (CHGTCPA). - TCP keep
alive . . . . . . . . . 5
3- General FTP Server Inactivity Timeout Value see the following
doc: The default inactivity timeout value is 300 seconds. The
default transfer timeout value is 420 seconds. Inactivity timeout .
. . . . . . 300
-http://www.ibm.com/support/docview.wss?uid=nas8N1011178
4- Timeout in SSH: Disconnecting Inactive SSH Sessions on the IBM I
The TMOUT and TIMEOUT PASE environment variables have a value of 600
seconds. If there is no activity within an SSH session for 10 minutes
-http://www.ibm.com/support/docview.wss?uid=nas8N1013311

Paul


-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf
Of Scott Klement
Sent: Tuesday, November 03, 2015 4:39 PM
To: Midrange Systems Technical Discussion
Subject: Re: SFTP client via PASE, large files possibly timing out

FWIW.. I have used sftp to send extremely large files, such as
whole server backups, without any problems at all. I did not have
to set up anything in particular, it just worked.

When you are having trouble with your larger files (imho, 110mb
isn't really very big) does it always stop at the exact same byte
position?
Or does it vary?

If it varies, I'd suggest this is probably a network issue rather
than a software issue. A flaky cable/switch/router/etc is causing
the data to get screwed up somewhere, causing the transfer to abort.

IF it's always the same, then I would look for some sort of size
limit being set up somewhere, most likely on the server-side.

Also, you could also try using scp rather than sftp and see if that
matters at all. Just as a lark...


On 11/3/2015 8:34 AM, Steinmetz, Paul wrote:

I changed the SFTP process to send a 3mb zip file instead of the
110mb uncompressed file.
SFTP now working with a zipped 3mb file.
Large file issue for SFTP still exists, possibly 30 to 40mb limit.
Still looking to resolve this issue.

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