Re: [Duplicity-talk] [ ftplicity-Bugs-2684345 ] Traceback with duplicity 0.5.06-2~bpo40+1]

[Kenneth Loafman]

Tell him to upgrade to 0.5.11.  Easier than upgrading NcFTP.

If he's using FTP, have him apply the very short patch at:
https://savannah.nongnu.org/bugs/?25838
He'll need that if he has network errors.  I thought auto-resume
defaulted to 'on', I should have checked further.  The patch forces it
on no matter what the default.

Or wait till .12, probably Sunday or so.

It's always something!

...Ken

address@hidden wrote:
> Perfect .. so the ftplicity user should either upgrade duplicity or
> ncftp ... sky all clear ..
> 
> regards ede
> -- 
> 
>> I don't need to re-implement it... ncftpput is not used anymore, so no
>> need to check for it.  As far as I know, ncftp itself never had this
>> problem, just the utility.
>>
>> ...Ken
>>
>> address@hidden wrote:
>>  
>>> I see .. exactly the versions I missed ;) .. so your going to implement
>>> it again?
>>> What about a nice error message explaining the matter?
>>>
>>> ..ede
>>> -- 
>>>    
>>>> The check is only in 0.5.06, .07, .08, it was taken out in 0.5.09
>>>> when I
>>>> changed to using ncftp directly, rather than ncftpput/get/ls.  The
>>>> check
>>>> was only intended to protect against ncftpput 3.2.0, but they all come
>>>> as a group, so it affects all of the group.
>>>>
>>>> We're up to .11, with .12 coming out next week or so.
>>>>
>>>> ...Ken
>>>>
>>>> address@hidden wrote:
>>>>  
>>>>      
>>>>> it says
>>>>>
>>>>> NcFTPLs 3.2.0
>>>>>
>>>>> maybe a letter case difference?
>>>>>
>>>>> ..ede
>>>>>
>>>>>           
>>>>>> That was fixed in v0.5.07, so maybe you're running an earlier
>>>>>> version?
>>>>>> If not, then what does the first line of 'ncftpls -v' say?
>>>>>>
>>>>>> You do the safe thing, verify everything.  Most folks do not.
>>>>>>
>>>>>> ...Ken
>>>>>>
>>>>>> address@hidden wrote:
>>>>>>  
>>>>>>               
>>>>>>> Sorry to be persistent on it ... finally it is your decision.
>>>>>>>
>>>>>>> Just to be clear. Because at some point in time ncftp 3.2.0
>>>>>>> segfaulted,
>>>>>>> this gives a hint that it was badly programmed and every data
>>>>>>> from it
>>>>>>> might get corrupted without somebody noticing it?
>>>>>>> Again mine is also 3.2.0 so why is it not banned? Ok I know that
>>>>>>> everything is fione because I verify every backup. But still.
>>>>>>> Shouldn't
>>>>>>> it be banned?
>>>>>>>
>>>>>>> ..ede
>>>>>>>
>>>>>>>                      
>>>>>>>> Short answer, yes, sort of.  It won't harm the system, but it may
>>>>>>>> harm
>>>>>>>> the program, or the data it generates.
>>>>>>>>
>>>>>>>> A segfault is an errant memory read/write to memory outside the
>>>>>>>> program
>>>>>>>> itself, i.e. it tries to read/write to a system area, or into
>>>>>>>> another
>>>>>>>> program.  If this errant read/write is to a legitimate location
>>>>>>>> inside
>>>>>>>> the program itself, you can get stack or data corruption, which is
>>>>>>>> very
>>>>>>>> hard to find, and annoying.
>>>>>>>>
>>>>>>>> This location can change when, for example, the compiler is
>>>>>>>> different or
>>>>>>>> even when the compile options are different.  Different distro's
>>>>>>>> use
>>>>>>>> different versions of the compiler, sometimes change the options
>>>>>>>> that
>>>>>>>> the author used, gen for 32-bit and 64-bit, any number of
>>>>>>>> changes can
>>>>>>>> move the target address, and move the problem.
>>>>>>>>
>>>>>>>> If I know that I have a program that may segfault in one
>>>>>>>> environment,
>>>>>>>> then I know that I have a program that may corrupt data in another
>>>>>>>> environment.  Its best not to trust to luck in an application that
>>>>>>>> serves a backup program.
>>>>>>>>
>>>>>>>> That said, I take back what I wrote earlier (entirely too much
>>>>>>>> blood in
>>>>>>>> my caffeine stream).  The check should stay in for that particular
>>>>>>>> version, and it is better to ask the user to upgrade.
>>>>>>>>
>>>>>>>> ...Ken
>>>>>>>>
>>>>>>>> address@hidden wrote:
>>>>>>>>  
>>>>>>>>                            
>>>>>>>>> Do I understand correctly that a segfault might compromise the
>>>>>>>>> systems
>>>>>>>>> stability or affect other programs running on the same machine? In
>>>>>>>>> that
>>>>>>>>> case I totally agree with you ...
>>>>>>>>>
>>>>>>>>> ..ede
>>>>>>>>> -- 
>>>>>>>>>                                     
>>>>>>>>>> Not sure that A was the right choice, but we're past that now.
>>>>>>>>>> It's
>>>>>>>>>> easily removed if you just remove the check in ftpbackend.py, so
>>>>>>>>>> maybe a
>>>>>>>>>> patch could be issued to remove the check, or maybe just issue a
>>>>>>>>>> warning
>>>>>>>>>> instead.
>>>>>>>>>>
>>>>>>>>>> I tend to err towards caution in handling errors.  A segfault may
>>>>>>>>>> not be
>>>>>>>>>> generated if the memory modified is not executed, but could
>>>>>>>>>> produce bad
>>>>>>>>>> data output instead, so unless I know the version has been
>>>>>>>>>> fixed, and
>>>>>>>>>> not just compiled differently, I would not really trust it.
>>>>>>>>>>
>>>>>>>>>> ...Ken
>>>>>>>>>>
>>>>>>>>>> address@hidden wrote:
>>>>>>>>>>  
>>>>>>>>>>                                             
>>>>>>>>>>> Thanks for this overview ... very interesting in every detail
>>>>>>>>>>> indeed
>>>>>>>>>>> ....
>>>>>>>>>>>
>>>>>>>>>>> Regarding your comments ...
>>>>>>>>>>>
>>>>>>>>>>> A) If ncftp 3.2.0 raises an error, but not always, why
>>>>>>>>>>> blocking by
>>>>>>>>>>> version and not by issuing the segfault or whatever error? E.g.
>>>>>>>>>>> in the
>>>>>>>>>>> case of the ftplicity user from the bug list... He used
>>>>>>>>>>> ftplicity/duplicity happily until now the new version refuses to
>>>>>>>>>>> work
>>>>>>>>>>> with a obviously working ncftp version.
>>>>>>>>>>>
>>>>>>>>>>> B) You explained that a version string is compared, so the
>>>>>>>>>>> question on
>>>>>>>>>>> put with list-files is obsolete :)
>>>>>>>>>>>
>>>>>>>>>>> Eventually, I agree totally ... Dogmatic Rules are for people
>>>>>>>>>>> that
>>>>>>>>>>> refuse development. Usually they don't last long .... Said
>>>>>>>>>>> that, why
>>>>>>>>>>> force somebody to upgrade, if there is only a chance of an error
>>>>>>>>>>> occuring but no certainty. This is like trying to keep children
>>>>>>>>>>> from
>>>>>>>>>>> danger. Impossible ;)
>>>>>>>>>>>
>>>>>>>>>>> ... ede
>>>>>>>>>>>
>>>>>>>>>>> PS: I really love the phrase of your french teacher :))
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Kenneth Loafman wrote:
>>>>>>>>>>>                                                        
>>>>>>>>>>>> address@hidden wrote:
>>>>>>>>>>>>  
>>>>>>>>>>>>                                            
>>>>>>>>>>>>                      
>>>>>>>>>>>>>> I have a suspicion there may be differences in the distro's,
>>>>>>>>>>>>>> some
>>>>>>>>>>>>>> with
>>>>>>>>>>>>>> bug fixes, some not.
>>>>>>>>>>>>>>                                                 
>>>>>>>>>>>>>>                                                 
>>>>>>>>>>>>> How does duplicity detect the faulty version? Or does it
>>>>>>>>>>>>> detect
>>>>>>>>>>>>> the
>>>>>>>>>>>>> fault itself?
>>>>>>>>>>>>>                                                            
>>>>>>>>>>>>>                         
>>>>>>>>>>>> The fault itself would be a segfault, so no, we don't do
>>>>>>>>>>>> that.  It
>>>>>>>>>>>> runs
>>>>>>>>>>>> the ncftp command and looks for the version string. 
>>>>>>>>>>>> Simplicity.
>>>>>>>>>>>>
>>>>>>>>>>>>  
>>>>>>>>>>>>                                            
>>>>>>>>>>>>                      
>>>>>>>>>>>>> But then, why does the list command issue a ftp put command?
>>>>>>>>>>>>>                                                            
>>>>>>>>>>>>>                         
>>>>>>>>>>>> You'll have to explain that one.  It should not.
>>>>>>>>>>>>
>>>>>>>>>>>>  
>>>>>>>>>>>>                                            
>>>>>>>>>>>>                      
>>>>>>>>>>>>> ..qeustions over questions ..ede
>>>>>>>>>>>>>                                                            
>>>>>>>>>>>>>                         
>>>>>>>>>>>> Back in the dawn of history, duplicity used ftplib.py for
>>>>>>>>>>>> direct
>>>>>>>>>>>> access
>>>>>>>>>>>> to ftp.  This was impossible to maintain because the
>>>>>>>>>>>> maintainers of
>>>>>>>>>>>> ftplib.py preferred standardization over functionality.  They
>>>>>>>>>>>> treated
>>>>>>>>>>>> the RFC's as gospel and anyone who's been around ftp long
>>>>>>>>>>>> enough
>>>>>>>>>>>> grows
>>>>>>>>>>>> to know that ftp servers are only 'mostly' standard.  I chose
>>>>>>>>>>>> NcFTP
>>>>>>>>>>>> because I had never had it fail to work on any server I
>>>>>>>>>>>> targeted.  I
>>>>>>>>>>>> chose functionality over standardization.  A note - do a
>>>>>>>>>>>> 'strings' on
>>>>>>>>>>>> NcFTP and you will find where they detect the problem FTP
>>>>>>>>>>>> servers and
>>>>>>>>>>>> this is something any ftp client needs to do.
>>>>>>>>>>>>
>>>>>>>>>>>> The 2nd incarnation of the ftp backend used the ncftpget/put/ls
>>>>>>>>>>>> utilities rather than the ncftp command directly.  After much
>>>>>>>>>>>> success
>>>>>>>>>>>> with pexpect driving ssh, and many problems with various
>>>>>>>>>>>> versions of
>>>>>>>>>>>> the
>>>>>>>>>>>> ncftp utilities, I decided to drive ncftp directly with pexpect
>>>>>>>>>>>> and not
>>>>>>>>>>>> use the utilities for anything at all.  I made the mistake of
>>>>>>>>>>>> thinking
>>>>>>>>>>>> that if ncftp was so solid, then the utilities would be
>>>>>>>>>>>> solid as
>>>>>>>>>>>> well.
>>>>>>>>>>>>
>>>>>>>>>>>> Thus the 3rd incarnation of the ftp backend.  This one still
>>>>>>>>>>>> has
>>>>>>>>>>>> some
>>>>>>>>>>>> issues, I'm sure, but those are being ironed out.  Unless
>>>>>>>>>>>> someone can
>>>>>>>>>>>> prove to me that they have a better functioning ftp server or
>>>>>>>>>>>> library, I
>>>>>>>>>>>> think we have finally found the functionality and robustness we
>>>>>>>>>>>> need
>>>>>>>>>>>> going forwards.
>>>>>>>>>>>>
>>>>>>>>>>>> I'm getting really tired of fixing bugs against a flaky
>>>>>>>>>>>> protocol
>>>>>>>>>>>> that
>>>>>>>>>>>> should have died years ago.  It wastes too much time.  It's
>>>>>>>>>>>> one of
>>>>>>>>>>>> those
>>>>>>>>>>>> things like French that I don't like to mess with.  As my
>>>>>>>>>>>> French
>>>>>>>>>>>> teacher
>>>>>>>>>>>> said on the day after it was too late to drop, "Throw away the
>>>>>>>>>>>> rules,
>>>>>>>>>>>> now we're going to learn French.".  FTP is like that.
>>>>>>>>>>>>
>>>>>>>>>>>> ...Ken
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>  
>>>>>>>>>>>> ------------------------------------------------------------------------
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
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>>>>>>>>>>>>                                                  
>>>>>>>>>>>>                       
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>>>>>>>>>>>                                                             
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>>>>>>>>>>                                                   
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>>>>>>>>>                                         
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>>>>>>>                         
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