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

[edgar . soldin]

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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