vsftpd corruption problem (Re: proftpd (and vsftpd too))

[Jason Tishler <jason at tishler dot net>]

On Tue, Apr 22, 2003 at 05:38:12PM +0200, Corinna Vinschen wrote:
> On Tue, Apr 22, 2003 at 10:42:25AM -0400, Jason Tishler wrote:
> >     1. vsftpd.conf must be in binary mode on a binary mount
> >     2. file transfers from/to text mounts can cause "corruption"
> >     3. ASCII transfer mode does not seem to work properly
> > [...]
> > I'm willing to contribute vsftpd with the above caveats and the
> > intention to solve the binary/text issues as time permits.  Is this
> > acceptable?
> 
> As a "test" release, sure!

I may have to renege on the above offer or at least add a *big* caveat
to the README.  Over the last few months, we have transferred tens of
thousands (possibly hundreds of thousands) of "normal" sized (i.e.,
<=100K) files with vsftpd put tunneled through ssh without any problems.
Unfortunately, I have recently discovered a corruption problem when
transferring large files (i.e., >=200MB) with vsftpd get tunneled
through ssh.

So far, I have been able to only trigger the problem on 4-way, NT 4.0
boxes with get when tunneled through ssh on a "slowish" (e.g., ~600
KB/s) network connection.  I cannot reproduce the problem on 1-way
systems, 2000, without ssh, put, or fast network connections (e.g., same
switch).

By constructing a specially formating file, I was able to determine that
after about 150 MB is transferred, a chunk of the file is erroneously
resent.

The special file contains lines with the following format:

    LLLLLLL:12345678901234567890123456789012345678901

where LLLLLLL is the line number zero padded to 7 digits.

The corruption looks like the following:

    3327913:12345678901234567890123456789012345678901
    3327914:12345678901234567890123456789012345678901
    3327915:12345678901234567890123456789012345678901
    3327916:12345678901234567890123456789012345678901
    3327917:12345678901234567890123456789012345678901
    33271234567890123456789012345678901
    3326608:12345678901234567890123456789012345678901
    3326609:12345678901234567890123456789012345678901
    3326610:12345678901234567890123456789012345678901
    3326611:12345678901234567890123456789012345678901
    3326612:12345678901234567890123456789012345678901

So in this case, after starting to transfer line 3327918, for some
reason vsftpd started to transfer data from line 3326607 and onward
again.  But, the file is otherwise not corrupt.  BTW, I have noticed a
200 MB file will be exactly 64 KB larger and a 300 MB file will be
exactly 128 KB larger.

Any ideas on how to debug this further will be greatly appreciate.

BTW, since proftpd CVS works under Cygwin now, should I just give up on
vsftpd and save my head banging for other more productive activities?

Thanks,
Jason

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