Re: 2.6.25-rc8: FTP transfer errors

[Mark Lord]

Jeff Garzik wrote:
> Mark Lord wrote:
> > Mark Lord wrote:
> > > Today I've been using 2.6.25-rc8 with an old embedded build system here
> > > for my empegs.  One shell script calls out to /usr/bin/ftp to transfer
> > > an image to a remote system, and then read it back again and compare.
> > >
> > > The compare is failing, most (but not all) of the time,
> > > but only on 2.6.25-rc8, not on 2.6.24.  Verified by switching
> > > back and forth between kernel versions for a short spell.
> > >
> > > The ftp client is netkit-ftp 0.17-16 on Kubuntu feisty.
> > >
> > > Switching to ncftpput/ncftpget avoids it on 2.6.25,
> > > but I wonder where the problem is.
> > ..
> >
> > Now verified that the data loss occurs in the outbound direction.
> > The readback data is the same, regardless of which client s/w is used.
> >
> > So something in 2.6.25 is incompatible with the ftp client binary, or 
> > libs, that are installed here.  Or some other problem.
>
> Or maybe it uses sendfile, and that is broken?
..

No, it uses read()/write() calls (from the strace).
Here's the most recent update:

> Recap, with more info:
>
> The host system is running 2.6.25-rc8-git.  It uses netkit-ftp to
> send a file to the remote system.  Using strace shows that the
> entire file was read, and passed to write() for the outbound socket.
>
> The remote system is running linux-2.2.xx, and is reporting -EPIPE
> from net/socket.c::sock_recvmsg() before all of the data has been received,
> and thus ends up with a short file, missing data at the end.
>
> This exact sequence, with the exact same software,
> works fine when the host system is NOT running 2.6.25-*,
> (eg. 2.6.11 through 2.6.24 are fine).
>
> Something may be broken here.
..

The failing FTP client software issues a close() on the socket after
the final data write().  This close seems to be propagated to the other
end before the data is fully received.

I suppose a wireshark capture is next, once I dig out my ancient hub
so we can sniff it from an independent box.

-ml 

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