Regression: 2.6.25-rc8: FTP transfer errors

[Mark Lord <lkml@rtr.ca>]

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.
..

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.