OpenSSH GSoC Project

[Iain Morgan]

On Tue, Mar 24, 2009 at 06:13:18 -0500, Salvador Fandino wrote:
> 
> > The best interactive terminal-based SFTP client i've used so far is LFTP
> > <http://lftp.yar.ru/>, by opening an URL like 'sftp://remote-host'.
> 
> lftp is also my preferred SFTP (and FTP) client. One of these utilities 
> I install on any machine I have to work with (if I can).
> 
[snip]
> 
> > Look at LFTP's interface for resuming ("continuing") a transfer.

While lftp supports resuming, I'm not sure that it addresses the issue
that the SFTP protocol allows file chunks to arrive out of order.
Addressing this issue for get's is straightforward (Damien previously
suggested a patch to sftp to address this) but addressing the issue for
put's would (presumably) require server-side mods.

[snip]

> > Again, look at LFTP for ideas.
> 
> as LFTP already seems to do everything we need (and much more) and it is 
> freely available, does really makes sense to reimplement its 
> functionality inside sftp? why not just recommend it on the docs?
> 

While lftp has a rich user interface and supports a number of protocols,
it does have some areas for improvement. As mentioned above, I'm not
sure that it's resume support for SFTP is completely safe, but I haven't
examined the code. The striping support is nice, but it only supports
striped get's (pget) and has not support for striped put's. The striping
model is also not ideal for single disk filesystems: it can cause a lot
of head travel. However, the striping can improve preformance for
high-latency connections. (It doesn't seem to be of benefit in the
low-latency case.)

I end up using a mixture of scp, sftp, and lftp for file transfers. If
the command-line support for sftp were improved sufficiently, I would
stop using scp. The biggest drawback for me with sftp is that it does
not have good command-line support for uploading files. Downloading
files is easy, but to upload you have to use batch mode. The main use I
have for lftp is it's readlines support and striped transfers.

I agree with Jim Knoble's comment that OpenSSH should provide a
reasonable file transfer utility rather than recommending that users use
a third-party utility.

-- 
Iain Morgan