Compression when using dropbear as an ssh/scp client ?

[Matt Johnston]

Dropbear client always uses compression if possible, when it
is compiled in. The -C argument is ignored.

Cheers,
Matt

On Mon, Sep 05, 2011 at 03:46:59PM +0200, Guillaume Dargaud wrote:
> Hello all,
> I'm using dropbear compiled from buildroot:
> $ grep DROP .config
> .config:BR2_PACKAGE_DROPBEAR=y
> .config:BR2_PACKAGE_DROPBEAR_DISABLE_REVERSEDNS=y
> .config:# BR2_PACKAGE_DROPBEAR_SMALL is not set
> 
> From the machine with dropbear, I seem unable to activate compression:
> # scp -C -p -i /etc/dropbear/dropbear_dss_host_key /root/*.dat user at remote:
> WARNING: Ignoring unknown argument '-C'
> 20110905-125726.dat 100%   16KB 16.5KB/s   00:00    
> 20110905-125745.dat 100%   16KB 16.5KB/s   00:00    
> 20110905-125803.dat 100%   16KB 16.5KB/s   00:00    
> 
> But the option is present:
> # scp
> usage: scp [-1246BCpqrv] [-c cipher] [-F ssh_config] [-i identity_file]
>            [-l limit] [-o ssh_option] [-P port] [-S program]
>            [[user@]host1:]file1 [...] [[user@]host2:]file2
> 
> It's actually the same thing with ssh:
> # ssh -C -i /etc/dropbear/dropbear_dss_host_key noy at lpsc-ssh
> WARNING: Ignoring unknown argument '-C'
> 
> Except that I don't even see -C as an option if I do "ssh --help"
> 
> 
> Compression actually works fine when using dropbear as a server:
> $ ssh -Cv root at embedded
> ...
> debug1: kex: server->client aes128-ctr hmac-md5 zlib at openssh.com
> debug1: kex: client->server aes128-ctr hmac-md5 zlib at openssh.com
> ...
> debug1: Enabling compression at level 6.
> 
> -- 
> Guillaume Dargaud
> http://www.gdargaud.net/