Compression when using dropbear as an ssh/scp client ?

[Guillaume Dargaud]

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/