slow logins -- some data for comparison

[William Welch]

Greetings,

First -- thank you for dropbear!  I have enjoyed using dropbear on various
smallish systems for years now!

But I have a problem with a specific system -- admittedly it is rather slow
-- only 50 BogoMips according to the linux kernel. It is a Microblaze.

I use the Buildroot system for many different routers and other small
systems here.  I have compared different versions of dropbear, against
openssh.

My issue is with the server mode -- sshd --  I note that on dropbear 0.52
(which I happen to run on other routers here), I can connect from my ubuntu
or mac, to dropbear sshd, in about 45 seconds.  This is having disabled the
RSA host key, and already generated the DSS host key.   But on more recent
versions of dropbear, e.g. 2013.58, several minutes elapse without a
connection.

In contrast, switching to openssh in buildroot, and also disabling the RSA
host key, connection time is 5 to 10 seconds!  Unfortunately, the openssh
has a huge 'footprint' in the flash filesystem that I would rather avoid.

The issue seems to be in the key exchange ( I can watch this by doing 'ssh
-v ' from my client connection).  Meanwhile, running 'top' on my Microblaze
shows near 100% cpu used.  the debug message is: expecting
SSH2_MSG_KEXDH_REPLY

Buildroot has the gnu cross tool chain set to 'optimize for size' in all
cases.

Suggestions welcome!

thank you,

William
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