dbclient can't connect to cisco

[Matt Johnston]

Hi Nik,

> 
> dbclient sends "SSH-2.0-dropbear_2018.76\r\n" and kexinit
> cisco sends "SSH-2.0-Cisco-1.25\r\n"
> then cisco waits "ip ssh time-out" seconds and then closes the TCP socket.
> 
> my conjecture is that cisco empties its receive buffer after sendind the identification string and then waits for the lost kexinit.
> To prove my idea I added a sleep() after the first write_packet(), and dbclient was able to connect to cisco (ios 12.4 and 15.1).

Yes, it seems some Cisco SSH versions are buggy. Older IOS is possibly OK (I did a bit of investigation about a year ago when someone reported similar). 

I'm not keen on changing dbclient, the current implementation saves a network roundtrip. It's perfectly reasonable according to the spec. If you have Cisco support could you report it to them?

Cheers,
Matt

rfc4253:
5.2.  New Client, Old Server

   Since the new client MAY immediately send additional data after its
   identification string (before receiving the server's identification
   string), ...