openssh-4.7p1 & RemoteForward to openssh-3.6.1p2 Disconnecting: Bad, packet length

[Will Angenent]

Hi,

I've just upgraded to openssh-4.7p1 on my gentoo box, and I've noticed a incompatibility with openssh-3.6.1p2 running on a redhat AS3 server.

If I ssh from my openssh-4.7_p1 client to the openssh-3.6.1p2 server, and RemoteForward a port, the ssh connection closes if I try to send more than roughly 300K through the tunneled port. The problem isn't present when I use openssh-4.6p1 as a client.

A typical error is:
Disconnecting: Bad packet length 327708.

The number varies with retries. The problem is easily reproducible.

Steps to reproduce:
- ssh from client ssh openssh-4.7p1 -> server openssh-3.6.1p2 with -R2000:127.0.0.1:2000
- on client: nc -l -p 2000 > /dev/null
- on server cat a_big_ish_file |nc 127.0.0.1 2000
=> the ssh connection terminates with the error

If I'd have a clue where to begin to look for, I'd give you more info, but I'm afraid I'm not too initiated in the openssh world. If I can do anything to help with the diagnosis, please let me know.

Regards,
Will



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