"on-the-fly" SSH Port Forwarding

Chris Mason chris at noodles.org.uk
Sun Sep 7 19:15:59 EST 2008


I am using the following version of OpenSSH for reference:

root at proxy:/root# ssh -V
OpenSSH_4.8, OpenSSL 0.9.7j 04 May 2006

root at proxy:/root# uname -a
OpenBSD proxy.localdomain 4.3 GENERIC#698 i386

I am developing an application which uses on-the-fly SSH port forwarding
by using the "~C" escape sequence to add local port forwards when needed
(through Expect). It would appear that there is no option to remove
local port forwards and only remote port forwards:

ssh> -h
      -L[bind_address:]port:host:hostport    Request local forward
      -R[bind_address:]port:host:hostport    Request remote forward
      -KR[bind_address:]port                 Cancel remote forward

I am hitting scalability issues as I am not able to cancel local
forwards and after about 251 tunnels I am unable to add any more. (I am
assuming this is platform/machine dependent as it complains about "No
buffer space").

How come there isn't an option to remove local forwards when there is to
remove remote ones? Is this by design or something that was never

Thanks in advance,

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