Remote port forwarding with sshd_config option 'GatewayPorts' set to "clientspecified" does not seem to work as specified, when configured from a "slave" ssh using a multiplexed connection. Ssh man page on remote port forwarding says:
"-R [bind_address:]port:host:hostport
...
By default, the listening socket on the server will be bound to the loopback
interface only. This may be overridden by specifying a bind_address. An empty
bind_address, or the address '*', indicates that the remote socket should listen
on all interfaces.
...
"
Now the following mux command (on client with ControlMaster connected and running and ControlPath set appropriately):
$ ssh -O forward -R ':0:localhost:3502' <hostaddr>
Allocated port 48293 for remote forward to localhost:3502
results in (on server):
$ netstat -lt
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 localhost:48293 *:* LISTEN
tcp 0 0 *:ssh *:* LISTEN
tcp6 0 0 localhost:48293 [::]:* LISTEN
tcp6 0 0 [::]:ssh [::]:* LISTEN
Port 48293 (set with an empty bind_address) should be bind to wildcard address, not localhost. The same -R option given for ControlMaster (or non-multiplexed ssh client) works as expected.
Looks like a bug in ssh client code?
Client version: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2, OpenSSL 1.0.1f 6 Jan 2014
--
Sami Hartikainen
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