Hello,
I found a problem with port forwardings specified in the
config file.
The following is run on OpenSSH 6.7p1:
Assume the following ~/.ssh/config:
Host some.host.name.com foo
Hostname some.host.name.com
DynamicForward 55555
When connecting to the real hostname everything is fine:
$ ssh -v some.host.name.com
...
debug1: Local connections to LOCALHOST:55555 forwarded to remote address socks:0
debug1: Local forwarding listening on ::1 port 55555.
debug1: channel 0: new [port listener]
debug1: Local forwarding listening on 127.0.0.1 port 55555.
debug1: channel 1: new [port listener]
...
But when using the short nickname:
$ ssh -v foo
...
debug1: Hostname has changed; re-reading configuration
...
debug1: Local connections to LOCALHOST:55555 forwarded to remote address socks:0
debug1: Local forwarding listening on ::1 port 55555.
debug1: channel 0: new [port listener]
debug1: Local forwarding listening on 127.0.0.1 port 55555.
debug1: channel 1: new [port listener]
debug1: Local connections to LOCALHOST:55555 forwarded to remote address socks:0
debug1: Local forwarding listening on ::1 port 55555.
bind: Address already in use
debug1: Local forwarding listening on 127.0.0.1 port 55555.
bind: Address already in use
channel_setup_fwd_listener_tcpip: cannot listen to port: 55555
...
The reason is that in the second case OpenSSH reparses the config
and then tries to adds the same forwarding rules again.
I looked into the source and there is a method compare_forward()
in mux.c that is used to prevent adding of duplicates.
Maybe that should be used also when parsing the config or
commandline in ssh.c / readconf.c?
Regards,
Sebastian
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