Re: opening multiply reverse tunnels in one session

[Oleksandr Shneyder <o.shneyder@xxxxxxxxxxxxx>]

Hello Andreas,

Am 10.01.2014 09:38, schrieb Andreas Schneider:
> On Sunday 05 January 2014 19:04:01 Oleksandr Shneyder wrote:
>> Hello,
>>
>> is it possible to open several reverse tunnels in one session? There is
>> no problem with direct tunnel, I can simple create a channels with
>> ssh_channel_new for every new tunnel that I need and then open
>> forwarding with ssh_channel_open_forward.
> 
> Sure, ssh_forward_accept() returns the opened channel. See the tutorial and 
> the RFC which explains how it works.
> 
> http://tools.ietf.org/html/rfc4254#section-7.1
> 
>> In case of reverse tunnel it seems that I only can listen to one port.
>> There is an example on
>> http://api.libssh.org/master/libssh_tutor_forwarding.html how to create
>> reverse tunnel and forward the port 8080. But what if I need to forward
>> more services in one ssh session?
> 
> Then request more ports on that session ... :)

This is the point, how can I request more than one port on session?
I requesting a port with:
ssh_forward_listen, for example to listen on port 9080:

rc = ssh_forward_listen(session, 0l, 9080, &bound_port)
that works, I can accept incoming connections with ssh_forward_accept()

but now I need to listen one more port (9090) so I trying to call
ssh_forward_listen again to request other port:

rc = ssh_forward_listen(session, 0l, 9080, &bound_port)
and it fail with error "Invalid state in start of global_request()",
because function global_request in channels.c need ssh_session to be in
state SSH_CHANNEL_REQ_STATE_NONE but sessions state is different after
first call of ssh_forward_listen

So it seems, that I can call ssh_forward_listen only once and request
only one port on a session, or there are other methods to request ports
on sessions?

And even if it would be possible to call ssh_forward_listen more than
once, for example:

rc = ssh_forward_listen(session, 0l, 9080, &bound_port);
rc = ssh_forward_listen(session, 0l, 9090, &bound_port);
and then accept incoming connections with
channel=ssh_forward_accept();
how can I know if new connection is on port 9080 or 9090 ?

In libssh2 for example, I can create "listeners" for each port:

LIBSSH2_LISTENER
*listener_9080=libssh2_channel_forward_listen(session,9080);

LIBSSH2_LISTENER
*listener_9090=libssh2_channel_forward_listen(session,9090);

and after that accept connections on each listener:

channel_9080 = libssh2_channel_forward_accept(listener_9080);
channel_9090 = libssh2_channel_forward_accept(listener_9090);

But with libssh I steel can not forward more as one port...

>>
>> It seems to be possible open several reverse tunnels in one session with
>> libssh2. But my project already uses libssh long time and I don't want
>> to switch to libssh2. So I wondering if I can make the same with libssh.
> 
> 
> See above :)
> 

regards
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