Debian Bug report logs - #731950
ssh -g has no effect if master socket already open

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Ken Sharp <imwellcushtymelike@googlemail.com>

To: submit@bugs.debian.org

Subject: ssh -g has no effect if master socket already open

Date: Wed, 11 Dec 2013 15:05:18 +0000

Package: openssh-client
Version: 1:5.9p1-5
Control: found -1 1:6.4p1-1

From the man page:
 -g      Allows remote hosts to connect to local forwarded ports.

When working with a control socket, this works fine if -g is included 
with the initial connect attempt, for example:

$ cat ~/.ssh/config
Host *
ControlMaster		auto
ControlPath		~/.ssh/%r@%h:%p

$ ssh -gTfNL 12345:localhost:12345 host
$ netstat -tln

tcp        0      0 0.0.0.0:12345             0.0.0.0:* 
LISTEN      -

$ lsof -n

ssh       182446        user    3u     IPv4           76397177       0t0 
     TCP 192.168.0.9:51181->192.168.0.15:ssh (ESTABLISHED)
ssh       182446        user    4u     IPv4           76397181       0t0 
     TCP *:3128 (LISTEN)
ssh       182446        user    5u     IPv6           76397182       0t0 
     TCP *:3128 (LISTEN)

and similarly:

$ ssh -g host
user@host:~$ exit
$ ssh -gTfNL 12345:localhost:12345 host
$ netstat -tln

tcp        0      0 0.0.0.0:12345             0.0.0.0:* 
LISTEN      -

However, if it isn't then -g is ignored on subsequent attempts to 
forward ports:

$ ssh host
user@host:~$ exit
$ ssh -g -L 12345:localhost:12345 host
$ netstat -tln

tcp        0      0 127.0.0.1:12345             0.0.0.0:* 
LISTEN      -

$ lsof -n

ssh       182399        user    3u     IPv4           76390396       0t0 
     TCP 192.168.0.9:51178->192.168.0.15:ssh (ESTABLISHED)
ssh       182399        user    4u     unix 0x0000000000000000       0t0 
76390976 /home/user/.ssh/user@host
ssh       182399        user    6u     IPv6           76392394       0t0 
     TCP [::1]:3128 (LISTEN)
ssh       182399        user    7u     IPv4           76392395       0t0 
     TCP 127.0.0.1:3128 (LISTEN)

This doesn't really make sense: ssh should still be capable of binding 
to the correct address as requested.

Originally reported:
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1259939

Message #12 received at 731950@bugs.debian.org (full text, mbox, reply):

From: Ken Sharp <imwellcushtymelike@googlemail.com>

To: 731950@bugs.debian.org

Date: Wed, 11 Dec 2013 15:39:03 +0000

Control: forwarded -1 https://bugzilla.mindrot.org/show_bug.cgi?id=2183

Built upstream source and the behaviour is the same.

Message #23 received at 731950@bugs.debian.org (full text, mbox, reply):

From: Russ Allbery <rra@debian.org>

To: Ken Sharp <imwellcushtymelike@googlemail.com>

Cc: 731950@bugs.debian.org

Subject: Re: Bug#731950: ssh -g has no effect if master socket already open

Date: Wed, 11 Dec 2013 13:29:03 -0800

Ken Sharp <imwellcushtymelike@googlemail.com> writes:

> However, if it isn't then -g is ignored on subsequent attempts to forward
> ports:

So far as I can tell, this is true for all port forwarding when used with
ControlMaster.  Across the board, it appears that all port forwarding has
to be specified on the original connection and is ignored for subsequent
connections.

I suspect this is inherent in the design.

-- 
Russ Allbery (rra@debian.org)               <http://www.eyrie.org/~eagle/>

Message #28 received at 731950@bugs.debian.org (full text, mbox, reply):

From: Ken Sharp <imwellcushtymelike@googlemail.com>

To: Russ Allbery <rra@debian.org>

Cc: 731950@bugs.debian.org

Subject: Re: Bug#731950: ssh -g has no effect if master socket already open

Date: Wed, 11 Dec 2013 21:49:23 +0000

> So far as I can tell, this is true for all port forwarding when used with
> ControlMaster.  Across the board, it appears that all port forwarding has
> to be specified on the original connection and is ignored for subsequent
> connections.

No I can add as many port forwards as I like after the master connection 
is established. All options I have tried are honoured except for -g.

Message #33 received at 731950@bugs.debian.org (full text, mbox, reply):

From: Russ Allbery <rra@debian.org>

To: Ken Sharp <imwellcushtymelike@googlemail.com>

Cc: 731950@bugs.debian.org

Subject: Re: Bug#731950: ssh -g has no effect if master socket already open

Date: Wed, 11 Dec 2013 13:57:48 -0800

Ken Sharp <imwellcushtymelike@googlemail.com> writes:

>> So far as I can tell, this is true for all port forwarding when used
>> with ControlMaster.  Across the board, it appears that all port
>> forwarding has to be specified on the original connection and is
>> ignored for subsequent connections.

> No I can add as many port forwards as I like after the master connection
> is established. All options I have tried are honoured except for -g.

Huh.  This is definitely not my experience.  I'm not sure why it behaves
differently for you.

-- 
Russ Allbery (rra@debian.org)               <http://www.eyrie.org/~eagle/>

Message #38 received at 731950-done@bugs.debian.org (full text, mbox, reply):

From: Ken Sharp <imwellcushtymelike@googlemail.com>

To: 731950-done@bugs.debian.org

Date: Fri, 19 Dec 2014 18:46:50 +0000

This should be fixed in 6.6 or 6.7 but I can't find it in the changelog. 
It is fixed upstream.

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