Arch Linux

sunnylx

Member

Registered: 2015-08-20

Posts: 43

Openssh Ethernet tunnel broken

Probably not a Arch Linux issue, but now I'm pretty sure that Ethernet tunnels on the latest Openssh version (OpenSSH_7.7p1, OpenSSL 1.1.0h  27 Mar 2018) is broken.

The "normal" tunnels work fine ( -L  and so on), but the -w with -o tunnel=ethernet does not work.

It is not a server issue since that using older Openssh versions  on the other machines, using several different distros of Ubuntu but with OpenSSH 7.2p2 work fine, the tunnel is created and can be used.

The symptoms (the below command is run as root so to be able to create the tunnel device):

ssh -o Tunnel=ethernet -w 0:0 -p 49657 root@MYREMOTESERVER

Gives:

Tunnel device open failed.
Could not request tunnel forwarding.

With debugging enabled:

Authenticated to MYREMOTESERVER (via proxy).
debug1: Requesting tun unit 0 in mode 2
debug1: sys_tun_open: failed to configure tunnel (mode 2): Operation not permitted
Tunnel device open failed.
Could not request tunnel forwarding.
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: proc
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0

From a Ubuntu machine to the server, the tunnel works.

Any ideas?

Last edited by sunnylx (2018-04-19 10:08:55)

firecat53

Member

From: Lake Stevens, WA, USA

Registered: 2007-05-14

Posts: 1,542

Website

Re: Openssh Ethernet tunnel broken

Did you see this page with its linked bug report?

Last edited by firecat53 (2018-04-19 12:40:06)

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Github

sunnylx

Member

Registered: 2015-08-20

Posts: 43

Re: Openssh Ethernet tunnel broken

Did you see this page with its linked bug report?

Yes. It still fails either with:

ssh -w any:any -o Tunnel=ethernet root@remoteserver

and also it fails with:

ssh -w 0:0 -o Tunnel=ethernet root@remoteserver

firecat53

Member

From: Lake Stevens, WA, USA

Registered: 2007-05-14

Posts: 1,542

Website

Re: Openssh Ethernet tunnel broken

Did you swap the position of the -w and -o arguments?

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Github

sunnylx

Member

Registered: 2015-08-20

Posts: 43

Re: Openssh Ethernet tunnel broken

Did you swap the position of the -w and -o arguments?

As per my original post, yes.  I was using first the -o and then -w.   Changing order does not solve the issue.

sunnylx

Member

Registered: 2015-08-20

Posts: 43

Re: Openssh Ethernet tunnel broken

Yep, openssh is definitly broken at least on the latest Arch release.

I have an older machine with also ArchLinux and with version of Openssh 7.6p1 and it works. Upgrading to 7.7p1, stops working.

Edit: Downgrading to version 7.6p1 solves the issue.

Last edited by sunnylx (2018-04-20 10:50:40)