Great Shuttle Service
Charly's Column – sshuttle
When he doesn't want to deal with OpenVPN version conflicts or congestion control problems during TCP tunneling, Charly catches a ride on sshuttle.
In untrustworthy networks, I let OpenVPN tunnel my laptop. There are certainly alternatives, and I would like to present a particularly simple one: sshuttle [1]. As the name suggests, the tool relies on SSH. The tunnel's endpoint is a leased root server, just like with OpenVPN. Sshuttle is very frugal. It only needs SSH access with user privileges on the server; root privileges are not necessary. Additionally, Python must be installed on the server – that's it.
This is because sshuttle loads and executes the required Python code on the server after the SSH connection is established. It also avoids version conflicts between server and client software. The following command is all it takes to set up the tunnel:
sudo sshuttle -r <User>@<Server>:<Port> 0/0
You can leave out the port number if it is the SSH standard port 22. The 0/0
means that Linux should direct all connections into the tunnel. However, this means that I cannot reach other devices in the local network. To keep the local LAN still visible, I define it as an exception using the -x
parameter:
sudo sshuttle -r --dns <User>@<Server> 0/0 -x 192.168.2.0/24
--dns
is included here. This means that DNS queries also run through the tunnel, which does not happen automatically. This is sshuttle's Achilles heel: It only transports TCP; ICMP and UDP do not pass through the tunnel, apart from DNS.
Congestion Alert
Whereas other VPN technologies work at packet level and rely on TUN/TAP devices, sshuttle works at session level. It assembles the TCP stream locally, multiplexes it over the SSH connection, while keeping the status, and splits it into packets again on the destination side.
This avoids the TCP-over-TCP problem which plagues other tools such as OpenVPN: TCP has an overload control (congestion control). The protocol defines a performance limit on the basis of dropped packets. If you tunnel TCP over TCP, you lose congestion control for the inner connection, which can lead to bizarre error patterns. Sshuttle is immune to the problem.
Verbose parameters can help if you do need to troubleshoot. Figure 1 shows a connection setup with -v
. With the verbose option, sshuttle is very long-winded, so I recommend redirecting the output to a file that can be evaluated in peace. My conclusions: Sshuttle is an excellent and simple VPN for people who can do without UDP and ICMP.
Infos
- sshuttle: https://github.com/apenwarr/sshuttle
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
TUXEDO Computers Unveils Linux Laptop Featuring AMD Ryzen CPU
This latest release is the first laptop to include the new CPU from Ryzen and Linux preinstalled.
-
XZ Gets the All-Clear
The back door xz vulnerability has been officially reverted for Fedora 40 and versions 38 and 39 were never affected.
-
Canonical Collaborates with Qualcomm on New Venture
This new joint effort is geared toward bringing Ubuntu and Ubuntu Core to Qualcomm-powered devices.
-
Kodi 21.0 Open-Source Entertainment Hub Released
After a year of development, the award-winning Kodi cross-platform, media center software is now available with many new additions and improvements.
-
Linux Usage Increases in Two Key Areas
If market share is your thing, you'll be happy to know that Linux is on the rise in two areas that, if they keep climbing, could have serious meaning for Linux's future.
-
Vulnerability Discovered in xz Libraries
An urgent alert for Fedora 40 has been posted and users should pay attention.
-
Canonical Bumps LTS Support to 12 years
If you're worried that your Ubuntu LTS release won't be supported long enough to last, Canonical has a surprise for you in the form of 12 years of security coverage.
-
Fedora 40 Beta Released Soon
With the official release of Fedora 40 coming in April, it's almost time to download the beta and see what's new.
-
New Pentesting Distribution to Compete with Kali Linux
SnoopGod is now available for your testing needs
-
Juno Computers Launches Another Linux Laptop
If you're looking for a powerhouse laptop that runs Ubuntu, the Juno Computers Neptune 17 v6 should be on your radar.