A bash script which calls ssh bound to a the local IPv6 Stable SLAAC address. Enables persistent ssh sessions across laptop sleep/awake cycles.
By default IPv6 will use temporary addresses (RFC 8981) for outbound connections, including ssh. While it possible to disable this feature, in most cases I prefer temporary addresses to be used (e.g. https sessions).
However, in the modern world, putting a laptop to sleep, will cause systemd to generate new temporary addresses, and the ssh connection will not be restored after waking up the laptop.
By binding the ssh session to a local Stable SLAAC address, the ssh session will remain connected after the laptop wakes up from sleep and reconnects to the network.
Apparently, I put my laptop to sleep a lot. I grew tired of re-establishing my ssh session, and all my GUI X-forwarded apps (mostly editors) as well.
By binding the ssh session with the -b <address> parameter, the sessions remain up, even through short sleeps.
This script merely automates the process of finding which interface has a valid Stable SLAAC Address, and then calls ssh with the appropriate bind address.
The script checks all the interfaces for a Stable SLAAC Address, and uses the first one it finds for the ssh session.
By default, the script will use a Global Unique Address (GUA) when selecting a Stable SLAAC Address. Use the -u option (as over v0.9.4). Or use ULAs all the time by commenting out the following line in the script:
# Comment out next line, if only using ULAs
PREFIX='2'
Like any script there is help. With this first release there is only -i <interface> which allows the user to control which interface is used, and -X for X11 forwarding.
$ ./6ssh.sh -h
./6ssh.sh - ssh using Stable SLAAC Source Address
e.g. ./6ssh.sh <host>
-i <int> use this interface
-u use ULA address (default GUA)
-X use X forwarding
-t test, show stable slaac address and quit
Bash is terrible at string handling, why write this script in bash? Because I wanted it to run on my router (OpenWRT), and just about every where else, with the minimal amount of dependencies. It is possible to run Python on OpenWRT, but Python requires more storage (more packages) than just bash.
The script is dependent on bash, ip, and grep, both of which should be readily available on any linux distro.
BSD support (as of v0.9.2) requires ip command emulator, download and place in same directory as 6ssh.sh.
All code by Craig Miller cvmiller at gmail dot com. But ideas, and ports to other languages are welcome.
This project is open source, under the GPLv2 license (see LICENSE)