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How to start a swanctl.conf configured tunnel automatically

Unix & Linux Asked on November 23, 2021

Environment: Debian 10, KDE, Full desktop

# ipsec --version
Linux strongSwan U5.7.2/K4.19.0-6-amd64

# swanctl --version
strongSwan swanctl 5.7.2

# systemctl status strongswan
● strongswan.service - strongSwan IPsec IKEv1/IKEv2 daemon using ipsec.conf
   Loaded: loaded (/lib/systemd/system/strongswan.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since Fri 2019-12-13 09:35:03 -03; 4h 34min ago
  Process: 6067 ExecStart=/usr/sbin/ipsec start --nofork (code=exited, status=0/SUCCESS)
 Main PID: 6067 (code=exited, status=0/SUCCESS)

# systemctl status strongswan-swanctl
● strongswan-swanctl.service - strongSwan IPsec IKEv1/IKEv2 daemon using swanctl
   Loaded: loaded (/lib/systemd/system/strongswan-swanctl.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2019-12-13 09:11:34 -03; 4h 56min ago
 Main PID: 6373 (charon-systemd)
   Status: "charon-systemd running, strongSwan 5.7.2, Linux 4.19.0-6-amd64, x86_64"
    Tasks: 17 (limit: 4915)
   Memory: 8.5M
   CGroup: /system.slice/strongswan-swanctl.service
           └─6373 /usr/sbin/charon-systemd

After spending almost two days learning and poking around IPSec and IKEv2 I managed to connect to the company gateway (Lancom LCOS, IKEv2 PSK, User-FQDN identities) using strongswan and swanctl.

After a reboot I have to run the following commands:

sudo /usr/sbin/swanctl --load-all
no files found matching '/etc/swanctl/conf.d/*.conf'
loaded ike secret 'ike'
no authorities found, 0 unloaded
no pools found, 0 unloaded
loaded connection 'IKEv2PSK'
successfully loaded 1 connections, 0 unloaded

and then sudo /usr/sbin/swanctl --initiate --child myVpn

[IKE] establishing CHILD_SA myVpn{2}
... lots of log lines ...
initiate completed successfully

I’d like to have the tunnel started automatically, maybe using a systemd unit something like

sudo systemctl swanctl-myVpn start

However I don’t find any documentation how to achieve this, which also makes me wonder if this is a bad idea?

One Answer

@ecdsa pointed me into the right direction. Adding a start_action to the config is the solution:

connections {
    IKEv2PSK {
        remote_addrs = SOME.DYNDNS-IP.COM, 81.81.81.81
        vips = 0.0.0.0
        version = 2
        dpd_delay = 30
        dpd_timeout = 90
        proposals = aes256-sha256-modp2048
        
        local {
            auth = psk
            id = @@[email protected]
        }
        remote {
            auth = psk
            id = 81.81.81.81
        }
                
        children {
            anicVpn {
                remote_ts = 192.168.0.0/24
                updown = /usr/lib/ipsec/_updown iptables
                esp_proposals = aes256-sha256-modp2048
                start_action = trap   # <----- trap: on traffic | start: on boot
            }
        }
    }
}

Now a simple ping to a server starts the tunnel. The option start could also be used to get the tunnel up and running directly on system start. Source: swanctl.conf

Update

Note that this doesn't work in Ubuntu, because AppArmor prevents the updown-script from running out of the box

Answered by Marc Wittke on November 23, 2021

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