charon-systemd

The charon-systemd daemon implements the IKE daemon very similar to charon but is specifically designed for use with systemd. It uses the systemd libraries for a native integration and comes with a simple systemd service file. The daemon is directly managed by systemd and configured by the swanctl configuration backend.

Build Options

To build the daemon, add

--enable-systemd --enable-swanctl

to the ./configure options. In order to disable the legacy ipsec backend, additionally add

--disable-charon --disable-stroke

to build a lightweight and clean IKE daemon using modern tools.

The systemd unit file directory is detected automatically using pkg-config but may be set manually using the --with-systemdsystemunitdir= ./configure option.

Behavior

charon-systemd gets installed as native systemd daemon and the service unit is named strongswan. The service unit has to be enabled once once with the command

sudo systemctl enable strongswan

The daemon can then be manually started with

sudo systemctl start strongswan

and stopped at any time with

sudo systemctl stop strongswan

Usually after a reboot systemd automatically starts the strongswan service and uses swanctl to load the IPsec configuration including connections, pools and credentials. If you are not sure whether the charon-systemd daemon is running you can check with

systemctl status strongswan

strongswan.service - strongSwan IPsec IKEv1/IKEv2 daemon using swanctl
     Loaded: loaded (/lib/systemd/system/strongswan.service; enabled; vendor preset: enabled)
     Active: active (running) since Wed 2022-01-26 16:53:41 CET; 5 days ago
    Process: 1354 ExecStartPost=/usr/sbin/swanctl --load-all --noprompt (code=exited, status=0/SUCCESS)
   Main PID: 1308 (charon-systemd)
     Status: "charon-systemd running, strongSwan 6.0dr13, Linux 5.13.0-27-generic, x86_64"
      Tasks: 17 (limit: 18891)
     Memory: 113.1M
     CGroup: /system.slice/strongswan.service
             └─1308 /usr/sbin/charon-systemd

Configuration

Many of the charon-specific configuration options in strongswan.conf also apply to charon-systemd. Actually, options set in the charon section are automatically inherited by charon-systemd.

The following options are specific to charon-systemd:

Key Default Description

journal

Section to configure native systemd journal logger, very similar to the syslog logger as described in Logging

Logging

By default, the charon-systemd backend logs to the systemd journal, which can be viewed using journalctl. Log levels can be configured very similar to the charon logger configuration but using a journal section:

charon-systemd {
  journal {
    default = 1
    ike = 2
    knl = 3
    # ...
  }
}

Of course, one may define traditional syslog and filelog loggers in the charon-systemd section of strongswan.conf. Refer to the logger configuration for details. To disable the journal logger and make it silent, set

default = -1

The journal-based logger provides some additional metadata in custom journal fields:

Field Description

LEVEL

Numerical strongSwan log level

GROUP

Logging subsystem string

THREAD

Numerical thread identifier issuing the journal entry

IKE_SA_UNIQUE_ID

IKE_SA unique identifier, if available

IKE_SA_NAME

Name of the IKE_SA configuration, if available

The MESSAGE field contains the log message, MESSAGE_ID uses a unique identifier specific to each log message type. The log levels are also mapped to values stored in the PRIORITY field (0 to LOG_NOTICE, 1 to LOG_INFO, everything above to LOG_DEBUG, see syslog(3)).