How can I find (or compute) a client MAC address when using the strongSwan DHCP plugin?

Question

Server strongswan.conf

libtls {
  suites = TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
}
charon {
  plugins {
    dhcp {
      # Always use the configured server address.
      force_server_address = yes

      # Derive user-defined MAC address from hash of IKE identity.
      identity_lease = yes

      # Interface name the plugin uses for address allocation.
      interface = eth0

      # Whether to load the plugin. Can also be an integer to increase the
      # priority of this plugin.
      load = yes

      # DHCP server unicast or broadcast IP address.
      server = 10.0.2.255
    }
  }
}

Client ipsec.conf

conn %default
    ike=aes256gcm16-sha384-modp3072!
    esp=aes256gcm16-sha384-modp3072!

conn ikev2
    auto=start
    [email protected]
    leftsourceip=%config
    leftauth=eap-tls
    leftcert=vpn-client.crt
    right=my-vpn.com
    rightid=my-vpn.com
    rightsubnet=0.0.0.0/0
    rightauth=pubkey

The client is getting a dynamic IP from isc-dhcp-server but I would like to assign a static one using the following in dhcpd.conf.

host client {
  hardware ethernet a1-b2-c3-d4-e5-f6;
  fixed-address 10.0.2.2;
}

According to https://wiki.strongswan.org/projects/strongswan/wiki/DHCPPlugin, the client MAC address can optionally be based on the IKEv2 identity of the client.

Answer 1

Not sure how to compute the MAC, but it can be found by running sudo dhcp-lease-list.