docker-l2tp-ipsec-http-proxy strongswan + xl2tpd + privoxy vpn.params VPN_SERVER=1.2.3.4 VPN_IKEV=ikev1 VPN_IKE=aes256-sha2_256-modp2048,... VPN_ESP=aes256-sha1,... VPN_PSK=secret VPN_MTU=1400 VPN_MRU=1400 VPN_USER=user.name VPN_PASS=password