https://github.com/mobtitude/docker-vpn-pptp

docker run -d --privileged -p 1723:1723 -v {local_path_to_chap_secrets}:/etc/ppp/chap-secrets mobtitude/vpn-pptp

https://github.com/siomiz/SoftEtherVPN

docker run -d --cap-add NET_ADMIN -p 500:500/udp -p 4500:4500/udp -p 1701:1701/tcp siomiz/softethervpn

• -e PSK: Pre-Shared Key (PSK), if not set: “notasecret” (without quotes) by default.
• -e USERNAME: if not set a random username (“user[nnnn]“) is created.
• -e PASSWORD: if not set a random weak password is created.

VPN_IPSEC_PSK=<IPsec pre-shared key>
VPN_USER=<VPN Username>
VPN_PASSWORD=<VPN Password>

sudo modprobe af_key

docker run \
    --name ipsec-vpn-server \
    --env-file ./vpn.env \
    --restart=always \
    -p 500:500/udp \
    -p 4500:4500/udp \
    -v /lib/modules:/lib/modules:ro \
    -d --privileged \
    hwdsl2/ipsec-vpn-server

https://github.com/hwdsl2/docker-ipsec-vpn-server