l2tp over ipsec OpenBSD for android/ios clients

# cat /etc/ipsec.conf
ike passive esp transport \
        proto udp from external.ip.add.ress to any port l2tp \
        main auth "hmac-sha1" enc "aes" group modp1024 \
        quick auth "hmac-sha1" enc "aes" group modp1024 \
        psk "mysuperstrongkey"

# cat /etc/npppd/npppd.conf
authentication LOCAL type local {
        users-file "/etc/npppd/npppd-users"
}
tunnel L2TP protocol l2tp {
        listen on 0.0.0.0
        listen on ::
}

ipcp IPCP {
        pool-address 192.168.1.2-192.168.1.254
        dns-servers 8.8.8.8
}

interface pppx0 address 192.168.1.1 ipcp IPCP
bind tunnel from L2TP authenticated by LOCAL to pppx0

# echo "net.pipex.enable=1" >> /etc/sysctl.conf

# cat /etc/npppd/npppd-users
user1:\
        :password=superstrongpass: