Strongswan IPsec with IKEv2 PSK

ipsec.conf

conn myikev2psk
	auto = add
	authby = psk
	#compress = yes
	keyexchange = ikev2
	type = tunnel
	dpdaction = clear
	dpddelay = 30s
	#rekey = no
	# a good convention is to use left for the local side,
	# and right for the remote side
	# default left = %any
	left = ${SERVERIP}
	#leftauth = 
	leftid = ${SERVERIP}
	#leftikeport = 
	leftsubnet = 0.0.0.0/0,::/0
	right = %any
	rightid = android
	rightdns = 8.8.8.8,8.8.4.4
	rightsourceip = <a pool cidr, like 10.134.76.0/24>

ipsec.secrets

# This file holds shared secrets or RSA private keys for authentication.

# RSA private key for this host, authenticating it to any other host
# which knows the public part.

 : PSK "YOURPSK"

strongswan.sh

#!/bin/sh

# This configuration is tested on Android client

apt install strongswan
<!-- libcharon-extauth-plugins libstrongswan libstrongswan-standard-plugins strongswan-charon strongswan-libcharon strongswan-starter -->
apt install strongswan-pki
<!-- strongswan-pki -->

# And you need to configure the iptables
iptables -t nat -A POSTROUTING -s <source cidr like 10.134.76.0/24> -o <interface like eth0> -j MASQUERADE