ArchLinux 配置 L2TP/IPSec VPN 流水帐。

安装软件包

pacman -S strongswan xl2tpd 

生成配置文件

VPN_SERVER_IP='your vpn server address'
VPN_IPSEC_PSK='your psk'
VPN_USER='your username'
VPN_PASSWORD='your password'

cat > /etc/ipsec.conf <<EOF
# ipsec.conf - strongSwan IPsec configuration file

conn myvpn
  auto=add
  authby=secret
  right=$VPN_SERVER_IP
EOF

cat > /etc/ipsec.secrets <<EOF
: PSK "$VPN_IPSEC_PSK"
EOF

chmod 600 /etc/ipsec.secrets

cat > /etc/xl2tpd/xl2tpd.conf <<EOF
[lac vpn-connection]
lns = $VPN_SERVER_IP
ppp debug = yes
pppoptfile = /etc/ppp/options.l2tpd.client
length bit = yes
EOF

cat > /etc/ppp/options.l2tpd.client <<EOF
ipcp-accept-local
ipcp-accept-remote
refuse-eap
require-mschap-v2
noccp
noauth
idle 1800
mtu 1410
mru 1410
defaultroute
usepeerdns
debug
connect-delay 5000
name $VPN_USER
password $VPN_PASSWORD
EOF

systemctl start strongswan-starter
ipsec up myvpn
systemctl start xl2tpd
echo "c vpn-connection" > /var/run/xl2tpd/l2tp-control

添加路由

ip route add xxx.xxx.xxx.xxx via yyy.yyy.yyy.yyy dev pppX

其中，xxx.xxx.xxx.xxx 是需要被路由的ip或网段，比如192.168.3.0/24, yyy.yyy.yyy.yyy是拨号成功后的ip地址， pppX是拨号成功后的虚拟设备， 可用ip address命令查看。

2022-03-16 更新说明

1. 更新 /etc/ipsec.conf ，去除无用配置项
2. 注意执行 ipsec up myvpn 时会有报错，不用处理，执行后续命令即可，然后 ping <ppp peer ip address> 测试

参考

1. Openswan L2TP/IPsec VPN client setup
2. setup-ipsec-vpn
3. strongSwan