Enabling L2TP over IPSec on Ubuntu 16.04

原文地址：http://blog.z-proj.com/enabling--over-ipsec-on-ubuntu-16-04/

Ubuntu has stopped shipping L2TP over IPSec support for Ubuntu since Precise. A workaround for this exists using network-manager-.

First you must install the prerequisites:

sudo apt install \  
intltool \  
libtool \  
network-manager-dev \  
libnm-util-dev \  
libnm-glib-dev \  
libnm-glib--dev \  
libnm-gtk-dev \  
libnm-dev \  
libnma-dev \  
ppp-dev \  
libdbus-glib-1-dev \  
libsecret-1-dev \  
libgtk-3-dev \  
libglib2.0-dev \  
xd \  
strongswan  

Then build the network manager again:

git clone https://github.com/nm-/network-manager-.git  
cd network-manager-  
autoreconf -fi  
intltoolize  

Make sure no errors have occurred.

Configure the build:

./configure \
  --disable-static --prefix=/usr \
  --sysconfdir=/etc --libdir=/usr/lib/x86_64-linux-gnu \
  --libexecdir=/usr/lib/NetworkManager \
  --localstatedir=/var \
  --with-pppd-plugin-dir=/usr/lib/pppd/2.4.7

Make sure no errors occurred.

Then make it:

make  
sudo make install  

Remove AppArmor settings for IPSec:

sudo apparmor_parser -R /etc/apparmor.d/usr.lib.ipsec.charon  
sudo apparmor_parser -R /etc/apparmor.d/usr.lib.ipsec.stroke  

Replace x2ltpd with libpcap:

sudo apt remove xd  
sudo apt install libpcap0.8-dev

wget https://github.com/xelerance/xd/archive/v1.3.6/xd-1.3.6.tar.gz  
tar xvzf xd-1.3.6.tar.gz  
cd xd-1.3.6  
make  
sudo make install  

Now restart your machine.

Network Manager should now have an option to use a L2TP VPN connection.