T1070 - docker build of vyos-strongswan (#31)

* T1070 - Added packages and readme notes about building strongswan

strongswan is easely built using a docker image, but needs special options to pass tests.
Added notes in the readme about building it and building instructions

* T1070 - Restructured build example for wyos-strongswan

Dockerfile

@@ -41,6 +41,30 @@ RUN echo 'deb http://ftp.debian.org/debian jessie-backports main' | tee -a /etc/
       python3-nose \
       python3-coverage
 
+# Packages needed for building vyos-strongswan
+RUN apt-get install -y -t jessie-backports \
+      debhelper &&\
+    apt-get install -y \
+      dh-apparmor \
+      gperf \
+      iptables-dev \
+      libcap-dev \
+      libgcrypt20-dev \
+      libgmp3-dev \
+      libldap2-dev \
+      libpam0g-dev \
+      libsystemd-dev \
+      libgmp-dev \
+      iptables \
+      xl2tpd \
+      libcurl4-openssl-dev \
+      libcurl4-openssl-dev \
+      libkrb5-dev \
+      libsqlite3-dev \
+      libssl-dev \
+      libxml2-dev \
+      pkg-config
+
 # Update live-build
 RUN echo 'deb http://ftp.debian.org/debian stretch main' | tee -a /etc/apt/sources.list.d/stretch.list &&\
     apt-get update &&\

README.md

@@ -153,6 +153,23 @@ After the docker container is running you can git clone the vyos-build repositor
 inside the container and follow up the bellow instructions in order to build the
 VyOS ISO image
 
+## Building subpackages inside Docker
+### Strongswan
+
+Prior to executing this you need to checkout and update the packages/vyos-strongswan submodule
+Building the strongswan package is for now only doable on a Linux system because tests fail when running on windows and OSX systems
+`/HOST_PATH/` is the path to your vyos_build directory. if youre in the vyos-build directory it can me replaced with `$(pwd)`
+
+`--sysctl net.ipv6.conf.lo.disable_ipv6=0` is needed to enable ipv6 inside the container. tests will fail if you don't have it.
+
+```bash
+$ docker run -it -v /HOST_PATH/:/vyos  --sysctl net.ipv6.conf.lo.disable_ipv6=0 vyos-builder \
+    bash -c '\
+      cd /vyos/packages/vyos-strongswan &&\
+      dpkg-buildpackage -uc -us -tc -b'
+```
+
+
 ## Building the ISO image
 
 Before you can build an image, you need to configure your build.