cross-compiling tinc for Windows under Linux using MinGW

Howto: cross-compiling tinc for Windows under Linux using MinGW

This howto describes how to create a Windows binary of tinc. Although it is possible to compile tinc under Windows itself, cross-compiling it under Linux is much faster. It is also much easier to get all the dependencies in a modern distribution. Therefore, this howto deals with cross-compiling tinc with MinGW under Linux on a Debian distribution.

The result is a 32-bit executable. If you want to create a 64-bit executable, have a look at the 64-bit cross-compilation example.

Overview

The idea is simple:

Install MinGW and Wine.
Create a directory where we will perform all cross-compilations.
Get all the necessary sources.
Cross-compile everything.

Installing the prerequisites for cross-compilation

There are only a few packages that need to be installed as root to get started:

sudo apt-get install mingw-w64 wine git-core quilt
sudo apt-get build-dep tinc

Other Linux distributions may also have MinGW packages, use their respective package management tools to install them. Debian installs the cross-compiler in /usr/i686-w64-mingw32/. Other distributions might install it in another directory however, for example /usr/i686-pc-mingw32/. Check in which directory it is installed, and replace all occurences of i686-w64-mingw32 in this example with the correct name from your distribution.

Setting up the build directory and getting the sources

We will create a directory called mingw/ in the home directory. We use apt-get to get the required libraries necessary for tinc, and use git to get the latest development version of tinc.

mkdir $HOME/mingw
cd $HOME/mingw
apt-get source openssl liblzo2-dev zlib1g-dev
git clone https://tinc-vpn.org/git/tinc

Making cross-compilation easy

To make cross-compiling easy, we create a script called mingw that will set up the necessary environment variables so configure scripts and Makefiles will use the MinGW version of GCC and binutils:

mkdir $HOME/bin
cat >$HOME/bin/mingw << 'EOF'
#!/bin/sh
PREFIX=i686-w64-mingw32
export CC=$PREFIX-gcc
export CXX=$PREFIX-g++
export CPP=$PREFIX-cpp
export RANLIB=$PREFIX-ranlib
export PATH="/usr/$PREFIX/bin:$PATH"
exec "$@"
EOF
chmod u+x $HOME/bin/mingw

If $HOME/bin is not already part of your $PATH, you need to add it:

export PATH="$HOME/bin:$PATH"

We use this script to call ./configure and make with the right environment variables, but only when the ./configure script doesn’t support cross-compilation itself. You can also run the export commands from the mingw script by hand instead of calling the mingw script for every ./configure or make command, or execute $HOME/bin/mingw $SHELL to get a shell with these environment variables set, but in this howto we will call it explicitly every time it is needed.

Compiling LZO

Cross-compiling LZO is easy:

cd $HOME/mingw/lzo2-2.08
./configure --host=i686-w64-mingw32
make
DESTDIR=$HOME/mingw make install

Compiling Zlib

Cross-compiling Zlib is also easy, but a plain make failed to compile the tests, so we only build the static library here:

cd $HOME/mingw/zlib-1.2.8.dfsg
mingw ./configure
mingw make libz.a
DESTDIR=$HOME/mingw mingw make install

Compiling LibreSSL

Tinc can use either OpenSSL or LibreSSL. The latter is recommended.

cd $HOME/mingw/libressl-2.3.3
CC=i686-w64-mingw32-gcc ./configure --host=i686-w64-mingw32
make
DESTDIR=$HOME/mingw make install

Compiling tinc

Now that all the dependencies have been cross-compiled, we can cross-compile tinc. Since we use a clone of the git repository here, we need to run autoreconf first. If you want to cross-compile tinc from a released tarball, this is not necessary.

cd $HOME/mingw/tinc
autoreconf -fsi
./configure --host=i686-w64-mingw32 --with-zlib=$HOME/mingw/usr/local
make

Testing tinc

Since Wine was installed, you can execute the resulting binary even on Linux. Wine does not provide a TAP-Win32 device, but you can use the DeviceType = dummy option to test it without. The following command should work in any case:

$HOME/mingw/tinc/src/tincd.exe --help