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Building project

Installing from packages

The resolver is packaged for Debian, Fedora, Ubuntu and openSUSE Linux distributions. Refer to project page for information about installing from packages. If packages are not available for your OS, see following sections to see how you can build it from sources (or package it), or use official Docker images.

Platform considerations

Project Platforms Compatibility notes
daemon UNIX-like1, Microsoft Windows C99, libuv provides portable I/O
library UNIX-like, Microsoft Windows2 MSVC not supported, needs MinGW
modules varies
tests/unit equivalent to library
tests/integration UNIX-like Depends on library injection (see)

Requirements

The following is a list of software required to build Knot DNS Resolver from sources.

Requirement Required by Notes
GNU Make 3.80+ all (build only)
pkg-config all (build only)3
C compiler all (build only)4
libknot 2.1+ all Knot DNS library (requires autotools, GnuTLS and Jansson).
LuaJIT 2.0+ daemon Embedded scripting language.
libuv 1.7+ daemon Multiplatform I/O and services (libuv 1.0 with limitations5).

There are also optional packages that enable specific functionality in Knot DNS Resolver, they are useful mainly for developers to build documentation and tests.

Optional Needed for Notes
luasocket trust anchors, modules/stats Sockets for Lua.
luasec trust anchors TLS for Lua.
libmemcached modules/memcached To build memcached backend module.
hiredis modules/redis To build redis backend module.
Go 1.5+ modules Build modules written in Go.
cmocka unit tests Unit testing framework.
Doxygen documentation Generating API documentation.
Sphinx documentation Building this HTML/PDF documentation.
breathe documentation Exposing Doxygen API doc to Sphinx.
libsystemd daemon Systemd socket activation support.

Packaged dependencies

Most of the dependencies can be resolved from packages, here's an overview for several platforms.

  • Debian (since sid) - current stable doesn't have libknot and libuv, which must be installed from sources.
sudo apt-get install pkg-config libknot-dev libuv1-dev libcmocka-dev libluajit-5.1-dev
  • Ubuntu - unknown.
  • RHEL/CentOS - unknown.
  • openSUSE - there is an experimental package.
  • RHEL - unknown.
  • FreeBSD - unknown.
  • NetBSD - unknown.
  • OpenBSD - unknown.
  • Mac OS X - most of the dependencies can be found through Homebrew, with the exception of libknot.
brew install pkg-config libuv luajit cmocka

Building from sources

The Knot DNS Resolver depends on the the Knot DNS library, recent version of libuv, and LuaJIT.

$ make info # See what's missing

When you have all the dependencies ready, you can build and install.

$ make PREFIX="/usr/local"
$ make install

Note

Always build with PREFIX if you want to install, as it is hardcoded in the executable for module search path. If you build the binary with -DNDEBUG, verbose logging will be disabled as well.

Alternatively you can build only specific parts of the project, i.e. library.

$ make lib
$ make lib-install

Note

Documentation is not built by default, run make doc to build it.

Building with security compiler flags

Knot DNS Resolver enables certain security compile-time flags that do not affect performance. You can add more flags to the build by appending them to CFLAGS variable, e.g. make CFLAGS="-fstack-protector".

Method Status Notes
-fstack-protector disabled (must be specifically enabled in CFLAGS)
-D_FORTIFY_SOURCE=2 enabled
-pie enabled enables ASLR for kresd (disable with make HARDENING=no)
RELRO enabled full6

You can also disable linker hardening when it's unsupported with make HARDENING=no.

Building for packages

The build system supports both DESTDIR and amalgamated builds.

$ make install DESTDIR=/tmp/stage # Staged install
$ make all install AMALG=yes # Amalgamated build

Amalgamated build assembles everything in one source file and compiles it. It is useful for packages, as the compiler sees the whole program and is able to produce a smaller and faster binary. On the other hand, it complicates debugging.

Tip

There is a template for service file and AppArmor profile to help you kickstart the package.

Default paths

The default installation follows FHS with several custom paths for configuration and modules. All paths are prefixed with PREFIX variable by default if not specified otherwise.

Component Variable Default Notes
library LIBDIR $(PREFIX)/lib pkg-config is auto-generated7
daemon BINDIR $(PREFIX)/bin
configuration ETCDIR $(PREFIX)/etc/kresd Configuration file, templates.
modules MODULEDIR $(LIBDIR)/kdns_modules 8
work directory $(PREFIX)/var/run/kresd Run directory for daemon.

Note

Each module is self-contained and may install additional bundled files within $(MODULEDIR)/$(modulename). These files should be read-only, non-executable.

Static or dynamic?

By default the resolver library is built as a dynamic library with versioned ABI. You can revert to static build with BUILDMODE variable.

$ make BUILDMODE=dynamic # Default, create dynamic library
$ make BUILDMODE=static  # Create static library

When the library is linked statically, it usually produces a smaller binary. However linking it to various C modules might violate ODR and increase the size.

Resolving dependencies

The build system relies on pkg-config to find dependencies. You can override it to force custom versions of the software by environment variables.

$ make libknot_CFLAGS="-I/opt/include" libknot_LIBS="-L/opt/lib -lknot -ldnssec"

Optional dependencies may be disabled as well using HAS_x=yes|no variable.

$ make HAS_go=no HAS_cmocka=no

Warning

If the dependencies lie outside of library search path, you need to add them somehow. Try LD_LIBRARY_PATH on Linux/BSD, and DYLD_FALLBACK_LIBRARY_PATH on OS X. Otherwise you need to add the locations to linker search path.

Several dependencies may not be in the packages yet, the script pulls and installs all dependencies in a chroot. You can avoid rebuilding dependencies by specifying BUILD_IGNORE variable, see the Dockerfile for example. Usually you only really need to rebuild libknot.

$ export FAKEROOT="${HOME}/.local"
$ export PKG_CONFIG_PATH="${FAKEROOT}/lib/pkgconfig"
$ export BUILD_IGNORE="..." # Ignore installed dependencies
$ ./scripts/bootstrap-depends.sh ${FAKEROOT}

Building extras

The project can be built with code coverage tracking using the COVERAGE=1 variable.

Running unit and integration tests

The unit tests require cmocka and are executed with make check.

The integration tests use Deckard, the DNS test harness.

$  make check-integration

Note that the daemon and modules must be installed first before running integration tests, the reason is that the daemon is otherwise unable to find and load modules.

Read the documentation for more information about requirements, how to run it and extend it.

Getting Docker image

Docker images require only either Linux or a Linux VM (see boot2docker on OS X).

$ docker run cznic/knot-resolver

See the Docker images page for more information and options. You can hack on the container by changing the container entrypoint to shell like:

$ docker run -it --entrypoint=/bin/bash cznic/knot-resolver

Tip

You can build the Docker image yourself with docker build -t knot-resolver scripts.

  1. Known to be running (not exclusively) on FreeBSD, Linux and OS X.↩

  2. Modules are not supported yet, as the PE/DLL loading is different. Library injection is working with ELF (or Mach-O flat namespace) only.↩

  3. Requires C99, __attribute__((cleanup)) and -MMD -MP for dependency file generation. GCC, Clang and ICC are supported.↩

  4. You can use variables <dependency>_CFLAGS and <dependency>_LIBS to configure dependencies manually (i.e. libknot_CFLAGS and libknot_LIBS).↩

  5. libuv 1.7 brings SO_REUSEPORT support that is needed for multiple forks. libuv < 1.7 can be still used, but only in single-process mode. Use different method <daemon-reuseport> for load balancing.↩

  6. See checksec.sh↩

  7. The libkres.pc is installed in $(LIBDIR)/pkgconfig.↩

  8. Users may install additional modules in ~/.local/lib/kdns_modules or in the rundir of a specific instance.↩