XDP: start document about setting up build environment

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

kernel/Documentation/networking/XDP/end-user/build_environment.rst

@@ -0,0 +1,47 @@
+==========================
+XDP/eBPF build environment
+==========================
+
+Tool chain
+==========
+
+The XDP program running (in the driver hook point) is an eBPF program
+(short for Extended Berkeley Packet Filters). Unless you want to write
+eBPF machine-code like instruction by hand, you likely want to install
+some front-ends, that allow you to write some pseudo C-code.
+
+Tools for compiling `kernel bpf samples`_ requires having installed:
+ * clang >= version 3.4.0
+ * llvm >= version 3.7.1
+
+Note that LLVM's tool 'llc' must support target 'bpf', list version
+and supported targets with command: ``llc --version``.
+
+.. _kernel bpf samples:
+   https://github.com/torvalds/linux/blob/master/samples/bpf/README.rst
+
+There is also toolkit called BCC_ (BPF Compiler Collection) that makes
+eBPF programs easier to write, and front-ends in Python and lua.  But
+it also depend on LLVM.
+
+.. _BCC: https://github.com/iovisor/bcc/blob/master/README.md
+
+Linux distros
+=============
+
+Fedora 25
+---------
+
+Since Fedora 25, the package BCC_ is included with the distribution,
+and LLVM+clang in the correct versions.
+
+Install commands for Fedora 25::
+
+ dnf install llvm llvm-libs llvm-doc clang clang-libs
+ dnf install bcc bcc-tools bcc-doc --enablerepo=updates-testing
+ dnf install kernel-devel
+ dnf install python3-pyroute2
+
+.. Note:: As of this writing (2017-01-18) BCC for F25 is still in the
+          updates-testing repository.
+

kernel/Documentation/networking/XDP/end-user/index.rst

@@ -10,4 +10,5 @@ Contents:
 .. toctree::
    :maxdepth: 2
 
+   build_environment