virtualbox-source 5.1.38-dfsg-0ubuntu1.16.04.2 (i386 binary) in ubuntu xenial

 VirtualBox is a free x86 virtualization solution allowing a wide range
 of x86 operating systems such as Windows, DOS, BSD or Linux to run on a
 Linux system.
 .
 This package provides the source code for the virtualbox kernel module.
 The virtualbox package is also required in order to make use of these
 modules. Kernel sources or headers are required to compile this module.
 .
 The source is placed under /usr/src, and after decompression it can
 be built to produce a virtualbox-modules-_KVERS_ providing
 "virtualbox-modules" package.