Those are the verbatim files, straight from BSD.
71940e9 bsd: block and network xen drivers
bsd/sys/dev/xen/blkfront/blkfront.c | 1428 ++++++++++++++++++++++
bsd/sys/dev/xen/blkfront/block.h | 320 +++++
bsd/sys/dev/xen/netfront/mbufq.h | 123 ++
bsd/sys/dev/xen/netfront/netfront.c | 2248 +++++++++++++++++++++++++++++++++++
4 files changed, 4119 insertions(+)
Upstream: github.com