/usr/include/netlink/ is in libnl-dev 1.1-8ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/netlink/addr.h
/usr/include/netlink/attr.h
/usr/include/netlink/cache-api.h
/usr/include/netlink/cache.h
/usr/include/netlink/data.h
/usr/include/netlink/fib_lookup/
/usr/include/netlink/fib_lookup/lookup.h
/usr/include/netlink/fib_lookup/request.h
/usr/include/netlink/genl/
/usr/include/netlink/genl/ctrl.h
/usr/include/netlink/genl/family.h
/usr/include/netlink/genl/genl.h
/usr/include/netlink/genl/mngt.h
/usr/include/netlink/handlers.h
/usr/include/netlink/list.h
/usr/include/netlink/msg.h
/usr/include/netlink/netlink-compat.h
/usr/include/netlink/netlink-kernel.h
/usr/include/netlink/netlink.h
/usr/include/netlink/object-api.h
/usr/include/netlink/object.h
/usr/include/netlink/route/
/usr/include/netlink/route/addr.h
/usr/include/netlink/route/class-modules.h
/usr/include/netlink/route/class.h
/usr/include/netlink/route/classifier-modules.h
/usr/include/netlink/route/classifier.h
/usr/include/netlink/route/cls/
/usr/include/netlink/route/cls/fw.h
/usr/include/netlink/route/cls/police.h
/usr/include/netlink/route/cls/u32.h
/usr/include/netlink/route/link.h
/usr/include/netlink/route/neighbour.h
/usr/include/netlink/route/neightbl.h
/usr/include/netlink/route/nexthop.h
/usr/include/netlink/route/qdisc-modules.h
/usr/include/netlink/route/qdisc.h
/usr/include/netlink/route/route.h
/usr/include/netlink/route/rtnl.h
/usr/include/netlink/route/rule.h
/usr/include/netlink/route/sch/
/usr/include/netlink/route/sch/cbq.h
/usr/include/netlink/route/sch/dsmark.h
/usr/include/netlink/route/sch/fifo.h
/usr/include/netlink/route/sch/htb.h
/usr/include/netlink/route/sch/netem.h
/usr/include/netlink/route/sch/prio.h
/usr/include/netlink/route/sch/red.h
/usr/include/netlink/route/sch/sfq.h
/usr/include/netlink/route/sch/tbf.h
/usr/include/netlink/route/tc.h
/usr/include/netlink/socket.h
/usr/include/netlink/types.h
/usr/include/netlink/utils.h