/usr/i686-linux-gnu/include/net/ is in libc6-dev-i386-cross 2.27-3ubuntu1cross1.
This file is owned by root:root, with mode 0o755.
..
/usr/i686-linux-gnu/include/net/ethernet.h
/usr/i686-linux-gnu/include/net/if.h
/usr/i686-linux-gnu/include/net/if_arp.h
/usr/i686-linux-gnu/include/net/if_packet.h
/usr/i686-linux-gnu/include/net/if_ppp.h
/usr/i686-linux-gnu/include/net/if_shaper.h
/usr/i686-linux-gnu/include/net/if_slip.h
/usr/i686-linux-gnu/include/net/ppp-comp.h
/usr/i686-linux-gnu/include/net/ppp_defs.h
/usr/i686-linux-gnu/include/net/route.h
/usr/i686-linux-gnu/include/netash/ash.h
/usr/i686-linux-gnu/include/netatalk/at.h
/usr/i686-linux-gnu/include/netax25/ax25.h
/usr/i686-linux-gnu/include/neteconet/ec.h
/usr/i686-linux-gnu/include/netinet/ether.h
/usr/i686-linux-gnu/include/netinet/icmp6.h
/usr/i686-linux-gnu/include/netinet/if_ether.h
/usr/i686-linux-gnu/include/netinet/if_fddi.h
/usr/i686-linux-gnu/include/netinet/if_tr.h
/usr/i686-linux-gnu/include/netinet/igmp.h
/usr/i686-linux-gnu/include/netinet/in.h
/usr/i686-linux-gnu/include/netinet/in_systm.h
/usr/i686-linux-gnu/include/netinet/ip.h
/usr/i686-linux-gnu/include/netinet/ip6.h
/usr/i686-linux-gnu/include/netinet/ip_icmp.h
/usr/i686-linux-gnu/include/netinet/tcp.h
/usr/i686-linux-gnu/include/netinet/udp.h
/usr/i686-linux-gnu/include/netipx/ipx.h
/usr/i686-linux-gnu/include/netiucv/iucv.h
/usr/i686-linux-gnu/include/netpacket/packet.h
/usr/i686-linux-gnu/include/netrom/netrom.h
/usr/i686-linux-gnu/include/netrose/rose.h