добрый день.
Конечно же ,в модулях ядра:
mas@centos1:~:21/12/14-14:57$ sudo find /lib/modules/`uname -r` -name "*gre*"
/lib/modules/2.6.32-431.29.2.el6.centos.plus.i686/kernel/net/ipv4/ip_gre.ko
/lib/modules/2.6.32-431.29.2.el6.centos.plus.i686/kernel/net/ipv4/netfilter/nf_nat_proto_gre.ko
/lib/modules/2.6.32-431.29.2.el6.centos.plus.i686/kernel/net/sched/sch_gred.ko
/lib/modules/2.6.32-431.29.2.el6.centos.plus.i686/kernel/net/sched/sch_ingress.ko
/lib/modules/2.6.32-431.29.2.el6.centos.plus.i686/kernel/net/netfilter/nf_conntrack_proto_gre.ko
/lib/modules/2.6.32-431.29.2.el6.centos.plus.i686/kernel/drivers/media/rc/keymaps/rc-pinnacle-grey.ko
