realm match: uses realm key from routing as match criteria similiar to
             one in packet classifier

/** snip from packet classifier documentation */
Routing tables based classifier
CONFIG_NET_CLS_ROUTE4
  If you say Y here, you will be able to classify outgoing packets
  according to the route table entry they matched. If unsure, say Y.
/** end snip **/


# Example
# add route
/sbin/ip route add 194.29.194.0/24 via 194.29.192.1 realm 10

# source realm is in realm with mask 0xFFFF0000,
# destination is in realm with mask 0x0000FFFF

# match destination realm
/usr/local/sbin/iptables -A OUTPUT -m realm --realm 10 -j LOG

# match realm of source, this is also determinated by routing,
/usr/local/sbin/iptables -A INPUT -m realm --realm 655360 -j LOG

THIS PATCH REQUIRES CONFIG_NET_CLS_ROUTE TO BE SET
