ipmap :: = mapblock | redir | map .

map ::= mapit ifname ipmask "->" ipmask [ mapport | mapicmpid ] .
map ::= mapit ifname fromto "->" ipmask [ mapport | mapicmpid ] .
mapblock ::= "map-block" ifname ipmask "->" ipmask [ ports ] .
redir ::= "rdr" ifname ipmask dport "->" ip [ "," ip ] [ ports ] options .

dport ::= "port" portnum [ "-" portnum ] .
ports ::= "ports" numports | "auto" .
mapit ::= "map" | "bimap" .
fromto ::= "from" object "to" object .
ipmask ::= ip "/" bits | ip "/" mask | ip "netmask" mask .
mapport ::= "portmap" tcpudp portnumber ":" portnumber .
mapicmpid ::= "icmpidmap" icmp idnumber ":" idnumber .
options ::= [ tcpudp ] [ rr ] .

object  = addr [ port-comp | port-range ] .
addr    = "any" | nummask | host-name [ "mask" ipaddr | "mask" hexnumber ] .
port-comp = "port" compare port-num .
port-range = "port" port-num range port-num .

rr ::= "round-robin" .
tcpudp ::= "tcp" | "udp" | "tcp/udp" .
portnumber ::= number { numbers } | "auto" .
idnumber ::= number { numbers } .
ifname ::= 'A' - 'Z' { 'A' - 'Z' } numbers .

numbers ::= '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' .